L. A. Pautova* and V. A. Silkin**
* Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia
** Institute of Biology of the Southern Seas, National Academy of Sciences of Ukraine, Sevastopol, Ukraine
Received April 13, 1998; in final form, December 10, 1998
Abstract—The succession in winter phytoplankton of the coastal shallow zone of the northwestern part of the
Sea of Japan and the mechanisms of its winter “blooming” in general correspond to the well-known scheme of
Margalef. According to this scheme, the species and quantitative structure of the phytoplankton community
depend on the intensity of mixing of the water column (in this case, the convective mixing). The strengthening
of convective mixing results from the advection of the deep waters from the open sea regions due to winter off-
shore winds; this strengthening results in the “blooming” of small centric diatoms (coldwater species of genera
Chaetoceros and Thalassiosira nordenskioeldii Cleve). Under the ice cover, this “blooming” occurs at a tem-
perature from –1.4 to –1.5°C, while without ice cover the blooming temperature is –1.7°C. In the absence of
advection of the deep waters and the resulting decrease of the intensity of convective mixing (homothermal con-
ditions with a temperature of –1.9°C), no winter “blooming” of phytoplankton was observed either in open
water or under ice cover. The mechanism of the influence of the intensity of the water column mixing on the
structure of winter phytoplankton is analyzed.
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