Resistance and Resilience of Adriatic Mesophotic Biogenic Habitats to Human and Climate Change Threats

Marine Mesophotic Biogenic Habitats (MBHs), lying in twilight conditions, have recently drawn the attention of researchers both for the growing evidence of their ecological role and for the opportunities offered by the enhancement of underwater exploration techniques. These habitats could be considered protected from natural (e.g. thermal stress, hydrodynamics) and anthropogenic (e.g. pollution, harvesting) disturbances affecting shallow habitats, suggesting their possible role as refuges for threatened species. Studies, carried out mostly in tropical areas, stressed the relevance of these habitats, but little is known about their distribution and role in temperate seas, and on their resistance and resilience towards anthropogenic impacts and threats due to Global Climate Change (GCC).
Mediterranean MBHs are mainly built by calcareous red algae, together with other calcareous organisms, and include "coralligenous" reefs and rhodolith beds. The present project aims to investigate Adriatic MBHs, mainly represented by coralligenous outcrops and rhodolith beds scattered on the sedimentary continental shelf. Being formed after the last glacial period, their investigation may disclose the recent history of the Adriatic Sea, and allow some inferences on the potential impacts of GCC on fragile Mediterranean ecosystems. MBHs are scattered on the sea bed and inhabited by metapopulations, potentially exposed to local extinctions due to their fragility and isolation. Resistance and resilience of these habitats to local and global environmental threats will be investigated by analysing patterns of species distribution and diversity. Responses of target species toward increasing temperature and water acidification, as possible effects of GCC, will be tested in lab experiments. Bioconstruction/erosion processes will be studied by lab and field experiments and by radiocarbon dating to quantify growth rates of the reefs. Target species of algae and invertebrates will be analysed using molecular tools to assess genetic connectivity among populations, and to identify areas that might act as sources and sinks of propagules and larvae, supporting migration among populations. Mathematical modelling based on water circulations and habitat mapping will allow to investigate major corridors and barriers to species dispersal, and to develop possible future scenarios of metapopulation dynamics, useful to define effective conservation strategies. Major threats related to GCC and local human impacts will be assessed using Biological Quality Elements and Biotic Indices, as requested by the Marine Strategy and by the Action plan for the conservation of the coralligenous and other calcareous biogenic habitats of the Mediterranean Sea. Data on biogeochemistry, biodiversity, connectivity, ecological processes, resistance and resilience of MBHs will be used to feed habitat suitability models in order to make predictions on their future distribution based on GCC scenarios.