Study the effect of low pH on Ruditapes decussatus (Mollusca: Bivalvia)

The grooved carpet shell clam (Ruditapes decussatus) is one of the most economically essential mollusks in Mediterranean lagoons and sandy beaches, with fisheries and aquaculture both contributing to its abundance. The goal of this research is to see how varying amounts of acidity affect this calcifying organism. 420 ppm (ambient control), 550 ppm, 750 ppm, and 1050 ppm were used to incubate juvenile clams in CO2 enriched saltwater. With increasing pCO2 , the biological parameters evaluated revealed a small decline. Differences, however, were not substantial. In terms of overall weight, the reduction was greatest at 550 and 1050 ppm. Furthermore, clams kept at 550 parts per million had the lowest condition index and the greatest mortality rate of 8%. Both the 550 ppm and the control 420 ppm groups demonstrated an increase in metabolic rate and ammonia excretion in the physiological response testing. With increasing acidification, the algal feed clearance rate declined, with the highest average value in the control (420 ppm) group and the lowest average value in the extremely high pCO2 (1050 ppm) group. Ocean acidification may put further strain on R. decussatus' health and economic value by the end of the century

Movements of Non-Migrant European Eels in an Urbanised Channel Linking a Mediterranean Lagoon to the Sea

Transitional ecosystems and, particularly, Mediterranean lagoons represent important habitats for the European eel (Anguilla anguilla) population. In these habitats many anthropogenic pressures can disturb eel movements and, in turn, negatively affect the population. Despite the importance of movements during the non-migrant growing stage in eels, this topic is understudied in Mediterranean lagoons. We thus aim to describe the diel and seasonal phenology and the effect of environmental drivers on non-migrant eel movements. Videos obtained from an Adaptive Resolution Imaging Sonar (ARIS) acoustic camera that continuously recorded from October 2018 to April 2020 were processed to evaluate the daily number of eels swimming toward the lagoon. More than 60% of the 7207 eels observed were females with a size >45 cm. Movements were year-round and predominantly during the night. A Boosted Regression Tree analysis demonstrated that, among the 10 environmental drivers studied, flow velocity, water temperature, discharge of the main tributary, wind velocity and atmospheric pressure, had the strongest influence on eel movement activity. Non-migrant eel movements should be better incorporated into lagoon management plans through actions such as limiting dredging activities from 18:00 to midnight, especially when the water flows toward the lagoon and when the water temperature is higher than 12 °C.

Patterns in Alpha and Beta Phytoplankton Diversity along a Conductivity Gradient in Coastal Mediterranean Lagoons

Understanding the diversity patterns of phytoplankton assemblages in coastal lagoons is clearly important for water management. In this study, we explored alpha and beta diversity patterns in phytoplankton communities across five Mediterranean lagoons hydrologically connected to Vistonikos Gulf. We examined the phytoplankton community composition and biomass on a monthly basis from November 2018 to October 2019. For this, water samples were collected from seven inshore, brackish and coastal waters, sampling sites covering a wide range of conductivity. We found significant spatial and temporal differences in phytoplankton alpha diversity and in phytoplankton biomass metrics explained by the high variation of conductivity. Evenness remained low throughout the study period, reflecting significant dominance of several phytoplankton blooms. Harmful algal blooms of Prorocentrum minimum, Alexandrium sp., Rhizosolenia setigera and Cylindrotheca closterium occurred. The system’s species pool was characterized by relatively high phytoplankton beta diversity (average ~0.7) resulting from high temporal species turnover (90%). Overall, alpha and beta diversity components were indicative of rather heterogeneous phytoplankton communities which were associated with the high differences in conductivity among the sampling sites.