Florida Coastal Everglades Long Term Ecological Research
Florida Coastal Everglades LTER - Current Working Groups
Current Working Groups

The current phase of the FCE LTER program is organized into four working groups and four cross-cutting themes. Each working group or cross-cutting theme focuses on a set of key research questions and/or major processes being quantified by the LTER program.
Working Groups Cross-cutting Themes
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Trophic Dynamics Working Group
Findings

FCE I: Our initial studies of consumer dynamics showed that the coastal ecosystem is much complex than we had previously thought and that assessing secondary productivity, especially within the mangrove ecotone regions, would be more difficult than anticipated because of the openness of the system and high mobility of consumers. Research showed that a balance of hydrological disturbance and biotic interactions (including behavioral ones) shape aquatic communities in marsh habitats. Food web studies revealed that detrital sources are very important to the consumer food webs, at least within upstream communities. Pilot studies of large consumers with broad salinity tolerances suggested that these mobile species might play an important role in the nutrient dynamics of the communities.

FCE II: Subsequent studies placed a special emphasis on exploring the fate of detrital organic matter in food webs and on elucidating drivers of consumer movements and related potential translocation of nutrients. Analysis of the fatty acid composition of primary benthic consumers showed detritus, rather than primary production, to be a strong, direct contributor to diets.

Consumer and prey distribution studies showed how availability of detritivores, along with the patterns of water distribution and salinity on the landscape, regulate the distribution of secondary consumers. Studies of four of these consumers showed strong responses to hydrological variability, perhaps related to indirect interactions with food quality. Modeled relationships between their abundance and expected water levels are helping to assess the ecohydrological status of the Everglades and to guide restoration activities (through reports to US Congress (http://www.sfrestore.org/documents/Final_System-wide_Ecological_Indicators.pdf).

Impact of 2010 cold snap on bull sharksBefore the 2010 cold snap, the proportion of bull sharks caught from different age-classes was relatively similar from ages 0-3, with a few older individuals caught in the estuary. However after the event, the proportion of sharks in older age-classes has dramatically decreased, with most individuals caught being age 0 or 1
Movement studies have shown that large-bodied predators vary considerably across taxa and that highly mobile top predators may play important, and unexpected, roles in the coastal Everglades. Using acoustic tracking arrays and stable isotopic analysis, we have found that alligators and sharks show considerable levels of individual specialization in trophic interactions that can be linked to movements. For example, some alligators and bull sharks make use of marine-derived resources despite spending considerable time in the low-salinity ecotone and appear to link marine and upstream habitats. In addition, seasonal movements of alligators in response to changes in salinity create links between the estuary and marsh habitats. Movements of gar and snook are less dramatic than those of bull sharks and alligators, and stable isotopic analyses suggest much less specialization in feeding with an almost exclusive reliance on freshwater and estuarine food webs.

Finally, we discovered that extreme events - such as the extreme cold snap of 2010 - can have profound impacts on some large predators. While alligators and gar were largely unaffected, bull sharks either permanently emigrated or died as did many snook. For sharks, the demography has remained altered for more than a year and a half. Recently, we initiated studies using fatty acids to elucidate food web structure in the estuarine zone. Studies are underway to elucidate fine-scale trophic structure and resolve biomarkers of detrital contributions to food webs that support upper trophic level consumers.
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National Science Foundation logo This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Cooperative Agreements #DEB-1237517, #DBI-0620409, and #DEB-9910514. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
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