The Black Sea Zooplankton Mortality, Decomposition, and Sedimentation Measurements Using Vital Dye and Short-Term Sediment Traps

Abstract

The principal objectives of this research are to measure the non-consumptive mortality rate of marine copepod zooplankton and the sedimentation rate of copepod carcasses, using short-term sediment traps, and to reveal a correlation between the rates of the two competitive processes—sedimentation and degradation of the carcasses under turbulent mixing conditions. The traps were moored in Sevastopol Bay and adjacent coastal waters (the Black Sea) during summer and autumn seasons. A simulation model was developed to describe a wide range of processes in the trap and the water column above it and to interpret the results obtained with the sediment traps. Significant changes in the abundance of copepod carcasses (from 280 to 12,443 ind. m−3) and their fraction in the total zooplankton abundance (53 to 81%) were observed in the waters over short time periods, indicating a high variability of zooplankton mortality, sedimentation, and decomposition rates. Despite the high concentrations of copepod carcasses in the water column, the rates of their accumulation in the traps proved to be extremely low, which could be due to intense turbulent mixing of the waters. The carcass sedimentation rate and the flow of swimmers (motile copepods) into the traps were significantly higher in waters subjected to weaker turbulent mixing. The obtained estimates of the sedimentation rate of copepod carcasses (0.012 to 0.39 d−1) were comparable in value with the rate of their microbial decomposition (0.13 and 0.05 d−1 in the bay and adjacent waters, respectively). This confirmed the hypothesis on microbial decomposition as one of the key controls of the fraction of live zooplankton organisms in zooplankton.

Zooplankton community and copepod carcasses and non‐predatory mortality in six tropical estuarine systems (Northeast of Brazil)

“…It was expected that environments with a wide variety of impacts and urbanization would show higher values of carcasses and non‐predatory mortality. This result can be explained by the possible large concentration of bacteria present in environments with a higher degree of anthropogenic influence and urbanization, which provide intense decomposition of carcasses in these locations, with only a fraction of living organisms remaining in the water column (Litvinyuk et al, 2022; Mukhanov & Litvinyuk, 2017). This leads to the erroneous interpretation that less anthropogenically affected estuaries show higher mortality rate values.…”

Ecology of Marine Zooplankton

“…In their paper, Litvinyuk et al [8] perform a study to assess the non-consumptive mortality rate of zooplanktonic organisms, mainly copepods, and the decomposition and sedimentation rates of carcasses in Sevastopol Bay. Their work reveals a high variability in these parameters, suggesting a reduced sedimentation rate of copepod carcasses in turbulent conditions, and a comparable rate of sedimentation and microbial decomposition, confirming the important role of copepod carcasses in coastal waters.…”

Response of the Black Sea Zooplankton to the Marine Heat Wave 2010: Case of the Sevastopol Bay

“…Based on the eutrophication E-TRIX-index assessments made in 2011-2012, the trophic level in the Sevastopol Bay was characterized as a transitional from medium to high [20]. Both pollution and trophic levels gradually decrease from the head of the bay to its mouth [21]. Being a port area, Sevastopol Bay is also heavily affected by maritime traffic, which contributes to invasions of alien species.…”