Benthic-pelagic relations of aquatic organisms in various water masses of the Chukchi Sea by the data of δ¹⁵N and δ¹³С

Abstract

To compare trophic characteristics for pelagic and benthic communities of zooplankton and zoobenthos in the Chukchi Sea, isotopic composition of carbon and nitrogen (δ15N and δ13С) was measured in two different water masses: i) the Bering Sea water with relatively high δ13С and low δ15N values that occupied the southern part of the sea (south of 71о N), and ii) the cold Arctic water prevailed in its northern part were δ13С value was considerably lower and δ15N value was higher in 1–3 %. Stable difference in the isotopic composition of carbon is found between zooplankton and benthic invertebrates in the southern Chukchi Sea that means that benthic organisms base mainly on the benthic trophic chain and role of organic matter from the upper layer is not significant. About 90 % of the studied species of benthic fish are locked into the benthic trophic web there. In the northern Chukchi Sea, the benthic community consumes mainly the suspended organic matter produced in the water column, with prevalence of ice algae. All samples of benthic fish collected in this area have minimum content of heavy carbon δ13С with the values comparable to pelagic fish that indicates the main role of pelagic objects (60–80 %) in their feeding. The δ15N value reflects predatory habits of the animals. These values vary over a wide range both in the southern and northern areas that corresponds to the diet of the first, second or third order consumers.

Keywords

• arctic
• chukchi sea
• zooplankton
• nekton
• benthos
• trophodynamic link
• pelagic layer