| The Hudson canyon, an east coast submarine canyon, is perceived as a "hot spot" for recreational and commercial fishing. The presence of high fish concentrations in canyons has been attributed to upwelling events that are associated with enhanced nutrients and higher zooplankton biomass than the adjacent shelf. Hudson canyon, in contrast, is characterized as a downwelling canyon. Downwelling is usually not associated with high fish or zooplankton concentrations. Therefore a fundamental question about secondary production in Hudson canyon remains: "Is Hudson canyon more productive than the adjacent shelf?"; Hudson Canyon was studied during a cruise (from May 7 to 17, 2001) aboard NOAA's RV, Albatross IV. Hydrographic data and zooplankton samples were collected from the Hudson Canyon area using a Multiple Opening Closing Net Environmental Sampling System (MOCNESS). Temperature, salinity, and density were used to define water types and measure horizontal and vertical changes in the environment of the canyon, adjacent shelf, and adjacent slope. Hydrographic data indicated shelf slope mixing at locations in the canyon only. Zooplankton biomass at the canyon head and adjacent shelf were similar to each other, but were different from other locations within and seaward of the canyon. Zooplankton biomass was positively correlated with copepod concentration and negatively correlated with temperature, salinity, and density. Although the Hudson canyon was not more productive than the adjacent shelf, variations in copepod concentrations in association with hydrographic changes suggest a relationship between zooplankton biomass and shelf-slope exchanges within the canyon. |
