Defining the Role of the Periphyton Mat in Shaping Food-Web Dynamics in the Florida EvergladesEPA Grant Number: U915916
Title: 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: Graham, Karen
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
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.
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.