172 individual deployments from 59 discrete geographic stations. Comparison of the physical, chemical, biologic and geologic features of these regions represented the major oceanographic theme of this Sea Semester.
1. Physical oceanographic studies focused on the distribution of surface and sub-surface (to 1200 m) water masses and the delineation of hydrographic boundaries. Specifically, North Atlantic subtropical mode water (18°C Water) and Antarctic Intermediate Water (AAIW) was studied in relation to the phase of the North Atlantic Oscillation (NAO). In addition, we conducted a comparison of sea surface temperature using historic (bucket thermometer) and contemporary
(electronic thermister from a seawater intake system) instrumentation.
2. Chemical oceanographic studies focused on the geographic and vertical distribution of nutrients (phosphate, nitrate, silicate), extracted chlorophyll-a, and pH. These chemical parameters were related to patterns in physical hydrography at various scales: sub-tropical convergence, fronts, Gulf Stream eddies, and water column stratification.
3. Biological studies focused on the geographic distribution of charismatic megafauna (seabirds, sea turtles, flying fish, and marine mammals), several meroplanktonic larvae including spiny lobster (phyllosoma) and eels (leptocephali), the floating macrophyte - Sargassum spp., size and abundance of pteropods, and density and diversity of the aggregate zooplankton community. In addition, patterns of phytoplankton community structure were examined on two scales: vertical zonation in relation to nutrients and light as well as a comparison of epiphytic colonisation on Sargassum versus marine plastic debris.
4. Geological sampling was focused on the collection of fossil pteropod shells to be used in laboratory experiments.
5. Two experimental studies were completed. The first was an examination of pteropod shell strength (as measured by impact force required to crack the shell) after exposure to different pH treatments. The second was the change in phytoplankton community structure after exposure to different nutrient enrichment experiments.
Sea surface temperature, salinity, fluorescence (chlorophyll-a and CDOM) and transmissivity levels; along with barometric pressure, winds, bathymetry, and geographic position were recorded continuously along the cruise track. Data is available upon request. Surface samples (41) of nutrients (phosphate, nitrate, silicate), chlorophyll-a, and pH were collected with all neuston net tows and dip nets during the cruise.
Jeffrey M Schell (Sea Education Association)
Florida coast, Sargasso Sea, east of the Lesser Antilles and the eastern Caribbean.