Benthic Suspension Feeders as Determinants of Ecosystem Structure and Function in Shallow Coastal Waters
Suspension-feeding animals are common macroscopic inhabitants of hardand soft-bottom habitats in shallow coastal waters. Many forms aggregate on specific bottom types where they take advantage of the free-energy subsidies provided by waves, tides and wind
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Publication No. 1259 of the Belle W. Baruch Institute for Marine Biology and Coastal Research.
1.1 Introduction Suspension-feeding animals are common macroscopic inhabitants of hardand soft-bottom habitats in shallow coastal waters. Many forms aggregate on specific bottom types where they take advantage of the free-energy subsidies provided by waves, tides and wind-driven currents that transport oxygen and particulate food to them, carry away waste, disperse larvae, and exclude predators. Because these organisms can move and process large amounts of material between the water column and the bottom, they are often major agents of benthic-pelagic coupling and nutrient cycling (Dame 1996; Wildish and Kristmanson 1997). As a group, they have been promoted as system filters or cleaners because of their suspension-feeding abilities (Newell 1988). Some reef builders are advocated as erosion-control mechanisms (Kirtley and Tanner 1968). All of these functional roles imply that benthic suspension feeders play a significant part in the overall functioning of many shallow coastal systems. To be certain that we are clearly understood regarding suspension-feeding terminology, there are a few terms that should be defined. The more general term "suspension feeder" refers to animals that retain particles from the water passing their feeding organs. The term "filter feeder" is often used synonymously with the term suspension feeder; however, filter feeding specifically describes feeding by passing water through structures that retain particles according to size and shape (J0rgensen 1966). For example, vermetids (Gastropoda) are suspension feeders that use mucus nets to ensnare particles, but, in that mode, they are not filter feeders because the net is not very selective and the animal does not control water flow by the net. In comparison, many Ecological Studies, Vol. 151 K. Reise (ed.) Ecological Comparisons of Sedimentary Shores © Springer-Verlag Berlin Heidelberg 2001
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bivalves are suspension feeders and specifically filter feeders. At the ecosystem level, suspension feeders form a functional group that may be composed of a number of similar species. When suspension feeders are abundant in a particular ecosystem they have the potential to directly modulate the availability of resources to other organisms and groups by causing physical state changes in biotic and abiotic materials (Carpenter and Kitchell 1988; Jones et al. 1994; Dame 1996). In this process, suspension feeders can modify, maintain and create habitats, and, as such, these animals are often referred to as ecosystem engineers (Jones et al. 1994). If they transform the environment via the structure of their bodies or skeletons we view these operations as autogenic (Jones et al. 1994). If they transform living or non-living materials from one physical state to another, Jones et al. (1994) calls these processes allogenic. Some suspension feeders, e. g., oysters in reefs, can exhibit both autogenic and allogenic characteristics (Dame 1996). The go
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