Ann Bucklin, Peter H. Wiebe, Dennis G. McGillicuddy,
Christopher Manning, Kaitlin G. Bonner, and Meredith A. Bailey
Abstract
The cryptic copepod species, Pseudocalanus moultoni and P. newmani, co-occur on Georges Bank and in the Gulf of Maine (Northwest Atlantic), but differ in spring-time patterns of distribution and abundance at both small- and mesoscales. Using a molecular protocol to discriminate the species, Bank-wide patterns of distribution and abundance were described for monthly snap-shots from January to June of 1999. Habitat usage was evaluated using a standard grid to partition the habitat into three vertical strata and five geographic regions defined by bathymetry and current flow. Additional small-scale observations examined distribution and abundance of the two species across a tidal-mixing front on Georges Bank and in near-shore waters of western Gulf of Maine. These studies suggest that water column stratification and stratified flow may differentially impact the two Pseudocalanus spp. Alternatively, the species may actively respond in some way that generates different vertical distributions with respect to turbulence, stratified flow, and other micro-habitat conditions. Small-scale processes and patterns may thus play a significant role in determining patterns of species distribution on larger spatial (i.e., mesoscale) and longer temporal (i.e., seasonal) scales.