1 Posidonia australis seagrass meadows of the Manning – Hawkesbury ecoregion 2 3 1. Description of the ecological community 4 1.1 Name of the ecological community 5 This advice follows the assessment of a public nomination to list the ‘Posidonia australis 6 seagrass beds’ as a threatened ecological community under the EPBC Act. 7 8 Posidonia australis is a sub-tidal meadow-forming seagrass species. The northernmost limit to 9 the distribution of P. australis on the east coast of Australia is Wallis Lake. Its distribution then 10 extends around the southern half of Australia to Shark Bay on the west coast encompassing 11 significant ecological and biogeographic variation. Given the close links between biodiversity 12 and the underlying abiotic drivers, the definition of the ecological community has been focused 13 on the assemblage of plants, animals and micro-organisms associated with seagrass meadows 14 dominated by Posidonia australis occurring in the temperate Manning Shelf and Hawkesbury 15 Shelf bioregions (IMCRA v4.01). Spalding et al. (2007) consider the Manning Shelf and 16 Hawkesbury Shelf bioregions to be a single ecoregion based on relative homogeneous species 17 composition and clear distinction from adjacent systems. 18 19 It is recommended that the ecological community be named Posidonia australis seagrass 20 meadows of the Manning-Hawkesbury ecoregion (hereafter referred to as the ecological 21 community). The name best describes the dominant component, structure and location 22 characterising the ecological community. 23 24 1.2 Location and physical environment 25 The ecological community occurs mostly within the sheltered environments of permanently 26 open estuaries along the warm temperate New South Wales coastline, from Wallis Lake (32°S) 27 to Port Hacking (34°S). The ecological community occurs wholly within the Manning Shelf 28 and Hawkesbury Shelf bioregions (IMCRA v4.0). Posidonia australis dominated seagrass 29 meadows occurring around islands within the geographic range are also included within the 30 ecological community. 31 32 The ecological community typically occurs in subtidal waters where salinity is close to marine ◦ 33 levels (30-50 /◦◦) (Meehan, 2001), dropping only for short periods following rainfall, at depths 34 ranging less than 1m to 10 m on sand and silty mud substrate (Cambridge and Kuo, 1979; 35 West, 1990). The ecological community is absent from brackish water (i.e. hyposaline) 36 conditions such as in coastal rivers and intermittently open lagoons. The ecological community 37 is known to occur at the following locations: Wallis Lake; Port Stephens; Lake Macquarie; 38 Brisbane Water; Hawkesbury River; Pittwater; Port Jackson (Sydney Harbour); Botany Bay; 39 Port Hacking (Creese et al., 2009); and in the lee of Broughton Island (West et al., 1989). 40 41 1.3 Vegetation 42 The ecological community occurs as almost pure stands of Posidonia australis (monospecific 43 meadows) or multispecies meadows (eg. P. australis, Zostera capricorni, Halophila ovalis) 44 dominated by P. australis. P. australis is a slow growing, long lived seagrass species, with 45 persistent rhizomes and is meadow-forming (Cambridge and Kuo, 1979). Its fronds can grow to 46 over 80 cm long and as much as 90% of the mass of the P. australis plant may be in the roots 47 and rhizomes (Keough and Jenkins, 1995). 48
1 Integrated Marine and Coastal Bioregionalisation of Australia Version 4.0 (Commonwealth of Australia, 2006).
1 The spatial structure of the ecological community is highly variable with meadows ranging 2 from nearly continuous to highly fragmented meadows arranged into a mosaic of discrete 3 patches. Areas of bare sand or other seagrass species that occupy edges, blowouts2 and small 4 areas of meadows (Kirkman and Kuo, 1990) are common in both continuous and patchy3 5 meadows of the ecological community. In some cases, sparse meadows of the ecological 6 community may have an understorey of smaller seagrass species (e.g. Halophila ovalis). The 7 macrophyte, Ruppia, is also found growing within the ecological community (Creese et al., 8 2009). 9 10 The wide, strap-like leaves of Posidonia australis provide substrate for the establishment of a 11 diverse assemblage of benthic flora, in the form of micro and macro epiphytes4 and algae and a 12 complex layer of periphyton5 (Klumpp et al., 1989; Keough and Jenkins, 1995; Carruthers et 13 al., 2007). The epiphytes and some components of the periphyton can photosynthesise and 14 contribute significantly to the overall primary production of the seagrass community. The 15 amount of cover of epiphytes on the seagrass depends largely on the nutrients available in the 16 water – generally, more nutrients means more epiphytes. 17 18 1.4 Fauna 19 The ecological community provides habitat, shelter and food for a large diversity and 20 abundance of fauna. Posidonia australis is generally considered to provide the greatest habitat 21 structure of any of the seagrass species found in New South Wales (Middleton et al. 1984; Bell 22 and Pollard, 1989; Creese et al., 2009). The P. australis fronds and rhizome matte provide a 23 stable substratum for the establishment of animals as epifauna and infauna, which in turn 24 support higher food chains (Walker et al., 1991) directly as a food source or via detritus 25 formation. 26 27 The macro-benthic fauna of the ecological community is dominated by polychaetes, 28 crustaceans and molluscs (Collett et al., 1984). These faunal groups process a significant 29 portion of the primary production of the ecological community, and provide an important food 30 resource for larger crustaceans, fish and birds. Common polychaetes include Armandia 31 intermedia, Barantolla lepte, Ceratonereis mirabilis, Eunice australis, Mediomastus 32 californiensis, Neanthes cricognatha, Notomastus torquatus, Onuphis sp., Prionospio 33 aucklandica, Prionospio cirrifera. Common crustaceans include Ampelisciphotis sp., 34 Amphithoe sp., Birubius sp., Cyamodus sp., Macrobrachium intermedium, Tethygeneia sp.. 35 Common molluscs include Anadara trapezia, Mysella sp. and Wallucina assimilis. Other 36 invertebrate taxa associated with the ecological community include sea anemones and 37 nemerteans (Collett et al., 1984). 38 39 The epibenthic fauna of the ecological community includes larger, often predatory, fish and 40 crustaceans. The majority of epibenthic fauna associated with the ecological community only 41 use it for a small part of their life history, as a temporary foraging area or refuge from 42 predation. The ecological community provides nursery habitat to the commercially important 43 Acanthopagrus australis (yellowfin bream), A. butcherii (black bream), Mugil cephalus (sea 44 mullet), Girella tricuspidata (luderick) (Burchmore et al., 1984; McNeill et al., 1992; West and 45 Jones, 2001). The most commonly sampled fish associated with the ecological community are
2 A blowout is an area in a seagrass meadow denuded of seagrass through natural or anthropogenic disturbance. Blowouts are typically areas of instability in sediment movement, shape and size and seagrass species composition (Kirkman, 1985). 3 Patchiness in meadows often reflects processes of recovery from disturbances, natural and human induced, as well as the particular hydrodynamic conditions of the seagrass habitat (Duarte et al., 2006). 4 Epiphytes are larger algae that grow on seagrass fronds (Keough and Jenkins, 1995). 5 Periphyton is a thin layer of microscopic organisms such as bacteria and single-celled plants which colonise exposed areas of the seagrass (Keough and Jenkins, 1995). 2
1 from the families Syngnathidae (including the protected Phyllopteryx taeniolatus (weedy 2 seadragon)), Clupeidae, Latridae, Monacanthidae (leatherjackets), Gobiidae (gobies), 3 Kyphosidae, Hemiramphidae and Mugilidae (Evans et al., pers. comm., 2014). 4 5 The ecological community also provides important foraging habitat for the NSW listed 6 endangered population of Eudyptula minor (little penguin) at Manly (Manly Council, 2009). 7 8 1.5 Key diagnostic characteristics and condition thresholds 9 National listing focuses legal protection on remaining patches of the ecological community that 10 are most functional, relatively natural (as described by the ‘Description’) and in relatively good 11 condition. Key diagnostic characteristics and condition thresholds assist in identifying a patch 12 of the threatened ecological community, determine when the EPBC Act is likely to apply to the 13 ecological community and to distinguish between patches of different quality. The ecological 14 community may exhibit various degrees of disturbance and degradation. This degree of 15 degradation has been taken into account in developing the condition thresholds. 16 1.5.1 Key diagnostic characteristics 17 The key diagnostic characteristics presented here summarise the main features of the ecological 18 community. These are intended to aid the identification of the ecological community, noting 19 that a broader description is given in the other sections. Key diagnostic characteristics for 20 describing the ecological community are: 21 Occurs from Wallis Lake (32◦S) to Port Hacking (34°S) within the Manning Shelf and 22 Hawkesbury Shelf bioregions (IMCRA v4). 23 Occurs in shallow subtidal coastal waters (<10 m) in locations with protection from 24 high wave energy, typically, permanently open estuaries. 25 Consists of seagrass meadows6 >1 ha and dominated7 by Posidonia australis. 26 Occurs on sand or silty-mud substrate. 27 28 1.5.2 Condition thresholds 29 Condition classes and thresholds provide guidance for when a patch of a threatened ecological 30 community retains sufficient conservation values to be considered as a Matter of National 31 Environmental Significance, as defined under the EPBC Act. This means that the referral, 32 assessment and compliance provisions of the EPBC Act are focussed on the most valuable 33 elements of the ecological community. Very degraded patches that do not meet the condition 34 thresholds will be largely excluded from national protection. However, it is recognised that 35 patches that do not meet the condition thresholds may still retain important natural values and 36 may be protected through State and local laws or schemes. Therefore, these patches should not 37 be excluded from recovery and other management actions. Suitable recovery and management 38 actions may improve these patches to the point that they may be regarded as part of the 39 ecological community fully protected under the EPBC Act. With respect to the ecological 40 community, management actions should, where feasible, aim to restore patches to at least meet 41 the good condition thresholds outlined below. 42 43 44 45
6 Seagrass meadow - a spatially contiguous area of seagrass of varying percent cover composition ranging from nearly continuous to highly fragmented and arranged into a mosaic of discrete areas of seagrass. 7 Dominated - >50% of total seagrass cover. 3
1 Good condition categories and thresholds (minimum condition) 2 Meadow Size
Small (≥1 ha) Moderate (≤10ha) Large (>10ha)
Percent seagrass >50% >30% >20% cover of total meadow area
and and and
Minimum shoot8 100 shoots/m2 25 shoots/m2 10 shoots/m2 density of Posidonia australis 3 4 5 1.5.3 Further information to assist in determining the presence of the ecological community 6 and significant impacts 7 8 Patch definition 9 A patch of the ecological community is defined as a Posidonia australis dominated seagrass 10 meadow9. The edge of the seagrass meadow is defined as the edge of the contiguous seagrass 11 cover. A patch (i.e. a meadow) may include bare area or substrate (e.g. sand) or small scale 12 disturbances such as boat mooring and propellar scours or blowouts that do not substantially 13 alter the overall functionality of the meadow. Functionality here refers to ecological processes 14 such as the movement of fauna, dispersal of plant propagules, provision of food, habitat 15 attributes such as refuge or nursery function, and sediment stabilisation, all of which can 16 operate at small to large scales. Where a meadow does not meet the minimum good condition 17 thresholds it is not considered part of the ecological community for EPBC Act purposes. 18 19 Timing of surveys 20 Identifying the ecological community and its condition is possible at most times of the year, 21 however, consideration must be given to the role that season and disturbance history may play 22 in an assessment. For example, the ecological community exhibits seasonality of growth, with 23 maximum growth occurring during the spring and summer. In the autumn and winter, much of 24 this growth dies and is broken off. Severe storms or flooding may also cause loss of seagrass 25 leaves, leaving only the rhizome layer or a few leaves. 26 Timing of surveys should provide for a reasonable interval after a substantial disturbance 27 (natural or human-induced) to allow for regeneration of Posidonia species to become evident, 28 and be identified. 29
8 Shoot: a structure comprising one to multiple leaves/fronds with a surrounding sheath at the base. 9 Seagrass meadow: a spatially contiguous area of seagrass of varying percent cover composition ranging from nearly continuous to highly fragmented (naturally and /or due to disturbance) and arranged into a mosaic of discrete areas of seagrass (such that areas of seagrass occur within reasonable proximity that they may act as a functional unit). 4
1 Buffer zones 2 Buffer zones enhance protection of a patch by avoiding or minimising potential disturbance 3 from surrounding land and sea uses or activities. While the buffer zone is not formally part of 4 the ecological community, it should be taken into account when considering likely significant 5 impacts during EPBC Act decision-making. 6 7 It is recommended that an appropriately sized buffer zone be applied from the outer edge of a 8 patch. The size of the buffer zone should increase with increasing intensity and likely impact 9 of threat. The impact of a threat on the ecological community will vary with the activity type. 10 Impacts of some activities are localised, for example, the damage caused by boat propellers and 11 moorings. To avoid localised impacts, a buffer zone of 50 metres is encouraged. Impacts from 12 other activities can occur kilometres away in the case of plume generation from dredging or 13 changed hydrology due to sea wall construction. In such circumstances an appropriate buffer 14 zone may be in the order of several kilometres. With regards to dredging activities, the 15 application of buffer zones should be in line with national and state guidelines on dredging 16 activities. 17 18 Rehabilitation 19 The ecological community can take decades to recover after major disturbance and frequently 20 the loss of the ecological community can lead to irreversible changes in the nature of the 21 environment and habitat, preventing the recovery of the ecological community (Seddon, 2004). 22 Significant efforts to restore the ecological community have been made, with some project 23 scale successes (Meehan and West, 2000; Wear, 2006). However, timeframes for recovery are 24 long (>20years). 25 While seagrass rehabilitation methods have improved significantly over the past twenty years, 26 no effective restoration strategies on ecologically significant scales (km2) have been 27 demonstrated (Wear, 2006). Therefore, the primary strategy for achieving the conservation 28 objective for this ecological community is to avoid further loss of the ecological community. 29 30 Other significance considerations 31 In the context of actions that may have ‘significant impacts’ and require approval under the 32 EPBC Act, it is important to consider the surrounding environment and seascape context of 33 patches that meet the condition thresholds. The following indicators should be considered when 34 assessing the impacts of actions or proposed actions under the EPBC Act, or when considering 35 recovery, management and funding priorities for a particular meadow: 36 Large meadow and/or large area to boundary ratio – larger area/boundary ratios are less 37 exposed and more resilient to edge effect disturbances. 38 Meadows with minimal evidence of disturbance. 39 Good faunal habitat as indicated by medium density seagrass cover, refuge and contribution 40 to movement corridors. 41 Presence of listed threatened or migratory species. 42 Connectivity to other meadows or marine habitats. In particular, a meadow in an important 43 position between (or linking) other meadows/habitats in the seascape including meadows of 44 the ecological community that are outside the minimum meadow size (taking into account 45 that connectivity should aim to not exacerbate the incidence or spread of threats e.g. 46 invasive species). 47 Minimal invasive species or where these can be managed easily.
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1 Remaining meadows in areas where the ecological community has been otherwise heavily 2 degraded. 3 At the edge of the range of the ecological community. 4 Unique variants of the ecological community. 5 6 Area critical to the survival of the ecological community 7 Areas that meet the key diagnostic characteristics and condition classes are considered critical 8 to the survival of the ecological community. Adequate light for photosynthesis is of critical 9 importance to the survival of the ecological community. Therefore, also critical to the survival 10 of the ecological community is the water column above the ecological community being of a 11 quality adequate for photosynthesis. 12 Additional areas such as adjoining habitats and a minimum 50 metre buffer zone, and areas that 13 meet the description of the ecological community but not the condition thresholds are also 14 considered important to the survival of the ecological community. 15 16 Geographic extent 17 Until more recently, the classification and mapping of seagrass habitat has not been undertaken 18 to the species or genus level. Consequently, an estimate of the former extent of the ecological 19 community is not available. However, historical aerial photography and field observations 20 indicate that the ecological community once had a much wider distribution near highly 21 urbanised and industrialised coastlines (eg. Larkum and West, 1990; Meehan, 2001) and the 22 most significant losses in the ecological community occurred before the 1980s (Creese et al., 23 2009) when the first comprehensive investigation of NSW estuaries was done and maps produced 24 showing the cover of seagrass, mangrove and saltmarsh (West et al. 1985). For example, in Botany 25 Bay between 1942 and 1984, the ecological community is estimated to have declined more than 26 50% (Larkum and West, 1990). 27 28 While changes in resource use and improved management of estuarine environments over the 29 last decade have improved conditions for Posidonia australis growth, surveys of seagrasses in 30 New South Wales conducted in 1985 (West et al., 1985) and 2005 (Creese et al., 2009) show 31 marked declines in the extent of the ecological community at some locations. For example, 32 suspected losses of approximately 25% in Wallis Lake, 50% in Lake Macquarie and 30% in 33 Brisbane Water (Creese et al., 2009). Further, aerial imagery captured since late 2009-early 34 2010 of Lake Macquarie, Pittwater, Sydney Harbour, Botany Bay and Port Hacking show 35 losses of meadow area in ecological community of between 30-50% (Evans et al., pers. comm., 36 2014). 37 38 Based on mapping by Creese et al. (2009), the current extent of the ecological community is 39 estimated to be 13 km2. However, the real extent of the community is likely to be much less 40 than this given estimates of more recent decline in the ecological community (Evans et al., pers. 41 comm., 2014). In addition, there are many instances where quite substantial bare patches occur 42 within meadows of the ecological community, often as a consequence of human activities such 43 as the installation of boat moorings. For example, it has been estimated that of the 99 ha of the 44 ecological community occurring in Lake Macquarie, at least 6 ha has been lost due to scouring 45 by boat moorings (Wright et al., 2013). 46
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1 1.9 National context and other existing protection 2 1.9.1 Bioregional distribution 3 The ecological community occurs in the Manning Shelf and Hawkesbury Shelf meso-scale 4 bioregions (IMCRA v4.0). 5 6 1.9.2 Other existing protection 7 Seagrasses are protected in New South Wales under the New South Wales Fisheries 8 Management Act 1994 (FM Act) as fish habitat. However there is no power within 9 habitat protection plans to control catchment development that may cause a decline in the 10 health of Posidonia australis (Meehan and West, 2002). 11 Posidonia australis populations in Port Hacking, Botany Bay, Sydney Harbour, Pittwater, 12 Brisbane Waters and Lake Macquarie are listed under the FM Act as ‘endangered 13 populations’ due to ongoing threats leading to a very high risk of extinction in the near 14 future (NSW FSC, 2010). 15 The ecological community occurs within the boundaries of 16 - aquatic reserves established under the FM Act (eg. Towra Point Aquatic Reserve and 17 North Harbour Aquatic Reserve); 18 - Port Stephens-Great Lakes Marine Park established under the New South Wales Marine 19 Parks Act 1997; 20 - marine areas of national parks and nature reserves (eg. Royal National Park and Towra 21 Point Nature Reserve) established under the New South Wales National Parks and 22 Wildlife Act 1974. 23 24 2. Description of threats 25 26 Coastal development 27 The distribution of the ecological community is within estuaries along a coastline hosting the 28 highest density of human population in Australia and the greatest degree of coastline utilisation 29 in terms of cities, harbours and industry (West, 1990). This makes the ecological community 30 susceptible to many environmental stresses caused by coastal development. 31 32 Coastal development includes construction of ports; foreshore structures such as reclamation 33 walls, moorings, jetties and boat ramps; buildings ranging from utility structures to highrise 34 apartments; and infrastructure, such as pipes and cables for the transport of gas, water and 35 energy. Coastal development can impact the ecological community directly through removal of 36 seagrass and indirectly through shading which limits the photosynthetic capacity of the 37 seagrass; increased runoff, sedimentation and pollution that decrease water and sediment 38 quality; and changes in wave or current patterns and sediment stability that lead to erosion and 39 burial of the seagrass. 40 41 A major source of disturbance to the ecological community in the Sydney metropolitan region 42 has been port and marina construction and operation. In addition to clearance of the ecological 43 community, the construction of ports and marinas is associated with changes in hydrology and 44 sediment transport patterns, involving both increased erosion and sediment accumulation along 45 adjacent and distant (kilometres away) coasts (Larkum and West, 1990; Meehan, 2001). These 46 changes can impact the ecological community by both erosion and burial associated with the 47 changing sedimentary dynamics (Larkum and West, 1990). The operation of ports and marinas 48 also entails substantial stress to the adjacent meadows of the ecological community (eg.
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1 Larkum and West, 1990), due to reduced transparency and nutrient and contaminant inputs 2 associated with boat traffic and servicing, as well as dredging activities associated with port 3 and navigation-channel maintenance (Duarte, 2002; Haines and Rollason, 2010; Wright et al., 4 2013). 5 6 7 Dredging 8 Dredging is carried out to maintain existing ports and navigation channels, for expansion to 9 allow access for larger ships and for the construction of new ports, as well as other activities 10 such as land reclamation, beach nourishment, laying of pipelines and cables and sand mining. 11 12 The ecological community can be impacted by dredging directly through physical removal at 13 the dredge site, or smothering by sediments at the dredge disposal site (McMahon, 2013). 14 Indirect impacts also occur through the generation of turbid plumes by sediment particles 15 which are suspended in the water column and reduce light reaching the meadows, and changes 16 to the hydrology of the area, wave or current patterns or sediment stability with consequent 17 impacts on meadow integrity and water quality (Larkum and West, 1990; McMahon, 2013). In 18 the case of contaminated sediment or sediments with high contents of organic matter, dredging 19 and resuspension may also lead to effects on water quality by the release of contaminants, an 20 increase in nutrient concentrations and reduced dissolved oxygen in the water column 21 (Erftemeijer and Lewis, 2006). 22 23 In Botany Bay between 1942 and 1984, dredging associated with the development of a port on 24 the northern side of Botany Bay contributed to major losses of the ecological community from 25 the southern foreshores of Botany Bay due to a changed wave regime. Dredging of the entrance 26 was undertaken to direct wave energy away from berthing facilities directing much of the 27 incident wave energy on to Towra Point, resulting in a 10-20% increase in wave height. The 28 new wave regime caused a loss of the ecological community from Towra Point both directly as 29 a consequence of mechanical disturbance and indirectly as a result of moving sediments 30 smothering the seagrasses (Larkum and West, 1990). 31 32 Boat mooring and other boating related activities 33 Activities relating to boating and storage of boats often directly remove or damage the 34 ecological community and also cause the fragmentation of meadows and increase the potential 35 for edge effects on meadows. 36 37 Moored boats and the ecological community favour the same sheltered conditions. Traditional 38 boat moorings located in the ecological community produce circular scours in the meadow as a 39 result of the slack chain from the mooring moving through the seagrass with each wind 40 direction change. While fragmentation and sand patches or ‘blowouts’ naturally occur in seagrass 41 beds (Kirkman and Kuo, 1990), the damage from boat moorings enhances and increases the rate at 42 which fragmentation occurs (West, 2011). Fragmentation across large areas of a meadow can 43 result in sediments becoming mobile, individual bare sand patches combining and forming larger 44 bare sand patches, deeper holes forming and ultimately leading to the entire meadow becoming 45 unstable (Kirkman, 1997; West, 2011). In Lake Macquarie, 6 hectares (0.06 square kilometres) 46 of the ecological community has been lost through damage from boat moorings and is equivalent to 47 6% of the total area of the ecological community remaining in Lake Macquarie (Wright et al., 48 2013). 49 50 Scouring is also caused by boat propellers removing seagrass leaves and rhizomes (West, 51 2011). Often the scouring is restricted to narrow widths (up to 50cm), but it can be many 52 hundreds of metres in length (West, 2011). In Botany Bay, boat scours have created 17.5 km of 8
1 exposed edge (Wright et al., 2013) in what would otherwise be a naturally continuous meadow. 2 Exposed edges within seagrass meadows are more susceptible to erosion resulting in further losses 3 of the ecological community (Wright et al., 2013). 4 5 The ability of Posidonia australis to recover from habitat fragmentation is considered extremely 6 low given its slow rate of growth. The rate of revegetation of bare patches in southeast Australia 7 was estimated to be approximately 8.4cm decade-1 (Meehan and West, 2000). Coupled with 8 increasing populations along Australia's coastline and a corresponding increase in recreational 9 usage, fragmentation resulting from boating activities is one of the most serious and ongoing 10 threats to the ecological community. 11 12 Catchment disturbance 13 Land cleared for agricultural, residential and industrial development is a major pressure in 14 many New South Wales coastal catchments (eg. Umwelt, 2000; Meehan, 2001; Manly Council 15 2008; Haines and Rollason, 2010) and is known to result in increased inputs of eroded 16 sediments, nutrients and organic material to the associated estuary (Roper et al., 2011). 17 Increasing population in coastal catchments exacerbates the impacts of catchment disturbance 18 with the associated increased pollution loads in stormwater and sewage overflows, disturbance 19 of riparian and foreshore vegetation, litter and general degradation of the environment (Roper 20 et al., 2011). 21 22 The most damaging form of pollution to the ecological community is the release of nutrients; 23 primarily nitrogen and phosphorus. Excess nutrients can trigger phytoplankton blooms or 24 excessive epiphyte growth, reducing the amount of light received for photosynthesis and 25 potentially smothering the ecological community (Shepherd et al., 1989; Kirkman, 1997). The 26 epiphytes and dead seagrass leaves fall to the substrate beneath, are broken down by bacteria 27 that use up oxygen, and this anoxic sediment gives off hydrogen sulphide that kills the benthic 28 flora and the whole seagrass ecosystem may be lost (Duarte, 2002) with subsequent changes in 29 habitats and the structure and function of estuarine food webs (Roper et al., 2011). 30 31 Nutrient inputs are associated with catchment disturbance as well as fertiliser application, 32 effluent discharges and urban stormwater. The ecological community may be impacted by 33 other pollutants such as industrial chemicals from factories, including heavy metals, 34 petrochemicals and toxic compounds that enter the sea via runoff and stormwater. The release 35 of sewage and industrial effluents along the northern shoreline of Botany Bay, from the 1830s 36 until the mid 1970s is considered to be a major factor responsible for the complete loss of the 37 ecological community along the northern shoreline (Larkum and West, 1990). 38 39 Fishing 40 Fishing by recreational and commercial fishers removes finfish and shellfish from the 41 ecological community and damage to the ecological community by boats, fishing gear and 42 people (eg. wading through meadows and bait digging) can also be associated with these 43 activities (Roper et al., 2011). Recreational fishing is regulated in all states and territories. 44 These regulations restrict the activities of anglers through measures such as fishing gear 45 restrictions; size and bag limits; and closed fishing seasons. The legal catch of a recreational 46 angler is unlikely to constitute a significant impact on native fish species. Some commercial 47 fishing methods (for example, prawn trawling) can impact the ecological community by 48 removal of leaf biomass and rhizomes. Under the New South Wales Fish Habit Protection Plan 49 No. 2, all commercial and recreational fishing gear needs to be designed and operated so as to 50 minimise damage to seagrass, including Posidonia australis (NSW DPI, 1997). 51 52
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1 Invasive Species 2 The invasive pest alga Caulerpa taxifolia has invaded many estuaries in New South Wales. 3 Recent research (Glasby, 2013) concludes that there is no evidence that C. taxifolia is driving 4 the loss of native seagrasses including Posidonia australis and does not appear to be preventing 5 the recovery of the native species. Rather, it is likely that parts of the ecological community 6 that are already under stress from other anthropogenic disturbances might become more 7 susceptible to impacts from C. taxifolia or that if the ecological community is removed, 8 C. taxifolia will potentially colonise the area previously occupied and prevent the complete 9 recovery of the ecological community (Glasby, 2013). 10 11 Climate change 12 Climate change is anticipated to significantly impact the ecological community over time as it 13 is particularly sensitive to a wide range of environmental changes resulting from climate 14 change, including changes in temperature, salinity, water clarity and nutrient loads and ocean 15 acidification, sea level rise, as well as the frequency or severity of cyclones (Pratchett et al., 16 2011). 17 18 While the ecological community may be positively impacted by increases in atmospheric CO2 19 which will lead to a higher proportion of dissolved CO2 in the ocean and should favour seagrass 20 productivity (eg. increases in seagrass biomass, in seagrass depth limits and an enhancement of 21 the role of seagrass beds in carbon nutrient cycles), the ecological community is expected to be 22 negatively impacted by sea level rise due to increases in water depth and increased turbidity of 23 coastal waters due to erosion of coastlines or more frequent incidences of flooding 24 (Poloczanska, 2006). Additionally, sea temperatures, UV radiation and frequency of natural 25 disturbance regimes such as storms and cyclones are also predicted to alter, and combined their 26 impacts may negate the benefits of increased CO2 availability (Poloczanska, 2006). 27 28 Overall, it is expected that current anthropogenic pressures coupled with the stressors of a 29 changing climate will threaten the persistence and resilience of the ecological community 30 (Poloczanska, 2006).
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1 3. Priority Conservation Actions 2 3.1 Conservation Objective 3 The conservation objective for the ecological community is to mitigate the risk of extinction of 4 the ecological community, and help recover its extent, biodiversity and function through the 5 protections provided under the Environment Protection and Biodiversity Conservation Act 6 1999 (EPBC Act) and through the implementation of the following priority conservation 7 actions. 8 9 3.2 Research and monitoring 10 Management and research priorities for the ecological community that would inform future 11 regional and local priority actions include: 12 High priorities: 13 Improve reliability of indicators and predictors of seagrass ecosystem response to 14 environmental change (both natural and human induced). 15 Identify locations of suitable donor populations for transplanting purposes. 16 Research and monitor the impact of different styles of ‘seagrass friendly’ moorings on the 17 ecological community to ensure intended performance. 18 19 Other priorities: 20 Implement a monitoring program, including a community based seagrass monitoring 21 program, to monitor:
22 o the condition of the ecological community, including the extent of physical damage 23 to meadows, density and patchiness of meadows in the ecological community, 24 epiphyte loads and recovery. 25 o water quality (eg. levels of nutrients and water clarity) particularly after rainfall 26 events and following weekend boating activity. 27 o effectiveness of installed pollution control devices. 28 Investigate sediment dynamics in seagrass communities to identify the significance of 29 sediment stabilisation imparted by the ecological community. 30 31 3.3 Priority recovery and threat abatement actions 32 Habitat loss, disturbance and fragmentation 33 Highest priorities: 34 Avoid further loss and fragmentation of the ecological community. 35 Avoid dredging or disposing of dredge spoil in or near to the ecological community. 36 Minimise loss and fragmentation of the ecological community through scouring from boat 37 propellers, anchors and moorings by 38 o relocating swing moorings in or adjacent to the ecological community. Where 39 relocation is not possible, replace swing moorings with ‘seagrass friendly’ moorings 40 (eg. screw moorings); 41 o providing mooring buoys in high use areas; 42 o introducing buffer zones; and 43 o introducing boating restriction zones over shallow patches of the ecological 44 community. 45 11
1 Other priorities: 2 Control turbidity and sedimentation effects from dredging in the vicinity of the ecological 3 community by minimising spill, overflow and leakage from the dredges and barges; 4 judicious selection of dredging equipment; seasonal or tidal restrictions; turbidity limits 5 triggering specific management responses; and reactive monitoring. 6 Avoid any changes to hydrology in corresponding coastal regions that may result in changes 7 to the natural hydrological regime influencing the ecological community, including training 8 walls, drainage and increase or decrease in run-off, salinity, or pollution. 9 Design foreshore structures such as jetties, boat ramps and seawalls to avoid shading or 10 physical damage to the ecological community. 11 Replace decking of jetties with mesh decking to allow sunlight penetration to the underlying 12 ecological community. 13 Implement water quality management in catchments to reduce nutrient and sediment loads 14 into receiving estuarine environments in which the ecological community occurs. 15 Maintain foreshore vegetation to act as a buffer zone. 16 Encourage stormwater reuse in the local government area through detention devices and 17 promoting and providing incentives for installing rainwater tanks with connections to toilets 18 and washing machines. 19 20 Communication and conservation information 21 High priorities: 22 Promote opportunities for inclusion of the ecological community in any proposed reserve 23 tenure or other conservation management arrangements. In particular, ensure that remnants 24 that are of particularly high quality or important for connectivity are considered for inclusion 25 in reserve tenure or other marine conservation measures. 26 Liaise with local councils and State authorities to ensure new coastal development, forestry 27 development or other activities involving substrate or vegetation disturbance do not 28 adversely impact on the ecological community. 29 Liaise with planning authorities to ensure that planning takes the protection of the ecological 30 community into account, with due regard to principles for long-term conservation. 31 In consultation with land and sea managers, local and state authorities and Aboriginal 32 groups, develop or support appropriate existing education programs, information products 33 and signage to help the public (in particular, boat users) recognise the presence and 34 importance of the ecological community, the need to manage water quality and their 35 responsibilities under state and local regulations and the EPBC Act. 36 37 Other priorities: 38 Undertake stormwater pollution education for schools, industries and local residents in 39 which impacts of stormwater pollution on the ecological community and marine ecology 40 more generally are defined and measures to reduce stormwater are developed. 41 Increase coordination between different government authorities to better manage the 42 ecological community, e.g. between NSW Fisheries and local councils. 43 44 3.4 Existing plans/management prescriptions 45 Australian and New Zealand Environment and Conservation Council, Agriculture and 46 Resource Management Council of Australia and New Zealand. (2000). Australian and New 47 Zealand Guidelines for Fresh and Marine Water Quality. Available at:
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1 http://www.environment.gov.au/water/publications/quality/australian-and-new-zealand- 2 guidelines-fresh-marine-water-quality-volume-1 3 Cardno (NSW/ACT) Pty Ltd. (2012). Coastal Management Plan for Brisbane Water 4 Estuary. Gosford City Council. Available at: http://www.gosford.nsw.gov.au/environment- 5 and-waste/environmental-management-and-planning/estuaries/estuary-management- 6 planning 7 Fairfull, S. (2013). Fisheries NSW Policy and Guidelines for Fish Habitat Conservation and 8 Management (2013 update). Available at: www.dpi.nsw.gov.au/publications 9 Great Lakes Council. (2009). Great Lakes Water Quality Improvement Plan: Wallis, Smiths 10 and Myall Lakes, Forster, NSW. Available at: 11 http://www.greatlakes.nsw.gov.au/Environment/Plans_and_Strategies 12 Lake Macquarie City Council. (2014). City of Lake Macquarie Environmental Sustainability 13 Action Plan 2012-2023. Available at: 14 http://www.lakemac.com.au/page.aspx?pid=109&vid=10&fid=147&ftype=True 15 Manly Council. (2011). Manly Cover Coastal Zone Management Plan: Final Report. 16 Available at: http://www.manly.nsw.gov.au/environment/marine-and-coastal/manly-cove/ 17 Manly Council. (2008). Contarf/Bantry Bay Estuary Management Plan: Final Report. 18 Available at: http://www.manly.nsw.gov.au/environment/marine-and-coastal/clontarf- 19 bantry-bay-estuary-management-plan/ 20 Marine Parks Authority. (2010). Port Stephens – Great Lakes Marine Park Operational Plan, NSW 21 Marine Parks Authority, Sydney. 22 NSW Department of Primary Industries. (1997). Fish Habitat Protection Plan No2: 23 Seagrasses. NSW DPI, Pyrmont, Sydney. Available at: 24 http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0019/202744/Fish-habitat-protection- 25 plan-2---Seagrass.pdf 26 NSW National Parks and Wildlife Service. (2001). Towra Point Nature Reserve Plan of 27 Management. 28 NSW National Parks and Wildlife Service. (2000). Royal National Park, Heathcote National 29 Park and Garawarra State Recreation Area plan of management. 30 Haines, P., Fletcher, M., Rollason, V. and Coad, P. (2008). Lower Hawkesbury Estuary 31 Management Plan. BMT WBM Pty Ltd. 32 Haines, P. and Rollason, V. (2010). Pittwater estuary management plan. Pittwater City 33 Council. Available at: 34 http://www.pittwater.nsw.gov.au/environment/water/estuaries/pittwater_estuary_manageme 35 nt_plan 36 Stewart, M. and Fairfull, S. (2007). Primefact 629: Seagrasses. NSW DPI, Sydney. 37 Available at: http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0019/203149/seagrasses- 38 primefact-629.pdf 39 Sutherland Shire Council. (2007). Port Hacking Integrated Environmental Management 40 Plan. Available at: www.sutherlandshire.nsw.gov.au/files/.../Port...Management_Plan.pdf 41 Umwelt (Australia) Pty Ltd. (2009). Living on the edge – Port Stephens foreshore 42 management plan. Available at: http://www.portstephens.nsw.gov.au/environment- 43 portstephenscd/water-quality-and-management-portstephen/1132949-port-stephens-myall- 44 lakes-estuary-manage
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1 Umwelt (Australia) Pty Ltd. (2000). Port Stephens and Myall Lakes estuary management 2 plan. Available at: http://www.portstephens.nsw.gov.au/environment-portstephenscd/water- 3 quality-and-management-portstephen/1132949-port-stephens-myall-lakes-estuary-manage 4 Wallis Lake Estuary Management Committee. (2005). Wallis Lake Estuary Management 5 Plan. Available at: http://www.greatlakes.nsw.gov.au/Environment/Plans_and_Strategies 6 Wallis Lakes Estuary Management Committee. (2003). Wallis Lake Catchment Management 7 Plan. Available at: http://www.greatlakes.nsw.gov.au/Environment/Plans_and_Strategies
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