Influence of environmental and biological drivers on the population dynamics of the ctenophore Bolinopsis vitrea in the Rio San Pedro (Bay of Cadiz, SW Spain)

Large accumulations of gelatinous zooplankton (GZ) occur in many coastal and estuarine regions worldwide. The ability of this species to rapidly reproduce and adapt to new habitats ensure them to inhabit different ecosystems with wide environmental and economic impacts on these areas and on the human activities occurring near the shore. The present study is a comprehensive analysis of the population dynamics of Bolinopsis vitrea, a native ctenophore of oligotrophic waters. The overall aims are to explore the connection of this species with the environmental variables to which it is exposed in the Rio San Pedro (RSP), an estuarine ecosystem in the Bay of Cadiz, and to investigate the influence of this species on the biogeochemical cycles in the ecosystem. Samplings were conducted every month from 2014 until 2017, to study the temporal variability at different scales, with a particular attention on the blooms that occur during spring and earlier summer. The environmental variables analyzed represented important stressors affecting the internal dynamics of the population, with direct and indirect effects on abundances and biovolume of ctenophores and mesozooplankton. Our results highlighted a coupling between the meteorological conditions in the area and the development of B. vitrea population, regulating the dimensions of the population and explaining the interannual differences in the phenology of its blooms occurring in the RSP. An eight yearlong dataset (2010-2017) has confirmed the high variability that can occur due to these conditions. Moreover, the excretion and respiration rates of this organism influence the biogeochemical cycles with a trend in increasing correlated with its size. Furthermore the excretion of TEP (transparent exopolymeric particles), that increases with the ctenophore’s size, may represent a link between the dynamic of B. vitrea and the bacterioplanktonic communities inhabiting its mucus and the water column surrounding the ctenophores

Methodologies for the analysis and interpretation of environmental datasets from areas interested by offshore activities

The exploitation of hydrocarbon reservoirs by the oil and gas industries represents one of the most relevant and concerning anthropic stressor in various marine areas worldwide and the presence of extractive structures can have severe consequences on the marine environment. Environmental monitoring surveys are carried out to monitor the effects and impacts of offshore energy facilities. Macrobenthic communities, inhabiting the soft-bottom, represent a key component of these surveys given their great responsiveness to natural and anthropic changes. A comprehensive collection of monitoring data from four Italian seas was used to investigate distributional pattern of macrozoobenthos assemblages confirming a high spatial variability in relation to the environmental variables analyzed. Since these datasets could represent a powerful tool for the industrial and scientific research, the steps and standardized procedures needed to obtain robust and comparable high-quality data were investigated and outlined. Over recent years, decommissioning of old platforms is a growing topic in this sector, involving many actors in the various decision-making processes. A Multi-Criteria Decision Analysis, specific for the Adriatic Sea, was developed to investigate the impacts of decommissioning of a gas platform on environmental and socio-economic aspects, to select the best decommissioning scenario. From the scenarios studied, the most impacting one has resulted to be total removal, affecting all the faunal component considered in the study. Currently, the European nations are increasing the production of energy from offshore wind farms with an exponential expansion. A comparative study of methodologies used five countries of the North Sea countries was carried out to investigate the best approaches to monitor the effects of wind farms on the benthic communities. In the foreseeable future, collaboration between industry, scientific communities, national and international policies are needed to gain knowledge concerning the effects of these industrial activities on the ecological status of the ecosystems