Meroplankton taxonomic composition and seasonal dynamics near the seaport Kavkaz, Kerch Strait

Abstract

Meroplankton taxonomic composition, distribution of abundance, and seasonal population dynamics were studied in the northern Kerch Strait (the seaport Kavkaz area). For the study, zooplankton material was sampled in different seasons in 2017–2019 in the seaport area and outside it. Zooplankton was sampled totally throughout the water column at depths 5 to 8 m with a large Juday net (opening diameter of 37 cm and mesh size of 120 μm). The samples were fixed in 2–4 % neutral formaldehyde and processed in the laboratory by the conventional method. In total, 32 meroplankton taxa were found. As noted, meroplankton density in the polluted area is not inferior to that of the relatively clean area and provides sufficient reproductive potential there. In the seaport area, barnacle (cirripedian) and mollusc larvae were widespread; outside, barnacle and bivalve larvae were common. The basis of meroplankton pool was formed by species tolerant to water eutrophication and bottom sediment sulfide contamination – larvae of gastropod Bittium reticulatum, larvae of bivalves Abra segmentum, Cerastoderma glaucum (in summer), and Mytilaster lineatus (in early autumn), and larvae of barnacle Amphibalanus improvisus (in spring). The seasonal dynamics of meroplankton in the study area revealed a summer–autumn increase in abundance which is common for the Black Sea water. The period of the greatest zoobenthos spawning and larvae release into the pelagial lasted April to October. Three density peaks were recorded (April, June, and September), and those were most pronounced in the seaport area in spring and in the open area in early autumn.

Keywords

• meroplankton
• abundance
• seasonal dynamics
• Kerch Strait