Characterization of Romanian Black Sea pelagic habitats based on mesozooplankton distributional pattern and proposal of a new integrative mesozooplankton index for assessing their quality status

Abstract

The paper presents the mesozooplankton population characteristics and distributional patterns within the coastal, transitional, and marine waters of the Romanian Black Sea shelf in August 2021. The results point out the utility of zooplankton as a biological indicator for delimiting the pelagic habitats due to its features strongly linked with the environmental variables. The assessment of water bodies’ quality based on the zooplankton indices agreed for the Black Sea according to the Water Framework Directive (2000/60/EC) and Marine Strategy Framework Directive (2008/56/EC), showed that in average 68% of indices were in GES, while the rest in non-GES. A new index, namely the Integrative Mesozooplankton Index (IMI), aiming to integrate the results of all three indices and percentage of water bodies in GES has been proposed. Three threshold classes for good, moderate and bad status have been established to delineate GES/nonGES threshold. At a threshold value of 6.6 – 9 proposed for the IMI GES, the overall quality status of the water bodies of the Romanian shelf in August 2021 did not achieve GES.