Assessing the Influence of Trophic State on Littoral Zone Fish Communities, Dissolved Oxygen Regimes, and Habitat Composition in Florida Lakes

We deployed mini-fyke nets and dissolved oxygen (DO) sondes in the littoral zones of four Florida lakes to assess the influence of trophic state on fish community composition, habitat composition, and diel dissolved oxygen regimes. Randomly selected sites were sampled in replicate across back-to-back weeks for each lake. Community composition was similar (Bray-Curtis > 75%) between weeks for all four lakes individually, but differed among lakes. Duration of hypoxia was compared within and among lakes to assess variability in diel dissolved oxygen regimes across a trophic gradient. Within lakes, duration of hypoxia did not differ between weeks, indicating low temporal variability of littoral zone DO within individual lakes. However, duration of hypoxia differed between lakes of lower productivity (i.e., oligotrophic and mesotrophic) and higher productivity (i.e., eutrophic and hypereutrophic), with lakes of higher productivity having significantly longer durations of hypoxia. Differences in habitat variables compared within lakes were not common, but significant differences were detected among lakes for a variety of habitat variables including aquatic macrophyte density and organic sediment thickness. Understanding how trophic state influences the relationships between physical habitat, dissolved oxygen regimes, and fish communities in near-shore lake environments is important for effective aquatic resource management and policymaking.