engleski

Monitoring tuna farms in the Adriatic: Reading the impact from the benthic community succession

Operational tuna mariculture facilities increase sedimentation of particulate organic matter to the bottom. Higher quantities of settled organics induce benthic communities to adjust their structure, both in biodiversity and abundance. The extent of change corresponds to the impact level of mariculture facilities. To find that correspondence we utilized all-season, ten year monitoring of 3 tuna fish farms in the Adriatic Sea. Monitoring on each site included SCUBA and photo survey of the benthos along transects below and around net pens. In response to increased sedimentation, we noticed that benthic communities succeed each other in a distinct pattern. Results from over 150 dives suggest that there are at least four zones of benthic community succession. Each zone has a dominant species or trophic level and we named them accordingly from the center of vertical projection of the cage: a) Begiattoa zone b) Scavangers zone c) Nitrophylic zone. There is another zone which forms in time d) Mussel shells zone. Formation of these zones also corresponds to the impact level of operational mariculture facility on the seabed: low, moderate, significant and excessive. By determining community structure along transects and comparing to the described stages, one can obtain valuable insight of mariculture impact on the benthos. We argue that, benthic succession zones can also be a useful ecological indicator in monitoring mariculture sites.

Tuna farms; environmental impact; benthic succession as indicator

nije evidentirano