: an aquatic jewel adjacent to

Rob Williams, Bob Creese, Tim Glasby, Greg West September 2011 Tidal cross section of estuarine foreshore Life in Saltmarsh

Life in Mangroves

Life in ‘bare’ sediments

Life in Seagrass

Photos by Dave Harasti Posidonia australis

Halophila ovalis

Zosterea capricornia are complex ecosystems

ƒ Chemical & biological processes ƒ Biodiversity ƒ Habitats ƒ Surrounded by fertile land – Rural impacts • increased sediments & nutrients ƒ Good places for harbours & cities – Industrial impacts • increased pollution, infrastructure ƒ Nice places for people to live near – Urban impacts • increased stormwater & sewage inflow Sealevel – the major driver of estuarine structure What are key estuarine habitats?

1. Natural physical features –Deep holes – Sand bars or mud banks –Rocky reefs What are key estuarine habitats? 2. Biological features – Mangrove forests - Saltmarsh – Seagrass beds - Algae What are key estuarine habitats? 3. Man-made physical features

• Marinas, jetties • Oyster farms • Port facilities • Artificial reefs NSWNSW hashas 184184 coastalcoastal waterbodieswaterbodies

ƒ Semi-enclosed embayments (6; e.g. )

ƒ Drowned river valleys (13; e.g. Port Hacking)

ƒ Barrier (51; e.g. estuary)

ƒ ICOLLs (110; e.g. Lake Conjola)

ƒ Brackish lakes (4) Australian Estuarine Classification Alternatives

• Roy (1984) – Geomorphological, 4 3 zones

• Rochford (1951, 1959) – Hydrological, 4 zones (DRV) DLWC photo Roy: Estuary evolution since sealevel stabilised 6,500 years ago – Catchment infilling Evolution of NSW Drowned River Valleys Proto-valley Evolutionary Stage: %Central Mud Basin Young Adolescent Adult Pensioner 90-60% 60-10% 10-1% <1% Stephens Port Stephens Hawkesbury Hawkesbury River (main channel) Pitt Middle H. Creek Parramatta Parramatta R. Georges Hacking (main channel) Clyde Clyde River

6,500 YBP Present

(after Roy et al. 2001) Geomorphic Zones in NSW Drowned River Valleys

RC FD CMB MTD

6 218 4 30km 60%

1 2103 Pittwater 16km 63%

Hacking River 35 6 14km 21%

Geo. R./ 28 612 2 49km 4%

Hawkesbury River 139km 100 30 8

(Total lengths from Roper et al. 2011) Rochford ‘s initial observation (1951)

MANGROVES

OPTIMUM FATTENING

OYSTERS OPTIMUM SPAWNING

ZOSTERA Rochford ‘s initial observation (1951)

ZONE FRESH- GRADIENT TIDAL MARINE WATER

MANGROVES OPTIMUM FATTENING

OPTIMUM SPAWNING OYSTERS

ZOSTERA Rochford (1951) “Estuarine System”

(River) (River/Estuary) (Estuary) Fresh- Gradient Tidal Marine water Chl. Sal.

20 35 30 25 11 20 15 10 5 00 Why map estuarine habitats?

ƒ Habitats give a guide to biodiversity – the more habitats there are, the more types of plants & animals there are likely to be.

ƒ Complex habitat arrangements are a good indicator of healthy estuaries.

ƒ The change in the amount of habitat over time can show improvement or deterioration.

ƒ Accurate spatial layers in a GIS can help in assessing risks and developing rehabilitation. Mangrove: an expanding commodity Coastal Saltmarsh, a NSW EEC

Saintilan and Williams (1999, 2000) Avicennia marina expansion in the Parramatta River (Ermington)

Photo: J. Kelleway (2007) Southward migration of mangrove in NSW: early 1980s – mid 2000s

Barrier estuary ~Distance Avicennia Aegiceras Exoecaria Rhizophora Brugeria from Qld. marina cornic- agal- stylosa border ulatum locha (km) 01 Tweed R. 0 X X X X X 05 Brunswick R. 40 X X X X X 09 Richmond R. 70 X X X X X 12 Clarence R. 135 X X X X 13 Sandon R. 165 X X X X 14 Wooli W. R. 190 X X X X X 21 Moonee Ck. 235 X X X 31 S. W. R. Ck. 310 X X X

X= West et al. (1985), X = N. Wilson, pers. comm. (2002, 2003), X = R. Glover, pers. comm. (2001) Saltmarsh 100000 In Out 10000 - 3

1000

100

10 Number of Crab Larvae m m Larvae Crab of Number

1 Mar Apr. May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug

0.1

Mazumder et al. (2009) Trophic interactions between different ecosystem components and consumers at Towra Point, NSW

Mazumder et al. (2011)

Saltmarsh Recent history of estuarine macrophyte cover in Port Hacking

Photo. Land Information Centre Photo. Land Information Centre 1930 1999 Area of Port Hacking’s estuarine vegetation 1930 - 1999

Seagrass 200 Mangrove Saltmarsh 180

160

140

120

100

80 Area (ha)

60

40

20

0 1920 1930 1940 1950 1960 1970 1980 1990 2000 Year

Williams and Meehan (2004) Cabbage Tree Basin 1942 Cabbage Tree Basin 1999

N N

Posidonia Zostera Mixed Mangrove

0500Meters 0500Meters Threats to estuarine habitats in Port Hacking

ƒ Dredging and other physical disturbance – Regular dredging of channels still occurs every 3-4 years – Damage from recreational boating still an issue

ƒ Sediment & nutrient input from catchment activities – Less of a problem than 4-5 decades ago – Still likely to be stormwater impacts

ƒ Invasive species – Fewer vectors occur (no commercial fishing, shipping or aquaculture) – But close to Botany Bay – Discards from home aquaria a high potential risk • Propeller scour •Mooring holes Area of Port Hacking’s estuarine vegetation 1930 - 1999

Seagrass 200 Mangrove Saltmarsh 180

160

140

120

100

80 Area (ha)

60

40

20

0 1920 1930 1940 1950 1960 1970 1980 1990 2000 Year

Williams and Meehan (2004) Hacking River 1951

Zostera N

01Kilometers

Hacking River 1999

N

0 1 Kilometers Hacking River Foreshores, 2009: natural & artificial South West Arm Macrophytes, 2009 Macrophyte change at RNP locations: 1951-1999

Geom. Location Saltmarsh Mangrove Seagrass Zone 7 Cabbage -37% +420% -92% Tree Basin 8 South +186% +100% -10% West Arm (?) 9 Hacking -50% +28% -83% River

From Williams & Meehan (2004) API Presumptive map of saltmarsh

Saltmarsh 2 Sm-4 Sm-1 Mangrove-2 Mangrove-3

M-1 Sm-3 Final map FN FN

FN

FP Final map FN FN

FN

FP

Saltmarsh polygons No. patches Area (m2) Presumed to exist 4 500 False positive -1 -50 Expose joins -2 500 False negative 7 100 Total 8 1050 (Williams et al. 2011) ƒ helicopter mapping allows greater control ƒ photos are taken under optimal conditions ƒ sub 1m accuracy ƒ density & health; not just extent Wallis Lake, Snake Island: ALOS vs QuickBird unsupervised classification

ALOS AVNIR QuickBird 10m spatial resolution 2.6m spatial resolution January 2003

Posidonia

February 2008 January 2007 (Glint affected)

sand September 2008 sparse seagrass/BMA sand

CSIRO L&W Introduced Caulerpa Cumulative distribution of Caulerpa

Note: Caulerpa not always present in these areas and it is often quite sparse Caulerpa vs Posidonia: 2005-2010 20 x 20 m fixed plots in each of 2 sites

Gunnamatta Bay Jibbon Ctax Pos (canopy) 100 Pos (primary) 100

90 90

80 80

70 70

60 60

50 50

40

% cover 40 % cover

30 30

20 20

10 10

0 0 DEC05 AUG05 MAR06 AUG06 MAY07 MAR08 NOV08 DEC10 DEC05 MAR06 AUG06 MAY07 MAR08 NOV08 DEC10 Overall change in Caulerpa: 2003-2011

Data from 17 x 250 m transects throughout Port Hacking

Caulerpa abundance - Port Hacking

0.5

0.4

0.3

0.2

0.1 Mean proportion Ctax per transect (+SE) transect per Ctax proportion Mean 0.0 MAR03 AUG03 MAR04 SEP04 APR05 AUG05 MAR06 AUG06 MAR11 Salient points re Caulerpa

ƒ Caulerpa taxifolia comes and goes – Discovered April 2000 – Overall distribution and abundance in Port Hacking has changed little since 2003, slight decline if anything ƒ Zostera capricorni comes and goes, Posidonia australis is more persistent – No evidence yet of direct impacts of Caulerpa on seagrasses – Seems that Caulerpa is opportunistic – colonises where Zostera has died for some reason – Experimental work on potential impacts is continuing Concluding Points

ƒ Catchment management issues relevant to RNP: – Dredging and other physical disturbances (e.g. recreational boating) – Sediment & nutrient input from catchment activities – Invasive species – Public access & education – Aquatic macrophytes • Seagrass loss appears stabilised • Saltmarsh cover appears stable • Mangrove cover has increased slightly ƒ RNP offers stable home for complex estuarine processes – Aquatic macrophyte cover has not been stable