 Great Sandy Strait |
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The Great Sandy Strait is a sand passage estuary between the mainland and Fraser Island and encompasses 93,160 hectares. The area contains 5,554 hectares of seagrass meadows growing on intertidal sand and mud flats. The tidal range in the strait is up to 4.1m. The Mary River flows into the northern region of the Great Sandy Strait before entering Hervey Bay from the south. The Mary River Catchment consists of both sewered and unsewered residential and urban areas fringing the coastline. Leakage from septic tanks into nearby drains and creeks and storm water run-off threaten the viability of near-shore seagrass ecosystems. Extensive land clearing for cane production and dryland grazing has also altered the catchment contributing to erosion and increased freshwater run-off into near-shore ecosystems. The catchment to the south of the strait encompasses the Cooloola National Park comprising native woodlands, heath and coastal dune vegetation. By comparison, much of the Boonooroo catchment consists of woodlands, extensive mangrove wetlands and modified agricultural lands. Two major watercourses, the Tuan and Poona Creeks drain the Boonooroo watershed from extensive pine plantations, cane farms and grazing lands.
Seagrass meadows provide a major marine habitat in the Great Sandy Strait. The meadows form part of significant Ramsar wetlands sites, are within the Great Sandy Marine Park, and provide critical nursery habitat for regional prawn and finfish fisheries.
Seagrass distribution was first mapped in the Great Sandy Strait in July/December 1973 (Dredge et al. 1977). Seagrass was only found south of the Moonboom Islands. A remote sensing mapping exercise was conducted in 1988, however results of the mapping do not appear reliable due to inadequate ground truthing. In October-November 1992 an aerial photographic survey of the Strait was conducted and significant increases in seagrass distribution, relative to 1973 surveys, were reported in the northern section of the Strait, between River Heads and Urangan (Fisheries Research Consultants 1993).
In 1994, a broad scale survey of the Great Sandy Strait seagrass meadows was conducted (mainly by air) which reported an increase in distribution of meadows south of Urangan to River Heads compared with 1992 (Fisheries Research Consultants 1994a). In June 1994, long-term monitoring transects were established throughout the Great Sandy Strait. Resurveys were conducted in March 1995, November 1996, February 1998, September 1998 and February 1999. Large decreases in seagrass distribution were recorded in 1996 and recovery to February 1999 remained low (Conacher et al. 1999).
In December 1998 a detailed dive and aerial survey of the Great Sandy Strait was conducted which reported dense Zostera capricorni with Halophila ovalis (mud/sandy) meadows present on mud/sand banks throughout the region (McKenzie et al. 2000).
Flooding of the Mary River and other tributaries in the Sandy Strait in February 1999 caused the complete loss of seagrass meadows in the northern Great Sandy Strait and loss of some other regions in the central and southern Sandy Strait region (McKenzie et al. 2000).
An aerial survey in February 2002 mapped 7007 ±1945 hectares of intertidal seagrass meadows on the mud/sand banks within the Great Sandy Strait
(McKenzie and Campbell 2003). This represented over 100% recovery in some regions of the Great Sandy Strait. In most areas the seagrass abundance recovered to pre-flood levels. At a few localities abundances were marginally lower, however this may have be a consequence of inter-annual differences. Only six seagrass species were observed in February 2002. No plants of the species Cymodocea serrulata which was present on the large subtidal bank between Kauri Creek and Tin Can Inlet, were observed during the survey.
Approximately 90% of the seagrass meadows in the Great Sandy Strait were Zostera capricorni dominated communities. The remainder were a mixture of Halodule and Halophila dominated (McKenzie and Campbell 2003).
Regional report card - December 2010
- Seagrass meadows throughout the Great Sandy Strait support significant fisheries, turtle and dugong populations
- Seagrass meadows in the Great Sandy Strait region were classified as fair in abundance in 2010.
- Seagrass abundance in the Great Sandy Strait has fluctuated since 1999 (fair to good), but there is no apparent long-term trend.
- Species composition has remained stable across the sites.
- Algal abundance is generally low, but seasonally increases in the middle of each year at most sites. Episodic algal blooms occurred in mid 2002.
- Epiphyte blooms regularly occur at most sites in the mid-latter part of the year, with a dramatic decline in the summer months. Epiphyte abundance has continued to increase (not significantly) at some sites on the western shores of the Great Sandy Strait.
- Sediment grain size has remained relatively stable of the monitoring period, with only a few sites becoming either more muddy or more sandy.
- Seagrass-Watch data provides understanding of seasonal trends and effects of climatic patterns on seagrass meadows
- Management controls depend on public and government support.
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Brown's Gutter
Monitoring: ongoing, annual
Principal watchers: Gordon Cottle, Robyn Bailey, Pat Cottle and Paul Bailey
Occasional and past watchers: Gary Nielsen, Steve Winderlich, John Lindberg, John Roberts, Anne O'Dae, Matthew Hamilton, Hanna Larson & Seagrass-Watch HQ
Location: shallow anchorage on the south western shores of Fraser Island
Site codes: BG1 BG2 BG3
BG1 position: S25.74305 E153.00058 (heading 50 degrees)
BG2 position: S25.75004 E153.00311 (heading 70 degrees)
BG3 position: S25.76155 E153.00830 (heading 70 degrees)
Best tides: <0.6m
Issues: stormwater & land runoff, boat traffic
Comments: dugong and turtle feeding grounds
Status (Dec10):
- seagrass abundance at Brown's Gutter is currently in a poor state
- BG1 has progressively increased in abundance since 2000, however seagrass abundance at BG2 & BG3 has fluctuated over the last 9 years, and currently at low levels.
- seagrass abundance appears seasonal within years, with lower levels from Jun-Aug and highest levels from Nov-Jan.
- episodic algal bloom occurred in mid 2002, however the algal abundances subsequently declined early in the new year. Epiphyte blooms regularly occur at most sites in the middle of the year.
- sediment grain size has changed little over the monitoring period.
- species composition has remained stable - dominated by Zostera.
- polychaete worms and gastropods (including mud whelks) common.
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Boonooroo
Monitoring: ongoing, triannual
Principal watchers: Gordon Cottle, Robyn Bailey, Pat Cottle, Paul Bailey & Seagrass-Watch HQ
Occasional and past watchers: John Roberts, Anne O'Dae, Steve Winderlich , Hana Larsson, Wayne Mathews, Peter Lusk, Bill Alston, Maryborough West School, Trischelle Lowry, Faye Fergurson & Mary Starkey
Location: on the western shores of the Great Sandy Strait, adjacent to Boonooroo township, between Big Tuan Creek and Maroom. BN2 is located close to Big Tuan Creek and BN3 is located approximately 1.6km north, with BN1 midway between BN2 and BN3. BN2 is considered the "impacted" site and BN3 the "control"/"reference" site
Site codes: BN1 BN2 BN3
BN1 position: S25.66866 E152.90736 (heading 100 degrees)
BN2 position: S25.68208 E152.89377 (heading 230 degrees)
BN3 position: S25.64812 E152.90670 (heading 280 degrees)
Best tides: <0.8m
Issues: Small unsewered village, boat traffic & land use
Comments: significant nursery grounds for juvenile prawns and fish. Dugong and turtle feeding grounds.
Status (Dec10):
- seagrass abundance at Boonooroo is currently in a poor state
- seagrass abundance at both “impacted” (BN1 & BN2) and “control” (BN3) sites declined from 1999 to 2005, however since 2005 seagrass abundance has continued to increase at BN3. Abundances similarly increased at BN1 & BN2 until 2010 when they declined.
- algae abundance appears seasonal at it generally increases in the middle of each year.
- epiphyte abundance, although highly variable, has continued to increase (not statistically significantly) over the monitoring period, possibly indicating elevated nutrients.
- sediment grain size has remained stable of the monitoring period.
- dugong feeding trails found year round, with the most intensive grazing occurred from May to November, coinciding with the nutritional demands of calving from September to December. During this period seasonal forces support high seagrass growth ensuring that losses from grazing are outweighed by tissue production.
- turtle feeding (cropping) was evident year round.
- polychaete worms and gastropods (including mud whelks) were common. The diversity and abundance of gastropods appears to be dependent on seagrass abundance, most likely due to associated detrital and prey food sources.
- species composition has varied over the monitoring period, particularly at BN1 where Zostera capricorni was becoming more dominant until recently when the meadow reverted back to Halodule uninervis. Halodule uninervis and Halophila ovalis are colonising species and may indicate levels of physical disturbance (eg wave action and sediment movement).
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Kauri Creek
Monitoring: ongoing, ad hoc
Principal watchers: Gordon Cottle, Robyn Bailey, Pat Cottle, Paul Bailey
Occasional and past watchers: Steve Winderlich, Gary Nielsen, Wayne Mathews & Anne O'Dae
Location: on intertidal bank (Ballast Bank) on the southern side of the mouth to Kauri Creek
Site code: KC1
KC1 position: S25.79597 E152.98675 (heading 130 degrees)
Best tides: <0.8m
Issues: defence land runoff
Comments: dugong and turtle feeding grounds
Status (Dec10):
- seagrass abundance at Kauri Creek is currently in a poor state
- seagrass abundance has fluctuated since monitoring was established, and abundances in 2010 were not significnatly different from 2007.
- canopy height is showing a close correlation with seagrass abundance.
- epiphyte abundance appears highly variable.
- sediment grain size and seagrass species composition appear stable.
- polychaete worms and gastropods were common.
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Poona
Monitoring: ongoing, triannual
Principal watchers: Gordon Cottle, Robyn Bailey & Hanne Larson
Occasional and past watchers: Gary Neilsen, Di-anne Duffield, Maryborough Special School, Mary Dixon, Sarah De Ghen, Trischelle Lowry, Wayne Mathews, Desley Nielsen, Anne O'Dae, Steve Winderlich & Seagrass-Watch HQ
Location: Intertidal banks adjacent to township
Site codes: PN1 PN2 PN3
PN1 position: S25.70853 E152.92433 (heading 30 degrees)
PN2 position: S25.71847 E152.91953(heading 117degrees)
PN3 position: S25.72980 E152.92285 (heading 15 degrees)
Best tides: <0.8m
Issues: small unsewered village increasing development, access channel dredging, boat traffic, stormwater, land runoff
Comments: significant fish habitat. Dugong and turtle feeding grounds
Status (Dec10):
- seagrass abundance at Poona is currently in a poor state
- seagrass abundance has fluctuated greatly since monitoring was established in 1999.
- seagrass composition appears relatively stable at PN1 and PN3.
- PN2 has changed the most of all sites at Poona, both in abundance and species composition. The site appears to be generally dominated by Zostera capricorni, however the composition of the colonising species Halodule uninervis and Halophila ovalis has fluctuated over the years and has become more dominant in 2008, suggesting a high level of localised physical disturbance.
- sediment grain size has remained relatively stable at PN1 and PN2, however PN3 appears to have become muddier (this corresponds with the abundance of Zostera which is better adapted to muddier sediments).
- dugong feeding trails were found year round, with the most intensive grazing occurred from May to November, coinciding with the nutritional demands of calving from September to December. During this period seasonal forces support high seagrass growth ensuring that losses from grazing are outweighed by tissue production. Turtle feeding was evident year round.
- polychaete worms and gastropods were common. The diversity and abundance of gastropods appears to be dependent on seagrass abundance, most likely due to associated detrital and prey food sources.
- seagrass meadows at Poona were predominantly composed of fine mud and fine sand with a high organic component. Meadows near Poona Creek (PN2) had low seagrass cover, contained muddy sediments with a low sand component. At meadows distant from freshwater inputs (PN3) sand rippling indicates the influence of tidal movement and/or a low exposure to catchment influences.
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Reef Islands
Monitoring: ongoing, biannual
Principal watchers: Gordon Cottle, Robyn Bailey, Hanne Larson, Paul Bailey & Seagrass-Watch HQ
Occasional and past watchers: Steve Winderlich, John Roberts, Anne O'Dae, Gary Nielsen, Michael Ford, Sarah De Ghen, Bill Alston, Jerry Comans & Sue Olsson
Location: central Great Sandy Strait
Site codes: RI1 RI2 RI3
RI1 position: S25.65463 E152.95354 (heading 240 degrees)
RI2 position: S25.65899 E152.94900 (heading 40 degrees)
RI3 position: S25.67718 E152.95652 (heading 90 degrees)
Best tides: <0.6m
Issues: Boat traffic, oyster leases, land runoff
Comments: significant nursery grounds for juvenile prawns and fish. Dugong and turtle feeding grounds
Status (Dec10):
- seagrass abundance at the Reef Islands is currently in a fair state
- seagrass abundance fluctuates (either doubling or halving) at times, but the long-term trend is stable.
- algal abundance is generally low with the exception being a significant algal bloom at RI1 in late 2003.
- epiphyte abundance appears seasonal with increases in the later part of the year, with a dramatic decline in the summer months.
- sediment grain size and species composition relatively stable over monitoring period.
- dugong feeding trails were found year round, with the most intensive grazing occurred from May to November, coinciding with the nutritional demands of calving from September to December. During this period seasonal forces support high seagrass growth ensuring that losses from grazing are outweighed by tissue production. Turtle feeding was evident year round.
- polychaete worms and gastropods were common. The diversity and abundance of gastropods appears to be dependent on seagrass abundance, most likely due to associated detrital and prey food sources. Filter feeding bivalves and oysters were found at Reef Island sites.
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Tin Can Inlet
Monitoring: ongoing, quarterly (every 3 months)
Principal watchers: Gordon Cottle, Robyn Bailey, Hanne Larson & Pat Cottle
Occasional and past watchers: Seagrass-Watch HQ, Wayne Mathews, Dennis Osborn, Marc Dargosch, Dean Richardson, Di-anne Duffield & Sarah De Ghen
Location: Southern Great Sandy Strait, including Pelican Bay and on intertidal flats in front of Tin Can Bay township
Site codes: TB1, PB1, PB2
PB1 position: S25.81285 E153.04767 (heading 145 degrees)
Best tides: <1.0m
PB2 position: S25.82231 E153.06244 (heading 50 degrees)
Best tides: <0.6m
TB1 position: S25.90615 E153.01533 (heading 115 degrees)
Best tides: <0.6m
Issues: Tourism (periodic camping) & urban development, vehicles, stormwater, sewerage & restoration of old wharf
Comments: Dugong and turtle feeding grounds, popular fishing (recreational & commercial)
Status (Dec10):
- seagrass abundance at Boonooroo is currently in a fair state
- seagrass abundance has remained low (generally less than 1%) at the site adjacent to the Tin Can Bay township (TB1). The sparse meadows are dominated by the colonising seagrass species Halodule uninervis (narrow leaf morphology) and Halophila ovalis. The intertidal banks are dynamic (sand movement and physical disturbance from sting rays etc) and predominately sand with shell/gravel. Results suggest that due to the dynamic nature of the intertidal banks and the persistence of colonising species, the banks are adverse to establishment of dense seagrass meadows and little change would be expected in the near future.
- seagrass abundance at PB1 (Inskip Point) has fluctuated greatly over the monitoring period, however it has since decreased in 2008 to 1999-2000 abundances (ie post 1999 flood).
- the site at Bullock Point (PB2) in Pelican Bay was last monitored in August 2005.
- algal abundance appears to increase seasonally in the winter months and epiphyte abundance is highly variable. No persistent long-term trends are apparent, suggesting elevated nutrients are not a significant issue at present.
- seagrass composition at TB1 appears stable, although sediment grain size is variable.
- polychaete worms and gastropods (including mud whelks) were common. The diversity and abundance of gastropods appears to be dependent on seagrass abundance, most likely due to associated detrital and prey food sources.
- seagrass meadows at Pelican Bay were predominantly composed of fine mud and fine sand with a high organic component.
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Tootoowah Creek
Monitoring: suspended
Principal watchers: Gordon Cottle, Robyn Bailey, Hanne Larson, Paul Bailey & Seagrass-Watch HQ
Occasional and past watchers: Wendy Jones, Gary Nielsen, Steve Winderlich, Jerry Comans& Seagrass-Watch HQ
Location: Shallow anchorage on the western shores of Fraser Island.
Site codes: TC1 TC2
TC1 position: S25.69122 E152.98925 (heading 70 degrees)
TC2 position: S25.69295 E152.98495 (heading 270 degrees)
Best tides: <0.7m
Issues: boat traffic, land runoff
Comments: Dugong and turtle feeding grounds
Status (Dec10):
- Sites have not been examined since June 2002, when nearly the entire loss of seagrass at the location was reported.
- Insufficient data to describe long-term trends.
- Current condition unknown
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Tinnanbar
Monitoring: ongoing, triannual
Principal watchers: Gordon Cottle, Robyn Bailey, Hanne Larson & Pat Cottle
Occasional and past watchers: Gary Nielsen, Peter Lusk, Wayne Mathews, Hans Van Roey, Sarah De Ghen, Steve Nicol, D. Eckert, Megan Dale, Nigel Woodward, Rex Coleman, Steve Winderlich & Seagrass-Watch HQ
Location: southern Great Sandy Strait on the intertidal banks in front of the Tinnanbar township & caravan park.
Site codes: TN1 TN2 TN3
TN1 position: S25.75617 E152.95235 (heading degrees)
TN2 position: S25.75827 E152.96378 (heading 15 degrees)
TN3 position: S25.75807 E152.96788 (heading 55 degrees)
Best tides: <0.8m
Issues: high urban development, boat traffic, stormwater, land runoff
Comments: Dugong and turtle feeding grounds. Popular fishing (recreational & commercial)
Status (Dec10):
- seagrass abundance at Tinnanbar is currently in a poor state
- seagrass abundance decreased between 2004 and 2006, and although TN1 increased between 2008 and early 2009, all sites have decreased since mid 2009.
- algae cover is generally low and epiphyte cover is high and variable.
- sediment grain size and species composition relatively stable over monitoring period.
- polychaete worms and gastropods were common.
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Wanggoolba & Bennett’s Creek
Monitoring: suspended
Principal watchers: Michael Ford & Seagrass-Watch HQ
Occasional and past watchers: Anne O'Dae, Bill Alston, John Lindberg, Peter Lusk
Location: On the western shores of Fraser Island in the northern Great Sandy Strait. Wanggoolba Creek is one of the main access points (ferry) to the World Heritage listed Fraser Island
Site codes: WC1 WC2
WC1 position: S25.41610 E153.00559 (heading 120 degrees)
WC2 position: S25.44732 E152.98397 (heading 105 degrees)
Best tides: <0.8m
Issues: access dredging & spoil disposal, boat traffic
Comments: Dugong and turtle feeding grounds. Wanggoolba Creek is a declared Fish Habitat Areas (FHA) to enhance existing and future fishing activities and to protect the habitat upon which fish and other aquatic fauna depend.
Status (Dec10):
- sites have not been monitored since July 2004
- seagrass abundance recovered significantly after it was lost in February 1999, the result of a major flood.
- canopy height continued to increase at the site in close correlation with seagrass abundance.
- algae cover is relatively insignificant at these sites.
- irregular epiphyte blooms occur at both sites from time to time.
- sediment grain size appears to be less muddy, with more sand present.
- seagrass species composition relatively stable over monitoring period.
- dugong feeding was absent until late 2001, coinciding with seagrass recovery. Feeding trails are regularly observed across the meadows.
- the high abundance of gastropods at Wanggoolba Creek may be due to high amounts of mud and organic detrital matter in the sediments. Polychaete worms and mud whelks (a type of gastropod) were abundant at Wanggoolba Creek. Both animals are detrital feeders and competition for available detrital matter may explain the dominance of one over the other. The occurrence of polychaete worms at sites low in seagrass abundance suggests that they are likely to survive on low amounts of food relative to the larger gastropods. They are possible indicators of low seagrass abundance.
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Correct citation: McKenzie, LJ., Yoshida, RL. & Coles, RG. (2006 - 2012). Seagrass-Watch. www.seagrasswatch.org. 228pp. Disclaimer: The views expressed on this site are those of the authors and not necessarily those of the Queensland Government. Website designed by McKenzie, LJ., Yoshida, RL. |
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