icolls - Sustainable Tourism CRC

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ECOLOGY, THREATS AND MANAGEMENT OPTIONS FOR SMALL ESTUARIES AND ICOLLS viii • Local management strategies, usually enforced by local government agencies, have substantial impacts on the ecology of ICOLLs. Specifically, artificial opening regimes strongly shape the biotic community composition in ICOLLs and tend to reduce the structural and ecological diversity of ICOLL environments across a broad geographic scale. • ICOLLs are impacted by sewage effluent in many regions and their natural hydrodynamics amplify the consequences of sewage discharge through long water residence time and reduced tidal flushing. • Recreational and commercial harvesting of biota from ICOLLs has the potential to significantly alter their biodiversity and food web dynamics, typically through changes in the relative abundance of toporder predators. • Local residents tend to view ICOLLs in a different light to visitors and tourists. In general terms, local residents do not see ICOLLs as attractive environments for recreation, especially swimming and recreational fishing, whereas visitors tend to readily use these systems for these purposes. • ICOLL food webs are temporally and spatially variable (more so than in large estuaries), although at any given time the diversity of fauna is generally quite low. • ICOLL food webs rely on marine subsidies (nutrients/organic matter, incoming biota and seaweed) as resources. Modifications of ICOLL opening regimes that increase or decrease the contribution of marine subsidies consequently have strong structural and functional influences on food webs. • These changes have implications for aesthetics, recreational use, management regimes and conservation. Future Action Our research has identified a range of areas that require future research attention. We have classified these into three distinct areas, namely: • Characterisation of recreational use of ICOLLs: This includes census of recreational activities and user loads at key ICOLLs of interest, as well as the development and implementation of targeted surveys that will profile ICOLL users, activities and attitudes. • Manipulative experiments testing our understanding of ICOLL biodiversity, ecology and food web structure and function: This research would investigate the impact of artificial opening regimes on ICOLL ecology and food webs, both through field examination of natural ICOLL entrance opening events, but also with respect to planned artificial manipulation of entrance status. • Development of indicators of ICOLL ‘health’ and sustainability: Monitoring tools and protocols are urgently needed to facilitate tracking of changes to the ecological integrity of ICOLLs in response to natural variations in driving variables, anthropogenic pressure and management activities. Research aligned with recent ST<strong>CRC</strong> initiatives to develop monitoring indicators and methods could facilitate the development of an holistic approach to assessments of ICOLL resilience and vigour in light of increasing catchment and coastal development.
Chapter 1 ECOLOGY, THREATS AND MANAGEMENT OPTIONS FOR SMALL ESTUARIES AND ICOLLS THREATS TO THE ECOLOGICAL HEALTH OF ICOLLS: A REVIEW WITH EMPHASIS ON SMALL ICOLLS IN AUSTRALIA Abstract This chapter reviews the physical and chemical pressures threatening the ecological health of intermittently closed and open lakes and lagoons (ICOLLs) and identifies the key knowledge gaps that impede the scientifically informed management of these systems. Significantly, we propose that whilst estuarine data are likely to be somewhat applicable to ICOLLs, the unique hydrodynamic characteristics of these coastal waterbodies suggest that processes of energy and nutrient cycling may be similarly unique. To date, very little research has attempted to determine the ecological structure and function of ICOLLs and their responses to human perturbations. Fish faunal surveys dominate the otherwise scant literature, owing to the numerous commercially valuable species that inhabit these coastal waterways. At present, there is a lack of integrated research investigating the major processes threatening the ecological health and sustainability of ICOLLs, namely the effects of eutrophication, contamination, fish extraction, modification of freshwater inflows, modification of opening and closing regimes, tourism, recreation and coastal development. Considerable research effort is required to develop a better understanding of the ecological and socioeconomic importance of ICOLLs in the coastal environment, as well as the role they play in sustaining biodiversity, ecological function and fisheries production in the coastal zone. The ecological status of ICOLLs in relation to increasing coastal development in Australia is of concern, particularly with regard to their sensitivity to altered freshwater inflows, artificial opening regimes, inputs from sewage treatment plants and excessive runoff from industrial, urban and agricultural land uses. These issues undoubtedly threaten the long-term sustainability of ICOLLs and the species that inhabit them in other parts of the world and certainly warrant more research attention. Priority research themes of particular relevance to ICOLLs are identified in this chapter. Introduction The coastal zone is arguably one of the most valuable (biologically and economically) yet heavily modified environments on the planet (Costanza, d'Arge, de Groot, Farber, Grasso, Hannon, Limburg, Naeem, O'Neill, Paruelo, Raskin, Sutton & van den Belt 1997; Blaber, Cyrus, Albaret, Ching, Day, Elliott, Fonseca, Hoss, Orensanz, Potter & Silvert 2000; Turner 2000; Kullenberg 2001; Nedwell, Sage & Underwood 2002; Valiela & Bowen 2002). Globally, the coastal zone has experienced a 50% population increase over the past 20 years (Roy, Williams, Jones, Yassini, Gibbs, Coates, West, Scanes, Hudson & Nichol 2001) and recent population projections indicate that coastal development is likely to continue at this rate well into the foreseeable future (Yapp 1986; Zann 2000; Roy et al. 2001; Struglia & Winter 2002; Tait, Cresswell, Lawson & Creighton 2000; Tappin 2002). Already, there are very few estuarine and offshore environments that have not been adversely affected by agricultural, urban and/or industrial development (Blaber et al. 2000; Zingone & Enevoldsen 2000; Hall 2001; Nedwell, Sage & Underwood 2002; Valiela & Bowen 2002). In this chapter, we review the anthropogenic processes that threaten the long-term ecological health of a particular subset of estuaries known as ICOLLs. Whilst the term is not widely recognised, ICOLLs are the most numerically abundant coastal waterways along the southeast coast of Australia (Pollard 1994a; Roy et al. 2001). ICOLLs are also found along the southwest coast of Australia (Neira & Potter 1992; Roy et al. 2001) and in New Zealand (Schallenberg, Burns & Peake 2003), South Africa (Allanson & Baird 1999; Vorwerk, Whitfield, Cowley & Paterson 2003), South America (Kjerfve, Schettini, Knoppers, Lessa & Ferreira 1996; Garcia, Vieira & Winemiller 2003), North America (Elwany, Flick & Hamilton 2003; Feller, Whigham, McKee & Lovelock 2003) and Europe (Alcorlo, Diaz, Lacalle, Baltanas, Florin, Guerrero & Montes 1997; Newton & Mudge 2003). ICOLLs have been variously defined in the scientific literature with respect to the intermittent nature of their connection to the ocean. Common descriptive names for ICOLLs include ‘barrier estuaries’ (Gray & Kennelly 2003) and ‘seasonally open estuaries’ (Neira & Potter 1992; Gaughan & Potter 1995) in Australia; ‘closed estuary’ (Hartgers & Buijse 2002) or ‘temporary lakes’ (Alcorlo et al. 1997) in Europe; ‘coastal lagoons’ (Kjervfe et al. 1996; Flores-Verdugo, Day, Mee & Briseno-Duenas 1998; Feller et al. 2003; Garcia, Vieira & Winemiller 2003) in North and South America; and a mix of ‘intermittently closed and open lakes and lagoons’ (Bell, Cowley & Whitfield 2001; Cowley & Whitfield 2001), ‘microtidal estuaries’ (Allanson 2001), ‘semipermanently closed estuary’ (Perissinotto, Walker, Webb, Wooldridge & Bally 2000) and ‘temporarily 1
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