icolls - Sustainable Tourism CRC

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ECOLOGY, THREATS AND MANAGEMENT OPTIONS FOR SMALL ESTUARIES AND ICOLLS ABSTRACT Over 60% of south-eastern Australia’s coastal waterways can be classified as intermittently closed and open lakes and lagoons (ICOLLs). At present, very little is known about the recreational use of ICOLLs and how such use varies geographically and temporally along the New South Wales coast. The impacts of tourism on natural environments are of increasing concern in Australia, especially in coastal areas, so it is timely that we investigate ICOLL ecology in conjunction with tourist use patterns to ensure that these systems are appreciated, used appropriately and managed sustainably. In comparison with large estuaries, relatively little is known of the ecology of these intermittently open systems and their responses to perturbations. This lack of knowledge of how these systems respond to anthropogenic activities threatens their long-term sustainability, particularly in light of the high human population density in coastal regions of Australia and increasing nutrient inputs from urban (sewage), industrial and agricultural sources. In addition, local management agencies often artificially alter the opening and closing regimes of ICOLLs to minimise the aesthetic effects of algal blooms and local flooding. In addition to these watershed scale perturbations, ICOLLs can be significant sites for recreation and fishing activities in the coastal zone, yet we know little about the effects of these activities on ICOLL health. In this study we investigated critical aspects of ICOLL ecology and asked: how do these systems respond to increasing coastal pressures in general and in particular, those directly or indirectly related to tourism and recreation in their catchments? We used a variety of mechanisms to tackle this question, ranging from detailed literature reviews of ICOLL responses to perturbations, to field investigations of ICOLL characteristics and fish assemblages, food web structure and sources of carbon (energy) fuelling ICOLL productivity. We were particularly interested in the influence of nutrient inputs (particularly from STPs) and entrance opening and closing regimes on the basic structure of the food web and in turn, the implications of these modifications for the sustainability and tourism appeal of ICOLLs. Specifically, we focused on aspects of the fish communities of ICOLLs, particularly the diets of commercially and recreationally valuable species like Yellowfin Bream (Acanthopagrus australis), Sand Whiting (Sillago ciliata), Dusky Flathead (Platycephalus fuscus) and Sea Mullet (Mugil cephalus). We found that ICOLLs tend to support a wide array of invertebrate and fish taxa and that diversity and the functioning of ICOLL food webs are strongly influenced by entrance opening and closing regimes. Furthermore, the diets of valuable fish species tended to be narrower in our study ICOLLs than in larger estuaries, highlighting dramatically different resource use patterns in these dynamic coastal waterbodies. The sustainability of ICOLLs for tourism and recreation is increasingly threatened by coastal developments and our research highlights the importance of maintaining ICOLLs as fish nursery grounds and significant recreational fishing sites along the Australian coastline. ACKNOWLEDGEMENTS The <strong>Sustainable</strong> <strong>Tourism</strong> Cooperative Research Centre, an Australian government initiative, funded this research. The Centre for Riverine Landscapes and Griffith University also supported this research through provision of expertise and equipment required for the field and laboratory work. The direction and outcomes of the project benefited greatly due to contributions from Professor Leon Zann (formerly of Southern Cross University), Dr David Rissik (NSW DIPNR now DEC), Chistopher Irons (Griffith University) and Peter Helman (Southern Cross University). In addition, Grant Russell made major contributions to the study, particularly the work reported in Chapter 4, during his eight week summer scholarship in the Centre for Riverine Landscapes at Griffith University. Field assistance from Grant Russell, Steve Mackay, Kim Markwell, Nerida Beard, Christy Fellows, Andrew Cook, Kate Smolders, Katrina Goudkemp, Ellie Dores and Kate Lawrance was greatly appreciated. Rene Diocares provided technical support and ran the stable isotope samples through the Mass Spectrometer. Laboratory and analytical assistance from Vanessa Fry was also beneficial. vi
ECOLOGY, THREATS AND MANAGEMENT OPTIONS FOR SMALL ESTUARIES AND ICOLLS SUMMARY Intermittently closed and open lakes and lagoons (ICOLLs) constitute over 60% of coastal waterways in southeastern Australia yet, in comparison with large estuaries, relatively little is known of the ecology of these intermittently open systems and their responses to perturbations. The importance of these unusual aquatic systems for recreation and tourism is widely recognised so it is timely that we investigate ICOLL ecology in conjunction with tourist use patterns to ensure that these systems are managed sustainably. ICOLLs play an important role in maintaining key coastal processes in south-eastern Australia, including provision of habitat for endangered species, nursery areas for commercially and recreationally valuable fish species, and important sinks for nutrients derived from industry and agriculture (Pollard 1994a; Roy, Williams, Jones, Yassini, Gibbs, Coates, West, Scanes, Hudson & Nichol 2001). In New South Wales, the Healthy Rivers Commission has suggested that many of the State’s ICOLLs are degraded beyond feasible ecological restoration, and therefore it is increasingly important to manage the less critically impaired systems in a manner that will ensure continued and/or enhanced beneficial uses, such as fisheries production, whilst not compromising important conservation and ecosystem health requirements. Current evidence suggests that pollution, habitat destruction and hydrologic changes threaten a considerable number of ICOLLs in northern New South Wales (Roy et al. 2001). Given that these changes have the potential to adversely affect coastal fisheries and the sustainability of coastal environments (Blaber, Cyrus, Albaret, Ching, Day, Elliott. Fonseca, Hoss Orensanz, Potter & Silvert 2000) there is a strong impetus for research investigating the key processes that maintain ecological structure and function in ICOLLs. Significantly, current coastal developments threaten the sustainable use of ICOLLs as important sites for tourism and recreation. Objectives of Study In this study we aimed to examine the ecological implications of coastal development, management strategies and visitor use of ICOLLs. Given the paucity of information on these systems in the scientific literature, we undertook basic ecological surveys in a series of ICOLLs in northern New South Wales in order to gather information that would underpin the development of conceptual models of the ecological structure and function of ICOLL ecosystems. Specifically, we aimed to assess the ecological consequences of the following perturbations on ICOLL ecology: • Artificial manipulation of opening regimes; • Excessive nutrient inputs from urban (sewage), agricultural and industrial sources; and • Removal of fish, molluscs and crustaceans as part of a recreational fishing resource. On the basis of our ecological surveys we developed a suite of conceptual models that related ecosystem structure and function to a series of anthropogenic perturbations. In addition to investigating the ecological resilience and resistance of ICOLLs to perturbations, we also sought to increase the national and international profile of this important subset of estuaries. We did this by running an ICOLL special session at an international conference in Ballina, New South Wales (20-25 June 2004). This conference had as its theme “Estuaries and Change” and focussed on human modifications of estuaries and their ecological responses. Co-hosted by the Estuarine and Coastal Sciences Association (ECSA) and the Estuarine Research Federation (ERF), the two largest societies of estuarine scientists in the world, this conference was an excellent venue for us to showcase our research and increase the exposure of ICOLL environments. Significantly, our ICOLLs special session received the highest number of submitted abstracts of all sessions at the conference and was consistently well attended over the duration of the conference. Abstracts from the ICOLL special session are included in Appendix C. Methodology Over the course of this study we used a wide range of methods to investigate aspects of the ecology of ICOLLs. In addition to conducting literature reviews investigating the ecology, threats and management of ICOLLs, we used natural abundance stable isotopes to examine and describe the structure and function of ICOLL food webs. The detailed methods used for these investigations are described in the relevant chapters of this report. Key Findings The key findings of this project are: • ICOLLs are important ecosystems along the Australian coastline, providing diverse habitat for wildlife and a wide range of recreational opportunities. vii
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Research Programs The Sustainable T
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