Affiliations: The Key Laboratory of Submarine Geosciences/Second
Institute of Oceanography of SOA, Hangzhou 310012, China.
[email protected] | State Key Laboratory of Estuarine and Coastal
Research, East China Normal University, Shanghai 200062, China | Laboratory of Marine Geology of MOE, Tongji
University, Shanghai 200092, China
Abstract: Based on the quantitative study of calcium (foraminifera and
ostracoda) and siliceous (diatom, radiolarian and sponge spicule)
microorganisms as well as the content of calcite in 41 surface sediments of the
Chukchi and Bering Seas, we find that planktonic foraminifera are almost absent
in the surface sediments, which could be attributed to the low surface primary
productivity and strong carbonate dissolution in the studied area. On the
contrary, benthic foraminifera are widely observed in most surface sediments.
It has been revealed that the distributions of benthic foraminifera and
siliceous microorganisms are mainly controlled by the sedimentary types,
surface primary productivity, carbonate dissolution and water masses. On the
shelf of Chukchi Sea the surface primary productivity is low due to the
influence of sea ice, low sea surface temperature and salinity. As a
consequence, benthic foraminiferal abundance and diversity are low, radiolarian
disappear and only few ostracoda are counted, while diatoms and sponge spicules
are abundant in the surface sediments. The surface primary productivity is much
higher in the surface sediments on the slope of Bering Sea than that on the
shelf of Chukchi Sea. Benthic foraminiferal abudance on the slope of Bering Sea
is one order higher than that in the shelf of Chukchi Sea, and higher diversity
is also observed in Bering Sea. Similar to calcium microorganisms, siliceous
microorganisms (diatom, radiolarian and sponge spicule) are more abundant in
Bering Sea than that in Chukchi Sea. According to the abundances of benthic
foraminifera and siliceous microorganisms, as well as the ratio of benthic
foraminiferal fauna of agglutinated tests and the contents of calcite changing
with the water depth in the Bering Sea, carbonate lysocline and compensation
depth (CCD) are probably located at the water depths of 2000 m and 3800 m
respectively.
