Benthic Habitat Mapping, Primary Productivity Measurements and Macrofauna Surveys in the Camden Haven and Hastings River Estuaries
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Benthic Habitat Mapping, Primary Productivity Measurements and Macrofauna Surveys in the Camden Haven and Hastings River Estuaries Damien Maher Peter Squire Bradley Eyre Centre for Coastal Biogeochemistry Southern Cross University October 2007 Prepared for: Port Macquarie Hasting Council Client Contact: Matt Rogers Prepared by: Centre for Coastal Biogeochemistry School of Environmental Science and Management Southern Cross University PO BOX 157 Lismore 2480 CCB Report No. 2007-05 Contact: Prof. Bradley Eyre Telephone: (02) 66203773; 041 9622824 Fax: (02) 66212669 Email: [email protected] Executive Summary Benthic habitat mapping of the Hastings River and Camden Haven Estuaries was undertaken during February 2006. Habitat within the Hastings River Estuary was found to be dominated by channel sediments, comprising of marine sands in the lower estuary and fluvial sands and gravel in the upper estuary. The Camden Haven Estuary had extensive seagrass beds accounting for nearly 40% of the total instream benthic habitat. Three seagrass species are found within the Camden Haven Estuary, Zostera capricorni, Halophila australis and Ruppia megacarpa. Benthic and pelagic productivity measurements and macrofauna surveys were undertaken seasonally from winter 2006 to autumn 2007. Benthic productivity in both estuaries showed distinct seasonality with the lowest productivity in winter and highest in summer. Temperature appears to be the driving factor in this seasonality as light and nutrient supply were generally optimal throughout all seasons. Benthic productivity was approximately 10 times higher in seagrass communities than non- seagrass communities and as such, these areas are extremely important in terms of total estuarine productivity. Pelagic productivity also showed distinct seasonality with the highest productivity occurring during summer. Negligible winter pelagic productivity was observed in the Hastings River estuary, suggesting that benthic productivity and terrestrial inputs is sustaining the higher trophic levels during winter. Macrofauna surveys showed distinct differences in community structure between seagrass and non-seagrass areas. Highest species abundance and diversity were generally found at seagrass and intertidal sand shoal sites, with general trend towards lower diversity and abundance at deeper sites with muddy sediments. In terms of benthic habitat and estuarine productivity the Camden Haven and Hastings River Estuaries are in good health. The estuaries support extensive commercial and recreational fisheries. To ensure the continued health of these estuaries it is recommended that benthic habitat mapping and macrofauna surveys be repeated at 2-3 year intervals for early detection of estuarine change. Investigations into the impact of red weed (Polysiphonia sp) blooms on benthic and pelagic processes in the lower estuaries are also recommended as data on these impacts is limited. Table of Contents Executive Summary ....................................................................................................... 3 Introduction .................................................................................................................... 6 1 Benthic Habitat Mapping ........................................................................................ 7 1.1 Methods ........................................................................................................... 7 1.2 Benthic Habitats .............................................................................................. 7 1.2.1 Hastings River .......................................................................................... 8 1.2.2 Camden Haven Estuary .......................................................................... 16 2 Benthic and Pelagic Productivity ......................................................................... 25 2.1 Sample Sites .................................................................................................. 25 2.2 Methods ......................................................................................................... 29 2.2.1 Benthic Productivity .............................................................................. 29 2.2.2 Pelagic Productivity ............................................................................... 31 2.3 Results ........................................................................................................... 32 2.3.1 Benthic Productivity .............................................................................. 32 2.3.2 Pelagic Productivity ............................................................................... 36 3 Macrofauna .......................................................................................................... 38 3.1 Methods ......................................................................................................... 38 3.2 Data ............................................................................................................... 38 4 Estuarine Health ................................................................................................... 44 5 Recommendations ................................................................................................ 47 6 References ............................................................................................................ 48 7 Appendix 1 Macrofauna abundance for Camden Haven and Hastings River Estuaries ....................................................................................................................... 49 Table of Figures Figure 1 Seagrass beds in the lower Hastings River estuary. ................................................... 9 Figure 2 Seagrass beds in the Maria River ............................................................................. 10 Figure 3 Seagrass beds in the upper Hastings River estuary. ................................................. 11 Figure 4 Habitat map of the lower Hastings River estuary. .................................................... 13 Figure 5 Habitat map of the Maria River. ............................................................................... 14 Figure 6 Habitat map of the upper Hastings River estuary. .................................................... 15 Figure 7 Seagrass distribution in Camden Inlet, Googleys Lagoon and lower Stingray Creek. ................................................................................................................................................. 17 Figure 8 Seagrass distribution in Queens Lake ...................................................................... 18 Figure 9 Seagrass Distribution in Watson‟s Taylor Lake. ...................................................... 19 Figure 10 Habitat map of Camden Inlet, Googleys Lagoon and Stingray Creek. .................. 22 Figure 11 Habitat map of Queens Lake .................................................................................. 23 Figure 12 Habitat map of Watson Taylors Lake .................................................................... 24 Figure 13 Sampling locations in the Hastings River estuary .................................................. 27 Figure 14 Sampling locations in the Camden Haven estuary ................................................. 28 Figure 15 Field core incubation setup. ................................................................................... 29 Figure 16 Benthic chamber array used for seagrass and intertidal sand shoal incubations. ... 30 Figure 17 Graph displaying typical diurnal changes in oxygen concentration ....................... 31 Figure 18 Oxygen fluxes for core incubations in the Camden Haven estuary ....................... 32 Figure 19 Oxygen fluxes for core incubations in the Hastings River estuary ........................ 33 Figure 20 Oxygen fluxes for chamber incubations in the Camden Haven and Hastings River estuaries. .................................................................................................................................. 34 Figure 21 Gross pelagic productivity in the Camden Haven and Hastings River estuaries. .. 36 Figure 22 Underwater photograph of red weed bloom during summer field trip ................... 37 Figure 23 Winter MDS ........................................................................................................... 40 Figure 24 Spring MDS ........................................................................................................... 40 Figure 25 Summer MDS ......................................................................................................... 41 Figure 26 Autumn MDS ......................................................................................................... 41 Figure 27 LINKTREE diagram for macrofauna sites during winter. ..................................... 42 Figure 28 LINKTREE diagram for macrofauna sites during spring ...................................... 42 Figure 29 LINKTREE diagram for macrofauna sites during summer ................................... 43 Figure 30 LINKTREE diagram for macrofauna sites during autumn. ................................... 43 Figure 31 Conceptual model of carbon flow in the Hastings River Estuary .......................... 45 Figure 32 Conceptual model of carbon flow in the Camden Haven Estuary ......................... 46 List of Tables Table 1 Benthic habitats as defined in the Hastings River Estuary .......................................