Abstract
Successful invasion of Mnemiopsis leidyi A. Agassiz, 1865 and Beroe ovata Mayer, 1912 into the Black Sea and their important role in this region pelagic ecosystem is stipulated mainly by the considerable eurythermy of these species. Many ecological-physiological characteristics of ctenophores—aliens are studied quite well. However, bioluminescence, one of the most important elements of the ctenophores ecology and the bioluminescence reaction temperature optimum for these individuals under different environment temperatures were not studied sufficiently. Therefore our researches in this scientific field are significant and conceptually novel for ctenophores ecology study. Experimental investigations were carried out in the period of 2008-2009 in the IBSS. Uni-sized (40 mm) ctenophores were collected in the Sevastopol coastal zone and divided in several groups, contained under different temperatures: from 10°C ± 1°C to 30°C ± 1°C. Ctenophore bioluminescence was investigated under chemical and mechanical stimulation. M. leidyi light emission maximal amplitude (1432.94 ± 71.64 × 108 quantum·s–1·cm–2) with duration of 3.54 ± 0.15 s is fixed under the temperature of 26°C ± 1°C. Temperature increase up to 30°C ± 1°C led to the 4 times decrease of the bioluminescence intensity. Under temperature decrease up to 10°C ± 1°C this parameter decreased 20 times (p B. ovata achieved maximal values under the temperature of 22°C ± 1°C (1150.12 ± 57.51 × 108 quantum·s–1·cm–2) with duration of 3.03 ± 0.15 s. The luminescence intensity decreased under the temperature increase to 30°C ± 1°C more than 20 times. Temperature decrease to the values of 10°C ± 1°C impacted decreasing the amplitude of bioluminescence up to the minimal –4.92 ± 0.22 × 108 quantum·s–1·cm–2. The data obtained testify that characteristics of the ctenophores bioluminescence can be conditioned not only by the modification the environment temperature but by the variability of their physiological condition.
Highlights
Temperature increase up to 30 ̊C ± 1 ̊C led to the 4 times decrease of the bioluminescence intensity
Maximal indices of the ctenophore signals amplitude were observed under the temperature of 26 ̊C ± 1 ̊C under chemical, as well as under mechanical stimulation
Further temperature decrease down to 10 ̊C ± 1 ̊C leads to more considerable bioluminescence intensity change, up to its minimal values 17.32 ± 0.83 × 108 under mechanical and 17.93 ± 0.89 × 108 quantum·s–1·cm–2 under the chemical stimulation correspondingly
Summary
Ctenophore M. leidyi, which invaded the Black Sea aquatorium with the ballast waters in the end of 80-ties, beginning of 90-ties, caused the mass growth of abundance [1] This alien-species affected the feed mezozooplankton biomass, having undermined feed base of the plankton-eating fish—the base of the Black Sea market, pelagic fishes: anchovy, sprat, scad [2] considerably, together with another factors (climatic changes, in particular). Mass growth of M. leidyi caused increase of the fish larvae share with the empty stomachs, which led to the food fish population decrease and their catches reduction more than 5 times by 1991 [3], resulted in economy loses because of the anchovy stocks decrease, evaluated in 240 mln dollars per year [4] Another ctenophore B. ovata, which eats mnemiopsis, invaded the Black Sea at the end of 90-ties. Mnemiopsis abundance had decreased by 2000-2001, because B. ovata ate 80% of this ctenophore day biomass and that influenced the feed base of plankton-eating fish and their larvae state improvement [3]
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