icolls - Sustainable Tourism CRC

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
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