engleski

Inshore capture-based tuna aquaculture impact on Posidonia meadows in Croatian part of the Adriatic Sea

Mapping and monitoring of Posidonia meadows in the Croatian part of the Adriatic Sea showed significant decline in meadows density in the area influenced by inshore capture-based tuna aquaculture. The methods of mapping Posidonia meadows are SCUBA diving with in situ recording and marine bottom survey by side scan sonar with the highly sophisticated QTC VIEW 5 program for seabed classification. The results of benthic biocoenoses survey in the area of Fulija Island, which are under the influence of tuna farms, will be presented. In this area nutrient enrichment and the risk of eutrophication is an impurtant issue. Aquaculture wastes are a source of nutrient pollution and stimulate blooms of phytoplankton or algae and lead to enrichment of organic matter in sediment. It appears that the Posidonia oceanica beds undergo significant alterations. Besides mapping, the condition and density of Posidonia meadows, both under the influence of tuna farms (Fulija island) and in a undisturbed control site (Mrtovnjak Island), has been analysed. Epiphytic fauna (i.e. Foraminifera, Bryozoa, Polychaeta) of Posidonia leaves have been analysed from both localities as well. Beside biological and standard basic chemical parameters, we investigated the the distribution of dissolved organic carbon (DOC) and surface active substances (SAS). Drastic negative changes which have been noted among seagrass communities indicate that tuna cages have been inadequatly placed. We point out that intensive aquaculture, within the nearshore fishing area of the Republic of Croatia, disastrously influences the marine ecosystems. We suggest that due to the vulnerability and strong competition for coastal resources, the future development should be focused on offshore cage technology like in many other parts of the Mediterranean.

tuna acquaculture; Posidonia meadows; Adriatic Sea

nije evidentirano