Browsing by Author "Moto, E."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Species composition, abundance and distribution of phytoplankton in the coastal waters off Zanzibar Island, Tanzania
    (INTERNATIONAL NETWORK FOR NATURAL SCIENCES, 2018-05-13) Moto, E.; Kyewalyanga, M.; Lyimo, T.; Hamisi, M.
    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. The objective of this study was to quantify the health ecosystem of Zanzibar coastal waters as phytoplankton are good indicator in studying an ecosystem. A total of 260 species belonging to 94 genera and 6 classes were recorded at both sites. The phytoplankton assemblage was dominated by Bacillariophyceae (diatoms) which accounted for 70% of the total phytoplankton. Dinoflagellates ranked second in terms of abundance (24%). Cyanophyceae accounted for 5% of the total phytoplankton and less than 1% of the total standing crop was attributed to chlorophyceae, dictyochophyceae and crysophyceae. 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. Diatoms were abundant due to their resilient ability to withstand the varied environmental factors. Some dinoflagellates in low densities were observed at both sites. The highest phytoplankton density was 9189 cells/l, while the lowest density was 2227 cells/l recorded at Bawe and Chwaka Bay, respectively. Southeast monsoon (SEM) season phytoplankton (15244 counts/l) were higher than the Northeast monsoon (NEM) season (13982 counts/ml). Also species diversity was higher during the SEM than the NEM (t =3.155, p = 0.0058). Higher abundance and diversity during SEM might be attributed by low sea surface temperature, higher salinity, sulphate and nitrate levels.
  • Thumbnail Image
    Item
    Variability of Chlorophyll-a in Relation to Physico-Chemical Variables in Zanzibar Coastal Waters
    (SCIENCE SIGNPOST PUBLISHING INC. (SSPub), 2017-12-25) Moto, E.; Kyewalyanga, M.
    The relationships between chlorophyll-a (Chl-a), nutrients and other physico-chemical variables are important for marine water management strategies. In this study, monthly Chlorophyll-a (Chl-a) concentration, temperature, salinity, pH, dissolved oxygen and nutrients were measured at two sites (Bawe and Chwaka Bay) in Zanzibar coastal waters from May 2012 to May 2013. The mean Chl-a concentration ranged from 0.69 mg/m3 to 1.86 mg/m3, with insignificant variation between the sites, and significant differences among the stations being higher in near shore stations than in open seawater stations (t= 5.296, P < 0.0001). The results revealed significant higher Chl-a concentration during the southeast monsoon (SEM) than the northeast monsoon (NEM) (t = 2.871, P < 0.0152). In addition, the results showed that, the concentration was significantly correlated positively with salinity (r = 0.640; p = 0.019) and negatively with NO3 (r = -0.563; p = 0.044). The results of this study suggest that high Chl-a concentration to the near shore station is due to sewage system which influence nutrients concentrations, hence result into high Chl-a concentration. Furthermore, the SEM experienced high Chl-a concentration due to strong winds which bring nutrients to the sea surface which favour growth of phytoplankton hence result into high concentration.