COS 14-3 - Environmental filters of wet-season aquatic communities into dry-season pools of the Florida Everglades

Monday, August 8, 2011: 2:10 PM
18C, Austin Convention Center
Aaron D. Parker, Southeast Environmental Research Center, Florida International University, North Miami, FL, Joel C. Trexler, Department of Biological Sciences, Florida International University, Miami, FL, Dale E. Gawlik, Environmental Science Program, Florida Atlantic University, Boca Raton, FL and Bryan B. Botson, Biological sciences, Florida Atlantic University, Boca Raton, FL

The annual drying of the Florida Everglades wetlands creates a challenge for fish and macroinvertebrates that must find refuges for the dry season. We hypothesize that landscape features and species-specific patterns of refuge finding determine the makeup of communities in drying pools that attract wading birds for dry-season foraging. Small fish and macroinvertebrates were collected using throw traps to evaluate this hypothesis. From 2005 through 2009, we collected wet-season samples from over 150 sentinel sites located throughout the Everglades, while in the following dry seasons we sampled at a subset of the wet-season sentinel sites, random drying pools, and at locations where wading birds were observed actively feeding. We tested whether fish communities in drying pools could be predicted by local wet-season community data and the local habitat matrix. We compared wet-season community composition to composition in foraging pools and randomly selected sites in the dry-season. Euclidean distances between wet and dry sites, and least-cost-path distances, using both dichotomous (permeable or impermeable) and cost-weighted landscape grids, were measured using ARCGIS.  This was done to measure theoretical swimming distances between sites through the heterogeneous Everglades landscape. These were incorporated into a multiple regression model to predict dry-season fish biomass


We found that the spatial distribution of wet-season wading bird prey biomass changed dramatically from 2005 to 2009, with the highest numbers in 2008 and 2009 in short-hydroperiod areas. Prey biomass in random drying pools was usually higher than in dry-season sentinel sites. Drying pools where wading birds were observed actively feeding often had very elevated densities of prey species. Using spatial cross-correlation analysis, wet-season prey fish biomass was a predictor of dry-season biomass when collected within 10 km, after which, there was rapid distance decay in predictability. Community composition was more dissimilar between wet and dry-season sites when water levels dropped quickly and when greater disparities were present in total biomass. Dry-season sample type (sentinel, random pool, or foraging sites) also affected the dissimilarity between wet and dry-season samples. Akaike's information criterion indicated that cost-weighted, but not Euclidean or dichotomous-swimming, distance was important for predicting dry-season fish biomass. Differences in drying pool communities resulted from different species' recruitment, habitat use, dispersal, and risk aversion in a seasonally-drying heterogeneous landscape.

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