Grantee Research Project Results
Defining the Role of the Periphyton Mat in Shaping Food-Web Dynamics in the Florida Everglades
EPA Grant Number: U915916Title: Defining the Role of the Periphyton Mat in Shaping Food-Web Dynamics in the Florida Everglades
Investigators: Liston, Shawn E.
Institution: Florida International University
EPA Project Officer: Packard, Benjamin H
Project Period: January 1, 2001 through January 1, 2004
Project Amount: $81,681
RFA: Minority Academic Institutions (MAI) Fellowships for Graduate Environmental Study (2001) RFA Text | Recipients Lists
Research Category: Biology/Life Sciences , Academic Fellowships , Fellowship - Natural and Life Sciences
Objective:
The objective of this research project is to: (1) characterize the floating periphyton-mat macroinvertebrate community in the Everglades; and (2) describe the trophic links between this community and externally feeding macroinvertebrates and fishes.
Approach:
Expansive floating periphyton mats in the Florida Everglades serve as both the base of the food web and a refuge for invertebrates creating a self-contained trophic system within the mat. This "periphyton-mat complex" also is an important food source for externally feeding macroinvertebrates and fishes. However, the macroinvertebrate community structure within the mat and the trophic dynamics between this community and the rest of the Everglades food web remain poorly described. An initial study was conducted using a nested sampling design at four sites in northern Shark River Slough, Everglades National Park (ENP) to describe the scale of spatial variation in macroinvertebrate communities inhabiting floating mats. Based on those results, I conducted a study to describe correlations in the floating periphyton mat and benthic macroinvertebrate communities with nutrient (P) enrichment and hydroperiod; these are two driving abiotic factors in this system. By sampling 10 sites of various hydroperiods over a range of ambient P levels, I found that macroinvertebrate community composition varied with both P enrichment and hydroperiod and that these effects were different in floating-mat and benthic communities. Floating-mat communities were driven primarily by P levels, but benthic communities were driven primarily by hydroperiod. Extremely high macroinvertebrate densities at enriched, short-hydroperiod sites also indicated possible top-down and bottom-up trophic interactions. Two mesocosm studies were conducted to determine how macroinvertebrates and fish interact with this community. In an in situ mesocosm study in Taylor Slough, ENP, I increased P levels to stimulate bottom-up effects, and I manipulated consumer (Gambusia holbrooki and Palaemonetes paludosus) densities to increase top-down pressure. Finally, in a mesocosm tank experiment, I investigated whether different consumer species (omnivores: G. holbrooki, P. paludosus; and herbivore: Poecilia latipinna) have different trophic relationships with the periphyton and its resident macroinvertebrate community. Results from the two mesocosm experiments are forthcoming. Because anthropogenic eutrophication is becoming a serious threat to this system and enrichment has a significant impact on the structure and composition of the periphyton mat, an understanding of the mat's relationship with both resident and peripheral consumer communities will aid in modeling and management decisions in the Everglades ecosystem.
Supplemental Keywords:
fellowship, periphyton mat, food-web dynamics, Florida, FL, Florida Everglades, omnivore, herbivore, ecosystem, Gambusia holbrooki, Palaemonetes paludosus, Poecilia latipinna., RFA, Scientific Discipline, Water, Ecosystem Protection/Environmental Exposure & Risk, Nutrients, Aquatic Ecosystems & Estuarine Research, Environmental Chemistry, Aquatic Ecosystem, Environmental Monitoring, Ecology and Ecosystems, Ecological Risk Assessment, marine food web, nutrient dynamics, trophic levels, food web, nutrient loading, macroivertebrate, Florida Keys, aquatic plants, marine biogeochemistry, periphyton mat, estuarine food webProgress and Final Reports:
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.