Meeting Abstract
P2.32 Jan. 5 Species diversity and distribution of thecosomatous pteropods in the North Pacific HOKE, D*; WEBB, J F; REILLY, R; SAUMWEBER, W; Villanova University; Villanova University; Pennsylvania State University; Sea Education Association jacqueline_webb@mail.uri.edu
Thecosomatous (shelled) pteropods are small pelagic molluscs found in the plankton throughout the world�s oceans. We collected pteropods in 6 oblique tows (0-100 m, 333�m mesh) and 27 neuston tows (333�m) along the N. Pacific cruise track of the SSV Robert C. Seamans (S-205) from Hawaii to Vancouver Island in May 2006. The goals of this study were to assess the distribution of pteropods following observations of McGowan (1971) who named indicator species for different Pacific biogeographic provinces, to compare their occurrence in oblique and neuston tows, and to attempt to correlate their abundance with physical and chemical oceanographic parameters. Pteropods were found in all of the oblique tows and 70 % of neuston tows. A total of 24 species were observed, representing >75% of the species observed by McGowan, plus another 9 species. Up to 9 species were found in each neuston tow and 18 in each oblique tow. Several indicator species observed by McGowan were found in oblique and neuston tows along the cruise track. A mean of 4.75 species was found at each station in the N. Pacific Subtropical Gyre, but a mean of only 0.57 species was found at each station in N. Pacific Transitional Zone. More species tended to occur in subtropical tows, while more individuals in fewer species tended to occur at stations in the vicinity of the Alaska Current. In oblique tows, the number of pteropods appeared to decrease with increasing nutrient levels (nitrates, phosphates, silicates), but, initial analyses of neuston tows did not show the same sorts of trends. Thus, observations made by McGowan and other investigators were confirmed to some extent in the oblique tows. The significance of the data from neuston tows, and a comparison of species composition in neuston vs. oblique tows will be discussed.
