Macrozoobentos on the shelf of the Kronotsky Gulf

Data about the taxonomic composition and spatial distribution of bottom invertebrates of Kronotsky Gulf were obtained on results of bottom grab survey carried in September 2002. Analysis of the samples revealed 72 species of Polychaeta, 21 species of molluscs (Bivalvia), 17 species of crustaceans (mostly Amphipoda), 2 species of echinodermata (Echinoidea and Ophiuroidea). The average biomass in the depth range 25–200 m was 242±116 g/m2 where average density was 306±51 organisms/m2. The most high values of biomass were observed in the outlet parts of the rivers Zhupanova, Semyachik, Kronotskaya, where contribution of sea dollar Echinarachnius parma communities was principal. Despite fluctuations of the biomass of particular taxons during 50 years, the total biomass keeps stable (206–242 g/m2). Like in 1949 E. parma plays the main role in most bottom communities.

THE EXPANSION OF THE BIVALVE ANADARA KAGOSHIMENSIS (TOKUNAGA, 1906) IN THE SEA OF AZOV

The dispersion of the Asian bivalve Anadara kagoshimensis in the Sea of Azov continues for more than 30 years. The study of the expansion of A. kagoshimensis is based on the materials of annual bottom grab surveys performed in the Sea of Azov in 1989-2018. The process of dispersion of the mollusk is considered through the changes of the range area, the indicators of abundance (specific abundance, biomass, total stock) and the structure of the population. The main stages of the invasion process are highlighted and discussed. The influence of various environmental factors on the distribution and quantitative indicators of the development of the mollusk population is estimated. It is shown that salinity is the key factor determining the expansion of the mollusk in the Sea of Azov.

Co, Hf, Ce, Cr, Th, and REE systematics of modern bottom sediments of the Barents sea

The Co, Hf, Ce, Cr, Th, and REE systematics are analyzed for modern sediments collected by a bottom grab during the 67th and 68th cruises of R/V “Akademik Mstislav Keldysh” and samples taken in the Barents Sea bays and inlets. Our results indicate that most modern bottom sediments are composed of fine silicoclastic material enhanced with a suspended matter of the North Cape current, which erodes the western coast of Scandinavia, and due to bottom erosion of some marine areas, as well as erosion of rock complexes of the Kola Peninsula, Novaya Zemlya, and Franz Josef Land (local provenances). Material from Spitsbergen also probably played a certain role. In the southern part of the Barents Sea, clastic material is supplied by the Pechora River.

Identifying lakebed nature: is it feasible with a combination of echosounder and Sonar5-pro?

Since a few decades, underwater substrata can be characterized by methods using acoustic technology. Compare to traditional in situ grabbing techniques (bottom grab sampler, video camera, …), these methods allow a better spatial resolution. Until today, these acoustical techniques required specialized signal processing materials. This document presents works about lakebed classification using single beam echo sounder and a post processing software (Sonar5) dedicated to the estimation of fish biomass. Indeed, an underwater substrate analyzing module based on the theory developed by Orlowski (Oceanologia 19 (1984), pp. 61–78) has just been implemented in the sofware. An optimum configuration have been selected and permitted to classify four different natures of substrata: silt, sand, sand & stones, and rock. A substrata nature map of an area known as an arctic charr (emblematic salmonid of the alpine big lakes) reproduction site has been done and shows the system's performances.