Omnivory and Periphyton Mats: Uncoupling and Quantifying Consumer Effects in the Florida Everglades

Pamela Geddes, Florida International University

Availability Unrestricted Thesis/Dissertation


The role of omnivores in structuring communities is poorly understood. I studied the effect of two abundant omnivores, grass shrimp (Palaemonetes paludosas) and eastern mosquitofish (Gambusia holbrooki), on periphyton biomass of the Florida Everglades. I performed field experiments to test for consumer top-down and “complex” top-down effects on periphyton biomass. My experiments suggested that shrimp and mosquitofish had consumptive effects on periphyton but in many instances, periphyton wet weight, AFDM, and chlorophyll a increased significantly with shrimp or fish density, suggesting compensation by nutrient regeneration or trophic cascade processes. I propose that characteristic periphyton mat structure and integrity deters herbivory and affects the outcome of the periphyton-consumer interaction. Results from a descriptive study and a laboratory experiment support this hypothesis. Overall, consumption by shrimp and mosquitofish was significant, but coupled with and sometimes compensated by “complex” top-down effects, making these consumers “functional” omnivores.


Rights Statement

Rights Statement

In Copyright. URI:
This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).