English abstract
Ten months (February - October 2012) sampling was carried out bi-weekly to investigate the nutrients load and composition in coastal water of Sohar Industrial Area, Sea of Oman and their relationship to phytoplankton abundance and species particularly harmful algal blooms in Majis Industrial Services Company (MISC) facility. Surface temperature, salinity, nutrients, dissolved oxygen, chlorophyll a (Chl a), and phytoplankton abundance of surface sea water were measured at four selected stations (IN, Mouth, Out & DiCH). The sea surface temperature followed typical seasonal summer high with significant drop within the period of June and August ranging (29 – 32 °C). A fluctuation of up to 4 °C was recorded during August. Salinity showed no particular fluctuation pattern with fairly constant concentration of around 36 PSU The concentration of nutrient (except ammonia) and chlorophyll a (below lug/L) were found to be within range of previously reported in the coastal water of Sea of Oman. Low chlorophyll a concentrations were recorded despite the high N concentrations (as ammonia NH4). The calculated N:P ratio (N:P> 50) found to be much higher than that of the Redfield Ratio (16:1). Phytoplankton taxonomy and cell densities revealed fluctuations with the dominance of diatoms in winter, while dinoflagellates dominated during summer. The maximum cell count was observed during April with value of 66,500 cells*L•' whereas, the minimum cell count was observed during June with value of 2,000 cells*L* dominated both with diatoms 96% and 77% respectively. The dominant species during the maximum cell count in April was Ceratium sp. comprising Ceratium furca 24%. Consistence presence of Ceratium furca was observed in subsequent months post Noctiluca scintillans bloom occurred at Intake Jetty of MISC. The prevalence of Ceratium furca cells at the harbour in comparison with natural semi enclosed system indicates that even "exposed" harbours, subject to frequent tidal renovation and wave action, may represent potential points of harmful species accumulation, source and/ or sink of HABs, as commonly observed in more confined areas. The disturbance of DIN:DIP ratio, is a good indication that elevated nutrient can influence the phytoplankton abundance and composition. Despite the fact of the limitations of this study and bearing in mind the multiple environmental factors which are responsible for phytoplankton blooms outbreak, it can be said that the coastal water of the industrial areas of Sohar could be classified as a fragile ecosystem requiring continuous monitoring especially in term of nutrient loads. Given the fact that there is limitation in sampling program in the coastal water of Sohar, Sea of Oman, our findings represent baseline for forthcoming research investigating the coastal ecosystem dynamics under multiple environmental stress.
