Fourteen species of benthic invertebrates, found to be indicators of hydrographic conditions by Blacker (1957), were recorded during research cruises between Finmark and north Spitsbergen during the summers of 1978, 1979, 1980 and 1981. The distributions were compared with those found during surveys carried out between 1949 and 1959.Both Atlantic and Arctic species were found to the north of Bear Island and along the west coast of Spitsbergen, and the temperature ranges at which they were found were greater than those found by Blacker (1957).
During the past century the annual mean temperature of the Arctic regions has undergone a considerable change. The warming of the regions began about 1885 (Willett, 1950) and peaked around 1938, when the mean air temperature of Spitsbergen was nearly 6 °C warmer than at the turn of the century (Hoel, 1953). The warming of the seas in the region seems to have started later - Jensen (1939) suggests 1917 - and sea temperature changes were detected north of Spitsbergen in 1921 (Schokalsky, 1936). This warming resulted in the reappearance of cod in great quantities on the Bear Island Bank, after the absence of any sustained quantities for about 40 years (Blacker, 1957).
The marine benthos of Svalbardf was surveyed during the latter part of the last century and the first half of this century (1878–1914,1923–31) when the benthos was recorded during several cruises in the region (see Blacker (1957) for review). The benthos was again recorded between 1949 and 1955 (Blacker, 1957) and 1955 and 1959 (Blacker, 1965); see Fig. lA.