Zooplankton Around Four Eastern North Pacific Seamounts.

Abstract : The influence of large seamounts on ambient oceanic biological, physical, chemical and geological environment was the focus of the 'Flow Over Abrupt Topography' (TOPO) ARI. The research reported here comprised the water column zooplankton ecology component of the ARI. Our field program (1989 to 1991), centered on Fieberling Guyot (32 deg 25'N, 127 deg 47'W), with three other seamounts investigated: Dowd Guyot (13 deg 27'N, 119 deg 53' W), Northeast Bank (32 deg 20'N, 119 deg 37'W) and Sixtymile Bank (32 deg 05'N, 118 deg 15'W). Support for the studies at the latter two seamounts came from the United States-Israel Binational Science Foundation. The zooplankton studies tested three hypotheses: (1) mesoscale patches (gaps) of reduced numbers of migrating zooplankton occur over seamounts; (2) these gaps increase the patchiness of migrating species in the surrounding waters. (3) increased numbers of empty and partly empty exoskeletons (carcasses) of crustacean zooplankton occur throughout the water column over submarine elevations shallower than about 500 m. Hypothesis 1 was supported by the data for most zooplankton, not just migrators (Genin et al, 1994). Hypothesis 2 has not been falsified by our analyses to date, but the sampling appears to have been insufficient to verify it.