Lateral variation in the composition of aquatic invertebrate communities across the floodplains of the Altamaha and Savannah Rivers

Floodplain connectivity is the linkage of the main river channel to that of the alluvial floodplain, and the degree of connectivity can cause biotic differences in the floodplain. The current study examined how river-floodplain connectivity affects total invertebrate biomass and abundance, and invertebrate community structure in floodplain areas with high, mid, and low connection to the river. Conductivity varied laterally across the floodplain while pH and temperature varied only seasonally. Fish richness and abundance were greater in areas with a higher connection to the river. Invertebrate community structure and many of the individual invertebrate taxa varied between study years. Invertebrate abundance and biomass were greatest in areas with the highest connection to the river and they decreased as the connection decreased. Caecidotea abundance and Tanypodinae biomass were the only individual taxa responses that varied among the connection regimes. Invertebrate community composition did not vary laterally across the floodplain.