First record of Mnemiopsis leidyi A. Agassiz 1865 in the Baltic Sea

The invasive ctenophore Mnemiopsis leidyi was first recorded in the Kiel Bight (western Baltic Sea) on 17 October 2006 during a regular weekly sampling program. The M. leidyi abundance gradually increased from 29.5±12.7 ind.m-3 in mid-October to 92.3±22.4 ind.m-3 in late November 2006. The occurrence of M. leidyi in the Baltic Sea is of great concern as this invader has caused negative impacts in the southern seas of Europe

Reproduction of the ctenophore, Beroe ovata, in the Caspian Sea water

The experiments with Beroe ovata showed that this ctenophore can survive and reproduce in the Caspian Sea water, though at far lower rate than in the Black Sea; larval growth in the Caspian Sea water was also slower and mortality higher. Maximum fecundity of 2210 and 240 eggs recorded in laboratories of Turkey and Iran, respectively. About 34 to 100% of eggs in the Caspian Sea water could not develop and hatch. Larvae were at different stages of development, usually with size between 1.2 to 2mm. The highest number of eggs and larvae were obtained in tanks where Beroe individuals were together with Mnemiopsis leidyi. The poor reproduction of B. ovata in the Caspian Sea water could be due to both the acclimation stress to low salinity and possible damage of individuals during the transportation

Seasonal changes and population dynamics of the ctenophore Mnemiopsis leidyi after its first year of invasion in the Kiel Fjord, Western Baltic Sea

We analyzed the seasonal variations of the ctenophore Mnemiopsis leidyi weekly collected since its first record in the western Baltic Sea in October 2006. The distribution pattern together with the seasonal dynamics and population outbreaks in late summer 2007 indicate recent successfully establishment of M. leidyi in this area. Seasonal changes showed two periods of high reproductive activity characterized by a population structure dominated by small size classes, followed by an increase of larger ones. These results further revealed that the bulk of the population remains in deep layers during the periods of low population density, whereas it appeared situated in upper layers during the proliferation of the species. We further emphasized the strength of the population outbreaks, which can reach abundances >10-fold higher in time periods shorter than a week. The predatory impact this species may have in pelagic ecosystems warns on the importance of its recent range of expansion

Environmental Control of Phase Transition and Polyp Survival of a Massive-Outbreaker Jellyfish

A number of causes have been proposed to account for the occurrence of gelatinous zooplankton (both jellyfish and ctenophore) blooms. Jellyfish species have a complex life history involving a benthic asexual phase (polyp) and a pelagic sexual phase (medusa). Strong environmental control of jellyfish life cycles is suspected, but not fully understood. This study presents a comprehensive analysis on the physicochemical conditions that control the survival and phase transition of Cotylorhiza tuberculata; a scyphozoan that generates large outbreaks in the Mediterranean Sea. Laboratory experiments indicated that the influence of temperature on strobilation and polyp survival was the critical factor controlling the capacity of this species to proliferate. Early life stages were less sensitive to other factors such as salinity variations or the competitive advantage provided by zooxanthellae in a context of coastal eutrophication. Coherently with laboratory results, the presence/absence of outbreaks of this jellyfish in a particular year seems to be driven by temperature. This is the first time the environmental forcing of the mechanism driving the life cycle of a jellyfish has been disentangled via laboratory experimentation. Projecting this understanding to a field population under climatological variability results in a pattern coherent with in situ records

Comprehensive study on probability of controlling Caspian Sea invasive Ctenophora Activity 4: The laboratory study on probability of controlling Mnemiopsis leidyi by use of Beroe ovata (reproduction study of B. ovata in the Caspian Sea water)

In 1999 Mnemiopsis leidyi was introduced to the Caspian Sea from the Black Sea with ballast waters from the ships. The comprehensive study on probability of controlling Caspian Sea invasive Ctenophora planned after a remarkable of decreeing in Kilka fish catches stocks and fisheris community problems. This study focus on reproduction experiments of Beroe ovata as the best candidate for control of Mnemiopsis population size in the Caspian Sea that was performed in Turkey and Iran during 2002-2003. At 2002, 87 specimens of B. ovata, 10-50 mm transferred to Caspian sea ecology research center from Marmareh sea where acclimated with Caspian sea water gradually. At 2003, experiments were performed near to Black sea (at Sinop) with freshly collected Beroe ovata, 40-65 mm size in three salinity level treatment, the Black sea water 18 , Mixed water 15 and Caspian water 12 . 130 individuals of Beroe ovata were brought from Sinop (Turkey) to Iran during 2003. A number of Beroe specimens were sent to Guilan province for reproduction studies and another part were sent to Mazandaran province for both reproduction and mesocosem studies. For control we had 1 Beroe, length 30 mm in the Black Sea water that was alive during of study in Iran. The Jars were examined each day for ova and larvae and they were collected and put into glass container of Caspian water for hatching and developing survey, some of them were left without any handling for larvae developing. Also in another experiment the eggs collected from jars were placed in the same three treatments for studying of growth and survival. The results were unsuccessful on propagation experiments at 2002 since the spawning and hatching rates were very low (20 ova) and, none of the larvae developed into adults in Caspian Sea water. The spawning was more in Marmareh sea water with 138 ova where only 7 larvae was hatched. Results showed that Beroe specimens is able to survive and reproduce in Caspian water but was not as well as Black Sea also the Beroe larvae growth rate is low in the Caspian Sea water. Maximum fecundity of Beroe individual was 2212 and 235 ovae in Caspian Sea water in site Sinop and Iran respectively. Results showed 34-100% eggs in Caspian Sea water were destroyed and did not develop. In Iran we obtained only one larvae with 5 mm length, other larvae were at different stages of development but most of them were 1.2 2 mm. The results of mesocosm survey showed most of ova and larvae have been obtained from the tanks where individuals B. ovata were with Mnemiopsis. Fecundity of Beroe in the control with Black Sea water were between 17 to 1879 with average of 828 ± 112 ova. The poor results of B. ovata reproduction obtained in this survey in Caspian Sea may be due to transportation and acclimation stress and low salinity of Caspian Sea water

A MSFD complementary approach for the assessment of pressures, knowledge and data gaps in Southern European Seas : the PERSEUS experience

PERSEUS project aims to identify the most relevant pressures exerted on the ecosystems of the Southern European Seas (SES), highlighting knowledge and data gaps that endanger the achievement of SES Good Environmental Status (GES) as mandated by the Marine Strategy Framework Directive (MSFD). A complementary approach has been adopted, by a meta-analysis of existing literature on pressure/impact/knowledge gaps summarized in tables related to the MSFD descriptors, discriminating open waters from coastal areas. A comparative assessment of the Initial Assessments (IAs) for five SES countries has been also independently performed. The comparison between meta-analysis results and IAs shows similarities for coastal areas only. Major knowledge gaps have been detected for the biodiversity, marine food web, marine litter and underwater noise descriptors. The meta-analysis also allowed the identification of additional research themes targeting research topics that are requested to the achievement of GES. 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license.peer-reviewe