INVERTEBRATE COMMUNITIES IN HYDROGEN SULFIDE SPRINGS IN THE HIGH NORTH (USA RIVER CATCHMENT, RUSSIA)

Abstract

In late July 2018, we studied the chemical composition of the water and benthic communities in two hydrogen sulfide springs in the catchment of the Iska-Shor Creek (lefthand tributary of the Usa River), as well as zoobenthos and plankton in the Usa River around the creek’s mouth. Compared to the reference site, water in the springs contained manyfold higher concentrations of chlorine, sodium, calcium, sulfate ions, and differed in the content of organic matter, heavy metals, and several micro elements. Water temperature did not exceed +6 °С. Zoobenthos abundance and biomass was low, comprising31 taxa of invertebrates. Chironomid larvae and harpacticoids prevailed. Chironomids were the most diverse group in the creek – 20 taxa, of which 17 were found directly in the springs. Tanytarsus verralli Goetghebuer, 1928 was the most numerous species. Apart from chironomids, we found nematodes, ostracods, cladocerans, first instar larvae of mayflies, stoneflies and caddisflies, and others Dipteran families. The diversityof planktic and benthic invertebrates, and the set of dominant species showed little variation among the sites surveyed in the Usa River. The dominants in terms of abundance in the river’s benthic fauna were chironomid species from the subfamily Chironomini: Tanytarsus verralli, Cladotanytarsus (Cladotanytarsus) mancus (Walker, 1856), and Polypedilum (Pentapedilum) exsectum (Kieffer 1916). The share of roundworms decreased and the share of cyclops and water mites increased in the zoobenthos of the river downstream from the mouth of the creek. Among zooplankton dominants, the abundance of Euchlanis dilatata Ehrenberg, 1832 decreased and the share of Cladocera from the genus Bosmina increased downstream the river. Inside the area directly affected bythe mineral water springs, we found a high abundance of euplanktic rotifers Asplanchna priodonta Gosse, 1850 and copepods Mesocyclops leuckarti (Claus, 1857), as well asan increased abundance of juvenile Cyclopoida. The studies have expanded our knowledge of the adaptive capabilities of invertebrates, and the ecology of aquatic communities forming in this extreme environment.

Keywords

• hydrochemistry
• zoobenthos
• zooplankton
• biodiversity
• adaptation
• sulfide waters
• extreme environments
• northernmost taiga