PARENT SESSION
Tuesday, August 8, 5:00-6:30 pm
Poster Session 8 - Aquatic ecology
Exhibit Hall, Ballroom Level, Cook Convention Center
Habitat alteration by an invasive aquatic plant and its impact on fish foraging and macroinvertebrate colonization.
Theel, Heather*,1, Dibble, Eric1, 1 Mississippi State University, Mississippi State, MS
ABSTRACT- Aquatic plants mediate ecological processes in aquatic habitats, specifically predator-prey (bluegill (Lepomis macrochirus)-macroinvertebrate) interactions. Macroinvertebrate colonization is directly and indirectly influenced by substrate heterogeneity, interstitial space, and surface complexity. Feeding and individual growth rates of many fish species are positively related to the abundance of macroinvertebrates. Exotic invasive plant species can alter the available structure in aquatic habitat thus affecting foraging fishes and the macroinvertebrate community. Since macroinvertebrates provide a food base for young phytophilic fishes, changes in their density and abundance may alter food webs. We investigate the hypothesis that a shift from a heterogeneous native aquatic plant bed to a homogenous invasive plant bed would directly alter bluegill foraging and indirectly invertebrate colonization by conducting a multi-scale experiment (ponds and aquaria). Experimental treatment included: (i) intermediate densities of native-mixed plants and (ii) hydrilla, (iii) high density of hydrilla, and (iv) no plants. We observed treatment effects on macroinvertebrate colonization and bluegill foraging. Aquatic plants, regardless of species, supported a two-fold increase in taxonomic richness compared to the no plant treatment. Macroinvertebrate abundance was two times greater in hydrilla dominated ponds than native plant ponds. Bluegill recognized 30% more food items in native mixed habitat versus a hydrilla dominated habitat. We suggest that when plant density and complexity rise above a moderate level due to a habitat shift to a homogeneous invasive plant bed, prey abundance increases, but predator recognition of available prey items decrease.
Key words: aquatic, exotic species, habitat alteration