Nitrogen fixation in polluted sea water of Alexandria coast, Egypt.
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The inshore area of the Mediterranean water, west of Alexandria, Egypt, is subjected to different types of pollutants. Nitrogen fixation rate was studied in this area in relation to some environmental factors such as pH, oxygen, organic matter, total and inorganic phosphorus and ammonia. In addition, numbers of Cyanobacteria, as nitrogen fixers, were also determined. In order to identify possible relationships between environmental conditions and N-fixation, correlation coefficients were determined for each environmental factor and rates of N-incorporation. Temporal and spatial variations were observed in the rate of nitrogen fixation, related to a number of factors. Positive correlations were found between the rate of N-fixation and organic matter, total and inorganic phosphorus and the densities of Cyanobacteria in the region. On the other hand, N-fixation was negatively correlated with both ammonia and oxygen concentration.