Macrozoobenthos of polychaete Ficopomatus enigmaticus (Fauvel, 1923) colonies in the Kerch Strait area (Azov-Black Sea basin)

Many invasive species are known to represent one of the most serious threats to natural ecosystems and human activities. The purpose of our study is to analyse the species composition and quantitative indicators of macrozoobenthos living in the colonies of the non-native polychaete Ficopomatus enigmaticus in the area of the Arshintsevskaya Spit of the Kerch Strait, which will allow us to trace the process of reef formation and its impact on the ecological situation in the region. The work is based on the materials obtained during an expedition carried out in the Kerch Strait region (N 45°20'50"; E 36°41'05") in September 2019, at stations restricted to depths from 0.1 to 0.2 m. The material was obtained using a bag of mill gas covering the colony and separating it from the substrate to which it was attached. Soil samples near the colonies were taken with a bottom grab with an area of 0.04 m2. The IFA index was used to identify the community. The Czekanowski-Serensen index was used to determine the fauna similarity in the compared lists. In this research we revealed the presence of colonial settlements of F. enigmaticus. It was for the first time in the waters of the Azov-Black Sea Coast of Russia and the community was singled out. Sixteen species of macrozoobenthos have been recorded, including 7 species of polychaetes (Alitta succinea (Leuckart, 1847), Fabricia stellaris (Muller, 1774), Ficopomatus enigmaticus (Fauvel, 1923), Perinereis cultrifera (Grube, 1840), Polydora cornuta Bosc, 1802, Scolelepis (Parascolelepis) tridentata (Southern, 1914), and Streblospio gynobranchiata (Rice & Levin, 1998); 5 species of crustaceans (Melita sp., Microdeutopus gryllotalpa Costa, 1853, Microdeutopus sp., Monocorophium acherusicum (Costa, 1853), and Rhithropanopeus harrisii (Gould, 1841)); 1 species of mollusks Modiolus adriaticus Lamarck, 1819 and unidentified species of Chironomidae, Ascidiidae, Actiniidae. Six of these species are invasive: F. enigmaticus, P. macrodactylus, Rh. harrisii, M. cf. setiflagella, P. cornuta, and S. gynobranchiata. The macrozoobenthos abundance in colonies varied from 1857 to 3277 ind./m2. F. enigmaticus is the dominant species on this parameter. The biomass varied from 36.873 to 277.312 g/m2, it was formed by the biomass of F. enigmaticus, Rh. harrisii, and representatives of Ascidiidae. The use of IFA allowed to identify F. enigmaticus community and its leaders: F. enigmaticus, R. harrisii and representatives of the Ascidiidae family. The trophic structure of macrozoobenthos of F. enigmaticus colonies is represented by three groups: polyphages, detritophages, and predators. It was found that in the biotope of loose bottom sediments, the species composition of macrozoobenthos is much poorer than in colonies: 2 species of polychaetes, 3 species of decapods, and Oligochaeta. The species composition of the fauna of different colonies mainly has a high degree of similarity (the Czekanowski-Sorensen index varied from 0.5 to 0.84). When comparing the species composition of macrozoobenthos of colonies and loose sediments, this index varied from 0.2 to 0.44, indicating a low degree of similarity of fauna between sites. For the first time, reef structures formed by tubes of the polychaete F. enigmaticus have been discovered on the Azov-Black Sea coast of Russia. The species composition and quantitative characteristics of the community were determined. The detection of major age groups of these species, presence of reproductive individuals and evidence of their successful breeding indicate the possibility of the formation of their self-reproducing populations in the Kerch Strait. In order to avoid negative consequences associated with a possible expansion of the habitat of invasive species, special measures are required to control the development of their populations in the adjacent waters of the Azov and Black Seas. The paper contains 6 Figures, 3 Tables and 40 References. The Authors declare no conflict of interest.

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