Temporal Patterns of Benthic Invertebrate Community Structure and Function in a Forested River-Floodplain of the Southeastern US (Altamaha River, GA)

River floodplains of the Southeastern US are sites of high biological productivity that rely on a predictable flooding event as a keystone process. This study took place in a river-floodplain area of the Altamaha River, an unimpounded large-order river in southeastern Georgia. Benthic macroinvertebrates were sampled monthly from December to April (2011-2013). Invertebrates were classified into functional feeding groups and biomass was obtained using published length-mass regressions. Year 1 (2011-2012) was characterized by severe drought and predators represented up to 63% of the community during the early stages of flood pulse (December-March), but were consequently replaced by filterers (45% of the community; March-April). Year 2 (2012-2013) was characterized by a large flooding event where collector-gatherers were the predominant FFG (82% of the community) in December, but were replaced by shredders (81% of the community) from February to April. Differences in FFG composition and biomass are predicted to be due to hydrology at the main channel and organic matter resource availability. Characterizing benthic invertebrate communities can aid in understanding the potential resiliency of a system to a multi-year drought disturbance.