ECOLOGICAL STATUS AND TRAJECTORIES OF CHANGE IN TEMPERATE AND TROPICAL REEFS

Amongst marine temperate and tropical ecosystems, Mediterranean rocky reefs and Maldivian coral reefs are the most productive and diverse, providing essential ecosystem services. Unfortunately, due to several co-occurring local and global pressures, they are ranked as the most threatened marine habitat. The present work attempts to analyse their ecological status and change over time in a global warming scenario. With this purpose, different methodological approaches have been adopted. Many studies have been conducted in Marine Protected Areas (MPAs), highlighting that the constant updating of species inventory and surveillance is still necessary, also after their establishment. Monitoring of target species is a valuable tool in assessing ecological status of the environment they live in. Tackling the case of a species in need of protection confirmed how detailed information on species distribution is mandatory to develop effective environmental management plans. Non-destructive techniques are to be preferred when studying and monitoring target species and valuable habitats. By comparing data collected from different observers, visual methods have proven reliable and effective in the characterization of habitat and evaluation of change over time. By applying standardized protocols and monitoring water temperature, mass mortality event and target species this work unveiled effects of climate change in all study areas, regardless of different latitude and level of protection. Due to the climate change marine ecosystems are increasingly exposed to the cumulative effects of different pressures. Analysis of short-term change in a benthic community showed that the cumulative effect of multiple stressors is stronger than that of any individual stressor, no matter how intense it is. As a result of local and global human pressures, marine ecosystems have undergone important changes that can only be detected by analysing long-term data series or revisiting sites already surveyed. By assessing change over time at three different level of complexity (i.e., population, community, and ecosystems), this work addresses the issue of decreasing abundance of native species in correspondence with increasing number of invasive species. The findings confirmed that in a given reef, a turnover in species composition determine a change in community structure. Biodiversity provides a buffer to maintain ecosystem functioning in the face of environmental changes, and decrease in functional redundancy, due to the community change, demonstrated reduced ecosystem resilience. Global warming, and the consequent changes in marine ecosystems, are occurring at an unprecedented rate and on a worldwide scale. In this context, a cooperative effort between research and international environmental policy is urgently needed.