Fish Community Responses to the Combined Effects of Decreased Hydroperiod and Nonnative Fish Invasions in a Karst Wetland: Are Everglades Solution Holes Sinks for Native Fishes?
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Short-hydroperiod Everglades wetlands have been disproportionately affected by reductions in freshwater inflows, land conversion and biotic invasions. Severe hydroperiod reductions in these habitats, including the Rocky Glades, coupled with proximity to canals that act as sources of invasions, may limit their ability to support high levels of aquatic production. We examined whether karst solution holes function as dry-down refuges for fishes, providing a source of marsh colonists upon reflooding, by tracking fish abundance, nonnative composition, and survival in solution holes throughout the dry season. We paired field surveys with an in situ nonnative predation experiment that tested the effects of predation by the recent invader, African jewelfish (Hemichromis letourneuxi) on native fishes. Over the 3 years surveyed, a large number of the solution holes dried before the onset of the wet season, while those retaining water had low survivorship and were dominated by nonnatives. In the experiment, mortality of eastern mosquitofish (Gambusia holbrooki) in the presence of African jewelfish was greater than that associated with deteriorating water quality. Under current water management, findings suggest that solution holes are largely sinks for native fishes, given the high frequency of drydown, extensive period of fish residence, and predation by nonnative fishes.
KeywordsFishes Short hydroperiod wetlands Karst Invasive species Source-sink dynamics Refuges
We greatly appreciate the field assistance of: R. Kobza, D. Padilla, X. Pagan, D. Riggs, H. Waddle, A. Martin, B. Shamblin, R. Urguelles, and P. George and personnel in J. Trexler’s lab. B. Dunker was invaluable in field work, trap construction, and sample processing. J. Kline (ENP) assisted as project representative for this study, and through discussions, fieldwork, and data sharing. D. Elswick and C. Fadeley (USGS) and J. Lorenz, J. Wolkowsky, and L. Canavan (Audubon Florida) helped immensely with budget and personnel needs. S. Howington (ENP) provided assistance as NPS Critical Ecosystem Studies Initiative coordinator and project administrator. B. Zepp assisted us with the ENP scientific permits. This publication was produced for a special issue devoted to investigating the ecological response of over 20 years of hydrologic restoration and active management in the Taylor Slough drainage of ENP. Support was provided by ENP (CESI IA F5284-04-0039), the Southeast Environmental Research Center, the Florida Coastal Everglades Long-Term Ecological Research program (National Science Foundation cooperative agreement #DBI-0620409), the Everglades Foundation, and the South Florida Water Management District.
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