Monitoring the organic enrichment and the trophic status of the aquatic environment beneath a long-line system of Mediterranean mussel culture

In Greece, aquaculture has experienced significant growth since the mid-1980s, including the cultivation of mussels, largely due to favorable environmental conditions and the fact that mussel farming does not require external feed inputs. Nevertheless, bivalve aquaculture has been identified as a potential source of organic enrichment and eutrophication because of the waste products generated by cultured organisms.
Mussels act as natural filter feeders, removing phytoplankton and suspended particles from the water column. At the same time, they excrete nutrients and produce feces and pseudofeces, which settle on the seabed. Consequently, mussel farming may exert both positive and negative environmental effects. Organic matter accumulated in surface sediments can serve as an important food source for benthic organisms; however, excessive accumulation may lead to oxygen depletion, the formation of toxic by-products under suboxic or anoxic conditions, and a subsequent decline in benthic species abundance and diversity, particularly in areas of intensive cultivation. Eutrophication of coastal waters is one of the major environmental challenges worldwide, often resulting in harmful algal blooms, increased water turbidity that reduces light penetration to benthic vegetation, and hypoxic conditions. Eutrophication occurs when aquatic ecosystems receive excessive nutrient inputs, leading to enhanced primary production and ecological imbalance. Chlorophyll-a (Chl-a), total phosphorus (TP), total nitrogen (TN), and the TN ratio are widely recognized as valuable indicators for assessing and monitoring eutrophication in aquatic systems.
The aim of this study was to evaluate the impact and spatial extent of Mediterranean mussel (Mytilus galloprovincialis) cultivation on water quality and the trophic status of the surrounding aquatic ecosystem. The results demonstrated that mussel farming contributed to organic enrichment and influenced the trophic status of the study area, indicating measurable ecological effects associated with aquaculture activities.