• Variability of Chlorophyll-a in Relation to Physico-Chemical Variables in Zanzibar Coastal Waters

    Edward Moto1, Margareth Kyewalyanga2

    1. Department of Biological Sciences, University of Dodoma, P.O Box 338, Dodoma,Tanzania.
    2. Institute of Marine Sciences, P.O Box 668, Zanzibar, Tanzania.

    Abstract: 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.

    Keywords: Chlorophyll-a, Zanzibar coastal waters, physico-chemical variables

    Pages: 475 – 492 | Full PDF Paper