Assessment of Romanian circalittoral soft bottom benthic habitats under Danube River influence

Abstract

Although numerous studies have focused on ecological quality status (EQS) assessments in the Black Sea, knowledge regarding the status of the soft bottom benthic habitats under Danube River influence is still lacking. Therefore, we investigated the diversity, distribution and EQS of benthic habitats located in the northern part of the Romanian continental shelf. In 2018, 34 samples were collected to analyse the macrozoobenthic fauna. A total of 71 species and 6 taxa belonging to 16 phyla were recorded. Two broad-scale circalittoral habitats (1 — terrigenous mud with Melinna palmata; 2 — mixed sediments with Dipolydora quadrilobata and biogenic reefs with Mytilus galloprovincialis) were encountered in the area based on Bray–Curtis similarity index. EQS analysis of the investigated habitats using a new approach based on the reconsideration of the ecological status of invasive species, resulting in the classification of D. quadrilobata as disturbance-tolerant (III) rather than second order opportunistic, allowed us to perform a realistic assessment of the ecological status. The good environmental assessment (GES) - non-GES threshold for AMBI, S, H and M-AMBI*(n) was calculated using a reference site dataset from the period 2014-2018. Overall, the EQS of the analysed habitats showed that 70% of the Dipolydora habitat is in GES according to M-AMBI Dipolydora III and M-AMBI*(n). Fifty percent of the Melinna habitat is in GES according to the same indices. In our study, for the first time on the Romanian coast, we documented the presence of the anthozoan species Edwardsia cf. claparedii.