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Abstract:
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The meta -ecosystem concept is an attempt to combine metacommunity , ecosystem and landscape ecology . In meta -ecosystems , both organismal dispersal and material movement between patches can have important effects on communities . This concept provides a more realistic framework of natural systems by considering both processes jointly .
My dissertation presents a case -study of natural metaecosystems by studying the role of waterfowl in structuring zooplankton communities in prairie pothole wetlands in South Dakota . I use observations of natural wetlands , microcosm and mesocosm experiments to show how dispersal of materials and organisms by waterfowl can affect zooplankton abundance and community composition . Waterfowl are conspicuous , behaviorally adaptable , highly mobile and economically important members of wetland habitats . They are thought to have possible effects on zooplankton communities either by dispersing zooplankton propagules among wetlands or by moving nutrients into (via defecation ) or out of (via consumption of macrophytes and invertebrates ) wetlands .
In this dissertation , I show evidence that waterfowl disperse a limited subset of locally rare zooplankton species between wetlands . I also provide experimental evidence that these dispersed species may have impacts on zooplankton community assembly .
I also show how input of waterfowl excreta may sometimes have strong impacts on the local community . Very large inputs of goose excreta promote abundance and diversity of zooplankton . However , inputs at more modest levels , such as those routinely found in nature , are rarely detectible . Additions of excreta at levels five -times that typically found in nature produce a possible shift in zooplankton community structure away from both no -excreta communities and communities fertilized with comparable amounts of nitrogen and phosphorus . I postulate that most excreta quickly sinks to the benthos and only a small fraction becomes available for use by zooplankton . On the time scales used in my dissertation , it is only with very large additions of excreta that shifts in the zooplankton community become apparent .
My dissertation is one of the first to apply the meta -ecosystem concept to a natural system . It also shows that waterfowl impacts on the zooplankton community may be most important in small wetlands or early in community assembly . |