During the September stage of the "Black Sea 2026" expedition conducted by Shirshov Institute of Oceanology (RAS), members of a benthic team — comprising researchers from Kovalevsky Institute of Biology of the Southern Seas (IBSS) — recorded new habitats for the mud crab Eurypanopeus depressus, a recent invader, in the Taman Bay and the Sea of Azov. Previously, this species had been observed along the Crimean coast of the Kerch Strait and the Sea of Azov, as well as in the western Black Sea. Additionally, a single specimen of the species was found in 2024 in the area of Taman Bay adjacent to the strait.
Mud crab Eurypanopeus depressus
Surveys conducted in September 2026 revealed that the crab has colonized the entire Taman Bay, including its inner reaches, and has also extended into the southeastern Sea of Azov as far as Cape Kamenny, where the species was recorded at a salinity of 14 PSU. The discovery of sexually mature, egg-bearing individuals may indicate the species' acclimatization to the region and the potential formation of a self-sustaining population. The new species typically inhabits aggregations of mytilid bivalves (mussels and Mytilaster) found on both natural and artificial hard substrates. Its primary food source consists of small invertebrates, including juvenile mytilids, which it crushes with its claws. Competition is possible with both native crab species and another invasive species—the Harris mud crab—which is widely distributed throughout Taman Bay and the Sea of Azov.
In addition, the expedition gathered extensive material for analyzing the trophic structure of coastal communities in Gelendzhik Bay, the Bugaz Spit, and Dinsky Bay, with the active participation of researchers from the Southern Branch of Shirshov Institute of Oceanology of RAS. Scientists collected samples of bivalve mollusks representing various trophic groups: detritivores, sestonophages, and symbiotrophs. Plans are in place to analyze stable carbon and nitrogen isotopes in the tissues of specimens from each of these groups. Based on these data, the researchers will reconstruct isotopic niches and determine the positions of the studied species within the trophic net. Bivalve mollusks play a significant role in the marine ecosystems of the Azov-Black Sea region, shaping the character and functioning of communities inhabiting rocky, sandy, and muddy substrates.
Rock-boring mollusks Rocellaria dubia
on the marly cliffs of the Gelendzhik carbon test site, at a depth of 6 m
Research on rock-boring mollusks has continued at the Gelendzhik carbon research site. These organisms can cause the degradation of natural and man-made carbonate substrates, as well as the shells of other mollusks, such as oysters; consequently, monitoring their population dynamics is crucial. Scientists conducted photographic and video surveys of rocky ridges at depths of 3–6 meters to estimate the abundance of the rock-boring mollusk Rocellaria dubia. The average population density increases with depth, ranging from 1–3 to several dozen individuals per square meter. These organisms were first recorded in the area of the research site in 2016, and their mass proliferation has been continuously observed since 2023 through visual inspections, field descriptions, and underwater video surveys. Prior to the 2010s, this species was considered rare and was encountered only sporadically off the coasts of Crimea and the Caucasus. In recent years, however, they have been found in large numbers in the Gelendzhik area, Anapa, and Crimea.
Staff members from the Laboratory of Coastal Benthic Community Ecology and the Analytical Laboratory of Shirshov Institute of Oceanology (RAS), as well as the Department of Benthos Ecology of Kovalevsky Institute of Biology of the Southern Seas (IBSS), participated in the work.
