Abiotic factors influence the dynamics of marine habitat use by a highly mobile “freshwater” top predator
Cross-ecosystem movements of mobile consumers are a primary mechanism by which energy and nutrients are exchanged between disparate ecosystems. While factors influencing variation in bottom–up subsidies between ecosystems have been well studied, much less is known regarding how biotic and abiotic factors influence the dynamics of mobile consumer-driven connectivity. In a literature survey, we found only 14% of studies examined factors contributing to variation in cross-ecosystem marine foraging by freshwater-adapted consumers. Here, we examine the relationships between abiotic factors and cross-ecosystem movements of a highly mobile freshwater-adapted top predator, Alligator mississippiensis (American alligator). As alligators lack physiological adaptations to survive in marine environments, we predict this linkage would be affected by factors that modify the ability to cope with high salinities. Our results reveal that multiple abiotic factors (e.g., relative humidity, temperature, total precipitation) are key explanatory variables of the duration of cross-ecosystem foraging trips by alligators, and that the absence of salt glands does not preclude them from performing long forays into marine environments. More broadly, our results expand our understanding of mobile consumer-driven ecosystem connectivity at the land–sea interface by demonstrating connectivity is highest when physical stressors are relaxed, and access to and availability of resources are maximized.
KeywordsAlligator mississippiensis Crocodilian Cross-ecosystem movement Ecosystem connectivity GPS–VHF telemetry Mobile consumer Trophic coupling
We thank R. Nifong, R. McNolty, M. Hensel, D. Penniman, R. McCarville, C. Conegemi, and C. Letcher for their assistance in field and with data processing. Special thanks are given to R. Nifong, J. Ferguson, and A. Rosenblatt for their comments on statistical analyses and on earlier drafts of this manuscript. This research was conducted under Georgia Department of Natural Resources Special Permits 29-WBH-08-178, 29-WBH-09-56, and 29-WBH-10-33 and University of Florida IACUC protocol 201005071. This research was supported by the Estuarine Reserves Division, Office of Ocean and Coastal Resource Management, National Ocean Service, and National Oceanic and Atmospheric Administration (Award No. NA10NOS4200022). This research was supported in part by the Georgia Coastal Ecosystems LTER Project (NSF Awards OCE-0620959 and OCE-1237140). Lastly, we thank the people of Sapelo Island, Georgia, and the Hog Hammock community for their support during this project.
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