The Role of Biotic and Environmental Factors in Spatial and Temporal Variability of Indian River Lagoon Copepod Communities
The role of zooplankton communities as the link between phytoplankton and secondary consumers is dependent on the species make-up of the copepod community. Copepods often dominate zooplankton in numbers and biomass and are frequently the dominant grazers. Species variabilities in behavioral and morphological traits, and seasonal variances in species make-up, have the potential to alter trophic dynamics in planktonic communities. The goal of this study was to identify the driving forces behind copepod community composition and better understand the role of key species in the Northern Indian River Lagoon (N-IRL). Copepods made up 76% of the N-IRL zooplankton community and have average densities of 2.3•10⁴ ± 4.5•10³ m⁻³. Three dominant species, Acartia tonsa, Oithona colcarva, and Parvocalanus crassirostris, make up >95% of the total copepod abundances. The relative dominance of these species shifts spatially between sites (p<0.01) and temporally between wet and dry seasons (p<0.05). Likely intrazooplanktonic predators (the chaetognath Sagitta sp., the ctenophore Mnemiopsis leidyi, and larval fish) had no apparent impact on copepod community abundance. Of all abiotic and biotic factors examined, copepod composition was most closely correlated to relative chlorophyll and Secchi depth (R=0.41), both of which were impacted by algal bloom events. Although communities did not display strong seasonality, their densities and composition do seem to be driven from the bottom up.