Fine-scale planktonic habitat partitioning at a shelf-slope front revealed by a high-resolution imaging system
- Publication date
- Publisher
- 'Elsevier BV'
Abstract
Ocean fronts represent productive regions of the ocean, but predator-prey interactions within these features are
poorly understood partially due to the coarse-scale and biases of net-based sampling methods. We used the In
Situ Ichthyoplankton Imaging System (ISIIS) to sample across a front near the Georges Bank shelf edge on two
separate sampling days in August 2010. Salinity characterized the transition from shelf to slope water, with
isopycnals sloping vertically, seaward, and shoaling at the thermocline. A frontal feature defined by the
convergence of isopycnals and a surface temperature gradient was sampled inshore of the shallowest zone of
the shelf-slope front. Zooplankton and larval fishes were abundant on the shelf side of the front and displayed
taxon-dependent depth distributions but were rare in the slope waters. Supervised automated particle counting
showed small particles with high solidity, verified to be zooplankton (copepods and appendicularians), aggregating
near surface above the front. Salps were most abundant in zones of intermediate chlorophyll-a fluorescence,
distinctly separate from high abundances of other grazers and found almost exclusively in colonial form (97.5%).
Distributions of gelatinous zooplankton differed among taxa but tended to follow isopycnals. Fine-scale sampling
revealed distinct habitat partitioning of various planktonic taxa, resulting from a balance of physical and biological
drivers in relation to the front.Keywords: Shelf edge, Georges Bank, Fronts, Gelatinous, Zooplankton, Larval fishes, Diatom aggregates, Predator–prey, Salp