Zooplankton community variability in the South Atlantic Bight (2015–2017)

Abstract

In the South Atlantic Bight (SAB), responses of zooplankton communities to physical dynamics were evaluated monthly at two sites on the continental shelf offshore from Savannah, GA, USA, between December 2015 and December 2017. Zooplankton were collected in oblique net tows (202-μm). Samples were collected in two regions of the middle shelf: inner edge (Site 1: 25 m isobath, n = 22) and outer edge (Site 2: 40 m isobath, n = 21). Samples were also collected at a third site on the 40 m isobath, ~20 nm south of Site 2 in July and August 2016. Temperature, salinity and fluorescence data were recorded at each site. Overall, 57 taxa were identified with total abundances varying from 1 × 103 to 81 × 103 ind.m−3. Small copepods predominated; notably Paracalanus spp. The highest abundance was recorded in October 2016 at Site 1, following deep mixing induced by Hurricane Matthew. Interannual variability of zooplankton abundance was significant, with higher abundances in 2016 compared with 2017, reflecting higher river runoff in 2016. Samples from Site 3 yielded the largest Dolioletta gegenbauri bloom documented in the SAB. This 2-year time-series, for the first time, suggests that zooplankton communities on the SAB middle shelf region are significantly influenced by continental precipitation patterns.