Micropollutants affect the ability of phytoplankton communities to track environmental changes

Human activities strongly influence environmental processes, and while human domination increases, biodiversity progressively declines in ecosystems worldwide. High genetic and phenotypic variability ensures functionality and stability of ecosystem processes through time and increases the resilience and the adaptive capacity of populations and communities, while a reduction in functional diversity leads to a decrease in the ability to respond in a changing environment. Pollution is becoming one of the major threats in aquatic ecosystem, and pharmaceutical and personal care products (PPCPs) in particular are a relatively new group of environmental contaminants suspected to have adverse effects on aquatic organisms. There is still a lake of knowledge on the responses of communities to complex chemical mixtures in the environment. We used an individual-trait-based approach to assess the response of a phytoplankton community in a scenario of combined pollution and environmental change (steady increasing in temperature). We manipulated individual-level trait diversity directly (by filtering out size classes) and indirectly (through exposure to PPCPs mixture), and studied how reduction in trait-diversity affected community structure, production of biomass and the ability of the community to track a changing environment. We found that exposure to PPCPs slows down the ability of the community to respond to an increasing temperature. Our study also highlights how physiological responses (induced by PPCPs exposure) are important for ecosystem processes: although from an ecological point of view experimental communities converged to a similar structure, they were functionally different.

Ruolo della gorgonia Paramuricea clavata (Risso 1826) nei popolamenti epibentonici coralligeni dell'Isola d'Elba

The red gorgonian Paramuricea clavata is considered a key species in Mediterranean coralligenous habitats and, when present at high density, its colonies may develop “gorgonian forests”, which are three-dimensional structures that increase habitat complexity. Mediterranean coralligenous habitats support high biodiversity but the structure and heterogeneity of communities can be strongly modified by several kinds of human-derived impacts. The global environmental change and human activity could threaten the coralligenous habitats and during the last few decades, Mediterranean suspension feeders have been involved in mass mortality events, in which P. clavata was one of the most affected. Without the complex three-dimensional structures formed by P. clavata, many benthic species may have not adequate sheltering and feeding opportunities. The aim of the present study was to investigate the ecological role of Paramuricea clavata in coralligenous habitats by comparing epibenthic assemblages established inside and outside gorgonian forests. This study was carried out in four sites randomly chosen, along the south-east coast of Elba island (north-western Mediterranean). The structure of the epibenthic assemblages were significantly different between area with and without gorgonians. Main differences concern very important taxa in the coralligenous bioconstruction processes like the encrusting red algae, Peyssonnelia spp. and Halimeda tuna, which were more abundant in presence of gorgonians. On the contrary, algal turf, mucilaginous algae and the invasive seaweed Caulerpa cylindracea were more abundant in areas without P. clavata. The presence of gorgonians may have a positive effect also on species diversity. The results of this study highlight the ecological role of P. clavata in the coralligenous habitats.