Application of eutrophication indices for assessment of the ecological quality of the Moroccan eastern Mediterranean coast: Ras Kabdana-Saidia

Abstract

Eutrophication of littoral seawater is estimated to be one of the main threats to marine biota. Therefore, continuous monitoring is necessary to define areas of potential risk. Our work is an essay to explore the possibility of applying the trophic state index (TRIX) to assess the state of eutrophication along the eastern coast of the Moroccan Mediterranean (Ras Kabdana-Saidia) in concert with a number of hydro chemical parameters and nutrients descriptors aimed at selection of relevant indicators of marine coastal area ecological quality. Seawater samples were studied monthly during 2018. The following environmental parameters have been considered: temperature, salinity, pH, suspended matter, turbidity, dissolved oxygen, saturation levels, nitrite, nitrate, and orthophosphate. Principal Component Analysis was applied in order to figure out and score the most relevant combination of parameters to discriminate between sites and select representative descriptors (pressure/state) of eutrophication. The following variables are defined as relevant descriptors for classification of the sites: nutrients (N, P) and their molar ratios (N/P), the capacity of the system to produce and sustain organic matter (chlorophyll a), and the trophic state index (TRIX). The results show TRIX values below 4, the eutrophication range indicated that there is no ecological risk. The Ras Kabdana-Saidia is located in an oligotrophic state.