Effects of hypoxia on the trophic structure of the polychaete communities in the northern Gulf of Mexico

Annelid polychaetes are the most abundant marine benthic invertebrates; they play significant functional roles in any aquatic system. Among many roles, their feeding mode promotes transfer of energy to the next trophic level. Polychaetes exhibit five different feeding guilds: herbivores, carnivores, filter-feeders, surface deposit feeders, and subsurface deposit feeders. The predominance of a feeding mode depends on abiotic factors such as rates of sedimentation, sediment type, organic carbon content, organic matter availability on and within sediments, redox potential, and biochemical oxygen consumption. This study investigates the polychaete community structure and feeding guild pattern in four different provinces with varying hypoxia frequency and history in the northern Gulf of Mexico. Macrobenthos and sediment samples were collected during September 2009 from the northern Gulf of Mexico between the Atchafalaya and Mississippi Rivers to study the effect of hypoxia on feeding guild pattern, abundance and species diversity. Macrobenthos samples were dominated by polychaetes at all four provinces; more than 28 families of polychaetes are represented. The abundance and diversity data were compared with the sediment properties of grain size, organic matter concentration, and sedimentation rate, to help explain the variability in the biological data among provinces using principal component analysis (PCA). The polychaete data were statistically analyzed for species richness and diversity using the Shannon-Wiener index. Bray-Curtis cluster analysis was performed to determine the similarity of the polychaetes communities.