Chemical Composition respiration and feeding ratesof the new alien ctenophore berae ovata in the black sea

Maximum daily rations of the ctenophore Beroe ovata Brugiere and predatory impacts on the Mnemiopsis leidyi A. Agassiz population were estimated via digestion time, prey biomass and predator and prey density in Sevastopol Bay and adjacent water regions. Digestion times ranged from 0.5 to 5.2 h and depended on the prey/predator weight ratio. Overall, the mean daily ration was 45% of B. ovata wet weight. Preliminary conclusions are given on the B. ovata population as an effective control of the M. leidyi population and on the dynamics and structure of the planktonic community as a whole

Chemical composition, respiration and feeding rates of the new alien ctenophore, Beroe ovata, in the Black Sea

Maximum daily rations of the ctenophore Beroe ovata Brugiere and predatory impacts on the Mnemiopsis leidyi A. Agassiz population were estimated via digestion time, prey biomass and predator and prey density in Sevastopol Bay and adjacent water regions. Digestion times ranged from 0.5 to 5.2 h and depended on the prey/predator weight ratio. Overall, the mean daily ration was 45% of B. ovata wet weight. Preliminary conclusions are given on the B. ovata population as an effective control of the M. leidyi population and on the dynamics and structure of the planktonic community as a whole

The ecological and physiological state of the ctenophore Mnemiopsis leidyi (Agassiz) in the Black Sea in autumn 1996

The survey was made in off-shore waters of the Black Sea near the Anatolian coast of Turkey during a research cruise of the R/V Bilim (24 Sept - 4 Oct 1996). The biomass of gelatinous macroplankton and the glycogen content in the body of the ctenophore Mnemiopsis leidyi were studied at 14 stations. Though the ctenophore still dominated the plankton in terms of biomass (average biomass +/- standard deviation 276 +/- 115 g/m(2)), this estimate was significantly lower than corresponding estimates obtained for the same months in recent years. A simultaneous reduction in the stock of small-sized fodder zooplankton and the large copepod Calanus euxinus indicates this case may be due to a general aggravation of trophic conditions for ctenophores. Data on the ctenophore's body glycogen content varied from 21 to 44 mu g/g fresh weight and accounted for 52.5 +/- 14.2% of total polysaccharide content on average, the condition of M. leidyi observed during the conducted survey corresponded to that expected after a two-day fasting period. Tentative experiments have shown that metabolic rates of the examined ctenophores were notably reduced. The rate of oxygen consumption (R, mu l O-2 . ind(-1) . h(-1)) was 1.7-1.8 less than that which would indicate a sufficient food supply; depending on the estimate of fresh body weight (UT, g) at 12-14 degrees C, it may be described by the following equation: R = 2.50 W-0.83

Effect of starvation on the biochemical compositions and respiration rates of ctenophores Mnemiopsis leidyi and Beroe ovata in the Black Sea

The proximate biochemical composition and metabolic rates of ctenophores Mnemiopsis leidyi and Beroe ovata from the Black Sea were examined with respect to starvation conditions. Although organic matter content in B. ovata was two times higher than that of M. leidyi (2.51 +/- 0.53 and 1.4 +/- 0.17 mg g(-1) of wet weight, respectively), these species did not significantly differ in their biochemical composition. In both species protein formed about 80% of the total organic matter, lipids amounted to about 10%. Carbohydrate and amino acids measured separately made up less than 6.5% of the total organic matter. Under experimental starvation (18 days at 16-18 degrees C for B. ovata and 8 days at 12.4 degrees C for M. leidyi), wet weights of both ctenophore species were reduced by 9.4% and 9.3% d(-1), respectively. The rate of organic matter decrease was nearly two times lower than that of wet weight being on average 5.9% d(-1) in M. leidyi and 5.5% d(-1) in B. ovata. There was no trend in percentage of the four major biochemical categories with starvation time. The glycogen content in polysaccharides reached maximum values in freshly collected ctenophores (76.0 +/- 7.9% in B. ovata, and 86.6% in M. leidyi), but it was reduced substantially (34.4 +/- 2.7% in B. ovata and 18.3-28.8% in M. leidyi) with starvation. Monosaccharide content, expressed as a percentage of total carbohydrate, decreased from 39.9% to 13.5% in B. ovata, and from 45.8% to 14.3-23.2% in M. leidyi. The relationship between respiration rate (R) and wet weight (W) of individuals during the starvation can be expressed by power function R = R-1 W-k (r(2)=0.85-0.94; P<0.001) for both ctenophore species. On average, k values were 0.95 and 0.83 in B. ovata and in M. leidyi, respectively. By the end of the starvation, metabolic rate per unit wet weight decreased by 33% in B. ovata and 46% in M. leidyi. Organic matter utilization was almost totally explained by respiration of ctenophores in the experiments and exceeded metabolic requirements of studied species by 11% and 15%, correspondingly. As compared with Mnemiopsis, Beroe has better tolerance to starvation which explains to some extent the success of the species survival during prolonged periods of food shortage in the Black Sea conditions

Feeding, respiration and growth of ctenophore Beroe cf ovata in the low salinity conditions of the Caspian Sea

The ctenophore Beroe cf ovata, which spontaneously entered the Black Sea in the 1990s and suppressed the previous ctenophoran invader Mnemiopsis leidyi by its predatory impact, is currently considered for intentional introduction to the Caspian Sea as well. In order to assess its impact on Mnemiopsis in the Caspian, Beroe was transported during 2002 from the Black Sea and the Bosporus to the Khazerabad laboratory (Mazandaran), on the Caspian coast of Iran, where experiments on its survival in Caspian water, and on various physiological characteristics (feeding, respiration, reproduction and growth) of both ctenophore species were performed. Beroe cf ovata was found to adjust to Caspian salinity conditions without problems

Population dynamics, ingestion, growth and reproduction rates of the invader Beroe ovata and its impact on plankton community in Sevastopol Bay, the Black Sea

The impact of the introduced ctenophore Beroe ovata on its prey Mnemiopsis leidyi, another invader ctenophore voraciously feeding on mesozooplankton, and consequently on the mesozooplankton community, was evaluated by undertaking both laboratory and field studies in the northern Black Sea. Ingestion and growth rates as well as the gross growth efficiency of B. ovata were estimated from laboratory experiments. The daily ration of ctenophores was related to food abundance within a wide range of prey concentration and never reached saturation. Beroe ovata required high food rations (not less than 20% of body weight per day) for growth. The abundances, biomasses and population structures of these two introduced ctenophore species were also monitored, along with mesozooplankton, in inshore waters of the northern Black Sea (i.e. Sevastopol Bay and adjacent regions) over a period of 3 years (1999-2001) which is after B. ovata's arrival. The annual dynamics of the M. leidyi population were similar for the last 3 years: very low abundances and biomass values were observed during most of the year (unlike the previous years), with a sudden increase in summer-early autumn, but only for about a 2 month period. The B. ovata bloom during the peak M. leidyi biomass resulted in the M. leidyi biomass falling sharply to extremely low values. The predatory impact of M. leidyi on prey zooplanton was found to be reduced during the period of study compared with before

Physiological characteristics of the ctenophore Beroe ovata in Caspian Sea water

Riparian countries of the Caspian Sea have been evaluating the pros and cons of the predatory ctenophore Beroe ovata as a control agent against the invasive ctenophore Mnemiopsis leidyi, which has enormous adverse impacts on the fishery resources as well as on the biodiversity in this once fertile sea. To assess the viability of B. ovata establishment in the Caspian Sea, the survival and some physiological characteristics (feeding, respiration, reproduction and growth) of the predatory ctenophore were studied in Caspian Sea water (12.6 ppt salinity) conditions using animals transported from the Black and Marmara Seas to a laboratory on the Iranian Caspian coast. The findings of the study showed that when salinity was gradually decreased from 22 to 12.6 ppt, B. ovata were able to adapt well to Caspian Sea water. Most of the predatory ctenophores began to swim actively and to feed on M leidyi within 15 to 30 min following each step of acclimation. The feeding rate of B. ovata ranged from 14 to 765% of body wet weight and was highest for smaller individuals (i.e. 13 to 16 nun). Over the measured weight range of 0.23 to 3.87 g wet wt, the weight-specific respiration rate was independent of weight. The daily specific growth rate of adult ctenophores was 7 to 11% of body wet wt. B. ovata specimens were spawned and their eggs were hatched in Caspian Sea water, but the larvae survived for only a few hours. The energy budget of B. ovata calculated from food consumption, respwiration and growth rates revealed a mean assimilation efficiency of 0.72 +/- 0.1, a gross growth efficiency (K-1) of 0.48 +/- 0.12 and a net efficiency (K-2) of 0.66 +/- 0.06. Based on these physiological data, we suggest that in the Caspian Sea, B. ovata will be able to ingest M. leidyi intensively. However, concerning the reduction of the M leidyi population and consequently the reversal of its adverse impact on this ecosystem, the failure of larval growth observed under experimental conditions (most probably due to poor handling) remains the main obstacle to overcome in the successful establishment of B. ovata in the Caspian Sea

Does the nutrient stoichiometry of primary producers affect the secondary consumer Pleurobrachia pileus?

We investigated whether phosphorus limitations of primary producers propagate upwards through the food web, not only to the primary consumer level but also onto the secondary consumers' level. A tri-trophic food chain was used to assess the effects of phosphorus-limited phytoplankton (the cryptophyte Rhodomonas salina) on herbivorous zooplankters (the copepod Acartia tonsa) and finally on zooplanktivores (the ctenophore Pleurobrachia pileus). The algae were cultured in phosphorus-replete and phosphorus-limited media before being fed to two groups of copepods. The copepods in turn were fed to the top predator, P. pileus, in a mixture resulting in a phosphorus-gradient, ranging from copepods having received only phosphorus-replete algae to copepods reared solely on phosphorus-limited algae. The C:P ratio of the algae varied significantly between the two treatments, resulting in higher C:P ratios for those copepods feeding on phosphorus-limited algae, albeit with a significance of 0.07. The differences in the feeding environment of the copepods could be followed to Pleurobrachia pileus. Contrary to our expectations, we found that phosphorus-limited copepods represented a higher quality food source for P. pileus, as shown by the better condition (expressed as nucleic acid content) of the ctenophore. This could possibly be explained by the rather high C:P ratios of ctenophores, their resulting low phosphorus demand and relative insensitivity to P deficiency. This might potentially be an additional explanation for the observed increasing abundances of gelatinous zooplankton in our increasingly phosphorus-limited coastal seas