Fig.1. RV “Ekolog” in the White Sea

Dr. V.P. Shevchenko was the chief scientist of the expedition on the R/V "Ekolog" (Fig. 1) with the following deputies: N.V. Politova, А.V. Tolstikov and R.E. Zdorovennov.

These studies were carried out in the framework of the "White Sea System" project (the head - academician A.P. Lisitzin) and the project on studying of features of natural processes in areas of tidal coasts of the White Sea (the heads are corresponding members of RAS Yu.S. Dolotov and N.N. Filatov).

Employees from following organizations took part in the expedition (Fig. 2):

• P.P. Shirshov Institute of Oceanology of RAS (including its North-Western Branch),
• Northern Water Problems Institute KRC of RAS,
• Federal State Unitarian Research and Production Company for Geological Sea Survey "Sevmorgeo",
• Skobeltsyn Institute of Nuclear Physics of Moscow State University,
• Ordzhonikidze Russian State Geological Prospecting University,
• Zoological Institute of RAS.

Fig.2. Cruise participants	Fig.3. Map showing expedition route and stations	Fig.4. Taking water samples in the Kem River to study suspended particulate matter.	Fig.5. CTD 90M probe in work

Our objective was to study the White Sea system during summer mean water using multidisciplinary approach that includes all oceanological sciences (physics, chemistry, biology and geology) in their dynamics and interaction in space and in time (the four-dimensional approach).

During the expedition the R/V "Ekolog" passed 496 nautical miles, 71 stations were performed, including two diurnal stations and one semidiurnal station. While the ship was busy performing diurnal stations, the zodiac boat "Kazanka 5M" was widely used. The expedition route is shown on Fig. 3. Expedition has been carried out in two legs. The 1st leg, 5-12 of July, was carried out in the Onega Bay, Dvina Bay and in the central part of the White Sea. The 2nd leg, 14-17 of July, was carried out in the marginal filter of the Kem River. On July, 13th partial change of cruise participants was made.

Our main tasks were:

• To study geochemical processes at the river-sea barrier ("marginal filters" of Kem River and Letnyaya Zolotitsa River (Fig. 4).
• To obtain data from ocean color satellites, build maps of distribution of suspended particulate matter (SPM), chlorophyll, surface water temperature.
• To verificate ocean color satellite data with surface water samples obtained on the move of research vessel (chlorophyll, SPM).
• To perform hydrophysical profiling by multi-parametric probe CTD 90M (Sea&Sun) (Fig. 5).
• To estimate water transparency by measuring depth of visibility of white Sekki disk.
• To filter water samples through membrane and glass-fiber filters to study quantitative distribution and composition of suspended particulate matter. Also to study dissolved phase (dissolved organic carbon, trace metals, hydrocarbons).
• To study bacterio- phyto- and a zooplankton.
• To recover sediment trap moorings deployed during the RV "Ekolog" cruise in July, 2008 (Fig. 6) and deploy new ones for the period till July, 2010.
• To collect sediments with a small grab sampler and a Neimisto corer (Fig. 7).
• To perform geophysical survey by means of the high-frequency profiler which constructive basis has been developed in "Sevmorgeo"

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Fig.6. Recovery of the sediment trap moored in 2008	Fig.7. Sediment core and near bottom water taken by Neimisto corer.	Fig.8. SPM distribution in the White Sea calculated using ocean color satellite data.	Fig.9. Recovered sediment trap with 12 sample bottles that contain sediment material

Preliminary results show that during the expedition concentrations of nutrients (Si, P-PO4, N-NO3), chlorophyll, SPM in the White Sea were quite low which is typical for summer mean water. For instance, SPM concentrations in the central part of the White Sea and in the Dvina Bay were below 1 mg/l (Fig. 8). SPM concentrations in the rivers Kem and Letnyaya Zolotitsa also were low (2-2.5 mg/l)
Two long-term (1 year) sediment trap moorings equipped with changing sample bottles were recovered during the expedition. Values of vertical particle fluxes and their seasonality with the resolution one month have been received (Fig. 9).
At present analytical procedures are performed.

Participants of the expedition wish to thank crew of the R/V "Ekolog" for their help. Our studies were financially supported by Russian Foundation for Basic Research (grants 09-05-10081, 09-05-00658, 07-05-00691 and 08-05-00860).