Ciliated protozoan communities over Cobb Seamount: increase in biomass and spatial patchiness

S p e c ~e s composihon, abundance biomass and patchiness of ciliated protozoa were examined for e v ~d e n c e of increasing standing stock in relabon to productiv~ty (chlorophyll a prlmary production) over an eastern subarctic Pacific seamount (Cobb, 46"45' N 130°48 W) Ciliates were unusually dlverse w t h 49 different taxa recorded ranging m size from 15 to 350 pm in length Their abundance was relahvely low whlle carbon biomass was very high compared to those of most marine systems This implies that over Cobb Seamount cil~ates counterbalance their low numbers by increasing in size partly due to exclusion of small planktonic common specles (Strob~hd~urn spp scut~cociliates hymenostome-type cells) by larger cells particularly plastidic ol~gotnchs of the genus Laboea Integrated b ~o m a s s to 80 m depth at hmes peaked at 0 6 g C m-2 which exceeds the standing stock of the entue microzooplankton in some oceanlc areas Statist~cal 2-dimensional analysis of the spatial structure showed the existence of patchmess Meso-scale and c~rcular patches (about 6 km or more in diameter, horizontally) were probably related to seamount-induced physical forcing w h ~c h likely generates microhabitats favorable to the growth of opportunlslc or physiologically adapted populations D~rect observahons showed that c~liates were a major component of the microzooplankton over the seamount