Green Sea Turtle and Dugong Food Resource Assessment Ashley Bunce and Peter Stratford 2007 Centre for Environmental Management Faculty of Science, Engineering and Health Central Queensland University Gladstone Qld 4680 Centre for Environmental MANAGEMENT FITZROY BASIN ASSOCIATION l!i l .• ...,<;;t~ - -!!..... QueellSiand ••,.""~ - Government Natural act on lferitage Salinity & Water Trust ll'ir,~t r.-.--..ut.-s Bcr;fj :tt; .A tt-f/Ntt/11 AUSTRA LI A ••, .... ~ ~ ·- llli a.tftM· ·~·. •• 363.70630994 35 23 Glad Pt Curtis Central Queensland l.!'IIVcRSJJ'\' Green Sea Turtle and Dugong Food Resource Assessment Fitzroy Basin Association and Queensland Parks and Wildlife Services Shoalwater Bay Seagrass Surveys: 2002 - 2006 Centre for Environmental MANAGEMENT Centre for Environmental Management Faculty of Science, Engineering and Health Central Queensland University Gladstone Qld 4680 Shoalwater Bay 2002 • 200iS TABLE OF CONTENTS TABLE OF CONTENTS ...................................................................................................................... I LIST OF FIGURES ............................................................................................................................ Ill LIST OF TABLES ............................................................................................................................ VII 1 EXECUTIVE SUMMARY ........................................................................................................... 1 2 INTRODUCTION ........................................................................................................................ 4 2.1 SEAGRASS SPECIES DISTRIBUTION ........................................................................................ 4 2.2 ICON SPECIES ...................................................................................................................... 5 2.3 OBJECTIVES ......................................................................................................................... 8 3 MATERIALS AND METHODS ................................................................................................. 10 3.1 SITE DESCRIPTION .............................................................................................................. 10 3.1.1 Sampling Sites Selection.......................................................................................... 10 3.2 TIMING OF SURVEYS ............................................................................................................ 13 3.3 SAMPLING DESIGN .............................................................................................................. 13 r-----·-- --......_ 3.4 CHOICE OF VARIABLES ...........................................................................................:.-: .......... 14 3.5 PRECISION ISSUES AND INDIVIDUAL SAMPLE SIZE ................................................................. 15 3.6 SAMPLE COLLECTION AND PROCESSING .............................................................................. 16 3.6.1 Percent Cover and Species Composition ................................................................. 16 3. 6.2 Biomass Sampling.................................................................................................... 16 3.6.3 Nutritional analysis ................................................................................................... 17 3. 7 PHYSICAL PARAMETERS ...................................................................................................... 17 3.7.1 Temperature ............................................................................................................. 17 3.7.2 Rainfa/1 ...................................................................................................................... 18 3.7.3 Wind speed ............................................................................................................... 18 3. 7. 4 Sediment Composition ............................................................................................. 18 3.7.5 Lyngbya majuscula ................................................................................................... 19 3.8 STATISTICAL ANALYSIS ....................................................................................................... 19 3.8.1 Analysis of Variance ................................................................................................. 19 3. 8.2 Multivariate Analysis ................................................................................................. 20 4 RESULTS ................................................................................................................................. 22 4.1 SEAGRASS COVER .............................................................................................................. 22 4. 1.1 Temporal and Spatial Changes in Seagrass Cover ................................................. 26 4.2 SPECIES COMPOSITION ....................................................................................................... 30 Zostera capricorni ..................................................................................................................... 34 4.2. 1 Halophila ova/is ........................................................................................................ 34 4.2.2 Halodule uninervis .................................................................................................... 34 4.2.3 Cymodocea serrulata ............................................................................................... 39 I Cnnt,·e for Environm,.ntci'Aar.r.geme::J. CerJr~ii i..'5i!;~(!ns!71mtfk,lv,~!Sfiy ,0(} flu.> 1."1., 9, Gr'.Jdstone ~.'id 4680 _Green Sea Turtle and Du;;ong Fcod Re~our,~e A.!>sessmel_!.l ___._. ______ .____ .... ----·--------- 4.3 SEAGRASS BIOMASS ........................................................................................................... 39 4.3. 1 Above versus Below Ground Biomass ..................................................................... 50 4.3.2 Nutritional quality of seagrass .................................................................................. 50 4.4 TEMPERATURE .................................................................................................................... 58 4.5 RAINFALL ........................................................................................................................... 58 4.6 WIND SPEED ...................................................................................................................... 60 4. 7 SEDIMENT COMPOSITION .................................................................................................... 60 4.8 LYNGBYA MAJUSCULA ......................................................................................................... 63 5 DISCUSSION ........................................................................................................................... 68 5.1 SEASONAL DISTRIBUTION .................................................................................................... 69 5.2 SEAGRASS DECLINE. ........................................................................................................... 70 5.3 DUGONGS AND GREEN SEA TURTLES .................................................................................. 72 6 CONCLUSION .......................................................................................................................... 73 7 ACKNOWLEDGEMENTS ........................................................................................................ 75 8 REFERENCES ......................................................................................................................... 76 ii --··--·---~- ---·--·------- --- -----·- ··---·--·- ---· ------- Environmental""""""" .. M ll."lAOE.Mh.'•IT Shoalwater Cay 2002 - 2006 -------------·--------·--···--·-------·-···--·--·-- -----------'"----- LIST OF FIGURES Figure 1: Location map of the five seagrass sampling sites within Shoalwater Bay, Queensland, Australia ............................................................................................................. 11 Figure 2: Sample collection at Duck Hole Creek, near Raspberry Creek in Shoalwater Bay..................................................................................................... ..................................... 12 Figure 3: Comparing seagrass sampling methods in Shoalwater Bay during pilot studies in November 2001. Note the size of the 1Ocm circle compared with the 50cm x 50cm quadrat. ......................................................................................................................... 15 Figure 4: Temperature loggers deployed on the Sabina Point seagrass meadow, March 2005........................................................................................................................................ 18 Figure 5: Mean seagrass cover (±SE) for each year of sampling at the five sites within Shoalwater Bay. Data are also shown as means for all sites combined. n = 480 quadrats x 5 sites x 4 years = 9,600....................................................................................... 23 Figure 6: Mean seagrass cover (±SE) for each season of sampling at the five sites within Shoalwater Bay. Data are also shown as means for all sites combined. n = 480 per season per site .......................................................................................................................