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The species composition and biomass of the phytoplankton, as well as the hydrophysical and hydrochemical characteristics of the water masses, were estimated for different areas of the White Sea at 24 stations for the period of August 26 to September 3, 2007. The micronutrient concentrations were lower compared to the average long-term values for the summer period. The total biomass of phytoplankton (Bt) varied from 87 to 1914 mg C/m2. For most of the studied sites, Bt was low; dinoflagellates were the most abundant species. Diatoms dominated in the areas of elevated hydrodynamic activity, i.e., in the Gorlo (vertical mixing of the water layers), in intrusions of the Gorlo water masses into the basin of the White Sea, and in the peripheral areas of the Dvina outflow current. The Bt was also the highest in the listed areas.

Results of optical studies of the Kara Sea waters are considered. The data of ship borne measurements are compared with satellite observations. The maximum values of the beam attenuation coefficient, the chlorophyll, and the yellow substance fluorescence were observed in the Ob gulf and in the coastal waters west of the Yamal Peninsula. The minimum values were observed in the central and western parts of the Kara Sea. Frontal zones with sharp changes of the parameters involved were observed. The distribution of the seawater’s optical characteristics was closely related to the hydrological structure of the Kara Sea’s waters. The data of the shipborne measurements were consistent with the satellite observations.

The distribution of the suspended particulate matter concentration in the Kara Sea is analyzed based on ship and satellite data. The statistical relationships between the suspended matter concentration and the optical characteristics were revealed. Charts of the distribution of the suspended matter concentration in the Kara Sea were plotted, which confirmed that the application of optical methods for analyzing the spatial distribution of the suspended matter is effective. The most turbid waters were observed in the Ob Gulf, Yenisei Bay, the Baidaratskaya Gulf, and the adjacent regions. The smallest concentrations of suspended matter were observed in the central and western parts of the Kara Sea.

Production parameters of surface phytoplankton were measured along three transects: La Manche-Cape Town (I); Cape Town-54°S (II); 0°-49°W (along 54°S) (III). The Canary upwelling waters were most productive along transect I, where the surface chlorophyll a (Chl 0) and the surface primary production (PP 0) were as high as 4.3 mg/m3 and 173 mg C/m3 per day, respectively. Mosaic patterns in the distribution of these parameters were recorded in the northeastern regions of the South Subtropical Anticyclonic Gyre (Chl 0 = 0.03–0.35 mg/m3; PP 0 = 1.6–12.6 mg C/m3 per day). Along transect II, the average twofold southward increase in Chl 0 (from 0.2 to 0.4 mg/m3) and the concurrent decline of the phytoplankton assimilation activity ( AN 0) resulted in deviations from typical latitudinal changes inPP 0. At most sites, PP 0 values varied between 6 and 15 mg C/m3 per day. Negligible changes in Chl 0 (0.36–0.85 mg/m3), PP 0 (8–19 mg C/m3 per day), and AN 0 (0.7–1.6 mg C/mg chl a per hour) were registered for the oceanic waters along transect III. Along all the transects, PP 0 depended on Chl 0 to a greater extent than AN 0. The values of the latter parameter were largely determined by the water temperature and showed a slight correlation with the insolation. Along transect II, the integrated primary production (PP int) and the layer-integrated chlorophyll a in the upper 200 m (Chl 0–200) generally varied from 180 to 360 mg C/m2 per day and from 30 to 70 mg/m2, respectively. In the Polar Front region, an increase in Chl 0–200, PP int, Chl 0, and PP 0 up to respective values of 190 mg/m2, 520 mg C/m2 per day, 1.2 mg/m3, and 32 mg C/m3 per day was observed. A comparison of the water column (0–100 m) stability with the vertical distribution of the primary production and chlorophyll content along transect II implies that the thick (>100 m) upper mixed layer (UML) formed in response to the strong water cooling and wind forcing was largely responsible for the limited primary production in the Subantarctic and Antarctic regions. The large UML thickness resulted in an intense removal of plant cells from the photosynthetic layer and light starvation of a significant (up to 60%) part of the phytoplankton community.

In October and November 2002, high and relatively high values of the chlorophyll a concentration at the sea surface (C chl) were observed in the English Channel (0.47 mg/m3), in the waters of the North Atlantic Current (0.25 mg/m3), in the tropical and subtropical anticyclonic gyres (0.07–0.42 mg/m3), and also in the southwestern region of the southern subtropical anticyclonic gyre (usually 0.11–0.23 mg/m3). The central regions of the southern subtropical anticyclonic gyre (SATG) and the North Atlantic tropical gyre (NATR) were characterized by lower values of C chl (0.02–0.08 mg/m3 for the SATG and 0.07–0.14 mg/m3 for the NATR). At most of the SATG stations, the values of the surface primary production (C phs) varied from 2.5 to 5.5 mg C/m3 per day and were mainly defined by the fluctuations of C chl (r = +0.78) rather than by those of the assimilation number (r = +0.54). The low assimilation activity of phytoplankton in these waters (1.3–4.6 mg chl a per hour) pointed to a lack of nutrients. An analysis of the variability of their concentration and the composition of photosynthetic pigments showed that, in the waters north of 30° N, the growth of phytoplankton was mostly restricted by the deficiency of nitrogen, while, in more southern areas, at the majority of stations (about 60%), the phosphorus concentrations were the minimum. At the low concentrations of nitrates and nitrites, ammonium represented itself as a buffer that prevented planktonic algae from extreme degrees of nitric starvation. In the tropical waters and in the waters of the SATG, the primary production throughout the water column varied from 240 to 380 mg C/m2 30° per day. This level of productivity at stations with low values of C chl (