Interannual temporal patterns of DeSoto Canyon macrofauna and evaluation of influence from the Deepwater Horizon

Abstract

Submarine canyons are highly dynamic and productive ecosystems, but time-series studies of metazoan benthic communities in canyons are scarce. Deep-sea macrofauna from the DeSoto Canyon in the northern Gulf of Mexico were sampled annually from 2012 through 2014 from five stations within the Canyon and from two stations in 2013 and 2014 on the adjacent open slope, for analysis of interannual dynamics, temporal variability, and potential influence of the Deepwater Horizon oil spill (DwH), which occurred nearby in 2010. At a few sites, elevated abundance was observed at the start of the time-series for overall macrofauna and for deposit feeder abundance. However, diversity metrics showed no difference within stations among time points. Community and feeding guild structure varied by station, as expected, but showed no statistical difference among time points within a station. Some temporal variability was visible in temporal trajectory overlays. Cluster analyses showed grouping more by station than by time point. Metrics utilized for measuring potential oil contamination impact and overall community stress including the benthic polychaete/amphipod ratio, feeding guild abundance, macrofaunal indicators designed from the DwH, and community dispersion, generally exhibited a paucity of evidence of impact, both yearly and with site-to-site comparisons. This suggests low levels of impact in the canyon consistent with the low deposition of hydrocarbons, the timing of sampling, and quick recovery of canyon foraminifera. Taken together these results suggest relatively low levels of temporal variability within the DeSoto Canyon macrofauna with little evidence of oil influence on these sites within the studied time range.