Prediction of ctenophore Beroe ovata Bruguiere, 1789 habitat expansion and control of invading Mnemiopsis leidyi Agassiz, 1865 in the Ponto-Caspian basin associated with climate change.

The seas of Ponto-Caspian basin (Black, Azov and Caspian) are exposed to species invasions, including harmful ctenophore Mnemiopsis leidyi A. Agassiz, 1865 and its predator Beroe ovata Bruguière, 1789. Current environmental conditions of invasive ctenophores M. leidyi and B. ovata occurrence, development and variability in the Ponto-Caspian basin have been compiled, based on own field observations and published data. Analysis of climatological data on basic environmental parameters (water temperature, salinity, chlorophyll concentration) and modeling approach were used to predict favourable for both ctenophores conditions, and changes of those conditions, associated with the climate variations. The role of B. ovata as a bio-controller of M. leidyi population has been assessed. Several climate change scenarios have been considered in this study i.e., uniform increase/decrease of SST throughout the year by 2 °C and only spring temperatures increase/decrease by 2 °C. The most sensitive to increase in SST in terms of M. leidyi reproduction duration are the western coast of the Black Sea and the Southern and Middle Caspian. On the other hand, B. ovata reproduction duration is expected to increase in several areas, including the northern coast of the Black Sea and the Southern and Middle Caspian. The coastal areas of the Black Sea and the transitional regions between the Southern and Middle Caspian are exposed to an earlier start of M. leidyi reproduction during warmer springs. Regarding B. ovata, the whole Black Sea is vulnerable to spring SST changes, but in the Caspian Sea B. ovata extends its reproduction duration only in the Middle Caspian during warmer springs. Since B. ovata consumes mostly M. leidyi, it is an important biocontrolling agent of M. leidyi, harmless for the ecosystem.

Patterns of invasive ctenophore Mnemiopsis leidyi distribution and variability in different recipient environments of the Eurasian seas: A review.

Harmful invader ctenophore Mnemiopsis leidyi's expansions in the Eurasian Seas, its spatio-temporal population dynamics depending on environmental conditions in recipient habitats have been synthesized. M. leidyi found suitable temperature, salinity and productivity conditions in the temperate and subtropical environments of the semi-enclosed seas, in the coastal areas of open basins and in closed water bodies, where it created autonomous populations. M. leidyi changes its phenology depending on seasonal temperature regime in different environments. We assessed ranges of sea surface temperature, sea surface salinity and sea surface chlorophyll values, sufficient for M. leidyi general occurrence and reproduction based on comprehensive long-term datasets, contributed by co-authors. This assessment revealed that there are at least two eco-types (Southern and Northern) in the recipient seas of Eurasia with features specific for their donor areas. The range of thresholds for M. leidyi establishment, occurrence and life cycle in both eco-types depends on variability of environmental parameters in their native habitats.

Effect of invasive ctenophores Mnemiopsis leidyi and Beroe ovata on low trophic webs of the Black Sea ecosystem.

The study focuses on the impact of life excretion and mucus released by the "biological pollutants" invasive ctenophore Mnemiopsis leidyi and its predator Beroe ovata on the marine environment and lower trophic levels of the Black Sea ecosystem (bacteria, pico-phytoplankton, nano-autotrophic/heterotrophic flagellates, micro-phytoplankton, chlorophyll a, primary production (PP), micro-zooplankton). The chemical and biological variables were analysed in two sets of lab experiments with natural communities from mesotrophic (Gelendzhik) and eutrophic (Varna) coastal waters. While both species altered the chemical properties of experimental media, exerting structural and functional changes in the low food-web biological compartments, the results showed a stronger effect of B. ovata, most likely related to the measured higher rate of excretion and amount of released mucus. In addition the alterations in the Gelendzhik experiment were more pronounced, indicating that environmental implications on lower food-web are more conspicuous in mesotrophic than in eutrophic coastal waters.

[New settlers comb jellies Mnemiopsis leidyi (A. Agassiz) and Beroe ovata Mayer 1912 and their influence on the pelagic ecosystem of the northeastern part of the Black Sea]. / Grebneviki vselentsy Mnemiopsis leidyi (A. Agassiz) i Beroe ovata Mayer 1912 i ikh vozdeistvie na pelagicheskuiu ékosistemu severo-vostochnoi chasti Chernogo moria.

We analyzed the condition of pelagic ecosystem of northeastern Black Sea influenced by expansion of a new settler Beroe ovata in 1999-2001. Expansion of B. ovata considerably decreased the population of another new settler Mnemiopsis leidyi that deformed the Black Sea ecosystem for over a decade. Reduction of M. leidyi population limited its influence on the ecosystem and, consequently, we observed reestablishment of the main components of the Black Sea pelagic ecosystem--zooplankton and fish, their spawn and larvae. The relationship between annual and seasonal variability of the population and biomass of the both new settlers M. leidyi and B. ovata are discussed.

[Study of the new settler Beroe ovata in the Black sea]. / Rezul'taty issledovanii novogo vselentsa Beroe ovata v Chernom more.

Primary data on population, size, and distribution of a new settler--comb jelly Beroe ovata--in the Black Sea are presented. We studied certain aspects of its nutrition, consumed organisms, and digestion time. Comb jellies Mnemiopsis leidyi and Pleurobachia pileus were established as the nutritional targets of B. ovata. Mnemiopsis proved to be more accessible and assimilable. Preliminary data on metabolic level and threshold oxygen content in B. ovata were obtained; proportions of dry and wet weight of B. ovata were determined. Population changes of new settler Mnemiopsis and other jellylike animals in the Northeast part of the sea induced by B. ovata were analyzed. We observed sharp decrease in population of Mnemiopsis, a species that induced degradation of the Black Sea ecosystem within the last decade.