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.

Studio geomorfologico dell'area carsica attorno alla Grotta Palombara (Melilli, Siracusa)

The following thesis attempts to study and analyse the geomorphological evolution of a relatively small coastal area located to the North of Syracuse (Southeastern Sicily). The presently inactive Palombara Cave is located in this area. The 800 metres of passages in this cave show an evolution in some way linked to the local topographic and environmental changes. This portion of coastline was affected more or less constantly by the tectonic uplift during the Pleistocene, which simultaneously to the eustatic variations have played a key role in the genesis of the marine terraces and the cave. Starting from a DTM made from Lidar data, using a GIS procedure several marine terraces have been mapped. These informations combinated with a geomorphological study of the area, allowed to identify and recognise the different orders of the Middle Pleistocene terraced surfaces. Four orders of terraces between 180-75 m a.s.l have been observed, illustrated and described. Furthermore, two other supposed terrace edges located respectively at 60 and 35 m, which would indicate the presence of two more orders, have been recognised. All these marine terraces appear to have formed in the last million years. The morphological data of the Palombara cave, highlights a genesis related to the rising of CO2 rich waters coming from the depths through the fractures of the rock mass, that ranks it as a hypogenic cave. The development has been influenced by the changes in the water table, in turn determined by the fluctuations in the sea level. In fact, the cave shows a speleogenetic evolution characterised by phases of karstification in phreatic and epiphreatic environment and fossilization stages of the upper branches in vadose conditions. These observations indicate that the cave probably started forming around 600 Ky ago, contemporary to the start of volcanic processes in the area.