Oxygen Minimum Zones
|Fishing for zooplankton in the ETP (Marianne McNamara)|
Karen Wishner (URI - GSO), Brad Seibel (URI)
Oxygen minimum zones are regions where high primary productivity at the surface and local hydrography interact to create regions where midwater oxygen concentrations are very low and dissolved inorganic carbon (DIC) is very high. These zones have profound influences in zooplankton distribution and physiology which have important implications for carbon flux and ecosytem functioning. Regions where oxygen minimum zones naturally ocurr are hotspots for global change. Increasing atmospheric CO2 leads to an acidification of the upper ocean as well increasing surface temperatures. As warming occurs, there is an increase in the stratification of the mixed layer and a decrease in gas solubility. These changes, and their effect on phytoplankton production, appear to be increasing the size and severity of hypoxic zones. This increase in hypoxia and high DIC at depth, combined with the warming and acidification of surface waters, is expected to synergistically compress the habitat of pelagic species. This project focuses on the region of hypoxia in the Eastern Tropical Pacific. In this region we are documenting the diel vertical distribution of the large zooplankton taxa in association with hydrography (Maas et al., in review). Physiological experiments of thecosomatous pteropods give insight into how these animals cope with the temperature, oxygen and DIC/pH across the depth range of their distrubion and provide insight into how this group of calcifying plankton may respond to climate change (Maas et al., 2012 Biogeosciences; Maas et al., 2012 Marine Biology).