Species composition, abundance and distribution of phytoplankton in the coastal waters off Zanzibar Island, TanzaniaĪlvarez-Góngora C, Herrera-Silveira JA. Higher abundance and diversity during SEM might be attributed by low sea surface temperature, higher salinity, sulphate and nitrate levels. Also species diversity was higher during the SEM than the NEM (t =3.155, p = 0.0058). Southeast monsoon (SEM) season phytoplankton (15244 counts/l) were higher than the Northeast monsoon (NEM) season (13982 counts/ml).

The highest phytoplankton density was 9189 cells/l, while the lowest density was 2227 cells/l recorded at Bawe and Chwaka Bay, respectively. Some dinoflagellates in low densities were observed at both sites. Diatoms were abundant due to their resilient ability to withstand the varied environmental factors. Abundant concentrations of diatoms composed mostly of several species which were observed throughout the sampling time which included Chaetoceros sp, Rhizosolenia sp, Thalassiothrix sp, Nitzschia sp, Guinardia sp, Bacteriastrum sp, Pleurosigma sp and Coscinodiscus sp. Cyanophyceae accounted for 5% of the total phytoplankton and less than 1% of the total standing crop was attributed to chlorophyceae, dictyochophyceae and crysophyceae. Dinoflagellates ranked second in terms of abundance (24%). The phytoplankton assemblage was dominated by Bacillariophyceae (diatoms) which accounted for 70% of the total phytoplankton. A total of 260 species belonging to 94 genera and 6 classes were recorded at both sites. The objective of this study was to quantify the health ecosystem of Zanzibar coastal waters as phytoplankton are good indicator in studying an ecosystem. Species composition, abundance and distribution of phytoplankton were studied in Zanzibar coastal waters for one year (May 2012 – May 2013) at two sites, Bawe and Chwaka Bay. VIEWS 9 | Download 3 Species composition, abundance and distribution of phytoplankton in the coastal waters off Zanzibar Island, Tanzania Edward Moto, Margareth Kywelyanga, Thomas Lyimo, Mariam Hamisi

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