The Eastern Bering Sea Shelf The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder easternberingsea00hood Year: 1981 Phytoplankton distribution 941 I I I may be an important cause of the dominance of Phaeocystis. Copepods have not been reported to ingest the lairge mucilaginous colonies of Phaeocystis, but green cell remnants of Phaeocystis were observed in the guts and fecal pellets of Bering Sea euphausiids of the genus Thysanoessa caught in surface waters where Phaeocystis was abundant (Iverson et al. 1979b). The stage-II phytoplankton succ
The Eastern Bering Sea Shelf The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder easternberingsea00hood Year: 1981 Phytoplankton distribution 941 I I I may be an important cause of the dominance of Phaeocystis. Copepods have not been reported to ingest the lairge mucilaginous colonies of Phaeocystis, but green cell remnants of Phaeocystis were observed in the guts and fecal pellets of Bering Sea euphausiids of the genus Thysanoessa caught in surface waters where Phaeocystis was abundant (Iverson et al. 1979b). The stage-II phytoplankton successional communi- ty in the middle shelf domain of the southeast Bering Sea is dominated by medium-sized diatoms. The major genera are Chaetoceros, Thalassiosira, Rhizo- solenia, Nitzschia, and Phaeocystis; these persist through mid- to late May (Fig. 56-5). The diatoms form long chains and in some cases have long spines, adaptations which may reduce predation. Only the larger copepods of the outer shelf domain are capable of effectively grazing these chain-forming diatoms; the smaller middle-shelf copepods do not appear to graze them. The stage-II group remains in the middle front region and in the middle shelf domain through- out late spring and early summer. Flagellates and dinoflagellates dominate the phyto- plankton of the outer shelf domain during stages II and III of the phytoplankton successional sequence (Figs. 56-4, 56-5). This may be the consequence of diatom removal by the large calanoid copepods which inhabit the outer shelf domain (Cooney, this volume). Wind-mixing events in early summer transport new nutrients to the photic zone in the Bering Sea as in southeast Alaskan fjords (Iverson et al. 1974). An example of the effects of this process is given in Fig. 56-6, where vertical profiles before and after a storm with a mean wind speed of 18 knots suggest that total chlorophyll a increased by about 50 percent in the water column after the storm. By mid-June nutrien
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