Aquifer Discharge Drives Microbial Community Change in Karst Estuaries
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Karst estuaries are unique systems governed by freshwater inputs that flow directly to the sea through karst conduits and/or matrices. Because they are found at the interface between terrestrial and marine environments, they can act as sentinels to climate change and as indicators of aquifer health. The physical and geochemical gradients formed in karst estuaries are a direct result of the interactions between inland hydrological conditions and sea level. To examine the influence these gradients have on microbial communities in the water column and sediment of a karst estuary, we studied the spring-fed Double Keyhole Karst Estuary in west central Florida for a 2-year period. Four sites were monitored within this system starting at the Double Keyhole Spring Conduit extending 2 km west through the estuary toward the Gulf of Mexico. Water column and sediment samples were collected quarterly at all sites from September 2011 through September 2013. Archaeal, bacterial, and microbial eukaryote communities were analyzed using quantitative PCR and length-heterogeneity PCR. The biological communities were analyzed in the context of hydrological, physical, and geochemical parameters in order to determine which factor(s) governed the observed changes of microbial abundance and richness. The major finding of this study was that microbial community change in this karst estuary was primarily driven by the volume of aquifer discharge and associated physical gradients, and less by the geochemical fluctuations within the system.
KeywordsBiogeochemistry Ecology Molecular Community Karst Estuary Microbial Environmental DNA
The authors thank the University of South Florida for supporting this project. We thank Pasco County, FL for allowing access to the site, Dave DeWitt of the South West Florida Water Management District, and Zachary Atlas of the Geology Department at USF for the assistance. Many undergraduates provided surface and logistical support in the field and helped process samples in the lab.
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no competing interests.
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