Fishing is one of the major contributors to habitat damage in the Mediterranean Sea. Most of this damage comes from trawling operations. Since fishing is most intense in the Western Medi- terranean, it is not surprising that impacts on marine habitats are particularly severe there (UNEP/MAP 2012). Benthic, or sea- bottom, habitats and the communities associated with them are especially vulnerable.
In sea-bottom habitats of the open seas, deep-water coral ecosys- tems, the feather star (Leptometra phalangium), the sea pen (Funi- culina quadrangularis), and bamboo coral (Isidella elongata) beds are considered most vulnerable to impacts from fishing (UNEP/ MAP 2012). The location and extent of these habitats, however, are not well known. Even less is known about vulnerable deep-sea fauna that inhabit abyssal plains throughout the Mediterranean.
Impact of disturbance in key benthic habitats
Physical damage to the sea floor can result from a number of hu- man activities, including offshore construction, dredging, and fisheries. The impacts of offshore construction in the Mediterra- nean, generally drilling rigs, wind farms, and other energy facili- ties, have not been systematically evaluated (UNEP/MAP 2012). The construction and operation of these installations could have direct and indirect impacts on the benthic community and ecol- ogy. The behaviour and ecology of pelagic organisms could also
be affected (for example, through avoiding areas with these in- stallations) (UNEP/MAP 2012).
Trawlers, dredges, and other kinds of bottom gear used in fishing can damage the seafloor in a variety of ways. These include: • Re-suspension, or stirring up of sediment, which impacts aquatic plants, bottom-dwelling animals and bottom-feeding fish, as well as stirring up contaminants;
• Removal of large benthic species, such as bivalves and crus- taceans, some of which are important to the movement and mixing of marine sediments; and,
• Changes in the structure of benthic communities.
The physical disturbance caused by trawls can have long-lasting effects on fragile marine ecosystems. Corals and sponge com- munities are particularly sensitive to disturbance. Deep-water coral ecosystems, found across the western Mediterranean, have been severely impacted by trawling (UNEP/MAP 2012). Trawling is responsible for the loss of coralline red algae com- munities across large areas of the Mediterranean (IAR 2011). Cold-water coral reefs can be destroyed by a single trawl (Gianni 2004 in EEA 2006).
Sea grass meadows provide important spawning and nursery areas for many fish species. Sea grass meadows, however, are declining, partly as a result of trawling and partly due to the mooring of boats (UNEP/MAP/MED POL 2005). Sea grass beds that are fished regularly show lower density and biomass (UNEP/ MAP/MED POL 2005).
HUMAN PRESSURE, STATE AND IMPACTS ON MEDITERRANEAN ECOSYSTEMS