VEAC Marine Investigation Potential Impact Of Climate Change on Victoria’s Marine Protected Areas
May 2014 Fisheries Victoria Science Report Series No. 3
Potential Impacts of Climate Change on Victoria’s Marine Protected Areas
Liz Morris and Rachael Bathgate Centre for Aquatic Pollution Investigation and Management, University of Melbourne
May 2014
Fisheries Victoria Science Report Series No. 3
Published by the Victorian Government, Department of Environment and Primary Industries, May 2014 © The State of Victoria, Department of Environment and Primary Industries Melbourne, May 2014 This publication is copyright. No part may be reproduced by any process except in accordance with the provisions of the Copyright Act 1968 . Authorised by the Victorian Government, 1 Spring Street, Melbourne. Printed by DEPI Queenscliff, Victoria. Preferred way to cite this publication: Liz Morris and Rachael Bathgate (2014)VEAC Marine Investigation. Potential impacts of climate change on Victoria’s Marine Protected Areas. Fisheries Victoria Science Report Series No. 3. ISSN 2203-3122 ISBN 978-1-74326-908-4 (Print) Author Contact Details: Liz Morris (CAPIM University of Melbourne) Fisheries Management and Science Branch, Fisheries Victoria PO Box 114, Queenscliff Vic 3225 Copies are available from the website www.depi.vic.gov.au/fishing For more information contact the DEPI Customer Service Centre 136 186
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Contents
Executive Summary 1
Introduction 13
Purpose and approach 13 Natural values within the Victorian MPA system 13 Future climate 13 Implications of future climate to Victoria’s marine environment 14 Omissions 14
Otways Bioregion 24
Background 24 Future climate 24 Habitat vulnerabilities to future climate 25 Case study – Discovery Bay Marine National Park. 27 Reef habitat 27 Soft sediment habitat 29
Central Victoria Bioregion 31
Background 31 Future climate 31 Habitat vulnerabilities to future climate 32 Case Study - Point Addis Marine National Park 34 Sea level rise, waves, rainfall and runoff, currents. 34 Reef habitat 34 Soft sediment habitat 36 Fish 36 Case Study - Bunurong Marine National Park 37
CO 2 - increased acidity - and temperature. 37 Reef habitat 37 Soft Sediment habitat 39
Flinders Bioregion 40
Background 40 Future Climate 40 Habitat vulnerabilities to future climate 41 Case Study – Wilsons Promontory Marine National Park 43 Reef habitat 43 Soft sediment habitat 45 Marine Mammals 46 Fish 46
Twofold Shelf Bioregion 48
Background 48 Future climate 48
VEAC Marine Investigation. Climate change and MPAs iii
Habitat vulnerabilities to future climate 48 Case study –Point Hicks Marine National Park. 50 Reef habitat 50 Soft sediment habitat 52
Victorian Embayments Bioregion 54
Background 54 Corner Inlet-Nooramunga, Shallow Inlet 55 Western Port 55 Port Phillip Bay 55 Future Climate 55 Habitat vulnerabilities to Future Climate 56 Case Study - Ricketts Point Marine Sanctuary, Port Phillip Bay 59 Reef habitat 59 Soft sediment habitat 61 Case Study - Yaringa Marine National Park, Western Port 64 Seagrass habitat 64 Mangrove habitat 65 Saltmarsh habitat 65 Unvegetated soft sediment habitat 65
Acknowledgements 68
References 69
Appendix 1 – Innundation Maps 77
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List of Tables
Table 1 Overview of predicted impact of climate change on physicochemical conditions. Taken from Mills et al . 2013 16 Table 2 Vulnerability ratings and potential impacts of different habitats to future climate. Vulnerabilities are indicated by colours: blue = high / moderate, green = low. Where no vulnerability rating is included this is because the ratings were very different across the state i.e. high in one region and low in another region. Source: Klemke and Arundel eds. 2013. Uncertainty ratings have not been included within this table but the reader should be aware that uncertainty was high for many of the vulnerability ratings in the source report...... 17 Table 3 . Major vulnerabilities of marine mammals to future climate. Source: Gill and Pirtzl (2013) ...... 20 Table 4 . Vulnerability ratings and potential impacts of different life history stages of finfish and sharks to future climate. Vulnerabilities are indicated by colours: blue = high; light blue = moderate; green = low. Source: Hirst and Hamer (2013) ...... 21 Table 5. Projected climate change impacts to phytoplankton and zooplankton. Source Hobday et al. (2006)...... 23 Table 6. Marine protected areas within the Otways Bioregion ...... 24 Table 7. Marine protected areas in the Central Victoria Bioregion ...... 31 Table 8. Vulnerability of habitats in MPAs in Flinders Bioregion to predicted climate stressors. Taken from Future Climate report (Klemke and Arundel eds 2013). blue=highly vulnerable, light blue=moderately vulnerable and green=low vulnerability ...... 42 Table 9. Marine protected areas in the Twofold Shelf Bioregion ...... 48 Table 10. Marine protected areas in Victorian Embayments Bioregion ...... 54
List of Figures
Figure 1 . Inundation map for Ricketts Point Marine Sanctuary based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry...... 63 Figure 2 . Inundation map for Yaringa Marine National Park based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry...... 67 Figure 3 . Inundation map for Point Cooke Marine Sanctuary based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry...... 78 Figure 4. Inundation map for Jawbone Marine Sanctuary based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry...... 79 Figure 5 . Inundation map for Swan Bay north based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry...... 80 Figure 6 . Inundation map for Swan Bay south based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry...... 81 Figure 7 . Inundation map for Churchill Island MNP based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry...... 82 Figure 8 . Inundation map for French Island east based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry...... 83 Figure 9. Inundation map for French Island west based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry...... 84 Figure 10. Inundation map for Nooramunga Marine and Coastal Park west based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry...... 85 Figure 11 . Inundation map for Nooramunga Marine and Coastal Park central based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry...... 86 Figure 12 . Inundation map for Nooramunga Marine and Coastal Park east based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry...... 87 Figure 13 . Inundation map for Shallow Inlet Marine and Coastal Park based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry...... 88
VEAC Marine Investigation. Climate change and MPAs v
Executive Summary
The marine protected areas system within Victoria includes 13 marine national parks, 11 marine sanctuaries and six other areas designated as marine parks, marine reserves or marine and coastal parks. The Victorian Environmental Assessment Council (VEAC) is undertaking an investigation into the performance of Victoria’s marine protected areas. As part of this investigation VEAC is required to assess any ongoing and future threats or challenges to the effective management of marine protected areas, particularly in relation to the biodiversity and ecological outcomes. This document will contribute to this assessment through informing VEAC of the likely implications of climate change for marine protected areas. The approach taken in this study was to use recent information on natural values within Victorian Marine Protected Areas (MPAs) (Barton et al . 2012a-e), climate change predictions for Victoria (Mills et al. 2013), and assessments of vulnerability to future climate for broad habitat types / taxonomic groups (Klemke and Arundel eds. 2013). The climate change predictions for Victoria drew on existing modelling and scientific literature of the physicochemical changes predicted to occur in Victoria’s marine environment by 2030, 2070 and 2100. These climate change predictions include mean sea level, astronomical tides, ocean currents and upwellings, wave climates, sea surface temperatures, salinities, ocean acidification and rainfall and runoff. Broad habitat types found within the five Victorian bioregions include rocky reef, soft sediment - unvegetated, seagrass, mangrove and saltmarsh – and open water or pelagic habitat. This information has been translated to MPAs within the five Victorian bioregions. Representative parks from each bioregion have been chosen for detailed case studies and much of the information included in the case study section for each bioregion will be relevant to all MPAs within that bioregion. An overview of the predicted general impacts of climate change across the MPAs, including variation at a bioregional scale, is provided below. Summary tables describing the potential impacts at the scale of MPAs within each bioregion are then provided at the end of this section. Further information is provided within the body of the report. In general responses to climate change are expected to be complex and hard to predict. Stressors associated with the changing climate will occur simultaneously, while for many species basic biological information is lacking (e.g. phytoplankton and zooplankton) making it difficult to determine species and assemblage responses to a changing climate. There are likely to be combinations of direct and indirect interacting effects that can change fundamental processes such as competition, predation, trophic relationships and nutrient cycling. There is uncertainty associated with many of the predictions of climate change and this uncertainty can be compounded when considering the ecological effects of a changing climate. As a consequence this report tends to focus on more common and well-studied species to demonstrate the complexities and potential interactions that will take place under climate change. Increased sea surface temperature will affect biota and ecological processes in MPAs in all bioregions to some extent, potentially leading to changes in community composition. Impacts of temperature change are likely to be greatest in MPAs on the east coast – due to the strengthening East Australia Current – and in MPAs in the Victorian Embayments bioregion, in particular Port Phillip Bay. Potential consequences of temperature increases are range shifts due to the introduction of warm water species and loss of cooler water species leading to altered assemblage structure and function. Habitat-forming kelps (brown algae) are particularly vulnerable to temperature increases with potential decreases in biomass and range retraction. There is potential for the emergence of new pests and pathogens and temperature may increase the vulnerability of organisms to other stressors such as pollutants. The timing and magnitude of reproduction and recruitment may alter in response to temperature change. Increased air temperatures will impact intertidal habitats, particularly where prolonged summer hot spells combine with daytime low tides. Altered distribution and abundance of prey-items in response to increased sea surface temperature may impact marine mammals. It is possible that some species may have the capacity to acclimate to temperature increases, as has been observed in some finfish species. Sea level rise, particularly when combined with storm surge and high tides, will lead to inundation of existing intertidal habitat and erosion of sandy and soft-rocky shorelines (e.g. sandstone). For organisms on rocky intertidal reefs, the impact of sea level rise will depend on geology, slope and aspect, with new reef potentially being created inland - where suitable conditions exist and depending on surrounding land use. Intertidal reefs and soft sediments in MPAs will become subtidal thereby increasing the area of shallow subtidal reef and soft sediment habitat in these MPAs. The upper and lower boundaries of seagrass meadows may shift landwards in response to sea level rise. The rates of landward colonisation by saltmarsh and mangroves in areas such as northern Western Port are unlikely to exceed rates of sea level rise with potential reduction in cover of these habitats - saltmarsh being particularly vulnerable. All sandy shorelines are expected to recede to varying degrees with increased storm frequency potentially altering soft sediment community composition.
VEAC Marine Investigation. Climate change and MPAs 1
Increased CO 2 will increase seawater acidity with likely impairment of carbon uptake and possibly dissolution of calcified structures in calcifying organisms such as molluscs, echinoderms, deep water coral and coralline red algae. Reduction in ocean pH will be greatest for MPAs in the west and less moving to the east of the State. Subtidal algae and seagrass may respond positively to increased CO 2 with enhanced photosynthetic rates and an increase in cover. Complex interactions between pH, temperature and other stressors necessitate further research on temperate systems to determine species and community-level response to increased CO 2. Changes to upwelling and runoff may alter productivity in coastal waters. Predicted strengthening of the Bonney upwelling may enhance marine productivity in MPAs in the Otways bioregion with flow on effects for krill, squid, fish and marine mammals. Alternatively, productivity may be limited by excessive turbulence from continual upwelling which has implications for the viability of baleen and toothed whales and seals. Decreased runoff and associated decline in nutrients to nearshore coastal environments may cause a decline in the growth of algae and seagrass, but may be beneficial for MPAs in embayments because of the associated decrease in sediments and toxicants from stormwater. Predictions for less frequent but more intense rainfall events may however create pulse disturbances, particularly in embayments. Predictions for increases in wave energy and wave height in the Otway and Central Victoria bioregions may increase disturbance of intertidal and subtidal habitats, and impact organisms adapted to lower wave energy environments or poor swimmers (e.g. fish larvae, seahorses and seadragons). A slight decrease in wave energy in MPAs in embayments is unlikely to have a significant effect. Larval dispersal, recruitment, and thus population connectivity of invertebrates and fish inside and beyond MPA boundaries may be altered by changes to wave action and currents. For example the decline in strength of the Leeuwin Current flowing from the west may potentially reduce larval dispersal distances in the Otway and Central Victoria bioregions. In embayments, increased salinities may increase physiological stress for organisms, while minor changes to tidal amplitudes, such predicted for Port Phillip Bay, are unlikely to impact species or ecological processes. The following summary tables have been produced for each bioregion detailing possible climate change impacts that might occur in each MPA within that bioregion. Varying degrees of uncertainty are associated with these predictions (Klemke and Arundel eds, 2013).
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Summary of potential climate change impacts in MPAs in the Otways bioregion
Discovery Bay MNP Merri MS The Arches MS Twelve Apostles MNP Sea level rise causes a reduction in Sea level rise causes a loss of Sea level rise causes a Sea level rise causes a reduction in horizontal horizontal intertidal reef habitat with horizontal intertidal reef platforms reduction in shallow subtidal reef intertidal reef habitat with possible impacts on seal possible impacts on seal haul out and Increased sea surface and air habitat haul out and Hormosira habitat. Hormosira habitat. temperatures cause a reduction in Increased wave action and sea Increased wave action and temperatures cause a Increased wave action and temperatures Hormosira – replaced by turfing algal surface temperatures cause a reduction in kelp species e.g. Hormosira and cause a reduction in kelp species e.g. assemblages reduction in subtidal kelp Macrocystis Hormosira and Macrocystis Increased wave action and sea biomass Increased wave action and sea level rise cause a Increased wave action and sea level rise surface temperatures cause a Range shifts due to introduction loss of subtidal band of Zostera cause a loss of subtidal band of Zostera reduction in subtidal kelp biomass of warmer water species and Range shifts due to introduction of warmer water Range shifts due to introduction of Range shifts due to introduction of loss of cooler water species alter species and loss of cooler water species alter warmer water species and loss of cooler warmer water species and loss of assemblage structure and assemblage structure and function function water species alter assemblage structure cooler water species alter Emergence of new pests and pathogens e.g. and function assemblage structure and function Emergence of new pests and Undaria pathogens e.g. Undaria Emergence of new pests and pathogens Emergence of new pests and Recruitment of taxa affected by changes to wave e.g. Undaria pathogens e.g. Undaria Recruitment of taxa affected by climate, currents and upwellings with possible Recruitment of taxa affected by changes Recruitment and growth of taxa changes to wave climate, consequences for other species e.g. Jasus to wave climate, currents and upwellings affected by changes to the timing and currents and upwellings with edwardsii with possible consequences for other frequency of upwelling events e.g. H. possible consequences for other species e.g. Jasus edwardsii Productivity of area changed with impacts on food species e.g. Jasus edwardsii rubra webs and feeding grounds of migratory species Productivity of area changed with All nearshore habitats affected by Ocean acidification has impacts e.g. pygmy blue whales. impacts on food webs and feeding changes in the frequency and severity on diverse mollusc and sponge assemblages Ocean acidification and temperature changes grounds of migratory species e.g. pygmy of storm events which will expose have impacts on diverse mollusc and sponge blue whales. areas to pulses of freshwater, Productivity of area changed assemblages. nutrients and sediments. with impacts on food webs and Ocean acidification has impacts on All nearshore habitats affected by changes in the diverse mollusc and sponge feeding grounds of migratory species e.g. pygmy blue whales. frequency and severity of storm events which will assemblages. Temperature also may expose areas to pulses of freshwater, nutrients impact deep reef sponge assemblages and sediments.
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Summary of potential climate change impacts in MPAs in the Central Victoria bioregion
Point Addis MNP Port Phillip Heads MNP – Pt Bunurong MNP/MP Lonsdale and Pt Nepean Sea level rise leading to reduction in Sea level rise leading to reduction Sea level rise leading to reduction in area of horizontal intertidal reef in area of horizontal intertidal reef area of horizontal intertidal reef habitat including at Ingoldsby Reef. habitat including existing rock habitat including existing rock pools. Loss of some species, capacity for pools. Loss of some species, Loss of some species, capacity for landward colonisation and persistence capacity for landward colonisation landward colonisation and persistence in others. Increase in relative and persistence in others. Increase in others. Increase in relative proportion of shallow subtidal reef. in relative proportion of shallow proportion of shallow subtidal reef. Increased wave height and frequency subtidal reef. Bunurong more sheltered;so of large wave events – increased Increased wave height and disturbance from projected increases disturbance in reef, soft sediment and frequency of large wave events – in wave height likely to be less seagrass habitats with possible increased disturbance in reef, soft extreme than for other MPAs in changes to species composition e.g. sediment and seagrass habitats bioregion. loss of Ecklonia and dependent with possible changes to species Some increase in erosion of species from reefs. composition e.g. reduction in area sandstone/limestone cliffs, recession Wave effects on larval fish - of algae Phyllospora comosa and of sandy beaches and increased settlement, swimming and feeding – dependent species from reefs. mobilisation of sediment – likely more and poor swimmers e.g. weedy Enhanced rate of erosion of frequent smothering and seadragon Phylopteryx taeniolatus . calcarenite cliffs and beaches - turbidity/decrease light to animals, Enhanced rate of erosion of increased sediment load in water algae and Amphibolis antarctica in sandstone/limestone cliffs and column. Possiblealtered species rockpools and subtidal. beaches - increased sediment load in composition in intertidal and Increased SST - altered species water column leading to altered shallow subtidal due to smothering range, physiological stress, changes species composition in intertidal and and shading of algae, Amphibolis to phenology, decreased larval shallow subtidal due to smothering antarctica and animals. developmental time, possible change and shading of algae, Amphibolis Increased SST - altered species in diverse brown and red algal antarctica, Zostera nigricaulis and range, physiological stress, communities. animals. changes to phenology, decreased Increased air temperature –higher Increased SST - altered species larval developmental time, loss of mortality of intertidal organisms range, physiological stress, changes canopy-forming macroalgae e.g. including Hormosir a – replaced by to phenology, decreased larval Phyllopsera comosa and Ecklonia turfing algal species. Loss of developmental time, loss of canopy- radiata . biodiversity. forming macroalgae e.g. Phyllopsera Wave effects on larval fish - Emergence of new pests and comosa and Macrocystis pyrifera . settlement, swimming and feeding. pathogens.
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Summary of potential climate change impacts in MPAs in Central Victoria bioregion continued.
Point Addis MNP Port Phillip Heads MNP Bunurong MNP/MP Pt Lonsdale and Pt Nepean
Increased air temperature –higher Increased air temperature –higher CO 2 and acidification leading to mortality in intertidal organisms mortality in intertidal organisms impaired calcification and/or including Hormosira – replaced by including Hormosir a – replaced by dissolution in e.g. molluscs, turfing algal species, loss of turfing algal species, loss of echinoderms, crustaceans, coralline biodiversity. biodiversity. algae and some species of deep Emergence of new pests and Emergence of new pests and water sponges and bryozoans. pathogens. pathogens. Possible positive benefits for photosynthesising species. CO 2 and acidification leading to CO 2 and acidification leading to impaired calcification and/or impaired calcification and/or Altered dispersal/retention of eggs dissolution in e.g. molluscs, dissolution in e.g. molluscs, and larvae of invertebrates such as echinoderms, crustaceans and echinoderms, crustaceans, coralline abalone and urchins, and fish, and coralline algae including rhodoliths. algae and some species of deep algal spores with possible Possible positive benefits for water sponges. Possible positive consequences for population photosynthesising species. benefits for photosynthesising connectivity. Altered dispersal/retention of eggs species. Reduced rainfall/runoff and shift to and larvae of invertebrates and fish, Altered dispersal/retention of eggs episodic events – decrease in and algal spores with possible and larvae of invertebrates such as nutrients entering nearshore habitats consequences for population abalone and urchins, and fish, and (decreased productivity – food webs) connectivity. algal spores with possible and freshwater to intertidal area – consequences for population possible change in community Reduced rainfall/runoff and shift to composition. episodic events – decrease in connectivity. nutrients entering nearshore habitats Reduced rainfall/runoff and shift to Altered pH and temperature increase (decreased productivity – food webs) episodic events – decrease in vulnerability to other stressors. and freshwater to intertidal area – nutrients entering nearshore habitats possible change in community (decreased productivity – food webs) composition. and freshwater to intertidal area – Altered pH and temperature possible change in community increase vulnerability to other composition. stressors. Altered pH and temperature increase vulnerability to other stressors.
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Summary of potential climate change impacts in marine sanctuaries – Central Victoria bioregion
Marengo Reefs MS Eagle Rock MS Point Danger MS Barwon Bluff MS Mushroom Reef MS
Sea level rise leading to loss of Sea level rise leading to Sea level rise leading to Sea level rise leading to Sea level rise leading to intertidal reef habitat and reduction in area of intertidal reduction in area of intertidal reduction in area of intertidal reduction in area of intertidal increase in shallow subtidal reef. reef habitat and increase in reef habitat and increase in reef habitat and increase in reef habitat and increase in Loss of intertidal species. Loss shallow subtidal reef. Loss of shallow subtidal reef. Loss of shallow subtidal reef. Loss of shallow subtidal reef. of seal haul out. some species, capacity for some species, capacity for some species, capacity for New basalt intertidal reef Increased wave height and adaptation and landward adaptation and landward adaptation and landward possibly exposed through frequency of large wave events colonisation in others if new colonisation in others if new colonisation in others if new erosion of overlying sediments intertidal area created by intertidal area created by intertidal area created by – increase disturbance and at landward edge of MS. dislodgement of algae and erosion of adjacent erosion of sand overlying reef on erosion of adjacent Amphibolis antarctica may have basalt/sandstone cliffs. landward boundary. basalt/sandstone cliffs. animals, erosion, turbidity and potential to colonise newly sediment deposition. Possible Increased wave height and Increased wave height and Increased wave height and created intertidal soft sediment change in subtidal community frequency of large wave events frequency of large wave events frequency of large wave events and reef. composition. – increase disturbance and – increase disturbance and – increase disturbance and Mushroom Reef relatively Increased SST - altered species dislodgement of algae and dislodgement of algae and dislodgement of algae and sheltered from wave action range, physiological stress, animals, erosion of cliffs and animals, beach erosion, turbidity animals, erosion, turbidity and compared to other MSs in changes to phenology, beach, turbidity and sediment and sediment deposition. sediment deposition. Possible bioregion but increase in decreased larval developmental deposition. Possible change in Possible change in community change in community sediments in water column may community composition. composition. composition. time, loss of canopy-forming affect fish, Amphibolis macroalgae e.g. Phyllopsera Increased SST-altered species Increased air temperature – Increased SST - altered species antarctica , and sediment comosa and Durvillaea range, physiological stress, higher mortality of intertidal range, physiological stress, deposition over reef may potatorum. changes to phenology, organisms including Hormosira changes to phenology, smother animals and algae. decreased larval developmental – replaced by turfing algal decreased larval developmental CO 2 and acidification leading to Increased SST - altered species impaired calcification in molluscs time, loss of canopy-forming species, loss of biodiversity. time, loss of canopy-forming range, physiological stress, (abalone) echinoderms, macroalgae e.g. Phyllopsera macroalgae e.g. Macrocystis changes to phenology, crustaceans, coralline algae and comosa and Durvillaea pyrifera and Durvillaea decreased larval developmental potatorum. potatorum. some species of deep water time, loss of habitat-forming sponges. Increased air temperature – macroalgae e.g. Ecklonia and higher mortality of intertidal Phyllospora. organisms including Hormosir a – replaced by turfing algal species, loss of biodiversity
VEAC Marine Investigation. Climate change and MPAs 6
Summary of potential climate change impacts in marine sanctuaries – Central Victoria bioregion continued
Marengo Reefs MS Eagle Rock MS Point Danger MS Barwon Bluff MS Mushroom Reef MS
Emergence of new pests and CO 2 and acidification leading CO 2 and acidification leading Increased air temperature – Increased air temperature – pathogens to impaired calcification in e.g. to impaired calcification in e.g. higher mortality of intertidal higher mortality of intertidal Altered pH and temperature molluscs, echinoderms, molluscs, echinoderms, organisms including organisms including increase vulnerability to other crustaceans, coralline algae crustaceans, coralline algae Hormosir a – replaced by Hormosir a – replaced by stressors. and some species of deep and some species of deep turfing algal species, loss of turfing algal species, loss of water sponges. water sponges. biodiversity. biodiversity.
Emergence of new pests and Emergence of new pests and CO 2 and acidification leading CO 2 and acidification leading pathogens pathogens to impaired calcification in e.g. to impaired calcification in e.g. Altered pH and temperature Altered pH and temperature molluscs, echinoderms, molluscs, echinoderms, increase vulnerability to other increase vulnerability to other crustaceans, coralline algae crustaceans, coralline algae stressors. stressors. and some species of deep and some species of deep water sponges. water sponges. Possible
Emergence of new pests and positive benefits for pathogens photosynthesising species. Altered pH and temperature Emergence of new pests and increase vulnerability to other pathogens. stressors. Altered pH and temperature increase vulnerability to other stressors.
VEAC Marine Investigation. Climate change and MPAs 7
Summary of potential climate change impacts in MPAs in the Flinders bioregion.
Wilsons Promontory Marine National Park, Marine Reserve and Marine Park.
Impact of increased wave energy will differ between west/south (exposed) and east (protected) coastlines. Sea level rise leading to reduction in area of intertidal reef habitat and increase in shallow subtidal reef. Loss of some species, capacity for adaptation and landward migration in others. Finfish, sharks and rays vulnerable to temperature change, particularly fish larvae (latter also vulnerable to altered wind/wave and currents). Species may show altered reproduction and recruitment, geographic range shifts, physiological acclimation, altered community composition. Varying degrees of vulnerability to other climate stressors, depending on life history stage. MNP a nationally significant area for great white shark, Carcharodon carcharias . Response of this temperate species unknown. Reduction in area of current seal haul out and nursery sites e.g. Kanowna Island. Seals influenced by potential change in prey abundance/prey type. Increased turbidity may alter feeding efficiency. Whales potentially impacted by changes to prey abundance but most feed elsewhere. Increased wave height and frequency of large wave events on west and south coasts – increase disturbance and dislodgement of algae and animals, erosion of beach and cliffs – but unlikely where cliffs are composed of relatively resistant granite. Increased mobilisation, and altered deposition, of sediments, possible recession of beaches, particularly on west and south coasts – turbidity, smothering. Possible change in community composition in intertidal/shallow subtidal habitats. Increased SST temperature - altered species range, physiological stress, changes to phenology, decreased larval developmental time, loss of canopy-forming macroalgae e.g. Phyllopsera comosa and Macrocystis pyrifera . Increased air temperature –higher mortality of intertidal organisms– loss of biodiversity.
CO 2 and acidification leading to impaired calcification in e.g. molluscs, echinoderms, crustaceans, coralline algae and some species of deep water sponges. Compound and flow on effects – e.g. of altered crustose coralline algae cover on abalone abundance.
Variable response of seagrass to sea level rise, increased wave energy, temperature and CO 2 - dependent on species and site (e.g. Zostera colonising species, tends to recover quickly post-disturbance but Amphibolis does better under high wave energy conditions, species have different light and temperature tolerances). Emergence of new pests and pathogens e.g. New Zealand screw shell (Maoriculpus roseus ). Altered pH and temperature increases vulnerability to other stressors.
VEAC Marine Investigation. Climate change and MPAs 8
Summary of potential impacts of climate change in the Twofold Shelf bioregion
Cape Howe MNP Point Hicks MNP Ninety Mile Beach Beware Reef MNP
Sea level rise causes Sea level rise causes Sea level rise causes Sea level rise causes reduction in horizontal reduction in horizontal reduction in intertidal reduction in horizontal intertidal reef which may intertidal reef which may habitat and breach to intertidal reef which may have implications for have implications for dune system have implications for connectivity of connectivity of Increase temperature connectivity of populations. populations causes range shifts that populations and seal haul Increased temperatures Increased temperatures alter assemblage out area may be lost. cause range shifts that can cause range shifts that structure and function Increased temperatures alter assemblage structure can alter assemblage Increased temperatures cause range shifts that and function e.g. C. structure and function within Twofold Shelf can alter assemblage rodgersii e.g. C. rodgersii contribute to increase structure and function Increased temperatures Increased temperatures bioregionalisation within e.g. C. rodgersii cause reduction in cause reduction in Victoria. Increased temperatures autogenic autogenic engineers Emergence of new cause reduction in engineers(e.g.kelp and (e.g.kelp and sponges) pests and pathogens. autogenic engineers (e.g. sponges) with associated with associated impacts Introduced pest species kelp and sponges) with impacts on understorey on understorey algae, such as the New associated impacts on algae, invertebrates and invertebrates and fish Zealand screw shell, understorey algae, fish Increased temperatures already present to east invertebrates and fish Increased temperatures within Twofold Shelf of MNP, can reduce the Increased temperatures within Twofold Shelf contribute to increased high biodiversity of soft within Twofold Shelf contribute to increased bioregionalisation within sediment assemblages. contribute to increased bioregionalisation within Victoria Altered pH, temp and bioregionalisation within Victoria Emergence of new pests salinity increase Victoria Emergence of new pests and pathogens e.g. vulnerability to other Emergence of new pests and pathogens e.g. abalone diseases stressors and pathogens e.g. abalone diseases Altered pH, temp and Increased acidification abalone diseases Altered pH, temp and salinity increase affects organisms with Altered pH, temp and salinity increase vulnerability to other calcified structures; salinity increase vulnerability to other stressors larval stages most vulnerability to other stressors Increased acidification impacted stressors Increased acidification affects organisms with Changes to EAC and Increased acidification affects organisms with calcified structures; larval upwellings may impact affects organisms with calcified structures; larval stages most impacted food webs and local calcified structures; larval stages most impacted Changes to EAC and densities of fish and stages most impacted Changes to EAC and upwellings may impact marine mammals Changes to EAC and upwellings may impact food webs and local upwellings may impact food webs and local densities of fish and food webs and local densities of fish and marine mammals densities of fish and marine mammals marine mammals
VEAC Marine Investigation. Climate change and MPAs 9
Summary of potential climate change impacts in MPAs in the Victorian Embayments bioregion – Port Phillip Bay
Port Phillip Bay Marine Sanctuaries Port Phillip Heads Marine National Park
Reduction in area of horizontal intertidal reef - Ricketts Point Marine Sanctuary Mud Islands increase in proportion of shallow subtidal reef. Loss of Cliffs and walls adjacent to MS may prevent Low-lying formation vulnerable to inundation some intertidal species, capacity for landward landward colonisation by intertidal organisms. particularly where high tides and storm surge colonisation and population persistence in others. Erosion of beach may expose new reef. Loss of combine – possible loss of intertidal seagrass and Highly urbanised coastline likely to create physical existing small area of saltmarsh. supralittoral vegetation. barriers to the landward colonisation of intertidal Jawbone Marine Sanctuary Swan Bay marine communities in MPAs, particularly on the eastern shoreline. Some capacity for landward expansion of Intertidal seagrass can potentially expand landward mangroves. Saltmarsh habitat likely to be lost. where suitable substrate exists, where no physical Recession of existing beaches. Changes to Upper and lower boundaries of seagrass could move barriers and new growth exceeds rate of sea level orientation and structure of soft sediment habitats – rise. Colonising ability varies amongst species. change in resident infauna. landward. Rate of change may exceed rate of colonisation at upper boundary. Zostera muelleri can act as pioneer species. CO 2 - acidification impacts on calcification and Seagrass may benefit from increased temperature An overall reduction in runoff may be beneficial to dissolution e.g. molluscs, corals, echinoderms and intertidal seagrass although increases in nutrients and CO 2, however possible loss of shallow and coralline algae. Emergence of new pests and and suspended sediments during storm events may diseases. intertidal seagrass through physical disturbance, turbidity and heat stress. negatively impact this habitat. Temperature-induced range shifts alter assemblage Boundary shifts in subtidal seagrass. structure and function. Point Cook Marine Sanctuary Weakening of the Leeuwin Current (LC) has Changes to cover of subtidal algae with associated Low-lying nature of Point Cooke coastline makes it highly susceptible to inundation. implications for recruitment of fish such as King shift in dependent species. George whiting into seagrass beds. Some capacity for landward shift of intertidal Changes to temperature, salinity and pH increase Portsea Hole vulnerability to other stressors and altered ecosystem populations into adjacent low-lying land depending functions (e.g. nutrient cycling). on geology and rate of change. Deep reef high vulnerability to CO 2-acidification, moderate to salinity and low to temperature. Altered connectivity between bay and coastal populations. Pope’s Eye Altered dispersal/recruitment and decreased survival Some change in vertical distribution of algae. of fish larvae and eggs. Range shifts in adult fish. Intermittent to permanent inundation of areas of upper rock habitat, particularly where storm events and high tides combine. Reduction in area available to birds and seals.
VEAC Marine Investigation. Climate change and MPAs 10
Summary of potential climate change impacts in MPAs in the Victorian Embayments bioregion – Western Port, Corner Inlet – Nooramunga and Shallow Inlet.
Western Port Corner Inlet-Nooramunga & Shallow Inlet Coastal and shallow marine habitats around Western Port Possible landward migration of seagrass but Saltmarshes particularly vulnerable as slow rate particularly vulnerable to storm surge. depends on species and rate of change. of landward colonisation relative to sea level rise. Sediment accretion may increase height of banks enabling Posidonia slow to colonise new patches. May be encroachment by mangroves. Human intertidal seagrass to persist, but rate of sea level rise likely Sediment accretion may increase height of banks barriers (e.g. levee banks) block landward greater than rate of accretion. enabling intertidal seagrass to persist, but rate of migration. Mortality of exposed intertidal seagrass from high sea level rise likely greater than rate of accretion. CO 2 - acidification impacts on calcification and/or temperatures. Possible increase in mortality of exposed intertidal dissolution e.g. molluscs, echinoderms, crustaceans. Variable species responses in Seagrass at all depths affected by increased turbidity, with seagrass from excessive and prolonged temperatures. algae, invertebrates, fish, and mammals: lethal- deeper seagrass also affected by loss of light through sea sublethal effects or resilience. level rise. Seagrass at all depths possibly affected by Possible positive effect of increased CO 2 on Enhanced sediment accretion beneficial to mangroves as increased turbidity, with deeper seagrass also affected by loss of light through sea level rise. primary productivity (mangroves, seagrass, new intertidal areas are created but rates of sea level rise saltmarsh). Seagrass could respond with likely to be greater than the rate of accretion - inundation of Enhanced sediment accretion beneficial to increase in area but overall response of seagrass mangroves at the seaward edge. mangroves as new intertidal areas for colonisation to combined stressors unknown. are created but rates of sea level rise likely to be Saltmarshes vulnerable as slow rate of landward Emergence of new pests and diseases. colonisation relative to sea level rise. Also, limited greater than the rate of accretion - inundation of availability of suitable habitat, and encroachment by mangroves at the seaward edge. Temperature-induced range shifts alter mangroves. Storm events increase physical disturbance of assemblage structure and function. soft-sediments and infauna – change in species Changes to temperature, salinity and pH - CO 2 - acidification impacts on calcification and/or dissolution e.g. molluscs, echinoderms, crustaceans. composition. increased vulnerability to other stressors and Variable species responses in algae, invertebrates, fish, Sea level rise - decrease in area of intertidal soft altered ecosystem functions (e.g. nutrient and mammals: lethal- sublethal effects or resilience. sediments. cycling). Temperature-induced range shifts alter assemblage Altered dispersal/recruitment and decreased Rate of predicted recession of beaches depends structure and function and facilitate new pests and survival of fish larvae and eggs. Range shifts in on location. May result in loss of beaches where diseases adult fish. retreat limited by geology. Changes to temperature, salinity and pH - increased vulnerability to other stressors and altered ecosystem functions (e.g. nutrient cycling). Increased physical disturbance of soft-sediments and infauna – change in species composition. Altered dispersal/recruitment and decreased survival of fish larvae and eggs. Range shifts in adult fish. Some intertidal reef in Churchill Island MNP inundated. Possible formation of new areas of reef at landward edge through erosion of sediments overlying basalt.
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Summary of potential climate change impacts in MPAs in the Victorian Embayments bioregion – Western Port, Corner Inlet – Nooramunga and Shallow Inlet continued.
Corner Inlet-Nooramunga & Shallow Inlet Corner Inlet Marine National Park Shallow Inlet Marine and Coastal Park Reduction in area of horizontal intertidal reef - Low-lying foreshore area has high risk of coastal increase in proportion of shallow subtidal reef. Loss inundation. of some intertidal species, capacity for adaptation Loss of surrounding saltmarsh habitat. and landward colonisation in others. Inlet is protected by narrow natural barrier along the Vertical shift of deep boundary for algae on subtidal open coast. Erosion and inundation across barrier reefs in response to light reduction - sea level rise. may make Inlet more exposed to ocean – possible Corner Inlet Marine and Coastal Park - loss of seagrass, altered soft-sediment infaunal and Nooramunga Marine and Coastal Park epifaunal assemblages. Erosion and inundation of sand barrier islands – possible alteration of hydrodynamics, loss of intertidal habitat including seagrass. Increased exposure of coastline to oceanic currents and waves. Increased mobilisation of sediments – altered patterns of deposition. Area important for white shark Carcharodon carcharias . Unlikely direct impact of multiple stressors on adults. Unknown impact on reproduction, early life history stages or habitat suitability/prey availability.
VEAC Marine Investigation. Climate change and MPAs 12
Introduction
Purpose and approach
The marine protected areas system within Victoria includes 13 marine national parks, 11 marine sanctuaries and 6 marine parks, marine reserves or marine and coastal parks. The Victorian Environmental Assessment Council (VEAC) is undertaking an investigation into the performance of Victoria’s marine protected areas. As part of this investigation VEAC is required to assess any ongoing and future threats or challenges to the effective management of marine protected areas, particularly in relation to the biodiversity and ecological outcomes. This document will contribute to this assessment through informing VEAC of the likely implications of climate change for marine protected areas. The approach taken in this study was to collate relevant recent information on natural values within Victorian Marine Protected Areas (MPAs) (Barton et al. 2012a-e), climate change predictions for Victoria (Mills et al. 2013), and assessments of vulnerability to future climate for broad habitat types / taxonomic groups (Klemke and Arundel eds 2013). This information was then translated to Victorian bioregions to consider the likely implications of climate change for marine protected areas within each bioregion. The climate change predictions for Victoria drew on existing modelling and scientific literature of the physicochemical changes predicted to occur in Victoria’s marine environment by 2030, 2070 and 2100. This information has been supplemented with emerging information from concurrent studies for the VEAC Marine Investigation on risks and processes within MPAs (Longmore 2013, Jenkins 2013) as well as the Strategic Risk Assessments for bioregions undertaken by Parks Victoria (Parks Victoria 2010). Representative parks from each bioregion have been chosen for detailed case studies and much of the information included in the case study section will be relevant to all MPAs within the bioregion. Responses to climate change are expected to be complex and hard to predict because stressors associated with the changing climate will occur simultaneously, while for many species basic biological information is lacking making it difficult to determine species and assemblage responses to a changing climate. There are likely to be combinations of direct and indirect interacting effects that can change fundamental processes such as competition, predation, trophic relationships and nutrient cycling. There is uncertainty associated with many of the predictions of climate change (Mills et al. 2013, and see Future Climate section below) and this uncertainty can be compounded when considering the possible ecological effects of a changing climate. For this reason predicting the effects of climate change is even more uncertain than predicting climate change itself (DSE 2012b). Despite these difficulties we have focused on a number of visible and relatively well studied species within the major habitats to provide examples of how the interactions between species and the effects of a combination of stressors associated with future climate might be realised within an MPA.
Natural values within the Victorian MPA system
As part of a national scheme of bioregionalisation, Victoria’s marine environment has been classified into five bioregions: Otway, Central Victoria, Victorian Embayments, Flinders and Twofold Shelf. Within each bioregion there are a variety of diverse and unique habitats and biological communities structured by a range of physical, chemical and biological processes (Barton et al. 2012a-e). Broad habitat types found within Victoria’s MPA system include rocky reef, soft sediment (unvegetated, seagrass, mangrove and saltmarsh) and open water or pelagic habitat. More details about the distribution and natural values of each habitat type within each MPA can be found in Parks Victoria’s marine natural values reports (Barton et al. 2012a-e). The open water or pelagic habitat is a large and important element of all MPAs. This habitat not only hosts fish and marine mammal species but assemblages of phytoplankton and zooplankton, recognised as being extremely important components of the ecosystem. Phytoplankton and zooplankton function as ‘producers’ that support higher trophic levels such as reef and soft sediment invertebrates, pelagic and demersal fishes and marine mammals, as well as playing a fundamental role in carbon, oxygen and nutrient cycles (Hobday et al. 2006). However in Victoria (and Australia in general) we have little information about the species composition, abundance and basic biology and ecology of the plankton (Hobday et al. 2006).
Future climate
It is recognised that the climate is changing and to date many of the predictions relating to the future climate have been made at a regional or national scale. A recent study reviewed available scientific literature and advice to provide a consolidated assessment of implications of future climate change scenarios for the local Victorian marine environment by 2030, 2070 and 2100 (Mills et al. 2013). This study included changes in mean sea level, astronomical tides, ocean currents and upwellings, wave climates, sea surface temperatures and salinities, ocean acidification and rainfall and runoff (Table 1). Mills et al. (2013) divided the coast into three coastal regions plus the embayments to broadly align with the boundaries of influence of major physical oceanographic processes operating in Victoria. These coastal areas
VEAC Marine Investigation. Climate change and MPAs 13
roughly correspond to the Victorian marine bioregions with the exception of the Flinders bioregion which has different oceanic conditions operating on the east and west coasts of Wilsons Promontory. Finer scale predictions are difficult because of the limited resolution of global and Australian-specific climate change models (Mills et al. 2013). Uncertainty exists around the predictions for the rate at which mean sea level will rise, the impact of climate change on wave climates and the impacts of climate change on the strength or frequency of upwelling events. There is reasonable certainty in rainfall projections and projections of oceanic pH (but the embayments are more difficult to project). There is a high certainty in the predictions of sea surface temperatures, sea surface salinity and ocean currents (Mills et al. 2013).
Implications of future climate to Victoria’s marine environment
The vulnerability of different habitats / broad taxonomic groups to a range of climate stressors has been assessed in the recent state-wide report that considered the implications of future climate on Victoria’s marine environment (Klemke and Arundel eds 2013). The term ‘vulnerability’ in this report is defined as a function of exposure to climate, sensitivity to change, and adaptive capacity (after Hobday et al. 2006). The likelihood of a potential impact was assessed via an exposure and sensitivity matrix. Vulnerability was then assessed by an impact and adaptive capacity matrix. Qualitative assessments of exposure and sensitivity to climate change predictions were made using a relative scale of high, medium and low based on a review of the scientific literature. An attempt was also made to incorporate adaptive capacity into the vulnerability rating, however a high level of uncertainty was usually recognised within this as well as within the overall vulnerability rating (Klemke and Arundel eds 2013). An overview of the relative vulnerability ratings of different benthic habitat types is shown in Table 2 - open waters, marine mammals (Table 3) and fish (Table 4). Seagrass and soft sediment habitats were assessed together so that the overall vulnerability score for soft sediments considers the combination of these habitats (Morris 2013). Due to the highly mobile nature of fish these taxa were not assessed by region but instead by life history stage for finfish and sharks (and their allies e.g. rays), with further information included for teleost species of economic importance (Hirst and Hamer 2013). Marine mammals were not given vulnerability ratings due to the general lack of information about the basic biology and ecology of many species (Gill and Pirzl 2013). Instead the potential impacts have been reviewed and are summarised as part of Table 3. Sea level rise, increases to sea surface temperature and changes in rainfall and run off were considered likely to impact all the shallow water and intertidal benthic habitats across the state (Table 2). Other stressors resulted in a high / moderate vulnerability for habitats or taxa in some parts of the state but not others. For example the changes to salinity are expected to be most pronounced in the embayments (and particularly Port Phillip Bay) due to a reduction in freshwater inflows and rainfall, increased evaporation and altered flushing times. For the open coast regions the projected change in sea surface salinity is expected to be less than the seasonal variations currently experienced although there will be localised impacts associated with changes in runoff. Changes to oceanographic conditions such as ocean currents and upwellings are considered important due to their potential effects on transport of propagules and delivery of nutrients. Larval stages may be most sensitive to changes in the physical and chemical properties of sea water such as temperature, salinity and pH. Some species are also likely to experience range shifts as a result of these changes with consequences for higher order species that depend on them for prey (Table 2, Table 3, Table 4). It is considered unlikely that the projected changes to the physico-chemical environment will harm marine mammals directly however changes in prey distributions and abundance brought about by the changing climate are likely to result in range contractions, expansions or even complete relocations as marine mammals track optimal conditions for feeding and breeding (Table 3, Gill and Pirzl 2013). It is recognised that the climate change projections listed in Table 1 will not happen in isolation. Different species within each of the systems will also have individual vulnerabilities to each of the stressors and will interact differently with the combination of climate induced changes to the environment as well as to other potential stressors (e.g. fishing, toxicants). A separate project undertaken as part of the VEAC assessment of ongoing and future challenges to the management of MPAs considers the possible human-based threats to MPAs under current and future climate (Jenkins 2013). Where possible, the effects of non-climate threats and potential interactions with climate change effects as well as the impacts on important processes have been incorporated into the case studies undertaken for each bioregion.
Omissions
It was not possible to include all habitats or broad taxonomic groups within the state wide vulnerability assessment report. A number of important omissions were made despite the recognition of their ecological importance within the marine environments of Victoria. Mangrove and saltmarsh habitat was not included in the statewide vulnerability assessments (Klemke and Arundel eds 2013), however a discussion of the potential implications of climate change has been included in the discussions of MPAs where relevant in this document.
VEAC Marine Investigation. Climate change and MPAs 14
Fish and marine mammals were assessed as part of the open water habitat in the statewide report (Klemke and Arundel eds. 2013) however plankton was not. Phytoplankton and zooplankton are recognised as being extremely important components of the ecosystem however there is very little specific information available on a statewide basis and even less at the scale of bioregions or MPAs. Hobday et al. (2006) summarise the projected climate change impacts to phytoplankton and zooplankton and this has been reproduced in Table 5 but due to the lack of information there has been little further discussion of these groups within the bioregion sections. It was also recognised that birds utilise marine habitats and are an important component of the MPA system within Victoria. Birds are not included within this report as compiling predictions would require projections for additional climate variables beyond those compiled by Mills et al. (2013) and was beyond the scope of this report.
VEAC Marine Investigation. Climate change and MPAs 15
Table 1 Overview of predicted impact of climate change on physicochemical conditions. Taken from Mills et al . 2013
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Table 2 Vulnerability ratings and potential impacts of different habitats to future climate. Vulnerabilities are indicated by colours: blue = high / moderate, green = low. Where no vulnerability rating is included this is because the ratings were very different across the state i.e. high in one region and low in another region. Source: Klemke and Arundel eds. 2013. Uncertainty ratings have not been included within this table but the reader should be aware that uncertainty was high for many of the vulnerability ratings in the source report.
Stressor Intertidal reef Shallow subtidal Deep subtidal Intertidal Subtidal seagrass Intertidal Shallow Deep subtidal reef reef Seagrass unvegetated subtidal unvegetated sediment unvegetated sediment Sediments Sea level Loss of reef Increase in Low vulnerability Loss of habitat, Deeper edges of Loss of habitat, Increased flooding Low vulnerability and tides habitat, changes horizontal habitat to sea level rise unsuitable seagrass meadows at changes to and coastal to mean sea to distribution may lead to substrate or light limit. Shorewards distribution and erosion may level rise. and orientation increase in algal barriers to migration but orientation. Change increase turbidity. of reef. cover but may also formation of new increased turbidity in shore profile and Shorewards be increase in intertidal areas. from flooding sediment structure migration of sedimentation on Rate of change possible. affect infaunal habitat likely. flatter reefs may exceed rate assemblages. of colonisation. Ocean Vulnerability Vulnerability Commercially Connectivity Connectivity between Difference between Differences Range shifts currents greatest in east greatest in east of valuable species between populations may be bioregions between and changes to of state (EAC). state (EAC). Range may be affected populations may impacted. Range increased, range bioregions phytoplankton Range expansions likely but uncertainty be impacted. expansions from shifts including increased, range populations expansions and larval dispersal about the effect Range north northerly species shifts including might impact likely and larval (mainly of expansions from that may affect northerly species faunal dispersal planktotropic oceanographic north infaunal structure that may affect assemblages (mainly species) affected. processes on and function infaunal structure that utilise planktotropic deep reefs and function phytoplankton species) as food source. affected. Upwelling Vulnerability Vulnerability greatest Vulnerability Vulnerability Vulnerability greatest Vulnerability Vulnerability Vulnerability greatest in east & in east & west of greatest in east & greatest in east & in east & west of greatest in east & greatest in east & greatest in east west of state. state. Propagule west of state west of state. state. Nutrients from west of state. west of state. & west of state. Propagule survival and Propagule Nutrients from upwellings may be Nutrients from Nutrients from Nutrients from survival and dispersal affected by survival and upwellings may be important to seagrass upwellings may be upwellings may be upwellings may dispersal affected changes in upwelling dispersal affected important to populations important to soft important to soft be important to by changes in nutrients. by changes in seagrass sediment sediment infauna. Effects upwelling upwelling populations assemblages. assemblages. on nutrients nutrients phytoplankton likely to impact fauna.
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Table 2. continued
Stressor Intertidal reef Shallow subtidal Deep subtidal Intertidal Subtidal Intertidal Shallow Deep subtidal reef reef Seagrass seagrass unvegetated subtidal unvegetated sediment unvegetated sediment Sediments Temperature Extreme temperature Timing of Range shifts can Extreme Extreme events Extreme events Timing of High uncertainty events may cause loss reproduction and cause changes to events can and timing of can cause loss reproduction but impacts of Hormosira banksia recruitment success community cause loss of reproduction of intertidal and recruitment likely to be and associated affected? Sensitivity structure and seagrass may affect species. success similar to changes to to bacterial potential loss of species. colonisation of Changes to affected. shallow subtidal assemblage. Vertical pathogens may biodiversity. Changes to new areas and vertical Increased in the long term. distribution may be increase. Stress to vertical connectivity distribution bioregionalisatio affected. kelp species may distribution between likely. n due to range increase disease likely. populations. shifts. Increase susceptibility. in pests and pathogens. Salinity Effects on parasites Embayments most No information Embayments Embayments Embayments Embayments Embayments and hosts may alter vulnerable, open available on how most most vulnerable most vulnerable, most vulnerable, most vulnerable, population dynamics. coast areas not deep reef vulnerable and and growth, changes to changes to changes to H. banksii may be considered assemblages will growth, physiology and infaunal infaunal infaunal affected with vulnerable. Health be impacted by physiology and seed assemblage assemblage assemblage associated changes to and development of changes to sea seed germination may structure likely structure likely structure likely assemblage. planktonic surface salinities. germination be affected. and possibly and possibly and possibly Embayments most dispersive stages may be Open coast processes such processes such processes such vulnerable. may be affected. Open areas not as recruitment. as recruitment. as recruitment. compromised with coast areas considered Open coast Open coast Open coast negative effect on not considered vulnerable areas not areas not areas not recruitment. vulnerable considered considered considered vulnerable vulnerable vulnerable Waves Western and Central Western and Possible wave Western and Western and Coastal infaunal Coastal infaunal Coastal infaunal bioregions most Central bioregions induced changes Central Central regions assemblages assemblages assemblages vulnerable. H.banksii most vulnerable. to mixing and bioregions most vulnerable. already likely to already likely to already likely to canopy may be Potential loss of stratification may most Deep band of reflect high reflect high reflect high reduced with changes canopy algae may affect the vulnerable. Zostera unable disturbance disturbance disturbance to other organisms alter community structure and Amphibolis to move deeper regime regime and regime and following. Sessile structure. Direct functioning of antarctica due to light distributions less distributions less invertebrates may effects on deep reef patches may limitation. restricted by restricted by have smaller body size invertebrates assemblages but be damaged light availability light availability and filter feeder possible e.g. a high level of and slow to systems might Heliocidaris uncertainty exists recolonise dominate. erythrogramma for predictions.
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Table 2. continued
Stressor Intertidal reef Shallow Deep Intertidal Subtidal Intertidal Shallow Deep subtidal subtidal reef subtidal reef Seagrass seagrass unvegetated subtidal unvegetated sediment unvegetated sediment Sediments
CO 2 & Taxa with Possible Potential Seagrass species Seagrass Taxa with calcified Taxa with Impacts on plankton acidification calcified increase to dissolution of not expected to be species not structures calcified likely to impact the structures likely turfing red calcareous vulnerable but expected to be negatively structures infaunal to be negatively algae biomass structures (e.g. there may be vulnerable but impacted. negatively assemblages impacted. and cover with sponges). complex changes there may be Responses impacted. through Hypercapnia associated Rhodolith beds in the seagrass complex expected to be Responses food/nutrient effects likely to reduction in may be habitat including changes in the complex and larval expected to be transfer. Impacts on be significant. kelp E. radiata . vulnerable to changes to seagrass habitat stages may be most complex and dispersal vectors ie Taxa with demineralisatio epiphytes and including impacted. larval stages larvae possible. calcified n of cell walls. epifauna. epiphytes and Hypercapnia effects may be most Hypercapnia effects structures Hypercapnia Photosysnthesis epifauna. likely to be impacted. likely to be negatively effects likely to and growth may Photosynthesis significant Hypercapnia significant impacted. be significant be enhanced. and growth may effects likely to Hypercapnia be enhanced. be significant effects likely to be significant Rainfall and A reduction in A reduction in Impacts less A reduction in Impacts on Decrease in rainfall Nutrients in Terrestrially derived runoff overall runoff overall runoff than for overall runoff may seagrass to and runoff might runoff likely to nutrients may be might benefit might benefit intertidal and be beneficial to reduced runoff reduce sediment be important to important in fucoid algae but fucoid algae shallow seagrass but will probably be inputs important in infaunal productivity of increased storm but increased subtidal reefs. increased storm site specific. replenishing assemblages. deeper areas but events with storm events Run off related events may bury Storm events intertidal areas. Storm events little information high sediment with high changes to seagrass. High with high Storm events can can deliver about how tightly and nutrient sediment and salinity and loads of nutrients, nutrient and cause smothering of increased coupled they loads and low nutrient loads temperature and sediment sediment loads the intertidal with a nutrients and actually are. Deeper salinity may and low salinity likely to be less combined with low and low salinity range of impacts. sediment to areas in negatively may negatively at greater salinity likely to be likely to be shallow subtidal embayments likely impact intertidal impact subtidal depths. stressful. stressful. environments to be impacted by assemblages. assemblages. Sedimentation affecting the reduction in runoff. may still have assemblage negative structure and impacts. function.
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Table 3. Major vulnerabilities of marine mammals to future climate. Source: Gill and Pirtzl (2013)
Stressor Baleen whales Toothed whales Seals
Sea level rise Not considered vulnerable Not considered vulnerable May affect haul outs but to sea level rise to sea level rise unknown whether haul outs on Victorian coastline are overall positively or negatively affected. Currents Strengthening EAC might Strengthening EAC might Strengthening EAC might displace principal prey displace prey species. displace prey species species – krill. Upwelling Changes to Bonney Changes to upwellings Changes to Bonney upwelling could have may affect prey species upwelling may affect prey profound implications for which will be manifested species of Australian fur viability of whale feeding as range changes in seals. grounds toothed whales. Temperature Baleen whales can adapt Most toothed whales The projected physically to a subtly expected to adapt to temperature changes changing thermal temperature changes but unlikely to cause physical environment but effects of effect on prey species stress to seal species but temperature increases on such as squid may cause effects on prey species prey likely to result in range shifts or have may result in range shifts. range shifts. implications for general fitness. Salinity Effects on whale species Not considered vulnerable Not considered vulnerable will be mediated through to changes in salinity to changes in salinity as effects on phytoplankton mainly because major main prey species not and zooplankton. prey species e.g. squid sensitive to changes in not considered sensitive salinity. to changes in salinity. Waves No major impacts of Not considered vulnerable Increasing wave action changes to wave climate to changes in wave may directly affect hauled anticipated climate out seals and inhibit foraging success in near- shore waters for some species. Acidity Concern about effects of Any direct impacts Any direct impacts increasing acidification on considered unlikely. considered unlikely. phytoplankton and Indirect effects resulting Indirect effects resulting zooplankton such as krill from changes to prey from changes to prey – will in turn impact populations possible but populations possible but baleen whales unknown. unknown. Rainfall and runoff Effects on whale species Foraging ranges may Foraging ranges may will be mediated through change dependent on change dependent on effects on phytoplankton prey species response to prey species response to and zooplankton. changes to rainfall and changes to rainfall and runoff. runoff.
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Table 4. Vulnerability ratings and potential impacts of different life history stages of finfish and sharks to future climate. Vulnerabilities are indicated by colours: blue = high; light blue = moderate; green = low. Source: Hirst and Hamer (2013)
Life-history Sea level & Ocean Currents CO & Rainfall & Group Temperature Salinity Wind/Waves Upwelling 2 stage Tides Acidification Runoff Dispersal / retention Temperature Dispersal / Productivity Sensitive to pH may be affected. extremes likely to retention may be may impact changes, may Eggs impact survival. affected. survival and affect survival growth Recruitment Dispersal / retention Increases likely to May affect Productivity Possible effects Recruitment of to nursery may be affected. reduce time spent as dispersal, may impact on development, some species habitats might Productivity impacts larvae and increase swimming, survival and growth and related to river Larvae be affected. survival and growth survival. Temperature settlement, growth survival through flow and run off extremes likely to vertical changes to food reduce survival. distribution and webs feeding efficiency Finfish Productivity may Temperature May affect Productivity impact survival and extremes likely to dispersal, may impact growth impact survival. swimming, survival and Juveniles settlement, growth vertical distribution and feeding efficiency Range shifts likely Productivity may impact Adults survival and growth
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Table 4. continued
Life-history Sea level & Ocean Currents CO & Rainfall & Group Temperature Salinity Wind/Waves Upwelling 2 stage Tides Acidification Runoff Temperature Eggs extremes likely to impact survival. Temperature Productivity extremes likely to impacts Juveniles impact survival. survival and Sharks and rays growth Productivity may Range shifts likely Productivity impact survival, may impact Adults growth and survival and reproductive growth capacity
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Table 5. Projected climate change impacts to phytoplankton and zooplankton. Source Hobday et al. (2006).
Phytoplankton Zooplankton Increasing sea surface temperature and southward flow Large southwards movements of tropical and temperate of East Australia Current (EAC) will drive phytoplankton species as ocean waters warm species southwards Changes in abundance of particular species with flow on Phytoplankton abundance already changing regionally in effects to their prey and predators Australia, including harmful algal blooms Earlier timing of appearance with warming (ie changes to Species with calcareous shells such as coccolithophores reproduction / recruitment patterns and consequent and foraminifera may decline in abundance changes to succession patterns in communities) Earlier timing of the peak in production of some Changes in timing could lead to decreased coupling with phytoplankton lower trophic levels (phytoplankton) and reduce fish Warming and increasing stratification will considerably yields alter phytoplankton community composition, e.g. the Species with calcareous shells such as echinoderms, productive southeastern temperate phytoplankton crustaceans and molluscs (especially pteropods) may province may shrink considerably in area not be able to maintain shell integrity in a more acidic Changes in phytoplankton abundance, distribution and ocean timing of production are likely to drastically impact most Increased incidence of jellyfish swarms with warming marine life. oceans.
VEAC Marine Investigation. Climate change and MPAs 23
Otways Bioregion
Background Table 6. Marine protected areas within the Otways Bioregion
Discovery Bay MNP The Arches MS Twelve Apostles MNP Merri MS
The oceanography of the Otways bioregion is primarily influenced by South Australia Current (SAC), an extension of the Leeuwin Current (LC) which runs southwards down the coast of Western Australia, wraps around Cape Leeuwin and runs along the southern coast. The LC is a warm, saline, nutrient poor current that is one of two main boundary currents influencing Victoria (Hutchinson et al. 2010). The LC is strongest in late autumn / early winter when it is reinforced by surface winds. As well as the influence of the major currents in the region, the habitats in the Otways bioregion are also affected by a key upwelling called the Bonney upwelling. The Bonney upwelling is driven by prevailing south easterly winds which draw cooler nutrient rich water from depths of up to 300 m to the surface coastal waters. Upwelling plumes are often observed in November / December and March / April along the coast west of Portland. Further details about temporal and spatial scales of the Bonney upwelling are included in a separate (VEAC) report (Longmore 2013). The main habitats found in the Marine National Parks (MNPs) and Marine Sanctuaries (MS) within this bioregion include intertidal and subtidal reef, intertidal and subtidal soft sediments including seagrass beds and open water habitat. Reef areas are characterised by habitat forming kelps and diverse invertebrate assemblages. Soft sediment habitat includes infaunal assemblages dominated by amphipods and a deeper band of subtidal seagrass has been recorded in the MNPs. Several species of wrasse, the sea sweep and the magpie perch are all abundant on the shallow subtidal reefs of the MPAs in the Otways bioregion (Barton et al. 2012a). In the open water habitat a number of conservation listed species of marine mammals are found including southern right whales, blue whales and humpback whales (Barton et al. 2012a). The shelf waters between north west Tasmania and Kangaroo Island that incorporate the Bonney upwelling are a globally important feeding ground for the pygmy blue whale (Gill and Pirzl 2013). Intertidal reef in the MNPs of the Otways bioregion also provides haul out areas for both Australian and New Zealand fur seals. Foot access is possible at all the MPAs in the Otways bioregion with the exception of the Arches MS which is situated 600 m offshore. In the Twelve Apostles MNP and the Merri MS there are rivers (Gellibrand and Merri Rivers) discharging directly into the park and the Warrnambool Sewage Treatment Plant also discharges effluent 500 m to the west of the Merri MS while the Hopkins River discharges to the east of the sanctuary. A concurrent study looking at major threats to the MPAs considered the introduction of pathogen and pest species and the possibility of a major oil spill to be the primary risks to MPAs within the Otways bioregion (Jenkins 2013).
Future climate
In the Otways bioregion, reductions in run-off volumes are predicted to be greater than for the rest of Victoria and increases in acidification are also expected to be higher than for the rest of Victoria (excluding embayments) (Table 1). The projected changes to wave climate are greatest in the Otways and Central Victoria bioregions although there is high uncertainty associated with the wave climate predictions. Changes to the Bonney upwelling are considered likely and will be an important regional consideration as the seasonal delivery of cooler nutrient rich waters to the surface allows for enhanced primary production that can attract aggregations of seals, whales and pelagic fish to the area (Gill and Pirzl 2013, Longmore 2013). South east winds are expected to strengthen in summer as the continent warms and this may lead to enhanced upwelling in the Otways bioregion in the summer months. There is also a minor decrease in transport of the Leeuwin Current predicted by 2100 and, as currents are thought to suppress coastal upwellings, this may also contribute to an increase in the Bonney upwelling (Mills et al. 2013).
VEAC Marine Investigation. Climate change and MPAs 24
Habitat vulnerabilities to future climate
The main benthic habitat vulnerabilities for the Otways bioregion are included in Table 2 while statewide assessments of the vulnerabilities for open water habitat are detailed in Table 3 (marine mammals) and Table 4 (fish) of the introduction. All benthic habitats were considered highly vulnerable to changes in ocean currents and upwellings (Table 2). The larvae of teleost fish were also considered vulnerable to changes to ocean currents (Table 4) while changes to the Bonney upwelling could have profound implications for marine mammals (Table 3). Changes to the Bonney upwelling are an important climate change consideration for the Otways bioregion. This seasonal influx of cool, nutrient rich water, at a time when light and sea surface temperature are maximised, results in increased phytoplankton growth which leads to increased production at higher trophic levels. This area of coast is recognised as being a highly productive environment that supports distinctly cold-water assemblages of fish, seabirds and whales and is known to be an important feeding area for large fish species i.e. southern bluefin tuna, Australian fur seals, as well as a summer feeding ground for pygmy blue whales (Gill and Pirzl 2013). Coastal waters in the Otways bioregion are generally oligotrophic and the Bonney upwelling is also an important source of nutrients to the nearshore coastal habitats. While there is reasonable certainty in the projection that upwellings will be strengthened, it is not clear whether this will increase productivity or not. In other parts of the world productivity is limited by too much turbulence from continual upwelling and insufficient ‘relaxation periods’ between upwelling events to allow maximised phytoplankton blooms (Gill and Pirzl 2013). The projected weakening of the Leeuwin Current, although minor, may reduce the transport of propagules arriving from the west as well as reducing connectivity of populations and affecting the delivery of phytoplankton and detrital food sources to benthic habitats. Species with planktotrophic larvae that spend a long time in the water column will be most affected by changes to currents. For example, Victorian populations of King George whiting have larvae that are thought to originate in South Australia, and are likely to be particularly vulnerable to a weakening of the Leeuwin Current (Hirst and Hamer 2013, Longmore 2013). Biodiversity within MNPs of the Otways bioregion may be reduced following a further weakening of the Leeuwin Current as species at the edge of their easterly range might contract. Alterations of large scale currents were also rated relatively higher in the Climate Change Strategic Risk Assessment that was conducted by Parks Victoria for the Otways bioregion (Parks Victoria 2010). All shallow water reef and seagrass habitats and larvae of teleost fish were considered vulnerable to changes in the wave climate (Table 2, Table 4), which is predicted to be greatest in the Otways and Central Victoria bioregions although there is high uncertainty associated with the projections relating to future wave climates (Mills et al. 2013). Increased wave action has the potential to cause physical damage to kelps and seagrass with associated impacts on a range of flora and fauna that depend on these autogenic engineers. Autogenic engineers are species that provide shelter, settlement habitat and food for a range of invertebrate, fish and other alga species. Larval stages are also likely to be impacted by increases in wave action through wave mediated effects on dispersal, swimming, settlement, vertical distribution and feeding efficiency (Klemke and Arundel eds 2013). All shallow water benthic habitats were rated highly vulnerable to predicted changes in temperature, consistent with the Climate Change Strategic Risk Assessment (Parks Victoria 2010), and rainfall and runoff. The projected increases in temperature, while lower than the other Victorian bioregions were still considered likely to result in range shifts, loss of individuals as a result of extreme weather events and may affect the emergence of pests and pathogens within the Otways bioregion. Timing of biological events may also be affected by temperature. In the Otways bioregion this may be particularly relevant as the same biological events may be dependent on the productivity of the Bonney upwelling and the local and larger scale currents. A disjunct between these processes may have important consequences for reproduction, larval dispersal and recruitment for a variety of species. Vulnerabilities as a result of rainfall and runoff mainly related to potential changes in the frequency and severity of storm events that will expose nearshore areas to pulses of freshwater, nutrients and sediments. In the Otways bioregion, this is predicted to happen against a backdrop of reduced rainfall and runoff into the region. Projected changes to rainfall and runoff will have most relevance for the Twelve Apostles MNP and the Merri MS, both of which have direct discharges into the park (Gellibrand River and Merri River respectively).
Vulnerability ratings for changes in mean sea level and CO 2 and acidification were high or moderate for all shallow water benthic habitats and larvae of teleost fish (Table 2, Table 4). A rise in mean sea level may mean a loss of
VEAC Marine Investigation. Climate change and MPAs 25
habitat due to barriers to the formation of new intertidal or shallow subtidal areas, the inability of species to colonise new areas at the same rate as sea level rise, a change in shore profiles or orientation and changes to sediment structure and transport (Klemke and Arundel eds 2013). The specific impacts of sea level rise within each MPA will very much depend on geology, sediment budget dynamics, and built structures or other barriers to coastal recession. Intertidal habitat within the Twelve Apostles MNP is likely to remain as the cliff erodes but the profile and orientation are likely to change. The intertidal habitat at Merri MS consists of flat rock platforms, high relief rock structures and low profile sandy beaches. The low relief habitat may be lost altogether with the projected sea level rise leaving only high relief rock structures and a more cobbled intertidal reef habitat plus shorter steeper sandy beaches. Shallow subtidal habitat within The Arches MS is also likely to be vulnerable to a rise in mean sea level as a shorewards shift of habitat is not possible i.e. there is no available habitat to replace the habitat lost. The projected decrease in pH (or increase in acidification) is greater in the Otways bioregion than the other bioregions within Victoria (excluding embayments). It is expected to impact calcifying species, and in particular larval stages, including calcified coralline algae and plankton species such as coccolithophores (Table 5). The highly diverse molluscan fauna of the reef habitats in the Otways bioregion may be particularly vulnerable. Changes to parameters such as pH, temperature and salinity are also liable to alter the toxicity of pollutants as well as affect the susceptibility of an individual to negative effects from other threats to MPAs within the region e.g. oil spills and the introduction of pathogen and pest species (Jenkins 2013).
VEAC Marine Investigation. Climate change and MPAs 26
Case study – Discovery Bay Marine National Park.
Discovery Bay MNP is part of the largest basalt formation in western Victoria and among the highest energy wave environments in the state. It has intertidal and subtidal calcarenite and basalt reefs with both high and low profile structures (Barton et al 2012a). The extensive subtidal soft sediment environment has a high carbonate content and the physical and biological attributes of this habitat reflect the high energy environment. Discovery Bay MNP also forms part of the Bonney Coast and so the ecological assemblages are influenced by cold, nutrient rich upwelled water and the associated increase in primary production. The high productivity of the area is important for maintaining commercially important species such as the blacklip abalone and the southern rock lobster and the area is also an important feeding ground for seals and whales. Shallow reef assemblages are characterised by abundant invertebrate assemblages with a high diversity of molluscs and deeper reefs have a highly diverse sponge fauna (Barton et al. 2012a). Soft sediment infaunal assemblages are less diverse than comparable sites in the east, but dominated by crustaceans, with molluscs poorly represented (Barton et al. 2012a). Potential changes to ocean currents, upwellings, temperature, wave climate, mean sea level and acidification are likely to affect the ecological assemblages found in Discovery Bay MNP. In particular assemblages may be affected by: • a change in the timing and extent of nutrient delivery; • a reduction in the connectivity between habitats; • a loss of habitat due to sea level rise and, when combined with increased wave action, a loss of subtidal seagrass habitat; • a reduction in kelp biomass and coverage due to increased temperatures and increased wave action; and • a possible reduction in the diverse mollusc fauna due to increased acidification.
Reef habitat Intertidal and shallow subtidal reef habitats were considered vulnerable to a range of climate drivers in the Otways bioregion (Table 2). The Bonney upwelling is an important driver within the region and changes to the strength and frequency of this upwelling will be important to reef habitats in Discovery Bay MNP. While there is reasonable certainty in the prediction that upwellings will be strengthened under climate change projections, it is not certain that this will increase primary productivity with all the associated benefits to other organisms (Gill and Pirzl 2013). This will depend on the timing and frequency of upwelling events. The predicted weakening of the Leeuwin current, while minor, may be very important to the transport of propagules that depend on this current for dispersal. At the same time as a reduction in the prevailing current is taking place, increased wave action may affect the ability of larvae to maintain their position in the water column, feed efficiently or swim and settle into new habitats. Increased temperatures may simultaneously be reducing larval duration, affecting the timing of larval / propagule settlement and impacting recruitment. The combined effect of these changes may be to restrict larval / propagule transport, reducing connectivity between populations and contracting the range of some species. The green alga Palmoclathrus stipitatus is at its eastern limit in Discovery Bay MNP (Barton et al. 2012a) and this species may retreat westwards. Increased temperatures will enable other changes, as warmer water species are introduced and cooler water species retreat as well as facilitate the emergence of new pest and pathogen species. All of the above are likely to threaten species of conservation value such as the southern hooded shrimp Athanopsis australis which is endemic to Victoria. Discovery Bay MNP is one of the two locations at which it has been recorded (O’Hara and Barmby 2000). Predicted increases in mean sea level are likely to reduce the amount of intertidal reef platforms within Discovery Bay MNP as the hard rock cliffs are unlikely to erode as a result of sea level rise and increased storm surge (DSE 2012b). While new intertidal habitat will be created on vertical cliff faces, the ecological assemblages will be different in that invertebrates will be favoured over algal species (Bellgrove et al 2013). Intertidal reef habitat is also an occasional ‘haul out’ for Australian and New Zealand fur seals although it is not known how seals will react to loss of ‘haul out’ habitat (Gill and Pirzl, 2013). The reef habitat in Discovery Bay MNP has an abundant invertebrate fauna and molluscs are diverse and abundant on intertidal and shallow subtidal reef, while there is a diverse sponge fauna on the deeper reefs. Molluscs are likely to be particularly vulnerable to increased acidification due to the fragile skeletons produced by their calcifying larvae and their calcified shells (Fabry et al. 2008, Byrne 2011). Some sponges are also calcifying organisms and these will also be susceptible to increased ocean acidification. Macroalgal species Macroalgal species are important autogenic engineers within the reef systems of Victoria. Impacts on kelp will have impacts on the entire assemblage that is dependent on the various functions kelp provides. Changes to productivity of
VEAC Marine Investigation. Climate change and MPAs 27
the nearshore waters may affect macroalgal recruitment, growth and reproduction. While there is a degree of uncertainty around the response of primary production to the predicted strengthening of regional upwellings, changes to the timing and delivery of nutrient rich water is likely to be reflected in the biomass, survival of recruits and contribution of individual plants to reproduction. Intertidal habitat within Discovery Bay MNP includes reef areas with Hormosira banksii which tends to be sparsely distributed on intertidal reef in the Otways bioregion (Bellgrove et al. 2013). H. banksii has been likened to a ‘keystone species’ where its presence provides shelter for some species but also reduces the biomass of microalgae, an important food source for certain grazing gastropods (Keough and Quinn 1998). Increases in mean sea level are likely to reduce the amount of H. banksii habitat. There is a predicted increase in the number of very hot days (>40°C; Mills et al . 2013). Research has shown that very hot days combined with afternoon low tides will cause ‘burn off’ of H. banksii making individuals less resilient to other stressors such as trampling by visitors to the park (Keough and Quinn 1998) or wave action. Increased wave action is likely to impact H. banksii canopies through dislodgement of newly settled zygotes and fronds. The combined effects of these climate change stressors may cause a proportionally greater canopy loss of H. banksii in the Otways bioregion and a switch to turf dominated assemblages that may limit the potential for re- colonisation by H. banksii (Bellgrove et al. 2013). This may have important consequences for the high abundance and diversity of molluscs found in the intertidal in Discovery Bay MNP (and other MPAs within the Otways bioregion). Subtidal kelp species are sensitive to high temperatures particularly during reproduction and recruitment. There is evidence that increased water temperature has led to extensive loss of Macrocystis pyrifera biomass and extent in Tasmania (Johnson et al. 2011) as well as range contractions at the northern distributional limits for Durvillaea potatorum , Ecklonia radiata and Phyllospora comosa (Bellgrove et al. 2013). It is considered likely that projected increases in sea surface temperatures for the Otways bioregion (between 1 and 3°C by 2100) will stress these species making them more vulnerable to other stressors (Wernberg et al. 2010) and with knock on effects on associated understorey algae, herbivorous fish, and invertebrates (Klemke and Arundel eds 2013). Ecological communities formed by the giant kelp Macrocystis pyrifera have been listed as endangered with the major threats to this habitat linked to climate change and including increasing sea surface temperatures, changes to nutrient availability in warmer waters, changes to weather patterns and large scale oceanographic conditions and range expansions by invasive species (s266B of the Environment Protection and Biodiversity Conservation Act 1999 ). All of these threats will be relevant within Discovery Bay MNP and the sparse stands of M. pyrifera may be reduced or disappear altogether although there is no evidence of this at present (M. Edmunds pers.comm.). M. pyrifera is a cold water species with a temperature range of 5- 20°C. Mean sea surface temperatures in Discovery Bay MNP range between 14-17°C with a projected increase of up to 3 degrees by 2100 (Table 1). This means future temperatures will be close to the upper physiological limit for M. pyrifera , making them less resilient to other stressors, with extreme temperatures potentially causing direct mortality. The introduction of pest species was considered one of the major threats to Discovery Bay MNP in a recent threat assessment (Jenkins 2013) and the spread of the Japanese kelp Undaria pinnatifida from Apollo Bay (where it was recently recorded) is a serious concern for MPAs in the Otways bioregion (Barton et al. 2012a). The invasiveness of U. pinnatifida is reviewed in more detail by Longmore (2013) in a separate VEAC study. Increased water temperatures, changes to the timing and extent of nutrient inputs and a reduction in kelp biomass may all be important in determining the success of this invasive species within Discovery Bay MNP. Haliotis rubra – blacklip abalone Changes to the kelp habitat also have the potential to affect other species currently found within subtidal reef assemblages. The blacklip abalone Haliotis rubra is found at Discovery Bay MNP and is a common component of all reef habitats within the MPAs of the Otways bioregion. It is a dieocious (separate male and female individuals) broadcast spawner with a larval duration of 3-7 days. Spawning is triggered during calm conditions when fertilisation is probably optimised and dispersal and recruitment of larvae is local (McShane et al. 1988, Huang et al. 2000). Studies in eastern Victoria found that H. rubra recruited to sheltered habitat including areas of dense kelp cover where current speeds were attenuated (McShane et al. 1988). In the high energy environment of the Otways bioregion, the importance of kelp forests to abalone reproduction and recruitment is likely to be high. The predicted increases in wave action and storm surge in this region may reduce the number of optimal ‘environmental windows’ for spawning and larval settlement may also be impacted. The predicted changes to temperature and pH contributed to a high impact risk rating for blacklip abalone in a risk assessment (Pecl et al. 2009) and further details are included in the Point Hicks case study of this document (Twofold Shelf bioregion). Mean sea surface temperatures are lower in Discovery Bay MNP compared to Point Hicks MNP and so these changes may not be evident until 2100 (projected temperature increase of 3°C). These impacts might increase the vulnerability of H. rubra to other stressors such as disease. While there has been no conclusive evidence that attributes increased incidence of disease to climate change, there have been documented increases in disease of H. rubra (Pecl et al. 2009). A viral ganglioneuritis has been spreading in abalone populations
VEAC Marine Investigation. Climate change and MPAs 28
across western Victoria since it was first recorded in abalone aquaculture tanks in 2006. The virus is already present in Discovery Bay MNP and mortality in natural populations due to the virus is known to be very high. In Discovery Bay MNP changes to upwellings and local currents might be very important in determining the quality and quantity of drift algae (abalone feed mainly on drift algae) delivered to reef habitats. The predicted increase in the Bonney upwelling may increase the quantity of drift algae although little is known about what constitutes high quality food for this species (Pecl et al. 2009). Jasus edwardsii –southern rock lobster The southern rock lobster is found in both MNPs within the Otways bioregion and is an example of a predatory species with a long larval duration. It has been rated as highly vulnerable to climate change in a risk assessment of key fisheries species in south eastern Australia (Pecl et al. 2009). Larvae (phyllosoma) are released to the plankton where they remain for 1-2 years. In this time they are thought to travel long distances transported primarily by currents that run parallel to the coastline from the south west of Western Australia to the east coast of Australia although due to complex eddies and offshore currents there is also likely to be some self-recruitment as well (Bruce et al. 2007). While little is known about the oceanic stage of the life history it is likely that changes to large scale currents such as the SAC are likely to impact southern rock lobster populations within Discovery Bay MNP. At the end of the larval phase and when adjacent to the continental shelf phyllosoma moult to puerulus and swim onshore and shift from a planktonic to a benthic existence (Pecl et al. 2009). In South Australia it is thought that storm events and wind stress and direction are instrumental in determining delivery of puerulus to onshore reefs in the main settlement months of June to August (Linnane et al. 2010). Linnane et al. (2010) also describe a secondary settlement phase in the summer months of February - March and this phase may be impacted by the increasing strength of summer south easterly winds pushing surface water offshore. Temperature is also thought to be important in settlement of rock lobster to inshore reef habitat. Settlement in Tasmania was shown to be lower in areas of higher temperatures (Pecl et al. 2009) while growth rates were shown to be higher in areas of higher temperatures (Pecl et al. 2009). In Discovery Bay catch per unit effort (CPUE) decreases as cold water upwelling increases (Longmore 2013). Pecl et al. (2009) predict an initial increase in overall biomass of southern rock lobster in the cooler areas of Tasmania, as sea surface temperatures increase and growth rates increase, followed by a decline in overall biomass as recruitment decreases. It is likely that similar changes will be seen in the rock lobster population of Discovery Bay MNP possibly exacerbated by a reduction in summer settlement due to the increase in south easterly winds. Juvenile rock lobsters recruit to inshore reefs moving offshore as they grow progressively older. Impacts on kelp habitats will therefore also detrimentally affect rock lobster recruits as well as interactions with potential prey species such as abalone (Pecl et al. 2009). Southern rock lobster are likely to play an important role in structuring benthic communities through trophic cascades (DPI Victoria, Fisheries Note number FN0596 2007, Boudreau and Worm 2012) and changes to rock lobster populations in Discovery Bay MNP may impact other taxa in turn. Sponges Sponges are important autogenic engineers of deep reef habitats. They have high filtration rates and have been shown to be important in nutrient and carbon cycling (Hutchings et al. 2007). Sponge assemblages form an important coupling point between benthic and pelagic habitats and changes to phytoplankton production and nutrient delivery may be very important to survival, growth and reproduction of these animals. Increases in water temperature are likely to impact sponge assemblages with more frequent and widespread microbial mediated disease outbreaks or disruptions to symbiotic relationships considered likely (Webster and Bourne 2012). There have been a number of sponge mass mortalities in the Mediterranean that have been associated with warmer waters (e.g. Cerrano et al. 2000) and species vulnerability to increases in temperature have also been related to the associated microbial assemblage (Cebrian et al. 2011). Temperature is also important in the timing of reproduction for many sponge species (Hutchings et al. 2007). Reproductive success and recruitment may be impacted if changes in the timing of reproduction are not also accompanied by pulses of appropriate food. Certain sponge species are calcifying organisms and so are likely to be vulnerable to increases in ocean acidification (Hutchings et al. 2007).
Soft sediment habitat The Bonney upwelling delivers cooler nutrient rich waters to inshore waters and is important in the phytoplankton production of the region. These factors are likely to be important to the productivity and diversity of the soft sediment assemblages within the generally oligotrophic waters of Discovery Bay MNP. Impacts following changes in the timing, rate and duration of the delivery of this upwelled water will depend on how important upwelled nutrients are for soft sediment assemblages and the life history strategies of different taxa; specifically the timing of reproduction and larval stages and their relation to the timing of upwellings (Morris 2013).
VEAC Marine Investigation. Climate change and MPAs 29
Intertidal soft sediment is not a major habitat within Discovery Bay MNP however increases in mean sea level are likely to reduce the amount of intertidal habitat available. Seagrass The band of seagrass found in Discovery Bay MNP (and Twelve Apostles MNP) is thought to be limited by light availability at the deeper edge of the stand and by wave action at the shallower edge (Morris 2013). Increases in wave action, even slight, may cause mechanical damage to seagrass fronds, rip up patches of seagrass or smother seagrass reducing access to light. In Discovery Bay MNP the seagrass stands may not be able to retreat seawards due to sea level rise and reduced light availability at increased depth. Infauna The subtidal infaunal assemblages within Discovery Bay MNP are comprised mainly of crustaceans and polychaetes with molluscs poorly represented (Barton et al. 2012). These more mobile fauna reflect the high wave energy environment where sediments are frequently disturbed and so are unsuitable for more sedentary tubiculous species. Infaunal assemblages may not be impacted by any further increases in wave energy. The infaunal assemblages may also be more resilient to acidification than the reef habitat. In a mesocosm experiment polychaetes were least affected by acidification and crustaceans were intermediate with molluscs and echinoids most affected (Hale et al. 2011). The dominance of crustaceans and polychaetes in the soft sediment assemblages of Discovery Bay MNP may mean effects of increasing acidification are less than may occur in the highly diverse mollusc assemblages found on the reef habitat. However initial impacts of acidification are likely to be sub lethal and depend on other water quality parameters (Morris 2013). An important potential impact of acidification may be to increase vulnerability of infaunal assemblages to other stressors; specifically the major anthropogenic threats for Discovery Bay MNP - oil spills or pest introductions (Jenkins 2013). The predicted increases in sea surface temperatures are likely to impact infaunal assemblages through range expansions, introductions of pest species, potential pathogens and phenological changes (i.e. reproductive cycles such as the timing of spawning). The latter may be of most importance as changes in timing of reproductive effort in invertebrate populations may depend on the timing of upwelling events in the region. Egg production, larval survival and recruitment may be reduced if the necessary food pulses are not available at the appropriate times.
VEAC Marine Investigation. Climate change and MPAs 30
Central Victoria Bioregion
Background Table 7. Marine protected areas in the Central Victoria Bioregion
Point Addis Marine Marengo Reefs Marine National Park Sanctuary Port Phillip Heads Marine Eagle Rock Marine National Park Sanctuary Point Lonsdale Point Danger Marine Point Nepean Sanctuary Bunurong Marine Barwon Bluff Marine National Park Sanctuary Bunurong Marine Park Mushroom Reef Marine Sanctuary
The Central Victoria bioregion extends along the coast from Apollo Bay to Cape Liptrap. The shore is characterised by cliffs and sandy beaches and steeply sloping seabed bathymetry. The climate is temperate and the biota in the bioregion is a diverse mixture of species from all of the adjacent biogeographical provinces in addition to cosmopolitan southern Australian species (Barton et al. 2012b). For the purposes of this report the coastal sections of Port Phillip Heads (PPH) Marine National Park (MNP) – Point Nepean and Point Lonsdale – are considered coastal sites as they experience the same physical drivers as the other coastal MPAs in the bioregion. Climate change predictions for physical conditions in this bioregion are outlined in Mills et al. (2013) with implications of these changes outlined for reefs (Bellgrove et al. 2013), seagrass and infauna in soft-sediment habitats (Morris 2013). Predicted impacts of climate change on fish and marine mammals have been reviewed at a state level because of the highly mobile nature of many of these species and the scale of likely impact (Gill and Pirzl 2013, Hirst and Hamer 2013). The bioregion is relatively exposed to swells and weather from the south-west and influenced by tidal and wind-driven currents (Barton et al. 2012b). The bioregion is influenced by the South Australia Current (SAC) – an extension of the warm-water Leeuwin Current arising in Western Australia – which flows from west to east along the Victorian coast, reaching Bass Strait (Mills et al. 2013). Water movement in Bass Strait itself is predominantly driven by tides and wind and lacks a predictable pattern, and this is thought to create a partial barrier to movement of (fish) species between the eastern and southern coasts of Australia (Gomon et al. 2008, Hirst and Hamer 2013). Much of the information about species occurring in MPAs in the bioregion has been gathered as part of Parks Victoria’s intertidal and subtidal reef monitoring programs (e.g. Parks Victoria 2007) so there is a heavy knowledge bias towards reef fauna as other habitats are not systematically surveyed. Intertidal rocky reefs and some shallow subtidal reefs are present in each MPA in this bioregion, as are intertidal and subtidal soft-sediments. Point Addis and Bunurong MNPs extend out to the state marine limit of 3 nm and also contain deep subtidal reefs. Reefs are mostly limestone or sandstone with basalt in some MPAs such as Barwon Bluff and Eagle Rock MSs. Hormosira banksia is the dominant alga on intertidal reefs with mixed algal assemblages of diverse forms (e.g. turfing reds and encrusting coralline algae) and species (e.g. Ulva , Codium spp., Cystophora spp. and Sargassum spp.). More exposed coasts are fringed with Durvillaea potatorum, with mixed Phyllospora comosa and Ecklonia radiata stands found on subtidal reefs. Small beds of Amphibolis antarctica seagrass occur on sand in more sheltered locations and in rockpools (Barton et al. 2012b). Rhodolith beds are found in Point Addis MNP, with unique assemblages of sponges, bryozoans, ascidians and hydroids on deep soft sediments (Barton et al. 2012b). In Bunurong MNP the deep reefs are dominated by sponges, stalked ascidians and bryozoans. Details of the physical and biological properties of MPAs in this bioregion are documented in Barton et al. (2012b), including information on flora and fauna species present in individual MPAs.
Future climate
Predicted changes in physical variables in the Central Victoria bioregion have recently been reviewed by Mills et al. (2013) and are summarised here (Table 1). Average sea levels are predicted to rise by up to 0.82 m by 2100, with
VEAC Marine Investigation. Climate change and MPAs 31
increased storm surge events at times producing greater extremes in sea level height. There are no projections for changes in astronomical tides for the bioregion. The Leeuwin Current/South Australia Current (SAC) has been observed to be weakening slightly and is predicted to be at similar levels in 2030, followed by further, slight weakening by 2070 and 2100. Sea surface temperatures (SST) are predicted to steadily increase by less than 1°C by 2030 and 3 °C by 2100. Mean annual air temperatures throughout Victoria are estimated to increase 0.6-1.2°C above 1990 levels by 2030, and 1.8-3.8°C by 2070 with an increase in the number of hot days (>35 °C) and longer warm spells (Victorian Government 2008). Air temperature increases will be smaller on the coast compared to inland areas. Projections are for a minimal change to sea surface salinity over the period to 2100 and an increase in wave energy due to a positive trend in the Southern Annular Mode (Mills et al. 2013). While there is currently no detailed modelling of the impact of climate change on the wave climate of the Victorian coastline, wave data indicates that there may be increased frequency of large wave events, increased wave heights and anticlockwise rotation of wave direction in response to southern shifts in storm tracks (Hemer et al. 2008; Mills et al. 2013). Large coastally trapped waves, which are seen as storm surges on the coastline, may result in more frequent inundation of low coastal areas in the bioregion with Central Bass Strait (and Western Port) exposed to the largest storm surge heights on the Victorian coastline (Mills et al. 2013). Seawater acidity is expected to increase throughout the Victorian marine environment, measured as a reduction in pH by approximately 0.085 units by 2030, and 0.28-0.29 units by 2100. Freshwater runoff volumes are projected to decline in line with a projected increase in evaporation rates and decrease in rainfall (Mills et al. 2013). In the Central Victoria bioregion this means a decrease in runoff of 12-18% by 2030, and 23-31% by 2070. Predicted declines in rainfall will reduce freshwater flows in creeks and rivers, and see more frequent closures of estuary mouths. There are no upwelling features in the bioregion.
Habitat vulnerabilities to future climate
A risk assessment of climate change on marine biodiversity by Parks Victoria (2010) found that the Central Victoria bioregion (along with Victorian Embayments bioregion) is the most vulnerable bioregion to threats such as sea level change and storm surge. Intertidal rocky shores and subtidal rocky reefs in the Central Victoria bioregion were identified as being particularly at risk (Parks Victoria 2010). There is a general trend for habitats and taxa close to shore (intertidal and shallow subtidal) to be highly or moderately vulnerable to the effects of climate change while deeper habitats tend to be less vulnerable to some impacts – for example changes to sea level height. Intertidal habitats in the Central Victoria bioregion – rocky reefs, soft sediments and seagrass – are considered highly vulnerable to increases in sea level rise through inundation, as are shallow subtidal rocky reefs (Bellgrove et al 2013, Morris 2013). Shallow subtidal sediments are considered moderately vulnerable (Morris 2013). Soft sediments and seagrass at all depths have been assessed as moderately vulnerable to altered currents in the bioregion because of the potential for range extensions of novel species including pests, with reefs having a low vulnerability (Bellgrove et al. 2013, Morris 2013). Extremes in salinity (high or low) are likely to be localised but may have a moderate impact on some organisms on intertidal reefs. For example, Hormosira banksia is sensitive to high and low salinities which can cause a decrease in cover and decline in recruitment (Bellgrove et al. 2013), while rock pool organisms may be affected by hypersaline conditions from increased evaporation and decreased rainfall and runoff. An increase in wave energy is predicted to have significant impacts with high vulnerabilities predicted for intertidal and shallow subtidal reefs, seagrass and unvegetated sediments in the bioregion (Bellgrove et al. 2013, Morris 2013). Effects may manifest through direct disturbance of algae, seagrass and animals, increased sediment mobilisation and turbidity, and altered sediment deposition. Increased wave energy may increase rates of erosion of sandy and rocky coastlines (depending on aspect and geology) and alter the profile of beaches. Deep water habitats are considered to have low vulnerability to altered wave regimes (Bellgrove et al. 2013, Morris 2013). Intertidal and shallow subtidal habitats are likely to be highly vulnerable to changes to rainfall and runoff (Bellgrove et al. 2013, Morris 2013) because of changes to nutrient levels entering marine systems that support primary production (e.g. macroalgal growth, phytoplankton) and food webs. Predictions are for more episodic rainfall events bringing large volumes in short time-frames, likely flushing greater levels of sediments (and nutrients) into the system at one time, rather than gradually over longer periods (Mills et al. 2013) with some shift in community composition likely (Bellgrove et al. 2013, Morris 2013). Increased sea surface temperature is predicted to be a significant stressor for all intertidal and shallow subtidal habitats while increased air temperature and extended hot spells may impact significantly on intertidal rocky reefs, and intertidal sediments (Bellgrove et al. 2013, Morris 2013). Temperature-related local extinctions, changes in species ranges, altered reproduction, dispersal and recruitment are possible, as are increases in the arrival of new marine pests and disease. Rocky reef habitats at all depths are considered highly vulnerable to the effects of increasing seawater acidity because of the predominance of calcifying animals (crustaceans, molluscs, echinoderms) and coralline algae. Acidity impairs the
VEAC Marine Investigation. Climate change and MPAs 32
formation of calcified structures such as shells and can dissolve existing ones, and for non-calcifying organisms high dissolved CO 2 levels can cause physiological stress concomitant with hypercapnia (Bellgrove et al. 2013, Fabry et al.
2008). Seagrass has been assessed as having low vulnerability to increased CO 2 while soft sediments are considered to have high/moderate vulnerability (Morris 2013, and see Table 2). Vulnerabilities of marine mammals that occur in some of the MPAs in this bioregion (e.g. humpback whales, Megaptera novaeangliae, in Bunurong MNP) have been assessed by Gill and Pirzl (2013) (Table 3 ). Seals may experience greater difficulty swimming and feeding in more wave-affected, turbid waters and seal haul outs may be directly affected by waves and sea level rise (Gill and Pirlz 2013). Other climate change stressors are unlikely to directly affect seals and mammals in the Central Victoria bioregion but may have consequences for existing ranges and animal health through reduction or geographical shifts in prey availability (Gill and Pirzl 2013). In general, finfish and sharks are predicted to respond to climate change stressors in a similar way, however there may be differences for particular species or life history stage (Hirst and Hamer 2013) (Table 4). Fish (particularly larval stages) may experience greater difficulty swimming and feeding in more wave-affected, turbid waters and larval settlement may be affected (Hirst and Hamer 2013, Gill and Pirzl 2013). Finfish larvae (e.g. King George whiting) in the bioregion are considered moderately vulnerable to sea level rise as recruitment to juvenile/adult habitats may be impacted. They are highly vulnerable to altered ocean currents as they are relatively weak swimmers hence dispersal and retention of both larvae and eggs may be affected (Hirst and Hamer 2013). The Leeuwin current is predicted to weaken slightly but impacts from current changes in the Central Victoria bioregion are likely to be less than for bioregions in the east of the State where waters of the East Australian Current penetrate (Twofold Shelf and Flinders). Temperature may have a significant impact on fish larvae by increasing development rates and thereby increasing survival, but above optimum temperatures survival will be reduced. Range shifts in adult fish (finfish, sharks and rays) are moderately likely, while extremes in temperature are predicted to decrease survival of eggs and juveniles (Hirst and Hamer 2013).
VEAC Marine Investigation. Climate change and MPAs 33
Case Study - Point Addis Marine National Park
Sea level rise, waves, rainfall and runoff, currents.
Point Addis Marine National Park (MNP) is a large protected area on an exposed coastline with high wave energy. The MNP extends 9 km longshore and ~5 km offshore to a depth of 58 m. The shoreline is characterised by sandy beaches and limestone intertidal platforms bordered by sandstone cliffs and limestone outcrops (Barton et al. 2012b). Point Addis is fringed by coastal and terrestrial reserves and semi-rural land (Barton et al. 2012b). Most of the intertidal zone is soft sediment, with some large areas of rock platform. The main intertidal reef is the prominent headland at Point Addis. This undulating, low profile platform is relatively exposed to wave action and can have extensive covering of Hormosira banksii and abundant molluscs (Barton et al. 2012b). Bull kelp Durvillea potatorum grows in the shallow subtidal, with Phyllospora comosa and Macrocystis pyrifera in deeper water. Seagrass Amphibolis antarctica grows on broken reef down to 11 m and in rock pools while sparse Zostera nigricaulis grows in shallow water beyond the surf zone (Barton et al. 2012b). The infauna in the soft sediments is species rich, particularly in deeper water, and dominated by small crustaceans and polychaetes (Parry and Heislers 2007). Important habitats in deeper water are created by aggregates of rhodoliths (globular coralline algae) and in other areas by sponges, ascidians, hydroids and soft corals (Barton et al. 2012b). Information on distributional limits within the MPA is confined to two species of red algae (family Rhodymeniales) thought to be at their eastern (Rhodymenia verrucosa ) and western ( Webervanbossea splachnoides ) limits (O’Hara and Barmby 2000, O’Hara 2002). Diverse fish assemblages are associated with reef, soft sediments and vegetated habitats in the park, and pelagic species such as yellowtail kingfish, Seriola lalandi , and salmon, Arripus spp., are transient visitors (Barton et al. 2012b). In the Point Addis MNP case study we have considered the potential impacts of sea level rise, wave climate, rainfall and runoff but the potential impacts of increased acidity and increased sea surface temperatures considered in the Bunurong MNP case study are equally relevant to Point Addis MNP and other MPAs in the bioregion. Reef habitat Sea level rise in Point Addis MNP, particularly when combined with storm driven waves and surge, are predicted to inundate intertidal areas, for example the low-relief rocky reef at the base of Point Addis cliffs, intertidal habitat at Ingolsby Reef and sandy beaches between rocky headlands. The adaptive capacity of intertidal reef biota to inundation is considered to be low, particularly because intertidal rocky reefs in the Central Victoria bioregion are largely horizontal in aspect (Bellgrove et al. 2013). Some of the intertidal reef in the MNP will become subtidal, with intertidal biota migrating higher on shore where suitable substrate exists or new areas of reef become exposed through erosive processes. Shore profiles - the spatial extent, geology and vertical relief - will determine the capacity for shoreward expansion (Bellgrove et al. 2013). Migration may be possible where there are no physical barriers to landward migration in the form of vertical cliff faces or coastal protection structures (Bellgrove et al. 2013). Increased wave energy in the bioregion combined with increases in sea level height and storm surge are likely to increase coastal erosion. In some locations erosion will expose new rocky substrates at rates comparable to sea level rise/storm surge increase and therefore may eventuate in no net loss of intertidal reef at that location. The cliffs on the landward edge of Point Addis MNP are predominantly sandstone with limestone outcrops (Barton et al. 2012b) making them relatively soft. Soft rock coasts can be prone to relatively rapid erosion, slumping and rockfall, while hard rock coasts are generally stable over human time-frames (DSE 2012b). Wave and tidal forces associated with large storms can undercut rocky shores and trigger landslides on cliffs. Landslides of cliffs in and adjacent to Point Addis MNP have been assessed as highly likely to occur (Surf Coast Shire 2010) which may result in smothering of intertidal communities. Increased coastal erosion and the vertical height of cliffs at this location may prevent the landward expansion of some intertidal species, particularly algae that require more horizontal substrates, resulting in local population extinctions. Other species may have greater capacity to migrate vertically, for example aggregating sessile invertebrates such as tube worms Galeolaria and mussels Limnoperna pulex ; moblie gastropods Siphonaria and Patelloida limpets, and snails Nodolittoria and Bembicium.
VEAC Marine Investigation. Climate change and MPAs 34
Increased wave energy, projected to slightly increase over time, may alter species composition in intertidal and shallow subtidal rocky reefs, favouring species capable of withstanding higher wave energies such as those in the Otway bioregion. Subtidally, increased wave energy can increase the disturbance within rocky reef communities, dislodging E. radiata and sponges, and creating new spaces available for colonisation by algae and invertebrates. An increase in the frequency and magnitude of disturbance events can change the composition of species within rocky reef assemblages, but deep reefs at Point Addis MNP are buffered from the effects of waves. Larval fish that recruit to a range of habitat types within the MNP may be affected by increased wave strength as settlement, swimming and feeding capacity may be more difficult or energy intensive. Adult fish of other species that are poor swimmers may be similarly affected – for example the protected Weedy Seadragon, Phylopteryx taeniolatus, and weedfish. Changes to timing, magnitude and duration of storm events are likely to impact on freshwater flows, and nutrients entering coastal waterways (Ross 2011). Climate models show there will be a decrease in mean rainfall of 2-10%, and a 6-10% increase in evaporation by 2070 (Morrongiello et al. 2011, Mills et al. 2013). Annual flows will be reduced while the number of zero flow days will be increased (Morrongiello et al. 2011) and these combined will result in a reduction in runoff volumes of 12-18 % by 2030 and 23-31 % by 2060 (Moran and Sharples 2011, Mills et al. 2013). Eight intermittent creeks discharge into the MNP and the Anglesea River lies 2.1 km to the west and these are likely to experience reduced flows. Precipitation events are anticipated to occur less frequently, but with increased intensity. Storms are likely to create significant rainfall in river catchments intersecting the coastal zone so coastal inundation due to extreme sea levels may also be accompanied by flooding of rivers and creeks due to rainfall (McInnes et al. 2009). A shift from regular but small volumes of runoff to periodically large volumes may be expected to drive changes in intertidal and shallow subtidal habitats in the bioregion (Bellgrove et al. 2013, Morris 2013) but it is difficult to predict how this may manifest in terms of species presence and abundance at Point Addis MNP. Decreased nutrients through reduction in rainfall and runoff may have a negative effect by reducing primary productivity – impacting on nutrient-dependent species of algae, invertebrates, and fish that inhabit near shore reefs (Bellgrove et al. 2013). Alternatively, reduced nutrients may benefit species such as macroalgae that are adapted to low-nutrient environments. Extreme rainfall events are likely to create local plumes of reduced-salinity, high turbidity water, with varying levels of contaminants, depending on the surrounding catchment uses. An increase in sedimentation and turbidity in marine waters may smother intertidal and shallow subtidal reef biota, creating less diverse assemblages (Bellgrove et al. 2013). Currents running along the coast in a north easterly direction from the Anglesea River may transport discharged material to the MNP but the distance means that impacts are likely to be diffused. There is a sewage outfall off Anglesea but any impact of the sewage outfall on the MNP is likely to remain unchanged under climate change unless the composition of the discharged material is altered (e.g. extreme rainfall event causing flooding at the treatment plant and contamination of discharge waters). The South Australian Current (SAC) drives water movement in a predominantly south-easterly direction and is strongest in late autumn/early winter. Although only slight, the weakening of the Leeuwin Current/SAC may cause a slight decrease in the dispersal distance of propagules (e.g. eggs, larvae, spores) that connect populations inside and outside MNPs (Mills et al. 2013, Bathgate 2010 ). For populations of invertebrates and more sedentary fish inside Point Addis MNP this may result in greater levels of self-recruitment with less contribution to recruitment from populations upstream (i.e. to the west) (Bathgate 2010). At the same time, this may mean that the MPA becomes less effective as a larval source for intertidal reefs downstream, particularly for those species with brief larval dispersal periods, such as the limpet Cellana tramoserica and topshell Austrocochlea constricta (Bathgate 2010). For species such as the red alga Rhodymenia verrucosa, which is at its easterly limit in the MNP (O’Hara and Barmby 2000), a weakening of the LC may result in range retraction because of reduced dispersal in an easterly direction.
VEAC Marine Investigation. Climate change and MPAs 35
Soft sediment habitat Slight increases in wave energy combined with storm surge may increase sediment loads in the water column and change sediment transport patterns (Water Technology 2008, Church et al. 2012). Modelling indicates there will be increased wave heights mobilising more sand with potentially significant impacts to both beach profiles and location of the mean sea level beach contour (Water Technology 2008). Under future climate, most Victorian beaches will eventually recede when erosion events become too frequent to allow full recovery between storms (DSE 2012b). At Point Addis the extent of recessions will depend on whether beaches are backed by bedrock and other local conditions (DSE 2012b). Because of the complexity in sediment transport and deposition it is not possible to predict the exact outcome of altered wave energy and tidal height on sandy shores at Point Addis. Seagrass Amphibolis in intertidal rock pools may become subtidal as sea levels rise, with seagrass in subtidal waters potentially retreating at the seaward edge if light penetration is reduced because of increased water depth. Landward migration depends on suitable substrate which may not be available at Point Addis due to the cliffs along the landward boundary of the MNP. In addition, Amphibolis is slow to colonise new habitats or extend its coverage (Walker et al. 2006, Morris 2013). Pulses of nutrients may enter the MNP through storm events and stimulate Amphibolis growth (Morris 2013). While nutrients can also increase the cover of epiphytes, phytoplankton and macroalgae that can block light to seagrass and cause die-off, overall nutrient levels are likely to decline at Point Addis as a result of a decline in runoff (Mills et al. 2013, Morris 2013). Temporarily elevated sediment loads as a result of episodic high rainfall events may potentially smother intertidal seagrass – and to a lesser extent shallow subtidal seagrass (Morris 2013). Any resultant impacts are likely to be temporary, unless sedimentation in the water column persists. Amphibolis is adapted to moderate to high wave energy environments and is likely to be unaffected by slight increases in wave energy. In contrast, Zostera sp. generally inhabit low-wave energy environments. While Zostera nigricaulis in the shallow subtidal may migrate shorewards with sea level rise, an increase in wave energy may reduce the already sparse cover of plants. Increased sediment loads in the water as the result of increased wave energy may have a detrimental effect on seagrass at this site through decreasing light available for photosynthesis. Infauna A rise in mean sea level will change existing intertidal soft sediments into subtidal habitats with a corresponding change in species composition. Intertidal soft sediment habitat is likely to remain but beach profiles may be altered such that species assemblages also change (Morris 2013). Increased wave energy may also deliver more drift algae and seagrass onto beaches - a food source for detritivores such as amphipods. This may potentially provide a nutrient pulse and stimulate productivity in these habitats. Mobilisation of soft sediments in the intertidal and shallow subtidal can disturb infauna living in the sediment and may affect biodiversity by favouring species of crustaceans, and mobile polychaetes that are better adapted to high wave energies. There is however, a lack of data that would enable any change to be detected (Morris 2013). Epifauna such as crabs and fish are likely to be more frequently mobilised by increased waves and storm events but are more mobile and may be able to escape the effects of increased wave height by moving. Increased turbidity as a result of more sediment in the water column may decrease light availability to seagrass, algae and rhodoliths, and any decline in cover of these habitats will likely decrease the diversity and abundance of associated organisms.
Fish Teleost fish (e.g. Blue throat wrasse), and particularly larval stages, may experience greater difficulty swimming and feeding in more wave-affected, turbid waters and larval settlement may be affected (Hirst and Hamer 2013). Fish larvae in the bioregion are considered moderately vulnerable to sea level rise resulting in possible reduction in recruitment to fish habitats. Larvae are highly vulnerable to altered ocean currents as they are relatively weak swimmers and dispersal/retention of both larvae and eggs may be affected (Hirst and Hamer 2013). As previously noted, slight but continued weakening of the Leeuwin Current may have less of an impact than current changes in other bioregions. Adult and juvenile sharks and rays such as the Port Jackson shark Heterodontus portusjacksoni , are considered to have moderate vulnerability to the flow-on effects of decreased primary productivity through altered currents and upwellings but this is unlikely to have a major impact in this bioregion. Increased temperature and acidity are recognised as significant stressors for a range of habitats and taxa in Point Addis MNP and potential impacts of these are discussed in the Bunurong case study.
VEAC Marine Investigation. Climate change and MPAs 36
Case Study - Bunurong Marine National Park
CO 2 - increased acidity - and temperature.
Bunurong Marine National Park (MNP) is located east of Cape Patterson in Gippsland, extending from the high water mark to 5.56 km offshore and 6km alongshore. Bunurong Marine Park lies at the east and west boundaries of the MNP but extends approximately 1 km offshore. Habitats and species present in Bunurong MNP have recently been reviewed by Barton et al. (2012b). Marine biological communities within the MNP are considered special because of the high algal diversity and unique assemblage of species that co-coexist. This distinct biodiversity is influenced by the matrix of rocky reefs, soft sediments and seagrass, local hydrodynamics and coastal currents (Barton et al. 2012b). The MNP is protected from the storm waves of the Southern Ocean to which most of the adjoining coasts is exposed (O’Hara et al. 2002). The potential ecological impacts outlined in this case study apply equally to the MNP and MP as habitats and species overlap between the two. Predictions for altered wind and wave patterns, sea level rise and storm surge height, coastal erosion/recession, inundation, sediment transport and rainfall relevant to Bunurong MNP have been reviewed by the Gippsland Coastal Board (2008), DSE (2012b) and Mills et al. (2013).
Increased seawater acidity from rising atmospheric carbon dioxide (CO 2) is a significant threat that has a high likelihood of affecting organisms on rocky reefs at all depths within the MNP (Bellgrove et al. 2013). Seagrass has been assessed as having low vulnerability to increased CO 2 while soft sediments are considered to have high/moderate vulnerability (Morris 2013, and see Table 2). The consequences of increasing acidity are acknowledged as an area of considerable uncertainty (National Academy of Science 2010), with consequences ranging from relatively minor (if pH changes little and organisms can adapt) to catastrophic with major ecosystem changes and alterations to fish and invertebrate populations (Fabry et al. 2008, Richardson and Gibbons 2008). Seawater CO 2 chemistry influences the ability of calcifying organisms to form calcareous skeletons, can dissolve existing skeletal structures and impair acid-base metabolism and oxygen transport (Fabry et al. 2008). Elevated partial pressure of CO 2 (pC0 2) in seawater (also known as hypercapnia) can cause physiological stress in both calcifying and non-calicifying organisms by acidifying body fluids and can lead to abnormal larval development and decreased fertilisation in invertebrates (Fabry et al. 2008, Havenhand et al.
2008). The same concentrations of aqueous CO 2 that are deleterious for some species may be beneficial for photosynthesising organisms, particularly subtidal algae and seagrass (Bellgrove et al. 2013, Morris 2013). Temperature is a strong determinant of species distribution and influences the rate of physiological and life-history processes such as timing of reproduction, development time of spores, eggs and larvae, and photosynthesis. An increase in air temperature, number of hot days and duration of warm spells may increase mortality of intertidal organisms in the MNP, may change reproductive and dispersal patterns, and cause range shifts or loss of cool water species. Temperature increases at the upper end or above normal tolerance ranges can cause physiological stress to organisms, making them more vulnerable to other stressors such as pollutants, pests and diseases. The spread of pests and diseases is predicted to increase with increasing temperature.
Reef habitat
In the intertidal zone in Bunurong MNP increased CO 2 is likely to affect calcification in crustose and branching coralline algae such as Corallina officianalis and common species of benthic calcifiers such as pulmonate limpets ( Siphonaria spp.), chitons, striped conniwinks, Bembicium nanum , and the mat-forming mussel Limnoperna pulex . Habitat-forming algae such as Homosira banksii , along with other intertidal algae and seagrass Amphibolis antarctica in rock pools may be unaffected or show a positive response to CO 2 if photosynthesis is enhanced. There is limited comparative research into vulnerabilities of different taxa. In one study, polychaetes (in soft sediments) were shown to be more resilient to increased acidity than crustaceans, with molluscs and echinoderms having the lowest resilience (Hale et al. 2011). It should be noted that some (reef) polychaetes such as Galeolaria caespitosa form calcified tubes so this observation is a general one. Gastropods and bivalves in the intertidal, and subtidally, molluscs Haliotis rubra , Turbo undulatus and sea stars Patiriella brevispina and Nectria ocellata may be most sensitive and experience disruptions to calcifying processes, dissolution of existing shells and acidification of internal fluids.
Subtidal red algae in the MNP may benefit from increased aqueous CO 2 but other algal groups such as subtidal brown algae (e.g. Seirococcus axillaris , Cystophora spp. and Sargassum spp) may not respond because of the way in which they assimilate CO 2. The population and community-level response of increased CO 2 on subtidal reef organisms is likely to be complex and is difficult to predict (Bellgrove et al. 2013). The impacts on deep habitats of CO 2 and temperature may possibly have a slight lag effect, because of the buffering effects of deep water, but eventually increases in average temperatures are likely to be reflected at all depths as Bass Strait is relatively shallow (Morris 2013). Calcium carbonate
(CaCO 3) solubility increases with decreasing temperature and increasing pressure (Fabry et al. 2008) but it is unclear if
VEAC Marine Investigation. Climate change and MPAs 37
this means deep biota such as calcareous sponges and bryozoans in the MNP will respond differently to shallow water calcifying species. Early developmental stage marine invertebrates – eggs, larvae and recruits - are particularly vulnerable to seawater acidification as the formation of the early shell may be disrupted (Doney et al. 2009). Calcification and growth rates can be reduced in response to high CO 2 and larvae may show malformed or unmineralised shells (Kurihara et al. 2007). Such larvae are therefore unable to settle and population size of individual species may then decline, with flow-on community effects likely (e.g. for prey, competitors). Non-calcifying larvae are also sensitive to acidity, with sea stars found to have reduced larval growth and larval mutation (Byrne et al. 2013). Research on larval gastropods has to date been laboratory focused, and the wider implications of seawater acidity for marine ecosystems are not well known (Doney et al. 2009). Intertidal reef inhabitants are likely to experience greater desiccation from extremes in temperature, particularly where they coincide with daytime low tides and this will vary among seasons (Bellgrove et al. 2013). Increased temperatures will increase the likelihood of die-off of intertidal algae and seagrass which will alter invertebrate and fish species composition on intertidal reefs. Rock pool fish such as toadfish and blennies are adapted to large variations in temperature and salinity however increased temperatures and evaporation may dry out smaller pools and cause significant heat stress in other pools in warmer months. Mortality of newly-settled marine invertebrates such as gastropods, anemones and ascidians may increase through heat stress and desiccation. Some mobile invertebrates such as chitons and Nerita atramentosa can shelter from sun and heat in crevices and undersides of rocks, while permanently attached mussels, barnacles and anemones cannot. Gelatinous egg masses, such as those laid by Siphonaria limpets, are also vulnerable to increased desiccation. Algae on shallow subtidal reefs may be buffered from the effects of extreme air temperature events except where these coincide with spring tides – potentially exposing upper subtidal algae (Bellgrove et al. 2013). Kelps (Order Laminariales) and other habitat-forming brown algae (Order Fucales) are most sensitive to temperature changes although there is a low abundance of Phyllospora comosa and Ecklonia radiata in Bunurong MNP. Ecklonia , Cystophora and Sargassum are particularly sensitive to temperature increases during reproduction and recruitment, and may decrease in density with an associated shift in the abundance and species of understorey algae and animals (Bellgrove et al. 2013). There has already been a major decrease in the giant kelp Macrocystis pyrifera within the MNP, the surrounding coast and throughout the south east Australian region (Barton et al. 2012b). This widespread decline is thought to be due to a combination of increased nutrients and temperatures from both El Niño and long-term increases in average sea surface temperature (Okey et al. 2006, Barton et al. 2012b). Kelps are also highly sensitive to other anthropogenic effects such as water quality and the combined effects of temperature and other anthropogenic effects can make these communities more vulnerable to invasions by new pest and warm-water native species of herbivores that may arrive (e.g. Centrostephanus Ling 2008). Similarly, for intertidal and subtidal reefs, soft sediments and seagrass, increased water temperatures may alter conditions in favour of warm water range expanders, invasive marine pests and pathogens (Lafferty et al. 2004, Harvell et al. 2002, Morris 2013). For fish and invertebrates, warmer waters can increase the rate of larval development, potentially reducing the planktonic period, and thus dispersal distances and connectivity amongst populations (Cowen and Sponaugle 2009). Increased temperatures as a result of climate change may alter the degree to which populations of some species inside MPAs are connected to populations outside. For example, the extent to which Bunurong MNP acts as a source or sink of larvae of intertidal snails, limpets and seastars may change in the future. Modelling that combines hydrodynamic data with species-specific biological information is required to investigate potential changes. An increase in sea surface temperatures can also change species phenology – that is, the timing and magnitude of reproduction including flowering, egg laying and spawning (Taylor and Maher 2006). The intertidal limpet, Cellana tramoserica , common in Bunurong MNP and other MNPs, has a brief reproductive period over December-January with larvae formed from external fertilisation (Parry 1977). Predicted warmer temperatures over a longer period may extend the reproductive period in this species so there are more opportunities for larval dispersal. Alternatively, temperatures may exceed optimal conditions for gamete development in this species – meaning fewer eggs and sperm are produced, with greater mortality of recruits through heat stress and desiccation. Fish growth is generally temperature-dependent. Growth rates can increase with increased temperatures, until reaching a thermal maximum after which rates decline quite rapidly (Hirst and Hamer 2013). Larvae of finfish (bony fish) such as wrasse Notolabrus tetricus and scalyfin Parma victoriae , are considered to be highly vulnerable to temperature increases, with other life-history stages moderately vulnerable (Hirst and Hamer 2012). Both eggs and larvae of bony fish are considered moderately vulnerable to increased CO 2 and acidification (Hirst and Hamer 2012). The potential response for chrondrichthyans (sharks, rays and their allies) such as draughtboard sharks Cephaloscyllium laticeps is less certain but all life history stages (eggs, juveniles and adults) are likely to be moderately vulnerable to temperature but have low vulnerabilities to CO 2 and acidification. Experiments involving exposure of anemone fish, Amphiprion melanopus , to combinations of CO 2 and temperature predicted under climate change show that parental effects can have a highly
VEAC Marine Investigation. Climate change and MPAs 38
significant influence on the performance of marine organisms under predicted ocean acidification (Miller et al. 2012).
Increased CO 2 and temperature cause an increase in metabolic rate and decreases in length, weight, condition and survival of juvenile fish but these effects do not occur or are reversed when parents also experience high CO 2 concentrations. This suggests that some species may have the capacity to acclimate to ocean acidification (Miller et al. 2012).
Soft Sediment habitat Infauna
Temperature and CO 2 impacts on infaunal organisms are hard to predict as the effects are likely to be sublethal and depend on other water quality parameters such as salinity, and interactive effects between stressors (Morris 2013). Animals living within intertidal soft sediments (infauna e.g. polychaete worms, amphipods and other small crustaceans and molluscs) may temporarily escape elevated air temperatures by burrowing, however intertidal infauna are likely to experience increased water temperatures through heating of sediment and pore water, particularly during low tides, possibly resulting in mortality (Morris 2013). Vulnerabilities of infaunal species to increasing temperature and acidity will be consistent with organisms in other habitats such as reefs in terms of altered phenology, effects on early life history stages, changes to nutrients and food sources, and arrival and establishment of new pests and pathogens (Morris 2013). Seagrass
Increased CO 2 and, to some extent temperature, may lead to an increase in primary production in the MNP. Photosynthesis in shallow subtidal seagrass A. antarctica may be enhanced by increased CO 2 with a possible increase in the sizes of patches in the MNP (Morris 2013). At the same time, epiphytes that grow on seagrass may also respond (Morris 2013) but is not known how this response will manifest or what this may mean for seagrass health in Bunurong MNP. Shallow subtidal seagrass may experience altered temperature-sensitive processes including growth, photosynthesis, reproduction, nutrient uptake, flowering and seed germination (Duarte 2002, Morris 2013). Temperature and acidity can also have interactive effects on organisms but for most species the outcome of these combined effects is unknown. It should be noted that most biological studies of acidity to date have been laboratory- based and have examined individual responses to climate change stressors. Such studies are necessary but are only a start towards determining in-situ population-level responses.
VEAC Marine Investigation. Climate change and MPAs 39
Flinders Bioregion
Background
The Flinders bioregion contains three contiguous MPAs – Wilsons Promontory Marine National Park (WPMNP), Wilsons Promontory Marine Park (WPMP) and Wilsons Promontory Marine Reserve (WPMR). Wilsons Promontory MNP is the largest MNP in the state and abuts the terrestrial National Park. The Flinders bioregion extends across Bass Strait and includes waters surrounding Tasmania’s Flinders Island and other granite islands. It is characterised by cool wet winters and warm summers, predominately granite and unconsolidated clastic sediments with rocky headlands and promontories interspersed by long sandy beaches, highly variable wave exposure, and high fish and plant species richness (IMCRA Technical Group 1998, Barton et al. 2012e). It is less exposed to swells than other bioregions but experiences high current flows and strong winds with some influence from the East Australia Current (EAC) (Barton et al. 2012e). Biota in the Flinders bioregion are cool temperate with some warm temperate species due to the influence of the EAC (Barton et al. 2012e). Reefs in the photic zone support algae Phyllospora comosa , Ecklonia radiata and Durvillea poratorum in the shallow subtidal with high invertebrate diversity and abundant fish on deeper reefs. Black lip abalone, echinoderms and wrasse spp. are common subtidal reef inhabitants. Unvegetated sediments dominate the habitat area in MPAs in this bioregion, with seagrasses found at some locations. Granite islands support significant populations of Australian and New Zealand fur seals and bird colonies, with humpback and southern right whales inhabiting pelagic habitats. Wilsons Promontory MNP is a nationally significant area for great white sharks, Carcharodon carcharias. Further detailed information on the biota in the Flinders bioregion can be found in Barton et al. (2012e). Details of zoning and permitted uses in the three MPA types are provided in the management plan (Parks Victoria 2006). Wilsons Promontory is a known geographic boundary for many marine species and genetic analysis of some gastropod species has shown a distinct east-west phylogeographical split at Wilsons Promontory (Waters et al. 2005). The distribution of species around Wilsons Promontory reflects both current oceanographic conditions and the historic coastline when the Bassian land bridge blocked gene flow between eastern and western marine populations (York et al. 2008, Burridge et al. 2004). The Promontory has distinct shallow subtidal reef communities on the highly exposed west and south reefs where moderate waves occur (wave energy of 18 kW/m) contrasted to those on sheltered reefs on the eastern shoreline (4 kW/m) (Parks Victoria 2010, Barton et al. 2012e). Around 120 species of marine flora and fauna are thought to be at their eastern or western distributional limits in the vicinity of Wilsons Promontory. Tidal characteristics (velocities and amplitudes) vary across the region with tidal range from 2–3 m, the largest range observed between the islands in the southern part of the region (Parks Victoria 2010).
Future Climate
There is limited information on projections of physical changes specific to the Flinders bioregion, therefore this review draws upon predictions outlined in the state-wide review for the two adjoining bioregions– the Twofold Shelf bioregion and Central Victoria bioregion (Klemke and Arundel eds 2013). The state-wide review considered the east coast of Wilsons Promontory to be similar to the Twofold Shelf bioregion in terms of the physiochemical processes operating. The west coast of Wilsons Promontory was considered to be similar to the Central Victoria bioregion (Mills et al. 2013). Predictions for these bioregions are summarised in Table 8. Sea level rise predictions of 0.82 m by 2100 along the coast of Victoria may be exacerbated by 0.1 m to the east of Wilsons Promontory due to a 20% increase in the strength of the EAC by 2100 (Mills et al. 2013). Sea surface temperatures are predicted to increase by <1.5-3°C in the same period but will increase by more than 3°C in the east of the state and potentially in the eastern section of the Flinders bioregion – again a result of changes to the EAC. Salinity is likely to decline by a small amount in coastal waters in the west of the bioregion, but increase slightly in the east. Wave energies in the Central Victoria bioregion and western section of the Flinders bioregion are predicted to increase with a possible reduction in wave energy in the east of the state and east coast of Wilsons Promontory. Seawater acidification is predicted to rise at a slightly greater rate in the Central Victoria bioregion and western section of Flinders bioregion (~0.28-0.29 pH units) compared to coastal areas in the east of the state (~0.27-0.28) (Mills et al. 2013). Significant declines in freshwater runoff are predicted for all Victorian coastal areas, but will be greater in the Central Victoria bioregion (23-31% reduction by 2070) than areas to the east of, and including the east coast of, Wilsons Promontory (15- 26%) (Mills et al. 2013).
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Habitat vulnerabilities to future climate
Parks Victoria’s risk assessment of climate change for the Flinders bioregion identified some species of algae as being at high risk due to ocean warming (Parks Victoria 2010). Other identified risks include kelp forest decline and increased air temperatures (particularly over summer) leading to desiccation of intertidal organisms. Declines in rainfall and runoff, reduced flushing volumes and increased incidence of closing of estuarine mouths are further risks to MPAs in the bioregion (Parks Victoria 2010). Ocean pH decline (i.e. increased acidity) was highlighted as a likely cause of future declines in carbonate dependent species (e.g. molluscs and coralline algae) with significant impacts on food webs (Parks Victoria 2010). The vulnerability of temperate marine habitats, mammals and fish to climate change has been comprehensively reviewed (Klemke and Arundel eds 2013) and is summarised in Table 1-Table 4). The approach taken in the Future Climate review (Klemke and Arundel eds 2013) was to divide the Flinders bioregion into two sections at the tip of Wilsons Promontory. The eastern section along the coast to the border with NSW is included in one oceanic sub-area (Eastern Region) and the west coast included in another sub-area (Central Region). There is some uniformity in predictions for eastern and western sections of the Flinders bioregion in terms of habitat vulnerability ratings. Vulnerability ratings for projected changes in CO 2 and acidification, and rainfall and runoff, are high for rocky reef communities at all depths and moderate for soft sediment and seagrasses at all depths. The impact of rising sea levels and tidal amplitude on vegetated and unvegetated soft sediments is likely to be high in intertidal areas, moderate in the shallow subtidal and insignificant in deeper water (>20 m). Deep reef habitats will be unaffected by sea level rise, but intertidal and subtidal reefs are assessed as highly vulnerable to sea level rise in the west, and moderately vulnerable on the east coast (Bellgrove et al. 2012). Changes in sea surface temperature are predicted to impact all habitats across the bioregion except for deep reefs in the west. Habitats in the intertidal and shallow subtidal have high vulnerabilities to future temperature increase, with deep reefs in the eastern section assessed as moderately vulnerable. Deep sediment habitats in the west and east are likely to be moderately to highly vulnerable respectively. Vulnerability predictions in respect to currents and upwellings differ significantly for the east (high rating for all habitats) and west where habitats are not influenced by upwelling but are likely to be moderately impacted by future currents (soft sediments and reefs at all depths). This difference is due largely to the observed and predicted strengthening of the EAC which brings warm waters and nutrients to the eastern region. Future wave regimes are not predicted to impact relevant habitats in the east as there is likely to be a reduction in wave energy due to reduced frequency of strong westerly wind conditions (Mills et al. 2013). Intertidal and shallow subtidal habitats in the west have been assessed as highly vulnerable to the increasing wave energies on the west coast although deep habitats are predicted to be unaffected. Altered salinity is predicted to have a moderate impact on intertidal reefs in the west, with intertidal reefs in the east rated as highly vulnerable, and intertidal and subtidal reefs moderately vulnerable (Bellgrove et al. 2013). In the open water habitat the larvae of teleost fish were considered highly vulnerable to increasing temperature, changes to ocean currents and the future wave climate (Table 4). The vulnerability to increasing temperature will be relevant to the whole bioregion while the vulnerability to changes in ocean currents will be most relevant to the east coast and changes to the wave climate most relevant to the west coast. Vulnerabilities of marine mammals were mainly driven by the impacts on prey species (Table 3).
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Table 8. Vulnerability of habitats in MPAs in Flinders Bioregion to predicted climate stressors. Taken from Future Climate report (Klemke and Arundel eds 2013). blue=highly vulnerable, light blue=moderately vulnerable and green=low vulnerability (Central Victoria bioregion)
West coast Rocky Reef Soft Sediments and Seagrass 1 Wilsons Prom. Physical Variable Intertidal Shallow Deep Intertidal Shallow Deep Subtidal Subtidal Subtidal Subtidal Sea level and tides Ocean currents Upwelling Temperature Salinity Waves
CO 2 and acidification Rainfall and runoff
(Twofold shelf bioregion)
East coast Rocky Reef Soft Sediments and Seagrass 1 Wilsons Prom. Physical Variable Intertidal Shallow Deep Intertidal Shallow Deep Subtidal Subtidal Subtidal Subtidal Sea level and tides Ocean currents Upwelling Temperature Salinity Waves
CO 2 and acidification Rainfall and runoff 1 Seagrass and soft sediment habitats were assessed together so that the overall vulnerability score for soft sediments considers the combination of these habitats. The biota of unvegetated soft sediments discussed in the above study are largely infauna (invertebrates living in sediments) rather than epifauna (invertebrates living on top of sediments).
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Case Study – Wilsons Promontory Marine National Park
The most significant impacts of climate for biota in Wilsons Promontory Marine National Park (MNP) are likely to be temperature, altered currents, increased CO 2 (seawater acidity), sea level rise and - particularly on the west coast – increased wave energy. Complex currents operate around Wilsons Promontory and transport fish and invertebrate larvae amongst populations inside and outside the MNP. Bass Strait water movement is predominantly driven by tides and wind with no consistent direction and this is thought to create an additional, albeit leaky barrier to movement of species between the eastern and southern coasts of Australia (Gomon et al. 2008, Hirst and Hamer 2013). The tail of the EAC has a relatively weak influence on water movement in the MNP while wind-driven surface currents can be strong (Barton et al. 2012e). Oceanographic studies of Wilsons Promontory have shown the dominant current is forced by westerly winds and coastally trapped waves, running anticlockwise around the west coast of the promontory and heading offshore at the tip creating a separation front and leeward eddy (Linsday 2013). This results in advective flows along the west coast encouraging dispersal, variable tidal flows on the east coast aiding larval retention and a separation front creating a leaky barrier to dispersal of larvae, eggs and adults of species with reduced swimming ability (Lindsay 2013). Lindsay (2013) examined settlement in mussels, Limnoperna pulex , and barnacles, Chthamalus antennatus , on both coasts of Wilsons Promontory and found settlement was consistently higher in the eastern region in line with his hypothesis of increased larval settlement within the promontory’s leeward eddy. A similar pattern of retention and recruitment may be found in other species and habitats such as soft sediment infauna. Altered current regimes around the Promontory as a result of changes to wind direction and speed, and strengthening EAC may alter current patterns of larval dispersal from, and into, the MNP.
Reef habitat Increased water temperature is predicted to cause differential loss of algae on subtidal reefs and change in community composition (Parks Victoria 2010). As it strengthens in response to global warming, the EAC may have greater influence on currents and species distributions in the MNP. Along with range expansion of Centrostephanus rodgersii , the altered flow of the EAC and increasing water temperatures are thought to have caused a poleward range shift in habitat forming algae such as Ecklonia radiata , Phyllospora comosa and Macrocystis pyrifera on the southeast coast of Australia (Wernberg et al. 2009). At present the influence of the EAC at Wilsons Promontory is minor but may increase as the EAC continues to strengthen under climate change. Phyllospora and Ecklonia are the dominant overstorey species in the MNP. These large canopy-forming species have a significant role in a range of ecological processes such as providing habitat and food, and their decline would have flow-on effects for other organisms, resulting in significant loss of associated species and ecological functions (Wernberg et al. 2009, Schiel et al. 2004, Ling 2008). No loss of these algae has been observed in the MNP since commencement of Parks Victoria’s subtidal reef monitoring program (Pritchard et al. 2012, Edmunds, M., pers. comm). Intertidal species may experience increased desiccation, however species inhabiting shallow subtidal habitats that naturally experience a wide range of temperature on a daily and seasonal basis may have some capacity to cope with predicted increases in temperature. Potential indicator species for climate change in Wilsons Promontory MNP were recently identified as part of Parks Victoria’s subtidal reef monitoring program (Pritchard et al. 2012). Species include the urchin Centrostephanus rodgersii , kelps Macrocystis pyrifera and Durvillea potatorum. These preliminary reef quality indicators of future climate were chosen based on the assumption that climate change may cause biogeographical changes in the species composition within the MNP toward that of adjacent, warmer bioregions, and loss of cold-water dependent kelps (Pritchard et al. 2012). This approach is in its preliminary stages, and no marked changes have yet been observed in fish bioregional affinities (Pritchard et al. 2012). It should be noted that Parks Victoria subtidal monitoring was not specifically designed to detect loss of kelps in the MNP. Barton et al. (2012e) note that D. potatorum is abundant at Wilsons Promontory where it grows in the lower littoral zone but it occurs in low densities at subtidal monitoring sites (Pritchard et al. 2012). Changes due to climate change may therefore be difficult to detect in subtidal surveys. Macrocystis pyrifera was only present on one survey period in the early 2000s in very low densities at Waterloo Bay and has not been observed in subsequent surveys. C. rodgersii was counted in the MNP in 2002 and 2004, and at densities of 5 individuals per 200 m-2 in Waterloo Bay in early 2010, but was not observed inside the park in late 2010 surveys.
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Elevated seawater temperature may increase the risk of disease becoming established and spreading and make organisms more vulnerable to infection if they are already experiencing physiological stress as a result of warmer temperature. This has been observed for black abalone, Haliotis cracherodii , in California which has been decimated by withering syndrome (Alstatt et al. 1996, Rogers-Bennett 2002). The bacterium causing the fatal condition is thought to divide and spread more rapidly in warmer conditions and abalone at elevated temperatures are more likely to die than those in cooler water (Rogers-Bennett 2002, Parker et al. 1992). The incidence of marine pest incursions and the arrival and establishment of warmer water species in the MNP are also considered likely to increase with increasing water temperatures and strength of the EAC further south into Victoria . Altered climate may help establish further spread and increase the impact of invasive species in temperate reef habitats (Wernberg et al. 2009). For example, the spread of the shore crab Carcinus maenas from Victoria into Tasmania is thought to have been assisted by increasing ocean temperature in response to a strengthening of the EAC (Thresher et al. 2003). Carcinus maenus is already in the MNP with the northern Pacific seastar Asterias amurensis found in Tidal River in 2012 and in nearby Andersons Inlet in 2004. High potential risk species include the New Zealand seastar Astrostole scabra and screw shell Maoriculpus roseus which already occurs in Point Hicks and Cape Howe. Elevated temperatures may cause local extinction of species that have northern range limits along the southern coastline (i.e., no poleward range shift possible) (Wernberg et al. 2009). Species most at risk from increased temperatures are those that are restricted to the MNP or southern coast of Australia. Marine invertebrates presumed to be endemic in Wilsons Promontory MNP are the gastropods Liotella vercoi , Cystiscus halli and chitons Eulima styliformis and Eulima victoriae . Around 120 species of marine flora and fauna are thought to be at their eastern or western distributional limits in the vicinity of Wilsons Promontory (O’Hara 2002, Barton et al. 2012e) and temperature changes may alter these distributions through either retracting, expanding or shifting their ranges, depending on the species and species interactions. It should be noted that these observations may reflect collection effort rather than actual Victorian distributions (Barton et al. 2012e). Species recorded at their eastern distribution (or presumed to be at their eastern limit) in the MNP include algae such as green Caulerpa brownii and C. longifolia ; brown algae Seriococcus axillaris and Sargassum decipiens ; the red alga Gelidium apserum , and weed fish Heteroclinus spp. Species thought to be at their western distribution in the MNP include the brown alga Dictyopteris archostichoides , gobies Giobiopterus semivestitus and eastern blue groper Achoerodus viridis . The marine snail, Pisinna columnaria , is presumed to be at its northern limit in the MNP and may be vulnerable to local extinction in response to increased temperature and acidity. Rather than causing direct mortality, gradual changes in temperature and acidity may have sub-lethal effects on biota (i.e. a decline in health or condition which is not immediately fatal) which may have population-level consequences by changing ecological processes. These include reproduction, recruitment, migration, competition and predation. For example, the gastropod Turbo torquatus has been observed to have lower recruitment success in warmer waters compared to periods of relatively cool water (Wernberg et al . 2008). T. torquatus occurs in the MNP, as does the abundant T. undulatus , and it is suggested that increasing temperature may put populations under pressure leading to eventual collapse (Wernberg et al. 2009). Similarly, recruitment success of Ecklonia radiata in Western Australia declines at higher temperature (Wernberg et al . 2010). Cool water species with restricted ranges that occur in the MNP are likely to be more vulnerable to increases in temperature than species with wide ranges and temperature thresholds. Temperature may increase physiological stress of algae and other organisms, gradually reducing their resilience to natural perturbations such as storms (Wernberg 2009). For example, projections are for increased wave energy on the west coast and a slight decline in wave energies in the east (Mills et al. 2013). Increased wave energy on the western shoreline may increase disturbance within the Phyllospora -dominated reefs and, combined with physiological stress from increased temperature, change the community from one dominated by canopy forming algae to one dominated by brown and red foliose algae (Wernberg et al. 2009, Bellgrove et al. , 2012). Increased seawater acidity will potentially impair the calcification process in calcifying organisms of molluscs, crustaceans, algae and other biota. Examples of species that may be affected are Plaxiphora chitons, mussels, limpets and snails such as Dicathais orbita and Turbo undulatus on intertidal reefs; and seastars Nectria macrobranchia and Patiriella brevispina on subtidal reefs. In addition to skeletons and shells, acidity may also affect the formation and function of otoliths and statoliths in fish and molluscs respectively, which are thought to play roles in navigation and hearing in fish, and vertical migration of mollusc larvae in the water column (Fabry et al. 2008).
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Other effects of increased seawater acidity may be the decline of encrusting and articulated coralline algae – the former creating extensive cover on reefs in the MNP (Pritchard et al. 2012). Crustose coralline algae is known to be favoured habitat for abalone and critical for recruitment success (Shepherd and Turner 1985). Loss of coralline algae would have negative impacts on blacklip abalone, Haliotis rubra , and the predators in the MNP that feed upon them, for example blue-throated wrasse Notolabrus tetricus and purple wrasse N. fucicola (Barton 2012e). Loss of abalone can in turn cause permanent shifts in algal community structure. In California, loss of abalone from an area has caused the community to change from one dominated by crustose coralline algae and bare rock to one with increased cover of invertebrates and erect algae (Rogers-Bennett et al . 2002). In contrast to coralline algae, elevated
CO 2 may have little negative or even positive effects on non-calcareous algae but there is some uncertainty as to whether productivity will be enhanced in marine algae (Russell et al. 2009, Wernberg et al. 2009, Bellgrove et al. 2012). Rising sea levels are likely to impact intertidal and shallow subtidal reef communities. Subtidal reefs in Wilsons Promontory Marine National Park have high species richness and abundance of flora and fauna (Barton et al. 2012). In contrast, intertidal reefs support low densities of intertidal species as they are typically steep, continuous granite slabs or large boulders with few rock pools and low surface complexity (O’Hara et al. 2010). Sea level rise may cause loss of intertidal habitat and force intertidal organisms to migrate landward. New areas of intertidal granite reef may be exposed on the landward edge through erosion of softer overlying material (DSE 2012b). Many of the dominant organisms on intertidal reefs can exist on more vertical surfaces, for example mussels, Limnoperna pulex , barnacles, Chthamalus antennatus and the anemone Actina tenebrosa found in the lower intertidal. Even given the opportunity to migrate, intertidal organisms may face increased stress and mortality through increased air temperatures over warmer months, particularly when elevated temperatures occur over numerous consecutive days (Barton et al. 2012). Decreased freshwater flows into the MNP as a result of reduced rainfall may result in decreased nutrients entering the MNP and decline in available nutrients for algae, potentially resulting in local changes in species community composition.
Soft sediment habitat Rising sea levels are likely to impact intertidal and shallow subtidal soft sediment environments. Where intertidal soft sediment habitats abut granite headlands or shorelines, erosion effects may be exacerbated by both the hard structures and, on the more exposed west and southern coasts, increases in wave action e.g. Norman Bay. In other areas (e.g. Whisky Bay) dune systems are likely to allow coastal recession. Beach profiles are also likely to change and the changes may be different on the different coasts of Wilsons Promontory. Erosive forces may be stronger on the western side of the promontory while the leeward eddy may facilitate sediment deposition on the eastern shores of the promontory. Seagrass There are significant seagrass beds of Amphibolis antarctica , Halophila ovalis in Waterloo Bay, and Zostera spp. in
Oberon Bay. Increased temperature and CO 2 may have a positive impact on seagrass by increasing the rate of photosynthesis (Morris et al. 2013) but the response in different species of seagrass is difficult to predict. Lower freshwater flows into the MNP as a result of reduced rainfall may result in decreased nutrients entering the MNP. A decline in available nutrients for seagrass could potentially alter community composition. Increased wave energy may increase physical disturbance of seagrass beds and mobilise sediments that can block sunlight to leaves. Seagrass inhabiting shallower habitats may naturally experience a wide range of temperatures on a daily and seasonal basis, and are therefore likely to have some capacity to cope with predicted increases in temperature and CO 2. Species such as Amphibolis antarctica, which is presumed to be at its eastern limit in the MNP and is restricted to cooler waters, may be less adaptable to the combined effect of climate change than other species such as Zostera which is better at recovering from disturbance (Morris 2013). Infauna The soft sediments of Wilsons Promontory Marine National park support highly diverse and abundant infaunal assemblages with species richness increasing with depth (Barton et al. 2012e, Heislers and Parry 2007). Grab samples taken off Oberon Bay and Waterloo Bay as part of a coastal survey of benthic fauna contained 39-734 individuals and 16-71 species consisting mainly of crustaceans including amphipods, cumaceans, isopods, ostracods and polychaetes (Coleman et al. 2007, Heislers and Parry 2007). Decreased freshwater flows into the MNP as a result of reduced rainfall may result in decreased nutrients entering the MNP and decline in available
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nutrients for infauna in soft sediments, potentially resulting in local changes in species community composition. Infauna biodiversity is considered highly vulnerable to existing and potential marine pests, such as the New Zealand screw shell, Maoriculpus roseus . (Heislers and Parry 2007, Jenkins 2013). In shallower habitats, many species naturally experience a wide range of temperatures on a daily and seasonal basis and may have some capacity to cope with predicted increases in temperature and acidity however some impacts on species and communities are likely. Intertidal animals may be detrimentally affected by increases in the number of very hot days although many animals have some protection from air temperatures through burrowing. As with the reef habitat increased seawater acidity will potentially impair the calcification process in calcifying organisms of molluscs, crustaceans, algae and other biota. Examples of species that may be affected are moon snails ( Polinices spp.) and soldier crabs ( Mictyris longicarpus ) on beaches in the MPAs. Again as described for the reef habitat increasing acidity may also affect the formation and function of statoliths in molluscs, affecting vertical migration of larvae. Increased wave energy may increase physical disturbance of infauna by mobilising sediments and animals. Repeated disturbance may alter the species composition in intertidal and shallow subtidal habitats (Morris 2013).
Marine Mammals Marine mammals are an important natural value within the MNP and surrounds. Climate change predictions for marine mammals and their prey in Victorian waters are still largely speculative because information is lacking about the biology, ecology and movements – particularly for cetaceans (Gill and Pirzl 2013). The New Zealand Fur Seal, Arctophoca fosteri , breeds on Kanowna island and presumably does some foraging in the park, while the Australian Fur Seal, Arctochephalus pusillus doriferus feeds in the MNP and breeds on the islands surrounded by the park, with a large breeding colony on Kanowna Island (Barton et al. 2012e). It should be noted that both fur seal species feed at considerable depths and also forage beyond the boundaries of the MNP. The endangered southern right whale, Eubalaena australis , humpback whale Magaptera novaengliae and killer whale, Orcinus orca , have been recorded in Wilsons Promontory MNP (Barton et al. 2012e). The southern right whale has been observed to calf in the MNP but feeds in Antarctica. As this species breeds in many temperatures throughout its range breeding is unlikely to be disrupted in the MNP by increases in Sea Surface Temperature (Barton et al. 2012, Gill and Pirzl 2013). However, reduced reproductive output of Australian southern right whales has been linked to El Nino events (Pirzl et al. 2008) which may increase with global warming (Latif and Keenlyside 2009, Gill and Pirzl 2013).
Increased CO 2 concentrations and seawater acidity may impact on zooplankton which is an important food source for predators such as fish and baleen whales (Gill and Pirzl 2013). Rising sea levels are likely to impact seal haul out sites to some extent (Gill and Pirzl 2013). Seals are most likely to be affected by rising sea levels which could directly impact on the availability of haul-out sites in some areas with the effect dependent on coastal geography. It is currently unclear how specific seal haul out sites in Victoria will be affected but generally seals are predicted to be able to adapt to sea level rise (Gill and Pirzl 2013). It is possible that increasing swell height could directly impact on hauled-out seals, or inhibit foraging success in near-shore waters by increasing turbidity and lowering visibility (Gill and Pirzl 2013). It is generally accepted that climate changes to the physicochemical environment (temperature, salinity and acidity) will not physically harm marine mammals directly, however there may be range shifts in response to changes in prey distribution and abundance (Gill and Pirzl 2013). For example, coastal krill, Nyctiphanes australis, is eaten by humpback whales on Australia’s east coast down to Tasmania in the spring southerly migration and the strengthening of the EAC has been shown to alter the structure of the nearshore zooplankton community (Gill and Pirzl 2013, Johnson et al. 2011). Similarly, killer whales in Victoria are thought to rely on abundant fur seal (and possibly migratory schools of southern bluefin tuna) and declines in these prey species would likely have flow on effects on this predator (Gill and Pirzl, 2012). Kirkwood et al. (2008) showed how the diet of Australian fur seals in Bass Strait varied with fluctuations in sea surface temperature, most likely due to change in abundance of prey species, and some fish species off south-east Australia are showing signs of a shift in range in response to climate change (Last et al. 2011).
Fish General predictions for fish (finfish, sharks and rays) to climate change stressors suggest that responses will be similar throughout Victorian marine waters. At finer taxonomic (i.e. species) (and possibly spatial) scales there may, however, be greater variation in responses with some species more resilient than others (Hirst and Hamer 2013).
Fish are thought to be relatively more tolerant to elevated CO 2 than many invertebrates, but may show behavioural
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changes in orientation, navigation and predator avoidance (Howard et al . 2012). All life history stages of chrondrichthyans and finfish are vulnerable to temperature increase with varying degrees of vulnerability to altered currents, sea level rise, acidification and other stressor, depending on the life history stage (Hirst and Hamer 2013). The effects of increasing temperature and acidity may not necessarily affect species if they are able to acclimate to gradual changes as has been demonstrated in the widely distributed, warm-water fish Amphiprion melanopus (Miller et al. 2012). A decline in rainfall may lead to rivers and estuaries including Growler, Frasers and Freshwater Creeks and Tidal River having reduced flow, becoming more saline and increasing the likelihood of mouth closure. Intermittent creeks may become permanently dry. This would have significant effects on diadramous fish that live in freshwater but have larvae that spend a period of time in the sea before returning to rivers and streams to complete their life cycle. Species include galaxids ( Galaxis spp.), freshwater flathead ( Pesudaphritis urvillii ) and eels ( Anguilla spp .). In years when river flows are low or estuaries close, recruitment of juvenile eels has been correspondingly reduced and in some years has resulted in recruitment failure (DPI 2013). Evidence-based predictions of species responses to climate change in temperate systems are very rare, particularly for the southern hemisphere, making it difficult to determine how marine habitats and species in Wilsons Promontory may ultimately change (Wernberg et al. 2009).
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Twofold Shelf Bioregion
Background Table 9. Marine protected areas in the Twofold Shelf Bioregion
Cape Howe MNP Beware Reef MS Point Hicks MNP Ninety Mile Beach MNP
The Twofold Shelf bioregion is primarily influenced by the East Australian Current (EAC). The EAC generates warm core eddies or circular flows that often drift south and enter Victoria, particularly over summer (Hutchinson et al. 2010). This incursion of warmer, more saline water into eastern Victoria has important ramifications for the biota of the Twofold Shelf bioregion which tends to include both warmer water northern species and cooler southern species. The EAC is also characterised by upwellings and is generally considered more nutrient rich and productive than the Leeuwin Current (the other main boundary current affecting Victoria). Upwelling in the Twofold Shelf bioregion occurs from Lakes Entrance to Croajingalong and intermittently delivers cooler more nutrient rich waters to the coastal regions. The main habitats found in each of the marine national parks and marine sanctuaries within this bioregion include intertidal and subtidal reef, intertidal and subtidal soft sediments and open water habitat. Habitat forming kelp species are common on reefs with differences in understorey species evident between the parks (Barton et al. 2012). Numerous species of wrasse are common on the reefs and warm temperate fish species such as the damselfish Chromis hypslepsis and Parma microlepsis are a feature of the shallow subtidal reefs within the Twofold Shelf bioregion (Barton et al. 2012). Large expanses of soft sediment are present in all parks except Beware Reef MS, and a survey of subtidal sediments recorded a high diversity of infauna in the region (Barton et al. 2012). Humpback whales, southern right whales and New Zealand fur seals are found in open water habitat within the bioregion (Barton et al. 2012). Foot or vehicle access to the Twofold Shelf MPAs is limited, with the exception of Point Hicks. Discharges into the MPAs are also intermittent (e.g. at Cape Howe) or non-existent. Threat assessments rated introduced species, pathogens and oil spills as the major risks for the habitats in the Twofold Shelf MPAs (Jenkins 2013). These threats were mainly considered likely to come from the shipping and fishing sectors.
Future climate
In the Twofold shelf bioregion one of the most important projected climate changes will be the strengthening of the EAC which will bring warmer more saline water into eastern Victorian waters. Sea level rise in this bioregion will be an additional 0.1 m when compared to the rest of Victoria due to thermal expansion effects associated with the changes to the EAC. There is a cold water upwelling within the Twofold Shelf bioregion that delivers cold nutrient rich water to the surface waters but little is known about the potential impacts of climate change on the strength or frequency of these upwelling events. There is a predicted increase in the strength and frequency of longshore easterly winds during summer which are the primary drivers of upwellings in Victoria, while at the same time the warmer water delivered to eastern Victoria via the EAC may result in a weakening of the Twofold Shelf upwelling. The decrease in oceanic pH is expected to continue although to a slightly lesser extent in the east of the state compared to central and western Victoria. Similarly the predicted decrease in runoff is lowest for the east of the state (Table 1, Mills et al. 2013).
Habitat vulnerabilities to future climate
Vulnerability ratings for projected changes in ocean currents and sea surface temperature are high for all habitats relevant to the Twofold Shelf bioregion (except deep reef) as well as for larval stages of teleost fish (Table 2, Table
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4). Vulnerability ratings for changes in upwellings in the eastern regions are also high for benthic habitats and moderate for certain life history stages of both teleost and chrondricthyan fish (Table 2, Table 4). These vulnerability ratings are consistent with the Climate Change Strategic Risk Assessment (Parks Victoria 2010) for the Twofold Shelf region. Changes to the oceanographic conditions and increases in temperature are likely to affect the productivity of the region, resulting in range shifts and possible species extinctions in the bioregion. The emergence of new pest species within the Twofold Shelf bioregion is also likely. Marine mammals will likely be impacted by changes to species that constitute major prey items for these animals (Table 3). Changes or loss of species are also likely to affect other mobile species that may aggregate in the area, including in the MPAs, for feeding (e.g. gummy shark pups) and spawning (e.g. Australian salmon Arripis trutta ). Increased temperatures may also affect the timing of biological events, such as spawning in fish such as A. trutta. It is possible that there then may be a disjunct between the timing of early life history stages present in the water column and the prevailing currents available that would normally transport them back to central Victoria. The biota within the eastern region of Victoria is likely to become more distinct in comparison to the rest of Victoria increasing bioregionalisation across the state.
Changes in CO 2 and acidification and a rise in mean sea level were associated with high or moderate vulnerability ratings for the majority of habitats within the Twofold Shelf bioregion (Klemke and Arundel eds 2013) and were also rated as relatively higher risks by Parks Victoria (2010). A decrease in pH (or increased acidification) is expected to impact species, and in particular larval stages, with calcified structures including calcified coralline algae and plankton species such as coccolithophores (Table 5). These changes may alter assemblage structure through impacts on recruits (i.e. larvae) and affect food chain dynamics. Changes to parameters such as pH, temperature and salinity can also alter the toxicity of pollutants as well as affect the susceptibility of an individual to negative effects from other stressors or threats. The main pollution risk in the MPAs of the Twofold Shelf bioregion is considered to be an oil spill (Jenkins 2013). A rise in mean sea level may result in a loss of habitat if there are physical barriers to the formation of new intertidal or shallow subtidal areas. The impact will depend on the rate or ability of certain species to colonise new areas, a change in shore profiles and orientation, and changes to sediment structure and transport (Klemke and Arundel eds 2013). The specific impacts of a rise in mean sea level within each MPA will very much depend on geology, sediment budget dynamics, built structures or other barriers to coastal recession. The coast adjacent to Ninety Mile Beach MNP forms part of a major barrier system that fronts the Gippsland Lakes and consists of a narrow single dune barrier that is at risk of erosion and breaches in the dune barrier system (DSE 2012b). At Beware Reef MS a rise in mean sea level may mean a loss of the entire intertidal habitat and while intertidal reef only comprises a small proportion of the sanctuary, it is used as a haul out for Australian and New Zealand fur seals for most of the year. While seals tend to be adaptable and highly mobile there is relatively little intertidal reef within the Twofold Shelf bioregion and it is not clear how such a loss might impact these species (Gill and Pirzl 2013). Loss of intertidal reef habitat may have wider implications for the bioregion as a whole through altering connectivity between reef populations of plants and animals (Bellgrove et al. 2013). The shallow water and intertidal habitats found in the Twofold Shelf bioregion and the larvae of teleost fish across the whole state were considered moderately or highly vulnerable to changes in rainfall and runoff (Table 4). This was mainly due to projected changes in the frequency and severity of storm events which will expose nearshore habitats to pulses of freshwater, nutrients and sediments. The relatively high vulnerability rating of rocky reef habitat to changes in salinity was also driven by potential variability in salinity as a result of extreme weather events (Bellgrove et al. 2013). Within the Twofold Shelf bioregion, Cape Howe MNP and Point Hicks MNP back on to National Park or wilderness areas with very limited freshwater inputs (Barton et al. 2012e) and Beware Reef is situated 2.6 km offshore. These areas will experience less exposure to large catchment derived loads of nutrients and sediments. Ninety Mile Beach may get storm surges that break the dune system causing discharges from Gippsland lakes into the MNP. There was no significant change in the projected wave climate within the Twofold Shelf bioregion (Table 1). Larval stages of teleost fish were considered highly vulnerable to increased /decreased wave energy (Table 4) however this rating would mainly refer to other bioregions within Victoria .
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Case study –Point Hicks Marine National Park. Point Hicks has been chosen for the case study as it is situated in the middle of the Twofold Shelf bioregion MPAs, has a number of biota presumed to be at their distributional limit and has the potential to be a good indicator of the combined effects of changes due to the strengthening of the EAC, upwelling and sea surface temperatures . Point Hicks MNP consists of sandy beaches backed by extensive dune systems and granite intertidal and subtidal reefs and extensive areas of subtidal soft sediment. The relatively narrow band of intertidal reef is backed by granite cliffs and the seabed has a relatively steep gradient with the reef descending into deeper water quite close to shore. Ecological assemblages consist of a mix of warmer water northern species and cooler southern species. Subtidal habitat and the invertebrate assemblages on the intertidal reefs have been described as being more similar to southern NSW than to intertidal assemblages found further west in Victoria (Hidas et al. 2007), although east coast species contributing to these differences have lower densities at Point Hicks than in NSW (Hidas et al. 2010). Subtidal soft sediment assemblages have been shown to be very diverse with a higher diversity at the greatest depth sampled (40 m) (Heislers and Parry 2007). The strengthening of the EAC and associated effects on temperature, salinity, mean sea level and possibly upwelling are likely to affect the ecological assemblages found within Point Hicks MNP. In particular reef assemblages are likely to be affected by a loss of habitat due to sea level rise, a reduction in kelp biomass and extent due to increased temperatures and increased densities of the barren forming urchin Centrostrephanus rodgersii . Soft sediment habitat is unlikely to be impacted by sea level rise but increased temperatures may increase densities of the introduced New Zealand screw shell Maoricolpus roseus affecting the highly diverse infaunal assemblages. Changes to the EAC and upwellings also have the potential to impact food webs and local abundances of mobile fish and marine mammal species.
Reef habitat There is likely to be a loss of intertidal reef habitat with sea level rise as intertidal reef backs onto granite cliffs which will not erode at the same rate as sea level rise (DSE 2012b). While new intertidal habitat will be created on vertical cliff faces the ecological communities will be different, in that invertebrates will be favoured over algal species (Bellgrove et al. 2013). Loss of the relatively sparse intertidal reef habitat within the Twofold Shelf bioregion may have important implications for habitat connectivity, recruitment and genetic diversity of intertidal reef populations. The limited intertidal reef habitat within this region may act as an important stepping stone for species recruiting between available habitats and a loss of habitat in such areas alters habitat availability and, as a consequence, species composition and richness within the region (Hidas et al. 2007). The strengthening of the EAC will deliver warmer more saline and nutrient rich waters in which propagules are entrained to the Twofold Shelf bioregion (Johnson et al. 2011). Propagules that rarely reach this region may be transported further by a stronger EAC and larval duration and hence mortality due to predation may also decrease. At the same time changes to productivity (possible increase in upwelled nutrients) at the time of settlement may affect recruitment. Within Point Hicks MNP this might result in range shifts, as warmer water species are introduced and cooler water species retreat, and an increased vulnerability to pests and pathogens. Centrostrephanus rodgersii – long spined sea urchin The range extension of the barren forming long spined sea urchin, Centrostrephanus rodgersii, has already been recorded with dramatic changes to reef assemblages in Tasmania (Johnson et al. 2011). This species is already present within Point Hicks MNP (Barton et al. 2012e) but the strengthening of the EAC and associated temperature rise may increase densities of C. rodgersii within the park. C. rodgersii is a voracious grazer and able to remove most erect vegetation including kelps, and also outcompete other large herbivorous grazers such as abalone when food is limited (Jenkins 2004). The complex interactions between species that occur following the introduction of C. rodgersii to an area are explored in more detail in a separate report that considers the scale of different processes within Victorian MPAs (Longmore 2013). Macroalgal species Macroalgal species are important autogenic engineers within the reef systems of Victoria and provide shelter, settlement habitat and food for a range of invertebrate, fish and other alga species. Impacts on kelp will have impacts on the entire assemblage that is dependent on the various functions kelp provides.
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Kelp species are sensitive to high temperature particularly during reproduction and recruitment (Bellgrove et al. 2013) and there is evidence that increased water temperature has led to extensive loss of Macrocystis pyrifera biomass and extent in Tasmania (Johnson et al. 2011) as well as range contractions at the northern distributional limits for Durvillaea potatorum , Ecklonia radiata and Phyllospora comosa (reviewed in Wernberg et al. 2011). It is considered likely that projected increases in sea surface temperatures for eastern Victoria will stress these species making them more vulnerable to other stressors (Wernberg et al. 2010) and with knock on effects on associated understorey algae, herbivorous fish, and invertebrates (Bellgrove et al. 2013). Macrocystis is considered an example of a “Maugean province” species i.e. a cooler water western species and has been included as a climate change indicator in the Subtidal Reef Monitoring Program (SRMP) (Edmunds et al. 2010). Macrocystis pyrifera has not been recorded at sites sampled as part of SRMP in the Point Hicks MNP since the 2004 survey. The SRMP has only been in place since 2001 and so there are not enough sampling occasions to determine if Macrocystis is usually present at Point Hicks MNP. However it may not be recorded in the future at this site due to increases in sea surface temperature. There are four species of red algae ( Plocamium diatatum , Porphyropsis minuta , Scageliopsis patens , Erythroneaema ceramoides ) recorded at the easterly limit of their distribution (Barton et al. 2012e) and these species are expected to contract westwards. Increases in acidification are expected to compromise the calcified structures of marine organisms and coralline algae, which is an abundant and important habitat in Victoria. Decreases in oceanic pH will also be accompanied by increases in aqueous CO 2 which will be of importance to some subtidal macroalgae as photosynthesis has been shown to be limited by dissolved inorganic carbon in certain species. Studies in South Australia found a large increase in understorey red algal turfs under future CO 2 and temperature scenarios (Russell et al. 2009). The diverse red algal understorey, which is an important component of the Point Hicks MNP reef habitat, may similarly increase.
Kelps are not predicted to be affected by the increase in aqueous CO 2 because they have functioning Carbon Concentrating Mechanisms and so the growth of these species is not limited by aqueous CO 2 concentrations (Bellgrove et al. 2013). Changes to productivity of the nearshore waters may also affect macroalgal recruitment, growth and reproduction. While there is a high uncertainty around the future of upwellings in the region, changes to the timing and delivery of nutrient rich water is likely to be reflected in the biomass, survival of recruits and contribution of individual plants to reproduction. Haliotis rubra – blacklip abalone Changes to the kelp habitat also have the potential to affect other species currently found within subtidal reef assemblages. The blacklip abalone Haliotis rubra is abundant at Point Hicks MNP and a common component of all reef habitats within the Twofold Shelf MPAs. It is a dieocious broadcast spawner with a larval duration of 3-7 days. Spawning is triggered during calm conditions when fertilisation is probably optimised and dispersal and recruitment of larvae is local (McShane et al. 1998, Huang et al. 2000). Studies in the Twofold Shelf bioregion found that H. rubra recruited to sheltered habitat including areas of dense kelp cover where current speeds were attenuated (McShane et al. 1998). Increased temperatures may also have direct effects on H. rubra and mortalities in Tasmania have been attributed to consecutive days of low wind and high temperatures (Pecl et al. 2009). Juvenile mortality has also been shown to increase at temperatures above 20°C (Russell et al. 2012) and mean summer temperatures within Point Hicks MNP are currently 19°C (Barton et al. 2012e). Laboratory experiments with abalone ( H. coccoradiata ) found that realistic future climate scenarios for temperature and pH affected larval stages as well as shell formation and growth (Byrne et al. 2011). The increased temperatures and decreased pH resulted in unshelled H. coccoradiata larvae in these experiments, a condition that prevents survival to the juvenile stage in abalone (Byrne et al. 2011). It is not known if larvae of other Haliotis species are equally sensitive or whether these types of highly sensitive species will be able to adapt to changing conditions. There is uncertainty about the effects of increasing acidification on marine organisms as experiments have shown that responses tend to be complex with some taxa negatively affected by increased acidification and aqueous CO 2 concentrations while other taxa responded positively to acidification scenarios (Klemke and Arundel eds 2013). Molluscs are expected to be one of the most vulnerable taxa however due to the fragile skeletons produced by their calcifying larvae and their calcified shells (Fabry et al. 2008, Byrne 2011). Changes to upwellings and local currents might be very important in determining the quality and quantity of drift algae (abalone feed mainly on drift algae) delivered to reef habitats within Point Hick MNP, in turn affecting competition for food with the sea urchin C. rodgersii and potentially influencing the ability of individuals to resist other stressors. One
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such other stressor might be the emergence of new diseases or pathogens not yet seen in the Twofold Shelf MPAs (see also Jenkins 2013). While there has been no conclusive evidence that attributes increased incidence of disease to climate change, there have been documented increases in disease of H. rubra (Pecl et al. 2009). A viral ganglioneuritis has been spreading in abalone populations across western Victoria although it has not been seen in abalone in the Twofold shelf bioregion, while a bacterial disease of abalone called Perkensis spp. is found in NSW. Notolabrus tetricus – blue throat wrasse Wrasse are common in all the Twofold Shelf MPAs, particularly the blue throat wrasse ( Notolabrus tetricus ) and in Point Hicks MNP the purple wrasse Notolabrus fucicola is also abundant (Edmunds et al. 2010). N. tetricus is a site attached protogynous hermaphroditic species (starts life as female and changes to male) that has been shown to be a major predator of small abalone (Shepherd and Clarkson 2001). N. tetricus has a larval stage of approximately 3 months and the population structure of this species is likely to be determined by factors operating at the early life history stages (Welsford 2003). While there is little direct information on the early life history stages of this species, changes to the EAC might be expected to affect larval recruitment in a number of ways. Larval dispersal might be affected with larvae potentially dispersed further; while increased temperatures might increase larval growth rates, reduce larval duration and mortality from predation resulting in higher recruitment (Hirst and Hamer 2013). Fish species have optimal temperature ranges for growth and survival and even short periods of temperature outside the optimal range could have significant effects on survival and distribution of larvae, juvenile and adult fish (Hirst and Hamer 2013). Increased temperature regimes may also affect the timing of spawning and time to exogenous feeding in the larvae (Welsford 2003) which may not correspond to times of peak food availability i.e. seasonal pulses of plankton ( Hirst and Hamer 2013). Juveniles of wrasse species have been shown to recruit to shallow, sheltered reef where they forage within algal beds. It is likely that this is true for N. tetricus as well and so impacts on algal cover are likely to detrimentally affect juveniles of this species. While N. tetricus has been shown to be an important predator of small abalone and able to directly impact recruitment of abalone, there is no evidence that this wrasse indirectly structures the community through a cascade effect (Shepherd et al. 2010). N. tetricus is a generalist predator and while changes to density and size structures of wrasse populations may impact abalone populations, changes to abalone populations may be less important to N. tetricus populations. Sponges Deep reef habitat in Point Hicks MNP has been described as a ‘garden of massive erect sponges, encrusting sponges and a variety of other species’ (Barton et al. 2013e). Sponges have high filtration rates and have been shown to be important in nutrient and carbon cycling (Hutchings et al. 2007). Sponge assemblages form an important coupling point between benthic and pelagic habitats and changes to phytoplankton production and nutrient delivery may be very important to survival, growth and reproduction of these animals. Increases in water temperature are likely to impact sponge assemblages with more frequent and widespread microbial mediated disease outbreaks or disruptions to symbiotic relationships considered likely (Webster and Bourne 2012). There have been a number of sponge mass mortalities in the Mediterranean that have been associated with warmer waters (e.g. Cerrano et al. 2000) and species vulnerability to increases in temperature have also been related to the associated microbial assemblage (Cebrian et al. 2011). Temperature is also important in the timing of reproduction for many sponge species (Hutchings et al. 2007). Reproductive success and recruitment may be impacted if changes in the timing of reproduction are not also accompanied by pulses of appropriate food. Certain sponge species are calcifying organisms and so are likely to be vulnerable to increases in ocean acidification (Hutchings et al. 2007).
Soft sediment habitat Open coast sandy beaches are highly mobile and variable and the impacts of sea level rise are usually hard to predict because of a lack of information on processes such as sediment supply and transport and how these interact with sea level rise and coastal morphology (DSE 2012b). However open coastal sandy beaches tend to commence recovery soon after an erosion event (i.e. a storm) as sand from the offshore bar formed during the storm is deposited onshore. Some eroded sand is permanently lost as sea level rises increase subtidal accommodation space and, under future climate change scenarios, most Victorian beaches will eventually recede (DSE 2012b). At Point Hicks
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MNP the dunes are likely to move landwards as the shore profile moves both upwards and landwards. This is unlikely to be a particular problem as Point Hicks MNP backs onto Croajingalong National Park. The change in beach profile may impact the sediment structure and, in turn, the infaunal assemblages that live there (Morris 2013). The general effects of the strengthening of the EAC, increasing acidification and changes to upwelling will be the same as described above for reef systems. The delivery of warmer, more saline waters from the EAC is likely to result in range shifts with warmer water species becoming established within Point Hicks MNP and cooler water species retreating. The exact nature of these effects is hard to predict because it will depend on the individual taxa involved and the functional roles they play in the ecosystem. Changes to upwelling events will be important to the delivery of nutrients and associated food webs within the soft sediment habitats. Infauna The infaunal assemblage of Point Hicks MNP (and the Twofold Shelf bioregion in general) has been shown to be extremely diverse and it is not known whether range shifts will have an overall effect on the biodiversity of the region. It is considered likely that increasing temperature will allow introduced or pest species to emerge that have not previously been seen in the region. In Point Hicks MNP the New Zealand screw shell, Maoriculpus roseus , has already been recorded in high densities (Heislers and Parry 2007) and is considered to be a threat to the highly diverse infauna with potential effects on structure and functioning of the soft sediment habitat of the MNP. This species has a wide temperature tolerance and depth range which will make it highly competitive in the future climate scenarios of sea level rise and temperature increase (Morris 2013). While there was equivocal evidence that the presence of M. roseus had reduced diversity within the Point Hicks MNP when sampled in 1998, this habitat has not been re-sampled recently and so longer term impacts are not known. Highly diverse ecosystems are considered likely to have a degree of resilience to stressors, in part due to a high level of functional redundancy. This means that there may be a number of different species that perform the same functional role (e.g. bioturbation / carbon cycling) and so a loss of species may not affect the overall functioning of the ecosystem. While more introductions are likely with strengthening of the EAC and increasing temperatures, it is hard to predict the outcomes of such introductions with the current state of knowledge.
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Victorian Embayments Bioregion
Background Table 10. Marine protected areas in Victorian Embayments Bioregion
Corner Inlet-Nooramunga Western Port Port Phillip Bay
Nooramunga Marine and Yaringa Marine National Park Ricketts Point Marine Sanctuary Coastal Park Corner Inlet Marine and Coastal French Island Marine National Jawbone Marine Sanctuary Park Park Corner Inlet Marine National Churchill Island Marine National Point Cooke Marine Sanctuary Park Park Shallow Inlet Marine and Coastal Park
The Victorian Embayments bioregion is a discontinuous region that includes all Victorian bays, inlets and estuaries with a minimum water area of > 1 km 2 (Commonwealth of Australia 2006; Barton et al. 2012d). Port Phillip Bay, Western Port and Corner Inlet contain marine national parks and marine sanctuaries. Marine and coastal parks, where fishing is permitted, cover large areas of Corner Inlet, Nooramunga and all of Shallow Inlet. Because these bays and inlets are geographically distinct and have unique bathymetry and hydrodynamics Western Port, Port Phillip Bay and Corner Inlet are discussed separately. Nooramunga and Shallow Inlet are grouped together with Corner Inlet because of their proximity and the continuity of habitats between Corner Inlet and Nooramunga. Embayments are generally shallow with a maximum depth generally < 20 m and some degree of water retention and because of this they experience more variable water temperatures and salinity than the open coast. They have low energy coastlines with large tides, influencing the extensive areas of subtidal and intertidal sediments (Barton et al. 2012d). Details of the natural values in marine national parks and sanctuaries in the Victorian Embayments bioregion are provided in Parks Victoria’s Marine Natural Values Study (Barton et al. 2012c,d). Habitats common to MPAs within Victorian embayments are unvegetated soft sediments and seagrass, with Corner Inlet-Nooramunga unique in Victoria in having extensive beds of broad-leaf seagrass, Posidonia australis . Mangroves (Avicennia marina subsp. australasica ) and saltmarshes are common on the fringes of Western Port and Corner Inlet- Nooramunga, but are only found in very small areas in Port Phillip Bay, most noticeably adjacent to Jawbone Marine Sanctuary. Rocky reefs occur in all MPAs in Port Phillip Bay, but tend to be low relief and small in area in Western Port. Rocky reefs are confined to a small section of Corner Inlet Marine National Park and are absent from Shallow Inlet Marine and Coastal Park. Little detail is available on reefs in Corner Inlet & Nooramunga Marine and Coastal Parks but as this is a soft-sediment-dominated system any reef would comprise a minor role in terms of overall biodiversity and ecosystem functioning. Port Phillip Bay and Western Port are influenced by Bass Strait and remotely influenced by the Leeuwin Current (LC) and Flinders Current (FC) – the LC becoming the South Australian Current (SAC) along the south coast of Australia. The SAC is a coastal current running in a predominantly eastward direction, and facilitates the transport of marine invertebrates, algae, plants and fish - such as King George whiting from South Australia towards Port Phillip Bay and Western Port. This eastward flow also transports organisms and particles arising in Port Phillip Bay to enter Western Port (Lee 2011). The East Australia Current (EAC) has some influence on Corner Inlet-Nooramunga as reflected in the warm water species (common to NSW) that occur in the MPAs in this region (Barton et al. 2013d).
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Corner Inlet-Nooramunga, Shallow Inlet
Corner Inlet-Nooramunga is a large tidal embayment consisting of a submerged plain covered by sand or mud flats, large sand islands and extensive seagrass beds (primarily Posidonia and Zostera spp.) with a radiating system of deeper channels. Mangroves, saltmarshes and permanent shallow water are other key habitats. The large area and the diversity of habitats in Corner Inlet create a highly biodiverse system supporting internationally significant populations of a number of fish, invertebrates and birds (DSEWPC 2011). The species composition of Corner Inlet MNP also results in part from the overlap of the distributions of warm water species characteristic of the NSW coast and cool water species found throughout Victoria (Barton et al. 2012d). Climate, particularly patterns in temperature and rainfall, control a range of physical processes and ecosystem functions (DSEWPC 2011). Corner Inlet Marine and Coastal Park covers most of Corner Inlet with Corner Inlet Marine National Park comprising two smaller separate sections in the south-east. Nooramunga Marine and Coastal Park extends over most of the Nooramunga complex, excluding privately owned islands and boating/shipping channels. Shallow Inlet Marine and Coastal Park encompasses a small (2,377 ha), shallow (< 6 m), tidal embayment on the western boundary of Wilsons Promontory National Park. Shallow Inlet has a single marine connection partly enclosed by a sand barrier complex of spits, bars and mobile sand dunes (CFL 1990). The inlet is tidally dominated with negligible freshwater input. The spring tidal range in Waratah Bay, in which Shallow Inlet is found, is 2.5 m (CFL, 1990). There are significant areas of seagrass and saltmarshes but no mangroves although records indicate these were historically present (Victorian Saltmarsh Study 2011). Much of the surrounding rural landscape has been heavily cleared for agricultural use.
Western Port
Western Port is a large shallow embayment with extensive intertidal mudflats, strong tidal currents and a tidal amplitude of almost 3 m. MPAs (Yaringa, French Island, and Churchill Island MNPs) contain habitats representative of the wider Western Port system - primarily vegetated and unvegetated soft sediments. Churchill Island has some small sections of reef. Predominant habitats in MPAs are seagrasses, algae, saltmarsh, mangroves, intertidal flats and deeper channels through which tidal waters drain and inundate flats (Barton et al. 2013d). Rhodolith beds and intertidal and deep subtidal reef are found outside MPA boundaries. Like Corner Inlet, the matrix of habitats creates a highly biodiverse system. Western Port is facing increased pressure from other anthropogenic stressors as a result of rapid urban expansion in the Casey-Cardinia growth area (Keough and Bathgate 2011).
Port Phillip Bay
Port Phillip Bay is a large, relatively sheltered embayment. Dominant habitats in the bay are deep central muds; in the eastern section - sandy shores, Pyura (sea squirt) beds and shallow reef habitats; and in the west - sheltered reef, seagrass, drift algae and estuarine habitats (Barton et al. 2012c). Currents in the south of the bay are primarily tidal, with wind-driven currents influencing habitats in the north. The bay has a relatively low tidal range – 0.2 m neap and 0.8 m spring tides and water retention time in excess of one year (Plummer et al. 2003, Black et al. 1993). Marine sanctuaries in the bay overlay intertidal and shallow subtidal reefs of varying form, and encompass vegetated and unvegetated soft-sediments. These are (from east to west) Ricketts Point Marine Sanctuary, Jawbone Marine Sanctuary and Point Cooke Marine Sanctuary. The coastline of Port Phillip Bay is heavily populated and these sanctuaries are located next to metropolitan areas. At the southern end of the bay and further from urban centres are four separate segments of Port Phillip Heads Marine National Park: Mud Islands, Swan Bay, Portsea Hole and Pope’s Eye.
Future Climate
Future climate projections for physiochemical conditions in Victoria have been reviewed by Mills et al. (2013) as part of the Future Climate report (Klemke and Arundel eds 2013) and are provided in the introduction of this report (Table 1). Climate change projections specific to the Victorian Embayments bioregion as identified by Mills et al. (2013) are summarised below.
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Predictions are for an increase in the mean sea level of 0.05-0.15 m by 2030 and 0.18-0.82 m by 2100. The impacts of sea level rise will be most severe in response to storm driven wave and surge events that can cause inundation and wave-induced erosion of coastlines (Church et al. 2012). The spatial pattern of 1-in-100-year storm tide heights show the highest coastal values, in excess of 2 m, occur in and around Western Port Bay (McInnes et al. 2013). Values of 1.8–2.0 m extend from just west of Port Phillip Bay to Wilson’s Promontory and Port Phillip Bay has low storm tide heights of 1.0–1.2 m (McInnes et al. 2013). It is anticipated that sea levels that presently occur during severe storms will be reached during much less extreme storm conditions in the future (McInnes et al. 2013). Modelling indicates that tidal range in Port Phillip Bay will increase slightly this century – 0.03 m higher than high tide and 0.03 m lower than low tide by 2070 (Black et al. 1990, McInnes et al. 2013). While there is currently no detailed modelling available for increased sea level on tidal propagation in Western Port and Corner Inlet it is suggested that there will be a slight reduction in tidal ranges (Mills et al. 2013). Sea surface temperature (SST) will increase by 0.5°C by 2030 in Port Phillip Bay. Victorian embayments have much higher spatial and temporal SST variability than the open ocean due to their small thermal mass and reduced rates of mixing with oceanic waters (Mills et al. 2013). Sites furthest from the Port Phillip Bay entrance - such as at Jawbone Marine Sanctuary at Williamstown - display the greatest seasonal variation in temperature (EPA 2011b). In Western Port, SST varies seasonally by 12°C and is projected to increase by 1°C by 2030 (cf 2004) (EPA 2011b). Modelling has yet to be done for 2070 and 2100 but these increases are expected to continue (Mills et al. 2013). SST in Corner Inlet varies seasonally by 12°C and while SST in Corner Inlet has not yet been modelled, it is suggested that it will be similar to the projected Western Port increase as Corner Inlet is of a similar semi-enclosed and shallow nature (Mills et al. 2013). There has been a 0.9°C rise in average land surface temperatures in Australia since the 1950s (CSIRO 2009). Air temperatures are predicted to increase by 0.6-1.5°C by 2030 and by 1-5°C by 2070 with the number of hot days over 35°C, and over 40°C, also predicted to increase (CSIRO and BOM, 2010). Salinity changes are projected to be far more pronounced in embayments than along the open coast because embayments are more susceptible to changes in run-off volumes (Mills et al. 2013). Port Phillip Bay is expected to become 0.2-3 PSU more saline compared to 2004-5 (EPA 2011b). Port Phillip Bay switched from a hyposaline (salinity 32-35 PSU) to hypersaline (salinity 36-39 PSU) system during drought years leading up to 2010 (EPA 2011b) and a similar shift is predicted under future climate (Lee et al. 2012, Mills et al. 2013). Although better flushed than Port Phillip Bay, Western Port is also predicted to increase in salinity by 2030, particularly in the north-eastern arm (EPA 2011b, Mills et al. 2013). There is no documented information on future salinity changes in Corner Inlet or Shallow Inlet. Rates of evaporation in Victoria are also expected to increase - the projected annual change by 2070 (from 1990) for the Port Phillip and Western Port region is 9% (range 2 to 17%) (DSE 2008).
Atmospheric CO 2 is absorbed by marine water bodies, increasing seawater acidity (i.e. lowering pH) and thereby restricting carbonate availability. Acidity is expected to increase in embayments with pH projected to decrease by 0.1 (2030) to 0.3 (2100) pH units. Changes in bays are expected to be more pronounced than in the ocean due to the already high variability in physical parameters in semi-enclosed, relatively shallow water bodies e.g. fluctuations in temperature and salinity (Mills et al. 2013). Wave energy is predicted to show a slight decrease in all embayments because of a reduction in the frequency of strong westerly winds, longer periods of relatively light winds and increased prevalence of easterlies (Mills et al. 2013). There are no upwelling events that directly influence MPAs in the Victorian Embayments bioregion. The main coastal currents having some influence on embayments are predicted to both strengthen (East Australian Current – Corner Inlet-Nooramunga) and slightly weaken (South Australian Current-Leeuwin Current).
Habitat vulnerabilities to Future Climate
Parks Victoria recently assessed MPAs in embayments (along with MPAs on reefs in the Central Victoria bioregion) as being most at risk of climate change as they face potentially substantial changes, primarily in sea level, storm surge, water temperature and salinity (Parks Victoria 2010). The low-relief shorelines characteristic of many embayments makes them particularly vulnerable to inundation. Within this bioregion, seagrass communities, sheltered intertidal flats including mangroves and saltmarshes, and estuaries (features reliant on freshwater flows) were identified as being at particular risk (Parks Victoria 2010).
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In the statewide vulnerability assessment (Klemke and Arundel eds 2013) all intertidal habitats were considered highly vulnerable to sea level rise, with shallow subtidal habitats less vulnerable and deep habitats having low vulnerabilities (Table 2, Bellgrove et al. 2013, Morris 2013). Saltmarsh in areas such as Jawbone MS are highly vulnerable to inundation (Figure 4) because the rate of sea level rise will exceed the rate of colonisation of new areas and because urban development at the landward edge present physical barriers to migration. While mangroves are stronger colonisers than saltmarsh species, rates of landward migration in Western Port are also reported to be below current rates of sea level rise (Boon 2011, Dittman 2011). In addition, the availability of suitable substrate for mangroves to migrate into, in Port Phillip Bay in particular, is very limited. These soft-sediment coastal habitats are particularly vulnerable to the effects of wind/waves and storm surge (DSE 2012b) and the creation of hard physical barriers can cause backwash and exacerbate erosion (Boon 2011). Innundation maps for the MPAs within the embayments bioregion are included in the Appendix (Figure 3 – Figure 14). These maps are based on simple ‘fill’ models and do not consider contextual tides, currents, or regional topography or bathymetry. Seagrass and soft sediment habitats at all depths are considered moderately vulnerable to changes to ocean currents while reefs have low vulnerability (Table 2). Ocean and coastal currents are the chief mechanism by which larvae, spores, eggs and adults are transported along the Victorian coast and into/out of embayments and are critical to connectivity of marine populations. LC (and SAC) has weakened over recent decades and this trend is predicted to continue (Mills et al. 20 13). This weakening has potential implications for connectivity of marine populations in MPAs in the bays to coastal populations, as well as possibly weakening the biological linkages between Port Phillip Bay and Western Port. Weakening of the LC also has implications for recruitment of fish such as King George whiting into seagrass beds in MPAs such as Swan Island (Port Phillip Heads Marine National Park) – larvae of this species are believed to originate around Kangaroo Island. Corner Inlet-Nooramunga is influenced by the EAC which is strengthening with warm waters from the north penetrating further south and south-east bringing new species and potentially pests.
Intertidal and shallow subtidal reef habitat are highly vulnerable to CO 2-acidification while unvegetated soft sediment habitat at all depths is considered to be highly/moderately vulnerable (Table 2). Seagrass has been assessed as having low vulnerability to increased CO 2 (Morris 2013, and see Table 2). Deep reefs were assessed as having low vulnerability to increased CO 2 and seawater acidification (Table 2, Bellgrove et al. 2013, Morris 2013). While intertidal and shallow subtidal seagrass and soft sediments are moderately vulnerable to changes in wave energy (Morris 2013), wave energy is expected to slightly decrease in embayments (Mills et al. 2013). In contrast to habitats in relatively well-mixed coastal waters, habitats in embayments are subject to variation in freshwater inputs, temperature fluctuations and evaporation because of their relatively long water-retention times and shallow depth. The average flushing time for Port Phillip Bay is in excess of one year and for Western Port is three months in the north and east, and a few days in the southwest (Lee 2011). These characteristics mean that biota in embayments experience greater extremes in temperatures and salinities than those on the open coast, and will also be subject to greater mean temperatures and salinities as a result of climate change. Increased temperatures and salinities in embayments are predicted to have significant impacts on all habitats, except for deep reefs which are assessed as having low vulnerability to increased SST and medium vulnerability to increased salinity (Table 2). Altered rainfall and runoff into marine waters is predicted to impact intertidal and shallow subtidal habitats, with low vulnerability for deep habitats. A predicted decline in annual rainfall, particularly over winter, will reduce nutrients entering embayments with implications for primary production. Episodic rainfall events will however carry large pulses of sediments and nutrients into embayments via rivers, creeks and stormwater drains. This could have negative consequences for marine biota, particularly for vegetation and sessile biota located near discharge points. It is also possible that increased nutrients may lead to increased productivity, with enhanced growth of ephemeral algae such as Ulva and possibly seagrass. Marine mammals are only transient visitors to some MPAs in the Victorian Embayments bioregion. Climate shifts in coastal bioregions are more likely to influence Victorian populations of seals, whales and other cetaceans and impacts are mainly related to shifts in prey abundance (Gill and Pirzl 2013, Table 3). General predictions for fish (finfish, sharks and rays) to climate change stressors suggest that species responses will be similar throughout Victorian marine waters. At finer taxonomic (i.e. species) (and possibly spatial) scales there may, however, be greater variation in responses with some species more resilient than others (Hirst and Hamer 2013) (Table 4). All life history stages of sharks and rays (chrondrichthyans) and finfish are vulnerable to temperature increase with varying degrees
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of vulnerability to altered currents, sea level rise, acidification and other stressors, depending on the life history stage (Hirst and Hamer 2013). There can often be an interaction between two or more threatening processes. For example, rising sea levels are likely to have a significant impact on intertidal habitats and the magnitude of this impact can be exacerbated by waves. Organisms and populations can also be affected by the interaction of climate change with non-climate related stressors such as oil spills, overfishing and toxicants. Such interactions for the Victorian marine environment have been investigated by Jenkins (2013).
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Case Study - Ricketts Point Marine Sanctuary, Port Phillip Bay
Ricketts Point Marine Sanctuary (MS) is located on the north eastern shoreline of Port Phillip Bay. The sanctuary extends 3 km longshore and approximately 450 m offshore, covering 120.6 ha. This coast is highly developed with dense residential areas inland –houses at some points are less than 100 m from the upper intertidal boundary of the sanctuary, although at an elevated level. Small sections of cliff and partially vegetated sand dunes lie landward of the high water mark boundary and beyond this is a small strip of coastal vegetation, roads and houses. The main intertidal rock platform at Ricketts Point is hard ferruginous Black Rock sandstone (DPI 2013). Sandy beaches, small areas of seagrass ( Zostera nigracualis ), subtidal sediments and subtidal reefs characterise the habitats. Concrete retaining walls run part-way along the length of the sanctuary – mainly in the northern end. Most of the sanctuary is shallow – less than 4 m depth. A slight increase in the tidal range in Port Phillip Bay of 3 cm (higher and lower) by 2070 (Black et al. 1990, McInness et al. 2013) is unlikely to have any pronounced effect on intertidal biota at Ricketts Point. This is in contrast to sea level rise which, combined with storm surge, is likely to have a significant impact on intertidal communities (Figure 1). The innundation maps are based on a simplified ‘fill’ model of land height relative to sea level. The model has a number of key limitations typical of such a model and these are the omission of contextual tides, currents, regional topography and bathymetry. Current rates of sea level rise of 3.1 mm/year (Church et al. 2012) are predicted to result in a sea level rise of 0.82 m by 2100 compared to 1990 (Mills et al. 2013). There is some uncertainty about the contribution of ice sheet melt to global sea levels and a larger rise may be possible. Climate change may lead to changes in the frequency and intensity of the meteorological drivers of storm surge. Storm tides at Ricketts Point are 1.1 m – considerably less than Western Port and the central and eastern coasts of Victoria (McInnes et al. 2013). However, an increase in the frequency of extreme storm events means a storm tide of this height could occur more frequently than every 10 years on average by 2030 (McInness et al. 2013). By 2070, climate change may result in a 1.1 m event occurring with an average recurrence interval of less than 2 years and by 2100 an event of 1.1 m may occur more than once a year (DCC 2009, McInness et al. 2013). The MS experiences episodes of lower salinities from the five stormwater drains that drain directly into the MS and the plume of the Yarra River which originates 16 km north west (Short 1996; Edmunds et al. 2011, Barton et al. 2012c) but freshwater discharges are predicted to decline under climate change scenarios (Mills et al. 2013) and the bay is predicted to shift to a hypersaline state (Lee et al. 2012). Predicted increases in salinity in Port Phillip Bay may alter the strength and direction of currents through stratification of the water column. As the sanctuary is relatively shallow (< 4 m) there is likely to be good vertical mixing within the boundaries, but currents that operate at a broader scale and carry nutrients or transport reproductive propagules (an important mechanism for connecting populations) to and from the MS may be altered (Lee et al. 2012). Wave energy at Ricketts Point is projected to decrease slightly for all periods (i.e. 2030, 2070, 2100). This is likely to occur as a result of reduction in the frequency of strong westerly winds with increased prevalence of easterly winds (Mills et al. 2013). Tidal and wind-driven currents, and to a lesser extent waves, are the main drivers of water flow in the north of Port Phillip Bay and mechanisms by which planktonic larvae of intertidal organisms are delivered onshore, bringing them into contact with suitable settlement substrates (Bertness et al. 1996). Decreasing wave energy may influence the onshore delivery of larvae, but because the reduction in wave strength is only slight in the bay, this process may remain unchanged at Ricketts Point. Currents in the north of Port Phillip Bay are largely wind driven (Harris et al. 1996) and this slight decrease in wind may lead to weakening of transport of larvae, eggs and spores from and into the sanctuary. Currents in the bay are complex and also influenced by temperature and salinity, therefore any wind-related effects need to be considered along with these factors.
Reef habitat The intertidal reef at Ricketts Point will become subtidal (Figure 1 – but note model caveats), with intertidal biota migrating higher on shore where suitable substrate exists, or is exposed through erosive processes, and where there are no physical barriers to landward migration in the form of vertical cliff faces or coastal protection structures (Bellgrove et al. 2013). Shore profiles – the spatial extent, geology and vertical relief – will determine the capacity for shoreward expansion (Bellgrove et al. 2013). Generally, the adaptive capacity of intertidal reefs in embayments to sea level rise is considered to be low because they are gently sloping and largely horizontal in aspect – and therefore
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readily submerged (Bellgrove et al. 2013). Intertidal species that have a preference for horizontal surfaces – for example some species of grazing gastropods that feed on microalgae such as Austrocochlea sp. and most algal species such as Hormosira banskii – may be disproportionately affected by the permanent submergence of horizontal rock surfaces because they are not able to survive on more vertical surfaces because water is not retained at low tide (Bellgrove et al. 2013). A decrease in the available area of intertidal reef is likely to increase inter-and intra-species competition as suitable habitat becomes limited. Coastal morphology will not stay constant under climate change with increases in mean and extreme sea levels altering the shoreline through erosion of beaches and soft cliffs (McInness et al. 2013). The cliffs at Table Rock Point for example, which are more influenced by marine processes than surface runoff (DPI 2013), are likely to experience a greater rate of erosion as a result of sea level rise and storm surge (see also Figure 1). Inland of Ricketts Point (north of Reserve Rd) is a low bluff, formerly a marine cliff of sandstone with a shore platform now covered by dunes and sand (DPI 2013). While sea level rise is likely to inundate existing intertidal reef, erosion – predominantly from marine waters - may expose this platform where it is not covered by hard artificial surfaces and structures – creating ‘new’ intertidal reef habitat for molluscs, sessile invertebrates and algae. In the supralittoral area (splash zone) of the main intertidal reef there are patches of the beaded glasswort Sarcocornia quinqueflora which will potentially experience the combined effects of increased UV, temperature and, eventually, inundation. The capacity of this small population to migrate inland depends on the rate at which comparable habitat becomes available – at this location, mildly undulating ferruginous sandstone rock platform with crevices and small pools. Saltmarsh also colonises soft sediments and has the capacity to migrate landward if the concurrent rate of sediment deposition allows (Parry et al. 2007). Species inhabiting the relatively shallow waters of Ricketts Point MS have adapted to large (approximately 14 °C) variations in sea surface temperature and average sea surface temperatures (SST) at Ricketts Point will continue to increase. Projected increases in surface temperature for Australia of 1-5°C by 2070, combined with an increase in the number of hot days will have a negative impact on the organisms inhabiting intertidal reefs through increased air and substrate temperatures. Increased temperatures will increase evaporation of rock pools and crevices - causing desiccation and mortality of intertidal algae and invertebrates at low tide. Existing rock pools may become uninhabitable for fish species such as the weedfish, Heteroclinus perpicillatus, and the dragonet, Bovichtus angustifrons. Newly settled invertebrate and algae recruits, along with juvenile life history stages, are highly vulnerable to desiccation so extreme heat events that cause large-scale mortality of young individuals may lead to a decline in population density. Subtidal reef organisms will be less affected by increased air temperatures, except in the very shallow subtidal where extreme air temperatures coincide with spring low tide (Bellgrove et al. 2013). Increased water temperature may also alter timing and magnitude of reproduction in fish, invertebrates, seagrass and algae and alter development and growth rates. An increase in salinity of Port Phillip Bay of 0.2-3.0 PSU by 2030/70 is anticipated as a result of decreased rainfall and runoff combined with increased evaporation (EPA 2011b). Salinity averages and extremes will be highest in the intertidal zone. Sedentary reef species such as algae and mat-forming invertebrates (e.g. mussels) are most at risk with possible reductions in growth and reproduction. The adaptive capacity of organisms will depend on the short and long-term osmotic tolerances of all life-history stages, and possibly through avoidance behaviours in more mobile animals (Bellgrove et al. 2013).
Increasingly acid seawater in response to dissolved CO 2 (measured as a reduction of 0.3 pH units by 2100) will potentially affect the calcification rates of coralline algae common on subtidal reef at this site (Barton et al. 2012c, Mills et al. 2013). Common species of benthic calcifiers such as limpets (e.g. Cellana tramoserica ), tube worms Galeolaria caespitosa , abalone ( Haliotis rubra ) and urchins (e.g. Heliocidaris erythrogramm ) may have reduced calcification and/or increased dissolution – impeding the formation of new calcified structures, and dissolving existing ones (Howard et al. 2012, Mills et al. 2013). Early life history stages such as eggs, larvae and juveniles of mollusc and echinoderms may be particularly vulnerable as the formation of the early shell may be disrupted. The same critical early life history stages in fish may be sensitive to both direct and indirect effects of changing seawater pH and carbonate chemistry (Hirst and Hamer 2013). Increased seawater acidity can also create physiological stress in both calcifying and non-calicifying organisms by acidifying body fluids (hypercapnia) and can lead to abnormal larval development and decrease fertilisation (Havenhand et al. 2008). In contrast, increased aqueous CO 2 may be beneficial for photosynthesising algae and other organisms, particularly subtidal algae (Bellgrove et al. 2013).
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A decline in rainfall and runoff, and shift to less frequent but heavy rainfall events is likely to have impacts on primary production and disturbance regimes (from flooding, runoff and stormwater) in the MS, but at present the effect of altered runoff regimes on biological assemblages is unclear. Less nutrients entering the system may limit algal growth, but fewer toxicants would be beneficial. Intertidal and subtidal algal species are sensitive to excessive nutrients and toxicants – with vulnerability dependent on species and their proximity to stormwater outlets. Excess nutrients tend to favour ephemeral species such as Ulva while sensitive, habitat-forming species such as Hormosira banksia in the intertidal zone and Ecklonia radiata or Sargassum -Caulerpa assemblages in the subtidal are negatively affected by excess nutrients. Poor water quality may interact with other climate factors such as increased temperatures and salinity to exert considerable physiological stress on organisms at Ricketts Point. Affected communities are likely to be less resilient to invasion by new marine pests such as the New Zealand screw shell ( Maoriculpus roseus ) or Chinese mitten crab (Eriocheir sinensis ), or may see an increase in the abundance or cover of existing marine pests such as the algae Codium fragile subsp. tomentosoides and Undaria pinnatifida which are better competitors in disturbed or sub-optimal environments (Barton et al. 2012c). Warm-water native species may also arrive at Ricketts Point and if able to establish, may alter the species composition of communities.
Soft sediment habitat Zostera muelleri is common in the intertidal soft sediment at Ricketts Point and a small amount of Zostera nigricaulis grows subtidally. As sea levels rise, the upper and lower boundaries of subtidal Z. nigricaulis may shift landwards if water quality conditions remain favourable – for example if there is no increase in the amount of suspended sediments in the water column. Z. muelleri could potentially migrate inland on soft sediments of existing beaches but may be obstructed by physical barriers such as rock walls (Morris 2013). There is little documented information on soft sediment invertebrates in the sanctuary, but rising sea levels are likely to create a general trend for lower intertidal soft sediment species to be replaced by subtidal species (Morris 2013). Depending on coastal processes and future sediment profiles, intertidal species may have the capacity to advance landwards, but as for other intertidal communities, may be prevented by solid structures and geological formations. Desiccation and die-off of intertidal seagrass and soft-sediment infauna is expected, particularly during low tide, and in warmer months (Morris 2013). For Z. nigricaulis in the shallow subtidal, temperature may affect various functions including photosynthesis, nutrient uptake and growth (Morris 2013). Infauna at Ricketts Point MS and other MPAs in embayments are at greater risk of increasing temperatures compared to those in MPAs on the open coast because they are already subject to large seasonal fluctuations in temperature (Morris 2013). This is because shallow systems have low thermal mass and reach higher temperatures than coastal waters. Zostera is relatively salt-tolerant and seagrasses can tolerate some variation in salinity although extreme variation can be detrimental (Morris 2013).
Seagrasses and soft sediment assemblages may be slightly less impacted by CO 2 effects than reef assemblages. Seagrasses may benefit through increased rates of photosynthesis, rates that may be further enhanced by increases in temperature (Morris 2013). Certain groups within soft sediment habitats such as bivalves and crustaceans that make up a large proportion of the biomass in soft sediments at Ricketts Point MS will likely be affected to the same extent as rocky reef species. The predicted average decrease in rainfall and runoff of 26% by 2060 in embayments is expected to be greatest in Port Phillip Bay and this reduction in overall runoff will reduce the total volume of freshwater and nutrients entering the sanctuary. Increased rainfall intensity is predicted during storms (Mills et al. 2013). A shift from regular but small volumes of runoff to periodically large volumes may be expected to drive changes in the intertidal and shallow subtidal habitats at Ricketts Point but it is difficult to predict how this may manifest in terms of habitat cover or species abundance (Bellgrove et al. 2013, Morris 2013). There are five stormwater drains that empty into the sanctuary (Barton et al. 2012c). Currently freshwater runoff, phytoplankton blooms and disturbance of nearby fine sediments frequently create turbid conditions in this MS (Barton et al. 2012c). Large volumes of stormwater entering the sanctuary in intense pulses during storm events are likely to carry high amounts of freshwater, nutrients, pollutants and sediments (Melbourne Water 2005). Seagrass and infaunal assemblages can be negatively affected through smothering by sediments, excessive growth of epiphytes (seagrass) from nutrient enrichment and toxicity from pollutants. There will be longer periods between rain events (Melbourne Water 2005) in which time water quality is likely to improve and potentially provide some opportunity for habitat recovery. Lower sediment and toxicant levels
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entering the system as a consequence of a reduction in mean runoff may therefore be beneficial to seagrass within Ricketts Point MS and in other seagrass beds in the north of the bay (Bellgrove et al. 2013, Morris 2013).
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Figure 1. Inundation map for Ricketts Point Marine Sanctuary based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry.
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Case Study - Yaringa Marine National Park, Western Port
Yaringa Marine National Park (MNP) is a soft-sediment-dominated system comprising significant areas of intertidal and subtidal seagrass, unvegetated soft sediments, mangroves and saltmarsh. Sparse to medium Zostera muelleri grows down to the shallow subtidal while Zostera nigricaulis grows deeper in the channels – these channels extending down to 12 m (Barton et al. 201d). Mapping has shown that seagrass cover in Yaringa MNP continued to decrease between 1999 and 2009 since losses were first observed in Western Port in the 1970s-80s (Walker 2011). Banks are comprised of fine sediments while sand is found on the shore and bottom of channels (Barton 2012d). The mangrove, Avicennia marina subsp. australasica grows on the shallow subtidal/intertidal zone - the only mangrove species occurring in Victoria. Corner Inlet is the southern-most distribution for this species. Saltmarsh communities lie on the landward side of mangroves and are comprised of shrubs (e.g. Tectincornia arbuscula , T. pergranulata , T. halocnemoides ), grasses (e.g. Austrostipa stipoides ) and herbs (e.g. Sarcocornis quinqueflora ) (Boon et al. 2010). Over 31 macroinvertebrate species live in the vegetated and unvegetated intertidal mudflats of Yaringa MNP (Butler and Bird 2010). Global sea level rises of up to 0.82 m are predicted by 2100 (Mills et al. 2013). Mean sea level rises of 0.17 m and 0.49 m have been projected for Western Port by 2030 and 2070 respectively (WPGA 2008) however, predicted extremes are in excess of these heights and are likely to have the greatest impact (Boon 2011) (Figure 2 – note the model caveats associated with inundation maps). Astronomical tides under future climate conditions are yet to be modelled for Western Port, but it is suggested there will be a minor decrease in tidal range (Mills et al. 2013). The impacts of sea level rise will be most severe in response to storm-driven wave and surge events that can cause inundation and wave-induced erosion of coastlines (Church et al. 2012). The coastal and shallow marine habitats around Western Port are particularly vulnerable to storm surge when compared to the open coast or Port Phillip Bay (Mills et al. 2013). The spatial pattern of 1-in-100 year storm tide heights show the highest coastal values, in excess of 2 m, occur in and around Western Port (McInnes et al. 2013). The frequency of 1-in-100 storm surge tidal heights is predicted to increase to 1-in-10 years by 2030 (McInness et al. 2013). By 2070, climate change may result in a tidal storm heights occurring on average less than 2 years apart (DCC 2009, McInness et al. 2013). The juxtaposition of diverse habitats in Western Port is thought to underpin the high levels of animal and plant biodiversity in Western Port, therefore any alteration or loss of habitat is likely to have flow on effects to species and communities.
Seagrass habitat Under future climate scenarios, intertidal seagrass may experience elevated air temperatures, heat stress and desiccation, particularly where spring low tides coincide with hot spells (Mills et al. 2013). This may exacerbate the loss of seagrass that has already occurred in Yaringa MNP and wider Western Port (Walker 2011). Seagrass in the shallow subtidal is likely to be reasonably tolerant to increases in mean temperature, but vulnerable to the effects of temperature extremes. Vegetated and unvegetated soft-sediment banks lie seaward of the shoreline in Yaringa MNP and are characteristic of much of Western Port. The banks are bifurcated by tidal channels and the upper banks are exposed at low tide. Seagrass on the tops of banks and intertidally may persist, be lost or alter in species composition as a result of sea level rise and temperature increase. The persistence of seagrass on the tops of banks (mainly Zoster muelleri ) may depend on whether sediment accretion keeps pace with sea level rise (no net loss of intertidal banks) or if sea level rise is greater than the rate of sediment deposition (more likely under upper limit climate change projections). Under the latter scenario current intertidal habitat may become permanently submerged, except perhaps at spring low tides (see also Figure 2 but note model caveats). Permanent inundation of existing intertidal areas may mean Z. muelleri is replaced by Z. nigricaulis which tends to grow subtidally. Intertidal seagrass may persist by extending landwards, but may be vulnerable to increased temperature and solar radiation which can burn leaves. Seagrass habitat that is directly in front of mangrove stands will not be able to colonise new areas if mangroves do not retreat at the seaward edge (Lovelock and Elllison 2007, Morris 2013). Sea surface temperature increase will be greater and more variable in Western Port compared to the open coast, with mean temperatures expected to increase by 1°C by 2030 (Mills et al. 2013). While warmer temperatures can enhance photosynthetic rates in seagrasses there is a concurrent increase in respiration rate up to a point where respiration exceeds photosynthesis. This leads to a net decrease in photosynthesis at higher temperatures (Lee et al. 2007, Morris
2013). At the same time, elevated CO 2 may also increase photosynthesis in seagrass (Morris 2013), making the net outcome of these interactive effects difficult to predict. Temperature is likely to cause phenological shifts in seagrass, for example by altering the timing and duration of flowering. Elevated temperatures may also cause a shift in community composition in seagrass meadows, with possible losses of cool water species at the northern edge of their range. An increase in the severity and frequency of storm surge events may cause direct disturbance to seagrasses. In addition to damaging plants and resuspending existing sediments, storms may also be accompanied by large volumes of rain, which is likely to exacerbate turbidity around Yaringa MNP, through sediment input (erosion and runoff). Sediments are
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known to be detrimental to seagrasses by blocking light and reducing photosynthesis. The tolerance of seagrass to climate change stressors varies amongst species, and while intertidal Z. muelleri grows relatively rapidly compared to other Victorian species it is vulnerable to smothering by sediments (Morris 2013). Common fish species inhabiting subtidal seagrass in Yaringa MNP include yellow eye mullet Aldrichetta forsteri and smooth toadfish Tetractenos glaber . Other species include the common galaxid Galaxias maculatus , short fin eel Anguilla australis , tupong Pseudaphritis urvillii , black bream Acanthopagrus butcheri and a number of gobies (Warry and Reich 2010). Bony fish such as these, along with cartilaginous fish such as sharks and elephant fish are thought to be highly vulnerable to temperature change (Parks Victoria 2005, Hirst and Hamer 2013). Larvae of bony fish are particularly vulnerable. Warmer waters may cause range shifts in adult fish, increase development rates in larvae with implications for dispersal/recruitment, and decrease the amount of dissolved O 2 available for critical metabolic functioning (Parsons et al. 1984). Temperature can interact with other effects such as acidity (from increased atmospheric CO 2) and salinity to cause a decline in survival rates of fish larvae and eggs. Increased seawater acidity from an increase in CO 2 may affect development of eggs and larvae in bony fish, but adult fish are considered to be relatively robust to acidification compared to calcifying invertebrates such as molluscs (Howard et al . 2012). A lack of research means that specific climate change predictions cannot be made for most fish species in Yaringa MNP, or elsewhere in Victoria, and it is possible that some species may have the capacity to acclimate to gradual change.
Mangrove habitat While sediment accretion may potentially be negative for intertidal seagrass, this same process is thought to be beneficial to mangroves because it provides more habitat for colonisation. Mangroves in sediment-rich estuaries may be the most resilient to the effects of climate change (Morrisey et al. 2010, Boon 2011, Dittman 2011). Mangroves in Yaringa showed some recovery following early clearing of existing mudflats as sediment accretion at the seaward edge of the mangroves allowed seedlings to grow (Dittman 2011). The adaptive capacity of mangroves to sea level rise in Yaringa MNP depends on the continued sediment accretion and maintenance of surface elevation relative to sea-level rise, together with landward retreat options (Boon 2011). Warmer weather may enhance seedling growth and survival (Morrisey et al. 2010) . Populations of gastropods, barnacles, and mussels that live on the trunks and pneumatophores of mangroves would benefit from an increase in the amount of habitat, although specific studies of the flora and fauna found in the Mangrove Shrublands of Yaringa MNP have not been conducted (Barton et al. 2012d). It is predicted that the current sedimentation rate in Western Port (1.4-2.5 mm/yr) will not be sufficient to sustain mangroves under worst-case scenario projections of sea-level rise of 2-8 mm/yr predicted for this century (Morrisey et al. 2010, Dittman 2011). Where sedimentation or sediment resuspension reach excessive levels it may begin to have a negative effect on growth and survival of mangroves, resulting in dieback (Morrisey et al. 2010, Dittman 2011). In addition, erosion of mangroves on the seaward boundary and backwash from any mitigation structures such as sea walls could lead to a rapid loss of mangroves (Dittman 2011).
Saltmarsh habitat To date, saltmarshes have been progressively lost around the western and northern shores of Western Port because of the expansion of agriculture, industry and, more recently, urbanisation. Saltmarshes in Yaringa MNP are likely to be very vulnerable to sea-level rise (Figure 2) and other consequences of climate change– especially rising air and water temperature (Boon et al. 2010). In theory sediment accretion would be beneficial to saltmarsh where sediments accumulate above the average height of neap tides (Morrisey 1995, Boon 2011). Mangroves in Western Port have, however, been moving into saltmarshes while at the same time saltmarshes have decreased in area (albeit at a lower rate) (Rogers et al. 2005b, 2006, Dittman 2011). Although landward sediment deposition is occurring around Yaringa MNP – for example on the shore of Quail Island - there has been no net increase in the elevation of saltmarsh and as a consequence, rising sea levels would increase the inundation frequency of saltmarshes and promote upslope mangrove expansion (Rogers et al. 2006). Landward expansion of saltmarsh is also limited by adjacent land use, and current human population growth in the Western Port region may limit any capacity for migration of saltmarsh as existing available land may be developed (Boon 2011). Higher ambient temperatures as a result of climate change (Mills et al. 2013) may affect saltmarsh phenology, growth, investment in reproduction, lifespan and interactions with other species (Boon 2011). Increased atmospheric CO 2 may favour some saltmarsh species over others and thus lead to a change in species composition within saltmarsh communities in Yaringa MS (Boon 2011).
Unvegetated soft sediment habitat Storm surge and sea level rise may impact soft sediment communities (Figure 2) through disturbance, alterations to sediment profiles and habitat loss. Intertidal and shallow subtidal soft sediment habitats and associated biological communities in Yaringa MNP are at risk from physical disturbance from storm-driven wave and surge events which will
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become increasingly frequent as a result of climate change. Storms can resuspend both the sediment and the animals that live there (Morris 2013). The predicted decrease in the total volume and frequency of freshwater entering Yaringa from Watsons Creek, Langwarrin Creek and Cannons Creek, combined with increased evaporation from elevated temperatures is expected to increase salinity in Yaringa MNP. Waters in the MNP are already seasonally variable (2-3 PSU on a background of 35 PSU) and under periods of low rainfall salinity in northern Western Port can reach 40 PSU (Two Bays 2007, Mills et al. 2013). Depending on their tolerance threshold, organisms such as the ghost shrimp Biffarius arenosus , polychaete worms Barantolla lepte , the sentinel crab Macrophthalamus latifrons and fish such as the common galaxid, Galaxias maculatus , may cope with the increase in salinity or become less prevalent inside the MPA. Reduced water flow from surrounding creeks, in particular Watsons Creek, may enhance the health of infaunal assemblages due to the high nutrient levels and pesticides currently found in these creeks (O’Brien A., CAPIM, pers. comm.). Butler and Bird (2010) found that the organic content, grain size, temperature and redox potential of the sediment influence the community composition of the mudflat macroinvertebrates in Yaringa MNP (Barton et al. 2012d). Increased temperatures in Western Port may therefore alter the types of infaunal species that occur here. Greater and more variable temperature and salinity can stress animals and plants and make them more vulnerable to other biotic pressures such as predation, competition, pests and disease. Species such as the introduced bivalve mollusc Musculista senhousia , have already been found in Yaringa MNP (Butler and Bird 2010). Other species of concern include the Northern Pacific seastar Asterias amurensis , found at the eastern entrance to the bay in 2011, the European fan worm Sabella spallanzanii and broccoli weed Codium fragile subsp. fragile which is already well established in the southern region of Western Port (Parks Victoria 2003).
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Figure 2. Inundation map for Yaringa Marine National Park based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry.
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Acknowledgements
The staff at the Victorian Environmental Assessment Council, and most particularly Dr Jo Klemke, are thanked for the guidance and information they provided for this report. Thanks to staff at Parks Victoria (particularly Steve Shelley and Dale Appleton) for providing inundation maps and advice regarding their interpretation. Thanks also to Dr. Andy Longmore for his peer review of this document.
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Appendix 1 – Innundation Maps
Innundation maps for the majority of the MPAs in the Victorian embayments bioregion are included here and predict average sea level and storm tide levels for 2100. These maps are based on a simplified ‘fill’ model of land height relative to sea level. The model has a number of key limitations typical of a simple bathtub model and these are the omission of contextual tides, currents, regional topography and bathymetry. Due to a lack of information regarding intertidal or shallow subtidal habitat at a relevant scale, inundation maps have not been included for the other bioregions.
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Figure 3. Inundation map for Point Cooke Marine Sanctuary based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry.
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Figure 4. Inundation map for Jawbone Marine Sanctuary based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry.
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Figure 5. Inundation map for Swan Bay north based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry.
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Figure 6. Inundation map for Swan Bay south based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry.
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Figure 7. Inundation map for Churchill Island MNP based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry.
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Figure 8. Inundation map for French Island east based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry.
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Figure 9. Inundation map for French Island west based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry.
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Figure 10. Inundation map for Nooramunga Marine and Coastal Park west based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry.
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Figure 11. Inundation map for Nooramunga Marine and Coastal Park central based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry.
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Figure 12. Inundation map for Nooramunga Marine and Coastal Park east based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry.
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Figure 13. Inundation map for Shallow Inlet Marine and Coastal Park based on a simplified ‘fill’ model of land height relative to sea level. Key limitations are the omission of contextual tides, currents, regional topography and bathymetry.
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Minerva Access is the Institutional Repository of The University of Melbourne
Author/s: MORRIS, E; Bathgate, R
Title: VEAC MArine Investigation. Potential impacts of climate change on Victoria's marine protected areas.
Date: 2014
Citation: MORRIS, E. & Bathgate, R. (2014). VEAC MArine Investigation. Potential impacts of climate change on Victoria's marine protected areas.. Victorian Government Department of Environment and Primary Industries.
Persistent Link: http://hdl.handle.net/11343/91885
File Description: Published version