The diatom flora of a eutrophic bay, the Eastern Harbour of Alexandria

Abstract

         The plantonic and benthic diatoms - epiphytes, litho­phytes and psammophytes - were investigated in relation to the pollution gradient. A distinct zonation is observed bet­ween the inner, turbid and heavily polluted bay and the outer »recovery« zone. The inner bay is characterised by a drastically improverished population, by the presence of some brackish forms, the exclusive occurence of the psammophytic species and the dominance of some planktonic dia­toms. On the average, the cells were smaller in volume in the »recovery« zone than in the inner bay. The quantitative cyle, compared to eariler observations, reflects the steady change resulting from the cessation of the Nile input accom­panied by intensified pollution.