Macoma calcarea (Gmelin, 1791), a poorly studied bivalve, in the Kara Sea: Distribution and growth variability

Macoma calcarea, one of the most common bivalves in the infauna of the Arctic seas of Russia, is still poorly investigated from an ecological viewpoint. We studied the distribution and growth of Macoma in the southwestern part of the Kara Sea. The samples were obtained at 119 stations at depths from 4 to 415 m in 2012–2013. The main trends in the distribution of this species corresponded to its feeding type (deposit-feeder), the biogeographic affiliation and the features of reproductive ecology. Macoma calcarea in the study area were mainly concentrated at depths of 20–50 m. Their density and biomass were, respectively, eight and two times higher on silty sediments than on sandy ones. The results of age assessment of M. calcarea by the external growth marks and the shell cross-sections were quite similar. However, age determination based on internal growth marks was found to be preferable for older individuals and individuals with heavily eroded shells. Group growth rate of M. calcarea was not very sensitive to environmental conditions. No site-to-site variability in the growth characteristics was found. The maximum size and age of M. calcarea (37 mm and 21 years respectively), as well as the average annual growth rate (about 2 mm/year), were close to the values of these parameters in other parts of the distribution of this species.