Mussel farming by the long-line system, in the shallow waters of the NW Thessaloniki Gulf, Greece, is a vital economic activity for the local communities. The management practices play an important role both in the environmental quality and the support of the healthy growth of mussels. Αn experimental line of mussels in suspension placed at different sock distances as a management practice was systematically monitored for nutrients, chlorophyll α and dissolved oxygen. The study at four different mussel densities (distances of the socks) lasted from July 2014 to April 2015, covering the growth, reproduction and harvest cycle of mussels. Additional sampling took place in two selected sock distances, 30 and 70 cm, in the second sampling period, May-August 2015. The variability of nutrients along with chlorophyll α and dissolved oxygen, seasonally, spatially and vertically, was examined with the application of multivariate statistical analysis. The results showed low variation of nitrates among the sites but statistically significant differences of dissolved oxygen, ammonium, phosphate and chlorophyll α. The application of environmental indicators (TRIX, EI) in the data set was a useful tool in the identification of different variation schemes of the measured parameters in the cultures of various mussel densities.
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