7. CHANGES OF THE PLANKTON COMMUNITY

This Section is targeted at illustrating the database's capability to document changes in the plankton communities of the Barents and Kara Seas. Two data groups have been selected: (i) data collected during the period of sharp Arctic warming of 1920-1930 (Fu et al., 1999); (ii) data collected since 1950, during the period of more severe climatic conditions (Fu et al., 1999). Searchable figures available from " Plankton Community Changes" section.

Phytoplankton. Barents Sea. Section Kola Meridian: 1921 vs. 1997

Data: a) cruise of R/V Sokolitsa, May 1921, 5 stations, 16 samples along the section Kola Meridian; b) cruise of R/V Pomor, May 1997, 7 stations, 35 samples along the section Kola Meridian.

Characteristics: Phytoplankton abundance, biodiversity coefficient (the Glisson coefficient), percent of Arctic and oceanic species. The graphs display substantial differences in the phytoplankton structure between 1921 and 1997.

Conclusion: Each of the analyzed characteristics shows that the conditions for phytoplankton development were more favorable in May 1921 than in May 1997.

Phytoplankton. Barents Sea: 1921-1957-1985-1997

Data: Data processing covers the data collected during the April - May of 1921, 1957, 1985, and 1997 within the region with a 15-mile radius and a central point with coordinates 71°N, 33°30´E. 37 samples from 8 stations were collected.

Characteristics: Spring season mean values of biodiversity coefficient (the Glisson coefficient) and phytoplankton cell abundance are calculated in m² for the years 1921, 1957, 1985, and 1997. This figure shows that values were greater in 1921 than in the years 1957, 1985, and 1997.

Conclusion: The conditions for phytoplankton growth in spring of 1921 were more favorable than in similar periods of 1957, 1985, and 1997.

Zooplankton. Kara Sea: 1936 vs. 1981

Data: a) cruise of the R/V Nerpa, August 1936, 38 stations, 143 samples in the Kara Sea; b) cruise of the R/V Dalnie Zelentsy, August 1981, 24 stations, 109 samples in the Kara Sea.

Characteristics: Occurrence (the number of species in percent from the total amount) of zooplankton species as indicators of the Arctic Waters has been calculated. It was substantially higher in 1981 than in 1936.

Conclusion: The climatic conditions in the Kara Sea were more severe in 1981 than in 1936.

Zooplankton. Southern Barents Sea: 1952-1959

Data: The materials of 84 cruises carried out during the period 1952-1959. 7137 samples from 1630 stations were collected.

Characteristics: The graphs characterizing variation of biomass, abundance, biodiversity index (the Glisson coefficient), and temperature anomaly during the period 1952-1959 are plotted. The tendency toward decrease in the values of 1952-1959 parameters is demonstrated.

Conclusion: The period from 1953-1955 had more favorable conditions for zooplankton development in comparison to the period from 1956-1958. One of the possible explanations for this phenomenon comes from the observed positive temperature anomalies in the period from 1953-1955.

CONCLUSION

The listed examples have demonstrated that more favorable conditions for plankton development in the investigated Arctic region existed in the period during 1920-1930 than during 1960-1980. This conclusion complies with existing observations of Arctic warming during the period 1920-1930 ( Fu et al., 1999).