Changes in seagrass coverage and links to water quality off the Adelaide metropolitan coastline



2 Cover photograph Aerial photograph of the Adelaide coastline at Point : Malcolm in 1996 clearly delineating bare sandy patches and darker seagrass beds . September 1998 Document Production Environment Protection Agency Department for Environment, Heritage and Aboriginal Affairs GPO Box 2607 ADELAIDE SA 5001 Telephone: 08 8204 2004 Facsimile: 08 8204 9393 Free Call (country): 1800 623 445 ISBN 0-7308-0243-4 © Copyright Environment Protection Agency Printed on recycled paper

3 SUMMARY The large areas of seagrass from the Adelaide coastline has been attributed to the loss of of discharges, as stormwater, sewage effluent and sewage sludge. effects such Protection Agency studies, to enhance understanding of the Recent Environment (EPA) beds, loss and health of the remaining seagrass seagrass and to determine of extent the loss, examined and assessed: changes shown in aerial photographs possible causes of the the of 47 years; the remaining seagrass beds; and epiphyte growth rates. over condition photography 4000 hectares that between 1949 and 1995 more than aerial of The indicates the between disappeared and Aldinga Beach along Largs near-shore seagrass Bay coastline. This loss is continuing. metropolitan rate of seagrass loss is not uniform across the whole area nor has it been constant The through time. In region from Glenelg to Largs Bay, for example, most loss occurred the 1970 and 1977 — a period population growth which saw increased stormwater between of effluent Glenelg sewage treatment works (STW), increased discharge from discharges, the Bolivar STW construction and the Port Adelaide STW sludge outfall, and the of outfall of the Sturt channel. The slower rate of loss in recent years concrete lining be linked to may the of the sludge outfalls for the Glenelg and Port Adelaide STWs. decommissioning overall the seagrass, survey work in April 1998 near Despite the old Port Adelaide loss of seagrasses. outfall has shown some regrowth of sludge The regrowth is confined to a site small area and it has yet to be determined whether it will survive and flourish. Nevertheless it indicates seagrasses could be re-established in areas where conditions that favourable if water conditions improve. This is unlikely to happen in the near­ are quality movement make or further south areas wave action and sand in areas it shore where for seedlings to take root. difficult rates on artificial substrates and the condition of seagrasses were studied Epiphyte growth of at a number along the coastline including sites near the Torrens and Patawalonga sites Port a reference estuary. The results were compared to outlets, and in the site, with River Gulf physical similar no major discharges, at Port Hughes in Spencer characteristics but where there are healthy seagrass beds. The results indicate that all the metropolitan sites have elevated epiphyte growth rates and seagrasses that generally in poorer condition than the reference site. Some sites, such as are in the epiphyte River, Glenelg South, and Port Noarlunga, show excessive those Port on substrates. growth artificial being taken to improve water quality, prevent Steps loss and maintain the long seagrass term sustainability of the metropolitan coastline, include: • raising community awareness of the issues facing the area through the document Protecting St Vincent: A statement on its health and future Gulf • developing an Environment Protection (Water Quality) Policy with the aim of preventing harmful discharges to waterbodies. waste • licensing larger industrial discharges to the gulf with conditions for environmental improvement and monitoring

4 • requiring four metropolitan STWs to develop and implement Environment the Programmes costing of approximately $210 million, with the aim a total Improvement reducing nutrients entering the gulf substantially of developing Codes of Practice for stormwater management with the aim of using • plans management integrated catchment management works to reduce pollutants and the the runoff into and gulf volume of works improving water • catchments through quality being undertaken by the in the Patawalonga, Torrens, Onkaparinga and the Northern Adelaide and Barossa Water Catchment Management Boards for implementing water quality monitoring programme ambient the Port River and • an bathing waters to metropolitan long-term trends in water quality and determine provide feedback on the success of the improvements being implemented • developing and implementing a Marine and Estuarine Strategy for South Australia understand • management tools to better long-term and manage the complex developing ecological processes of the system, starting with an EPA initiated integrated ecological study of the coastal waters off Adelaide.

5 CONTENTS 1 INTRODUCTION ... 1 ... WHAT ARE SEAGRASSES? 1 1.1 ... IMPORTANCE 1.2 ... 2 OF THE SEAGRASS DEGRADED LOST? ARE SEAGRASSES ... 2 1.3 AND HOW 2 ... Turbidity ... Epiphytes ... ... Nutrients and 3 ... 3 Sediment ... ... ... Toxicants 3 ... 4 1.4 BLOWOUTS OF SEAGRASS DECLINE ... 5 1.5 EFFECTS DETERMINATION OF 2 LOSS USING AERIAL PHOTOGRAPHY ... 6 SEAGRASS 2.1 METHODS ... 6 ASSESSMENT Seagrass Loss 6 Determining ... OF IMAGES PHOTOGRAPHIC ASSESSMENT ... 7 THE 2.2 ... 7 Bay–Aldinga Largs Bay–Glenelg ... Largs 9 ... Glenelg–Marino ... ... 11 Rocks TO DEVELOPMENTS 2.3 HAVE CONTRIBUTED THAT SEAGRASS LOSS ... 13 MAY 3 MEASUREMENT OF EPIPHYTE GROWTH ... 14 3.1 ASSESSMENT ... 14 METHODS Substrates ... 15 Artificial ... OF ASSESSMENT GROWTH RATES ... 15 3.2 EPIPHYTE epiphytic growth between sites ... 15 Comparison of of dry weight of epiphytes ... 17 Measurement results ... and October surveys Comparison of 17 of April A scale for epiphytic growth ... 18 reference Correlating epiphytic growth with ambient water quality ... 19 4 ASSESSMENT SEAGRASS HEALTH ... 20 OF COMPARISONS ... THE DIFFERENT INDICATORS 4.1 20 BETWEEN cover Percentage ... 20 of seagrass Measurements of standing crop ... 20 5 STEPS BEING TAKEN TO STOP FURTHER LOSS ... 22 6 REMARKS ... 23 CONCLUDING 7 ACKNOWLEDGEMENTS ... 24 8 FURTHER READING ... ... 25

6 LIST OF AND FIGURES TABLES 1 Changes in area between Largs Bay and Aldinga ... 7 Table sand in area between Largs Bay and Glenelg... 9 2 Changes sand Table in sand area between Glenelg and Table Rocks ... 11 3 Changes Marino 4 Dates various developments that could of contributed to seagrass loss ... 14 Table have 5 and Table assessment of epiphyte growth ... 19 6 Qualitative Figure healthy seagrass meadow in Holdfast Bay... 1 1 A 2 A meadow with heavy epiphyte growth ... 2 Figure seagrass 3 Complete loss of seagrass ... 3 Figure 4 Monitoring movement Figure and blowouts with rods ... 4 sand 5 A Figure escarpment ... 4 blowout’s Figure 6 Metropolitan Adelaide seagrass study area (1949–1996) ... 6 Figure 7 Seagrass loss 1949–1996 between Largs Bay and Aldinga Beach... 8 Figure 8 Seagrass 1949–1995 between Largs Bay and Glenelg... 10 loss 9 Seagrass 1949–1995 between Glenelg and Marino Rocks ... 12 Figure loss 10 Rate of seagrass loss 1949–1995 between Figure Bay and Glenelg ... 13 Largs Figure Epiphyte monitoring sites along 11 metropolitan coastline and Port River estuary... 14 the Figure 12 Artificial substrates... ... 15 Figure 13 of epiphyte growth on flexible substrates at all sites... 16 Comparison 2 14 Total dry weight of epiphytes (mg/cm Figure ) ... 17 Figure 15 Epiphytic growth categories based on a colour scale ... 18 Figure Standing crop measurements of seagrass... 21 16 leaves ... 21 17 Productivity measurements of seagrass Figure

7 1 INTRODUCTION areas of have been lost from the Adelaide coastline. This loss has been Large seagrass effluent the discharges, such as stormwater, sewage of and sewage to effects attributed better understand the extent of seagrass loss, the condition or health of sludge. To the seagrass and to determine possible causes of the loss, the Environment remaining beds, (EPA) commissioned studies to provide some answers. These studies Protection Agency using aerial photographs taken involved the period from 1949 to 1996 to assess the over change extent of seagrasses (Hart 1997a, b and 1996), and a survey that assessed the in the growth of seagrass beds and determined remaining rates of epiphytes on condition the substrates (Harbison and Wiltshire 1997). This artificial summarises the findings of report these studies. (photo: 1 A seagrass meadow Figure Bay healthy V Neverauskas 1984). in Holdfast 1.1 WHAT ARE SEAGRASSES? Seagrasses are the ‘grass meadows’ of coastal waters. They are flowering plants with roots, making them very from algae. distinct anchoring system the uptake of nutrients and for for them Their extensive root is essential into the sand. firmly 2 that seagrasses cover 5000 km the of It is sheltered estimated waters of Gulf St coastal Vincent and Sprigg 1976). The dominant seagrasses are the (Shepherd Posidonia sub-tidal (ribbon-weed) and Amphibolis (wire-weed) species, and intertidal Halophila (paddle-weed), Heterozostera (gar-weed), and Zostera (eel-grass) species (Edgar 1997, Poiner and Peterken 1995, Clark 1987). Prior the 1960s, the dominant species off the Adelaide metropolitan coastline in the to and from Bay to Aldinga were Posidonia region Amphibolis . However since the mid Largs 1960s Amphibolis has virtually disappeared from this area. Intertidal species of seagrass areas occur commonly in the Port River estuary area and in the shallower more north of the Port River around St Kilda. 1

8 1.2 THE IMPORTANCE OF SEAGRASS are important the following reasons. Seagrasses for animals provide a large variety of marine for including fish. They habitat • stabilise underlying sand and • erosion. They reduce They to reduce wave energy and help storm damage to coastlines. • prevent They occur offshore from mangrove habitats—providing refuges • juvenile fish and for prawns. chain (converting They basis of the food the light into energy). • are Their roots trap and bind sediment and organic detritus. • They • a stable surface for colonising epiphytes (algae). provide • provide habitat for epiphyte grazers (zooplankton and fish). They • They contribute to the detrital food chains. • They to nutrient trapping and cycling. contribute (1995), information found in Keough and Jenkins be Connolly and Butler (1996), More can (1995a,b, 1994a,b,c), Walker Connolly McComb (1992) and Clark (1987). and Figure seagrass meadow with heavy epiphyte growth 2 A V Neverauskas 1984). (photo: 1.3 HOW ARE SEAGRASSES DEGRADED AND LOST? Many factors can lead to seagrass loss and often these are interlinked. They include: Turbidity • stormwater, dredging, land Sewage discharges, works and changes in land reclamation use can increase turbidity in the water column. This leads to less light reaching the increase seagrass results in a decrease in photosynthetic activity and an leaves which in stress on the plant. 2

9 Nutrients and Epiphytes Nutrients discharged the marine environment can increase algal growth. Algae can • into or floating as epiphytes (epiphytes are plants grow animals that attach free be or leaves and stems). Small epiphytic algae which grow on seagrass are also themselves on periphyton. called • algae contribute to overall turbidity levels whist epiphytic algae have the floating Free nutrients of the diffusion of gasses and reducing to seagrass leaves, shading direct effect thereby reducing photosynthetic activity, and increasing leaves and weight on the the seagrass leaves. For The epiphytes can cause the seagrass leaves to break from the stem. of • weight species, a break such as this leads to irreversible damage since the leaves and Amphibolis ‘growing part’ of the leaf is above a distinct erect stem. The leaves of Posidonia the the species have to regrow as their ‘growing part’ occurs at the base of the plant, ability valuable of however, energy may be used up in the process. reserves 3 Complete loss of seagrass (photo: V Neverauskas 1984). Figure Sediment • Loss of seagrass creates a cycle of further seagrass loss. As sediments become dislodged and resuspended, penetration in other seagrass areas is further reduced. Once sand light begins, seagrass ‘blow-out’ is created and increases in erosion is rapidly lost as a sand dislodged erosion result in healthy plants being Severe and washed ashore. size. can Some of the problems associated with sand loss along our metropolitan beaches • due are to seagrass and the reduced ability of the meadows to bind sediment together. losses of Toxicants of is known of the direct or indirect effects • low concentrations of toxicants such as Little herbicides or heavy metals including lead, zinc, copper and cadmium on seagrasses. Heavy metals are in the metropolitan waters in elevated concentrations, often present guidelines of the protection exceeding marine ecosystems (ANZECC 1992, for Protection Authority 1997a). Metals accumulate in sediments and can bio­ Environment accumulate in marine organisms (Ward 1989). In one study concentrations in seagrasses in the were found low compared with that found be water (Maher 1986), however, the to effects of metals on epiphyte grazers, particularly zooplankton and fish, may be impacting on seagrass communities indirectly. 3

10 1.4 BLOWOUTS are root between seagrass beds that expand with time due to erosion at the Blowouts areas erosional level. are characterised by an Blowouts scarp on the seaward side, a bare zone sandy area in the centre and a seagrass colonising edge on the landward side. Expansion of erosion the of faster seagrass is a result than seagrass re-colonisation. Scarp blowout heights vary and extend to 0.75 metre and move up to 2 metres per year. Figure Monitoring sand movement and blowouts with rods 4 (photo: D Fotheringham). Figure 5 A blowout’s escarpment (photo: D Fotheringham). 4

11 1.5 EFFECTS OF SEAGRASS DECLINE effects of seagrasses along the Adelaide metropolitan coastline include: The loss of in the the benthos to a phytoplankton dominated community a change • structure of no habitat for many important marine organisms which provides biodiversity: estimated loss of forty times more benthic invertebrates, fish and macro- • an adjacent associated seagrass than with with bare sand communities crustaceans are it has generally been found that • Posidonia and Amphibolis do not readily grow species of back have been lost for reasons which may include: once they Posidonia has a very slow rhizome growth rate making recolonisation • australis (conditions required for recolonisation are not well understood but difficult in other to attempts recolonise seagrass have generally not been areas successful) coastline depth along the Adelaide • is generally only 2 metres deep and if sand eroded, exposes hard calcareous material and clay, excluding seagrass colonisation (common areas) in blow-outs recolonisation Sabella ) invades and possibly excludes worm (Blackburn pers • (fan comm). increased sand erosion of the Adelaide beaches: the Coastal Protection • annual Board’s 3 /year, combined approximately 160 000 m beach replenishment programme of sand each with dredging costs over $1 million offshore year (SA Coastal Protection biennial Board 1993); between September and October 1997 the Coastal Protection Board moved 3 600,000 m further dredging and the replenishment of average; three times this annual will cost $4 million (Fotheringham pers comm). More information about seagrasses can be obtained from Short and Wyllie-Echeverria al (1996), and Jenkins (1995), Walker and McComb (1992), Shepherd et Keough (1989), Sergeev et al (1988), Neverauskas (1987a,b,c) and Clark (1987). 5

12 2 OF SEAGRASS LOSS USING AERIAL DETERMINATION PHOTOGRAPHY 2.1 ASSESSMENT METHODS Largs Bay between photography Aerial undertaken 1996 was used to identify and 1949 and of seagrass change off the delineate areas (Hart 1997a). The metropolitan coastline Point Malcolm surveyed is area shown in extent of the 6. figure All were digitised, photographs and distortions for (corrected orthorectified classified. The ground controls) and area is within orthophotography over the Torrens Outlet 000 better. As mapping such 50 accuracy 1: or to epoch and within the images fit epoch to metres 10 over areas epochs to within 7 away control the from points. Patawalonga Outlet Glenelg Seagrass Determining Loss was assumed the study, it For the purpose of directly that the increase in exposed sand was related in decrease seagrass. a to the was made more difficult Classification by Marino presence of detrital matter, rocks and other features (such infestations as of marine the worm Sabella ). South Australia Onkaparinga Outlet Adelaide Metropolitan Seagrass Study Area Aldinga 6 Metropolitan (1949–1996). area study Adelaide seagrass Figure 000 Scale: 1: 50 6

13 2.2 ASSESSMENT OF THE PHOTOGRAPHIC IMAGES of the area was divided into three regions based on the Coverage metropolitan available 1949 to aerial surveys from coverage 1996 and technical issues photographic from The with the features in the photographs. of three regions surveyed associated assessment Bay to Aldinga, Largs Bay to Glenelg, and Glenelg to Marino. were Largs surveys used The for region are summarised below: each Bay to Largs Bay to Glenelg Glenelg to Marino Aldinga Largs 1949 1949 1949 1996 1965 1965 1971 1971 1977 1977 1983 1983 1995–96 1995–96 Largs Bay–Aldinga Largs Bay The Aldinga coverage provided information on all seagrass loss between the to years 1949 to 1996 over the whole region. This survey did not provide a breakdown of times of largest loss. exposed (table a substantial increase in the area of show sand since 1949. A total Results 1) 2 been (4086 hectares) of seagrass has 1949. This since study area lost in the 40.8 km of to of 1949 total seagrass area. equates 32% 1 Table in sand area between Largs Bay and Aldinga. Changes Epoch Area of sand Difference Rate 2 2 (year) km km ha ha/year ha 1949 2625.7 26.3 40.86 4086.1 86.9 1996 67.1 6711.8 See figure 7 for map of sand change between Largs Bay and Aldinga. Beach Note seagrass was found south of Christies : No in any of the photos used for this study. 7

14 Port Adelaide sludge outfall in 1992) (ceased Legend outlet Torrens River Sand Glenelg outfall sludge STW 1992) in (ceased Seagrass outlet Patawalonga Seagrass loss Ocean Rock Land Onkaparinga Outlet Kilometres 5 0 10 Bay 7 Seagrass loss 1949-1996 between Figure and Aldinga Beach. Largs 8

15 Largs Bay–Glenelg of the in this region shows a retreat of seagrass away from the Assessment coverage 1949 and a widening the ‘sand lanes’ or blowouts between the seagrass of coastline since between the years is summarised below. changes The patches. description for area between Glenelg and West Beach Year Seagrass change Some 1949–65 no thinning of seagrass patches visible. • retreat, Major lane widths seaward, sand 1965–77 increased. • retreat Landward 1977–83 stable, small patches of seagrass disappearing. • edge 1983–88 Edges of seagrass patches • contracting. • Sand lanes continue to expand at the expense of seagrass patches. 1988–94 exposed (table an increase in the amount of show sand since 1949 in the Largs 2) Results 2 lost in the been has seagrass of study 21.7 km a total Overall, area. study Bay–Glenelg of since 1949. This equates to 22.8% of 1949 total seagrass area. The rate of seagrass loss area through varied and across the region. time 1977 but greatest of The between 1971 and period the rate of loss was still high in loss was 1983. The area between Glenelg North and West Beach suffered the greatest loss between 1971 and 1977 when (or 50% of the total seagrass in the area) disappeared. 182.3 hectares 2 Changes area between Largs Bay and Glenelg. Table in sand of sand Difference Rate Epoch Area 2 2 ha km (year) ha km ha/year 10.2 1949 1019.3 14.0 1399.5 3.8 380.2 23.8 1965 15.6 1.6 158.3 26.4 1971 1557.8 24.8 2475.4 9.2 917.6 152.9 1977 1983 28.7 4.0 395.7 66.0 2871.1 1995 3194.3 3.2 323.2 26.9 31.9 Figure 8 shows exposed sand change from 1949 to 1995. Each colour represents the progression of through each epoch. The mapping shows that the sand increase, and sand seagrass the along implied coastline. The area with greatest sand accretion loss, varies off between The grey area is extensive. Point Malcolm in the 1996 survey 1971–77 (yellow) represents a deep water region thought to be denuded of its seagrass during the 1970s discharged (Hart at the same time as sludge from the Port Adelaide STW was 1997a), into the area. This area was not surveyed in earlier aerial photography. 9

16 Seagrass SeagrassSeagrass Bay Largs LegendLegendLegend Sand Progression Sand Progression Sand Progression 19491949 1949 t Malcolm Poin 196196196 5 1971 19711971 1977 19771977 191919 83 199199199 5 19961996 1996 Study area Kilometres 2 2 2 2 1 1 00 0 1 1 1 Glenelg Figure Seagrass loss 1949-199 between Largs Bay and Glenelg. Seagrass loss 1949-199 between Largs Bay and Glenelg. Figure Seagrass loss 1949-199 between Largs Bay and Glenelg. Figure

17 Glenelg – Rocks Marino has been of seagrass similar to that in the northern coastline study area There a retreat Rocks, and the between Glenelg and Marino coastline a widening of the ‘sand away from between the seagrass patches since lanes’ 1949. Results 3) show an increase in the amount of exposed sand since 1949 in the Glenelg– (table 2 of seagrass has been lost in the study area study area. A total of 5.37 km Marino Rocks since 1949. This equates to 47.3% of 1949 total seagrass area. Table 3 in sand area between Glenelg and Marino Rocks. Changes Area sand Difference Rate Epoch of 2 2 ha km km (year) ha/year ha 1949 2.2 223.1 1965 3.2 321.1 0.9 98.0 6.1 1971 3.8 382.1 0.6 61.0 11.1 1977 4.7 0.8 80.6 12.4 468.9 1983 571.0 1.0 102.1 17.0 5.7 1995 7.6 760.6 1.9 189.6 15.8 change See 9 for map of sand figure between Glenelg and Marino Rocks. 11

18 Glenelg Legend Sand Progression 1949 5 1949 - 196 S erton om Park 0 - 197 65 19 - 1977 70 19 - 19 83 1977 5 - 199 983 1 Brighton ining R ema 5 199 Seagrass om cluded Study Ex fr Rock Seacliff or Land D ee pwater arino M etres om il K 2 0 0 1 2 1 0000 Figure 9 Loss 1949 - 19 95 between Glenelg and Mar ino Rocks. Seagrass

19 DEVELOPMENTS THAT MAY HAVE CONTRIBUTED TO SEAGRASS LOSS 2.3 seagrass. the on impact an had have may years the Developments over Table loss of 4 seagrasses that impacted have may on developments of a number summarises below and 10) the they occurred. The graph (figure observed decline plots these dates against the dates area. Largs to Marino the for in seagrasses Bay of 4 Dates Table various developments that could have contributed to loss. seagrass Development Comment Period Nutrients and 1943– outfall sewage turbidity treated Glenelg constructed Harbor Outer 1949– Breakwater accretion/ Sediment sedimentation constructed Nutrients and turbidity 1957– Patawalonga flood gates turbidity and Nutrients outfalls and drains Stormwater 1960s constructed 1968– and turbidity Nutrients outfall sewage Bolivar treated 1968–1992 and Nutrients outfall sludge Glenelg turbidity 1975– Sturt River concrete lined Nutrients and turbidity turbidity and nutrients Erosion, sludge and excavations Pipeline 1977–1992 Port Adelaide commences at outfall Shepherd See also et al (1989). 90 85 80 75 70 65 1985 1990 1945 1950 1955 1960 1965 1970 1975 1995 1980 Gl enelg Glenelg STW STW STW Glenelg Adelaide Port Port Ade de lai Glenelg STW Adelaide Begin Glenelg ST W l STW Glene g Beginning outfal (pipeline 1) l STW Glenelg outfall outfall sludge sludge STW outfall STW sludge stormwater outfall ll outfa sludge water storm begins discharge outfall discharge to sea ceased to outfal sea l sea outfallto discharge drain discharge drain to sea ends discharge increased increased commences begins construction increased construction increased Adelaide Port 3) (pipeline 2) (pipeline STW sludge Port Adelaide River Sturt STW Bolivar River Sturt Harbour Outer Patawalonga STW olivar B outfall to sea sludge STW concrete outfall Glene lg and concrete flood gates breakwater outfall ends outfallto sea lining outfa sludge ll lining constructed constructed commences begins constructed Bay and Glenelg. – 1949 loss between seagrass of Rate 10 Figure 1995 Largs 13

20 3 MEASUREMENT EPIPHYTE GROWTH OF epiphyte growth can growth of seagrasses (Day 1994, Environmental Excessive affect 1993, Larkum al 1989, Neverauskas 1987c). An objective of this Australia et Consulting to determine the relationship between epiphyte growth study ambient water was and This achieved by examining epiphyte growth was artificial substrates and quality. on growth rates with ambient water quality. correlating ASSESSMENT METHODS 3.1 substrates were placed the metropolitan coastline and the Port River Artificial along water quality monitoring sites (Environment Protection Authority 1997a,b) estuary at EPA two for (April and October 1996) of six weeks each. Five additional sites were periods included October study (Henley, in the North, West Beach South, Glenelg West Beach North and Somerton ) to encompass areas affected by the Torrens and Patawalonga outfalls (figure 11). Ki da l *St Little River Para *Barker r e et Inl v i R t r o P * Bay *Largs *North Creek Dry Arm Point Malco lm River To r r e n s *Grange ADELA DE I Beach *Hen ey l River Outlet To r r e n s Sewage Outfall Glenelg West Beach North South West Beach Patawalonga River) (Sturt Out et l North Glene g l *Glenelg Somerton i *Br ghton Sturt River South Field River Austra lia *Port Hughes Chr st e Creek i i Metro Bathing Waters Out et River Onkaparinga l l *Port Noar unga 2.5 0 Kilometres Figure 11 Epiphyte monitoring sites along the metropolitan coastline and Port River estuary (*denotes EPA ambient water quality monitoring sites). 14

21 Artificial Substrates plastic strips seagrass), fixed 15 cm lengths of 40 mm PVC piping and Flexible (artificial tags acetate from plastic sheets were used as substrates from which 150x40 mm cut of were made (figure 12). Three replicates of the flexible measurements epiphyte growth fixed pipe substrate and two replicates of and acetate strips were located at each site. the Acetate were used to collect samples to determine species composition and the strips phosphorus of calcium content nitrogen, epiphytic material. and of 12 Figure used at one Artificial the sites (top) and acetate substrates strips with epiphytic growth ready for species identification (bottom). 3.2 ASSESSMENT OF EPIPHYTE GROWTH RATES of growth between sites Comparison epiphytic results of epiphyte growth on flexible (figure 13) and rigid The indicate that the substrates reference at Port Hughes had the site epiphyte growth during both survey periods. least Other sites with little epiphyte growth include Brighton, Grange and Largs Bay. During the of April greatest epiphyte growth was observed at each the the Port River sites, survey, Glenelg and Port Noarlunga. Port Noarlunga exhibited greatest growth during the October survey. 15

22 a s t g e e n r l y h m u e n a g r l I n v r a g u i e B l A o r a d t g l e H R e s i o h h n n t k t t g K g r r r r N a r i e l r t r o a o o t a S B G G P B P L N P April (a) 1996 h h t t r u o o h h N S t t a r s u t h h g o e o c e c r n l y h n S N m a a u e n r a l g o I e e v r t g g a e i u A B l l r y r B a B d g e e R l e H e e s t o h i t l n t n n t k t s g s r m n r K a N r r r e e e r e l l o o e o t t a o a G S G G N P S P H W L B P W (b) October 1996 flexible Figure Comparisons of epiphyte growth on 13 substrates at all sites. 16

23 Measurement of weight of epiphytes dry results of the total dry weight of epiphytes from all flexible strips The measurements of greatest are 14. The results show that the in figure growth was at each site from shown Port River and Port Noarlunga. Of the five additional sites surveyed in North Arm, Beach the greatest epiphyte growth. October, Henley had 18 October 16 Apr il 14 12 10 8 mg/cm2 6 4 2 0 Inlet Arm Kilda North River Largs Beach Beach South Port Grange Hughes St *Henley *Glenelg North *Brighton South Port Noarlunga North *Somerton Barker Port *West *West *Glenelg assumption that Apr il growth is approximately half October growth for sites with no Apr denotes * il data 2 ). weight of epiphytes Total per cm 14 dry Figure (mg of results of April and October surveys Comparison 14 shows was epiphyte growth Figure higher during October than in April. Growth that also Some in the Port River estuary compared with metropolitan coastline sites. was higher reasons for are differences possible discussed below. these area Stormwater • the Adelaide metropolitan runoff is greater during the winter from months. This increased load of nutrients may account for higher epiphytic growth during October. The October differentiated epiphyte growth between the Barker Inlet • survey clearly the Dry coastline sites (figures 13a, b). Industry, and Creek, the Little sites metropolitan into and stormwater drains discharge directly numerous the Port River Para River In addition, estuary. Bolivar STW outfall at St Kilda would also contribute to the elevated in the estuary leading to greater epiphyte growth. The sheltered nutrients more minimise potential waters nutrient dispersion unlike the the open coastline for sites (Environment Protection Authority 1997c,d). • Enhanced growth at Henley Beach may be due to flows from the River Torrens. Enhanced growth South during both survey periods could be caused by at Glenelg from or adjacent sewage outfall nutrients from discharges from the Patawalonga. the There are two possible causes for the dense epiphyte growth at Port Noarlunga. • Nutrients from the Christies Beach sewage outfall (2 km north of Port Noarlunga) could and be site under prevailing weather the tidal conditions. The high affecting biodiversity of the adjacent Noarlunga reef could be providing a rich source of be epiphytes colonisation on substrates, however, this would for expected to increase biodiversity not biomass. 17

24 A reference scale epiphytic growth for based and identified three general categories of epiphytic growth (1997) Harbison Wiltshire a colour scale illustrated in figure 15. on Prolific epiphytic growth Scale 4–5 • Moderate epiphytic growth Scale 2–3 • Low negligible epiphytic growth Scale 1 • or 1 : Little or Scale growth no (Appears clean and light blue in colour) Scale 2 : Thin cover of epiphytes (No obstruction blue surface or of strip) Scale : Thin cover of epiphytes 3 appear (Strips brown) light Scale 4 : Even coating of epiphytes (Blue colour masked by an olive green coating) Scale 5 : Dense coating of epiphytes (Appears dark brown or black) Figure 15 Epiphytic growth categories based on a colour scale. 18

25 Correlating epiphytic with ambient water quality growth between epiphytic using the colour scale above, and water quality Comparisons growth, Authority 5. are summarised in table Protection (Environment 1997c,d) EPA Qualitative of 5 for both surveys at assessment Table epiphyte growth water quality monitoring sites. ambient Epiphyte growth category Ambient water Site quality (nutrients) Port Hughes Low Good St Kilda Moderate Moderate Inlet Barker Moderate Moderate North Arm Moderate–Poor Prolific Port River Prolific Poor Bay Largs Moderate Moderate Grange Moderate Moderate Henley Moderate Moderate Glenelg South Prolific Moderate Brighton Low Moderate Port Noarlunga Prolific Moderate Note: Ambient water quality was derived using the methods detailed in Environment Protection Authority (1997c,d). 6 Qualitative of epiphyte growth for both surveys at Table assessment epiphyte monitoring additional sites. Site Epiphyte growth category West Beach North Moderate West Beach South Moderate Glenelg North Moderate Somerton Moderate were no significant There between epiphytic growth (dry weight) and water correlations quality (geometric means of oxidised nitrogen and ammonia; P>0.05). Generally, all metropolitan sites exhibited moderate epiphytic growth and had moderate coastline ambient water quality. The Port River had poor ambient water quality and exhibited had excessive The reference site at Port Hughes epiphyte growth. good water quality and low epiphyte growth. 19

26 4 ASSESSMENT SEAGRASS HEALTH OF of seagrass condition include seagrass productivity as measured by Measures health or and shoot (Environmental Consulting Australia 1993, Ainslie et al leaf robustness density include growth characteristics along pollution gradients measures 1994). Other Australia 1993, Burkholder et al (Environmental Consulting 1992). study the following indicators to determine their effectiveness in assessing This examined condition of seagrasses: the health or • percentage cover of seagrass length of • leaves seagrass • of seagrass shoots per unit area. number COMPARISONS THE DIFFERENT INDICATORS 4.1 BETWEEN Percentage cover of seagrass the April survey, the percentage cover of seagrass was measured at Port Hughes During at four metropolitan coastline sites. The percentage cover was highest at Port Hughes and Largs cover) by Brighton (50%), Grange (5%), (80–90% (5%) and Glenelg (1%). By followed this index Port Hughes had the healthiest seagrass and Glenelg the least healthy. Measurements of standing crop period standing growth measurements were made over a seven week and in Seagrass crop 1996. April The data indicated: the average length of seagrass leaves significantly greater at Port • than at Hughes metropolitan sites; the shortest seagrass leaves measured at Glenelg (figure 16) coastline greater seagrass growth at Port Hughes significantly • than growth at Glenelg and leaf Largs, but not significantly different to Brighton and Grange 2 by ) lowest at Largs, followed Grange, Port seagrass blades (leaves of per m • density Glenelg South and Brighton Hughes, 2 followed Hughes, Port and by ) greatest at Brighton per m crop standing • (grams 2 ) per seagrass productivity and Largs; average Grange (grams per m Glenelg South and leaf highest at Port Hughes, followed by Brighton, Glenelg South and Largs (figure 17). 20

27 Standing Mean length of seagrass leaves (mm) Crop: 400 350 300 250 Mean leaf length 200 (mm) 150 100 50 0 85) Bay Kilda South Hughes Glenelg St Grange (128,84) (35,127) Brighton (157, (141,98) (359,108) Largs (174,187) Port (N, Site sd) seagrass. 16 Standing crop measurements of Figure productivity per leaf (g) Productivity: Mean 0.12 0.1 0.08 Mean leaf 0.06 productivity (g) 0.04 0.02 0 Bay Port South (1108) (1700) (1375) (2983) Grange (750) Hughes Glenelg Brighton Largs (N leaves/m2) Site 17 Productivity measurements of seagrass leaves. Figure occurs These that the healthiest seagrass indicated at Port Hughes, followed by results Brighton and Grange. Glenelg and Largs Bay were sites exhibiting the least healthy seagrass. and results suggested that length of seagrass leaf blades The average productivity of individual leaves provides the best index of seagrass health. 21

28 5 STEPS TAKEN TO STOP FURTHER LOSS BEING number of are being taken to improve water quality, prevent seagrass loss and A steps long sustainability of the metropolitan coastline. These include: the term maintain community awareness of the issues facing the area • the release of the Raising through Protecting St Vincent: A statement on Gulf health and future . document its The development of an Environment Protection (Water • Policy with the aim of Quality) preventing harmful discharges to waterbodies. waste relating Licensing discharges to the gulf with conditions industrial to • larger improvement and monitoring. environmental Requiring the four metropolitan sewage treatment works to • and implement develop Environment Programmes (EIPs) with the aim of substantially reducing Improvement nutrients the gulf. These programs will cost approximately $210 million. entering • The development of Codes of Practice for stormwater management with the aim of using management and integrated catchment management works to reduce plans and volume of runoff into the gulf. pollutants the Works being undertaken by the Patawalonga, Torrens, Onkaparinga, and the Northern • and Catchment Water Adelaide Management Boards to improve water quality Barossa catchments. in the Implementation of an ambient water • monitoring programme for the Port River quality and metropolitan bathing waters to determine long term trends in water quality and provide feedback the success of the improvements being implemented. on Marine The • implementation of a development and Estuarine Strategy for South and Australia. • Development of long term management tools to better understand and manage the is complex processes that are occurring in the system. To this end the EPA ecological the initiating integrated ecological study of an coastal waters off Adelaide. 22

29 6 CONCLUDING REMARKS degradation and Adelaide’s metropolitan coastline is a problem directly Seagrass loss along quality related to Aerial photography shows that between 1949 and 1996 in the water gulf. and 4000 hectares disappeared between Largs Bay seagrass Aldinga Beach than more of metropolitan coastline. The average rate of loss has been approximately along the 87 per year. loss is continuing. hectares The time. Most seagrass been constant through not loss occurred between rate of loss has The this 1971 and that there was an increase in the effluent discharged from 1977. Around time Glenelg STW, the was discharged from the Glenelg STW to the gulf, the Bolivar sludge STW and Port Adelaide STW sludge outfall were constructed, and the concrete outfall the of River channel was completed. Since Sturt removal of sludge outfalls at lining the and Port Adelaide, rates of loss have reduced slightly. Glenelg has work Survey April 1998 near the old Port Adelaide sludge outfall site undertaken in shown some regrowth of seagrasses that occurring (Neverauskas and Kirkegaard pers is coms). The regrowth is confined to a small area and it has yet to be determined whether it will survive flourish over a number of seasons. Nevertheless it indicates that if water and of conditions be possible to re-establish some it may the lost seagrass in quality improve where conditions are favourable. This is unlikely to be the case in the near shore areas areas or areas further south where wave action and sand movement make it difficult for in seedlings to take root. young healthiest epiphyte growth indicates The the rate study seagrass occurs at the reference that site at Port Hughes, followed by Brighton and Grange. The least healthy seagrass occurs at Glenelg and Bay. Largs exhibits growth on artificial substrates epiphytes a broad correlation with the The of status of coastal waters, with high growth nutrient occurring in waters having rates elevated concentrations, and low growth nutrient associated with low nutrient rates concentrations. rates The estuary had the highest River of epiphyte growth followed by the Port metropolitan coastline sites. The reference site at Port Hughes site had the lowest growth. Growth rates at all sites were higher in spring (October) than in autumn (April). 23

30 7 ACKNOWLEDGEMENTS acknowledge Environment would like to Agency the financial support of The Protection Patawalonga and Torrens Water the Management Boards in undertaking the Catchment epiphyte seagrass health studies that and been summarised in this report. have The Resource Information Group of the Department for Environment, Heritage and aerial Aboriginal the collection and assessment of the undertook photography and Affairs this work is gratefully acknowledged. The use of photographs of seagrass taken by Vic Neverauskas and Doug Fotheringham is appreciated. 24

31 8 FURTHER READING RC, Johnson, and Offler, EW. 1994. Growth of the seagrass Posidonia sinuosa Ainslie, DA Kuo Cambridge to, and remote from, a power station thermal at locations et near Society of Spencer Australia. Transactions of the Royal South outfall in northern Gulf, 197–216. , 118(3), South Australia Ward, RD. 1997. Allozyme variation in the marine fanworm Sabella Andrew, J and of spallanzanii European and introduced Australian : Comparison native Ecology Series, 152, 131–143. Marine Progress populations. Australian water quality guidelines for fresh ANZECC. waters . Australian and 1992. and marine Zealand Environment and Conservation Council. New JM, Mason, KM and Glasgow, HB. 1992. Water column nitrate enrichment Burkholder, decline promotes eelgrass Zostera marina , evidence from seasonal mesocosm of Marine Ecology Series , 81, 163–178. experiments. Progress marine and status of the introduced 1995. The fanworm, Sabella G Evans, D. Clapin, Australia: A spallanzanii investigation. Technical Report 2. in Western preliminary for Research on Introduced Marine Pests, CSIRO, Tasmania. Centre SM. 1987. Seagrass-sediment dynamics in Holdfast Bay: Summary. Clark, 11(2), 4–10. Safish, Connolly, and Butler, AJ. 1996. The effects of altering seagrass canopy height on small, RM invertebrates Mediterranean shallow motile embayments. Marine Ecology , 17(4), of 637–652. George 1995a. Diet of juvenile King Connolly, whiting Sillaginodes punctata (Pisces: RM. Sillaginidae) in the Barker Inlet–Port River estuary, South Australia Transactions of the Royal South Australia , 119, 191–198. Society of RM. 1995b. of removal of seagrass canopy on assemblages of small, motile Connolly, Effects Ecology Series, 118, 129–137. Marine Progress invertebrates. 1994a. A comparison of fish assemblages from seagrass Connolly, unvegetated RM. and of a southern Australian estuary. Australian Journal of Marine and Freshwater areas 45, 1033–1044. Research, RM. Connolly, The role of seagrass as preferred habitat for juvenile Sillaginodes 1994b. (CUV. or VAL.) (Sillaginidae. Pisces): Habitat selection punctata feeding? Journal & Marine Biology 180, 39-47. of Experimental and Ecology, on RM. 1994. Removal of Connolly, canopy: Effects 1994c. small fish and their seagrass prey. Journal of Experimental Marine Biology and Ecology , 184, 99–110. Day, B. Seagrasses as a primary indicator of water quality . URL: 1994. Environment 1993. BHP Marine Australia. Studies 1992 . BHP Environmental Consulting Products division, Whyalla SA. Long and animals GJ. Australian marine life: the plants 1997. of temperate waters . Kew, Edgar, Victoria: Reed Books. Environment Protection Authority. 1997a. Ambient water quality monitoring of Gulf St Vincent’s metropolitan waters. Report no. 1 . Adelaide: Department for bathing Heritage and Aboriginal Affairs, South Australia. Environment, Environment Protection Authority. 1997b. Ambient water quality monitoring of the Port River Heritage Estuary. Report . Adelaide: Department for Environment, no. 1 and Aboriginal Affairs, South Australia. 25

32 Environment Protection 1997c. Protecting Gulf St Vincent: A statement on its health Authority. . Adelaide: Department Environment and Natural Resources. and future of Authority. Environment monitoring and assessment of 1997d. Protection Workshop on th DENR report, South Australia. June. 16 seagrasses: Adelaide, D. 1997. Determination of epiphyte growth Harbison, and seagrass health. P and Wiltshire, rates . Adelaide: Environment Protection Authority, South Australia. 1–3 Parts 1997a. Near-shore Hart, change between 1949 and 1996—Mapped using digital DGD. seagrass Adelaide Largs Bay–Aldinga, South aerial orthophotography—Metropolitan area: Data Services, Information Group. DENR report. . Image Resource Australia 1997b. Near-shore seagrass change Hart, 1949 and 1995—Mapped using digital DGD. between Adelaide area: Southern Adelaide area: Glenelg– aerial orthophotography—Metropolitan South Australia . Image Data Services, Resource Information Marino, DENR Group. report. DGD. 1996. seagrass change between 1949 and 1995—Mapped using digital Hart, Near-shore area: Adelaide area: Largs Bay– Adelaide aerial orthophotography—Metropolitan Northern Data Services, Resource Information Group. DENR report. Glenelg . Image the RK FT. 1986. Seagrass growth and survivorship under Short, influence of Howard, and grazers. Aquatic Botany , 24, 287–302. epiphyte Jernakoff, Brearley, A and Nielson, J. 1996. Factors affecting grazer–epiphyte interactions P, in temperate meadows. Oceanography & Marine Biology, 34, 109–162. seagrass MJ inhabitants. Jenkins, GP. 1995. Seagrass meadows and their Keough, In AJ and Australia and Chapman (eds), Coastal marine ecology of temperate Underwood , pp MG 221–239. Randwick NSW: UNSW press. Kinhill Metcalf & Eddy. 1994. Mapping of historical changes in marine communities in the region of the Bolivar outfall . Draft Final Report. WWTP AWD, McComb, and Sepherd, SA (eds). 1989. Biology of seagrasses: A treatise on Larkum, AJ of seagrasses region special reference to the Australian biology . Amsterdam: the with Elsevier. . Ocean Seagrass: Lloyd, too important to mow 1997. Rescue 2000, Sea Notes. URL: D. A lawn WA. metal Maher, concentrations in marine organisms from Gulf St Vincent, 1986. Trace Australia. Air, Soil Pollution , 29, 77–84. South Water, VP. 1987a. Monitoring seagrass beds around a sewage outfall in South Neverauskas, Marine Pollution Bulletin , 18(4), 158–164. Australia. works VP. Port Neverauskas, sewage treatment 1987b. outfall effect of discharge on the Adelaide adjacent marine environment. Final report . EWS Lib ref: 87/28. Neverauskas, VP. of periphyton biomass on artificial substrates 1987c. Accumulation a sewage outfall in South Australia. Estuarine, Coastal and Shelf deployed near sludge Science, 25, 509–577. VP. 1984. Port Adelaide sewage treatment works Neverauskas, outfall effect of discharge on sludge the marine environment . Progress adjacent . EWS Lib ref: 85/6. report Poiner, IR and Peterken, C. 1995. Seagrasses. In LP Zann and P Kailola (eds). State of the marine report for Australia: Technical annex: 1—The Marine Environment , environment pp 107–117. Great Barrier Reef Marine Park Authority, for the Department of the Environment, Sport and Territories, Ocean Rescue 2000 Programme: Townsville. 26

33 Reference Group the Minister for the Environment and Natural Resources. appointed by Report of the of the Management of Adelaide Metropolitan Beaches . 1997. Review Environment Department Resources. and of Natural of SM Shepherd, Clark, 1988. Motile macroepifauna and the seagrasses, VN, Sergeev, SA. Posidonia , and unvegetated sandy substrata in Holdfast Amphibolis South and Bay, Transactions Royal Society of South Australia, 112, 97–108. Australia. of the and subtidal ecology and SA 1976. Substrates, sediments Sprigg of Gulf St Vincent Shepherd, RC Strait . In: Twidale CR et al (eds ) Natural History of the Adelaide and Investigator , pp of Soc Region Australia: Adelaide. 161–174. Royal SA, McComb, Bulthius, DA, Neverauskas, V, Steffensen, DA and West, R. Shepherd, AJ, and of AWD Larkum, AJ McComb In SA Shepherd (eds), 1989. Decline seagrasses. seagrasses: a treatise on the biology of seagrasses with special reference to Biology of the Australian , pp: 346–387. Amsterdam: Elsevier. region FT Wyllie-Echeverria, S. 1997. Natural and Human-induced disturbances of Short, and Environmental Conservation , 23(1), 17–27. seagrasses. Adelaide Coastal Board. 1993. Coastline —Maintaining the Protection Coastline . Bulletin SA No. 28. State of the Environment Advisory Council. 1996. Australia State of the Environment . Canberra: CSIRO. DA. 1984. St Vincent water pollution studies. Phase 2, 1976–1983 . EWS Lib ref: Steffensen, Gulf 84/12. DI Walker, AJ. 1992. Seagrass degradation in Australian coastal waters. and McComb, Bulletin, 25(5–8), 191 – 195. Pollution Marine TJ. 1989. The Ward, and effects of metals in seagrass habitats. In AWD accumulation Larkum, McComb and SA Shepherd (eds), Biology of seagrasses: a treatise on the AJ , pp biology special reference to the Australian region with 797 – 820. of seagrasses Amsterdam: Elsevier. West, RJ, Jacobs, NE and Roberts, DE. 1990. Experimental transplanting of seagrasses in Botany Bay, Marine Pollution Bulletin, 21, 197–203. Australia. for LP Sutton, D (eds). 1995. State Zann, marine environment report and Australia: of the Technical annex: 2—Pollution . Townsville: Great Barrier Reef Marine Park Authority, for the Department of the Environment, Sport and Territories, Ocean Rescue 2000 Programme. Zann, 1995. Our sea our future : LP. findings of the state of the Marine Environment Report Major for Australia . Townsville: Great Barrier Reef Marine Park Authority, for the Territories, Department the Environment, Sports and of Ocean Rescue 2000 Programme. 27

Related documents