Publisher: Bachudo Science Co. Ltd

Phytoplankton Productivity In The Okrika Port Harcourt Sector of Bonny Estuary Nigeria

G. C. Onuoha
KEYWORDS: Phytoplankton, Okirika Port-Harcourt sector. Bonny estuary, Niger Delta, Nigeria


This study concerns the phytoplankton flora and primary productivity of the Bonny river estuary. The objectives of the study were to provide baseline information on the impact of the refinery effluent on the Bonny estuary - the recipient environment, to Investigate the phytoplankton composition and abundance, and compare the water quality of the affected and unaffected stations. The studies on water quality and phytoplankton productivity were carried out from 1991 to 2001 at ten regular sampling stations of the Okrika ar,n (downstream), and the University of Science and Technology (U.S.T upstream), of the Bonny estuary of the delta area of Port Harcourt, Nigeria. Sampling program and techniques were such that spatio-temporal variations in the physico-chemlcal factors might be revealed. Primary productivity was highest upstream at the unaffected UST stations. Total productivity values temporal and spatial (column or depth variations) for the period under study were highest at UST stations. Productivity values ranged from 25.63mg C/m3/hr _, to 193.13mg C/m3/hr"1 in comparison to a range of 18.00mg C/m3/hr"1 to 62.00mg C/m3/hr"1 at the affected jetty stations. Biomass (Chlorophyll §) for the unaffected area was also highest, and ranged from 0.73 to 16.29mglm3: while that for the affected area ranged from 0.73 to 11.77mglm3• Gross production for all the stations or sample points around the jetty area was 317.98mglm3 chlorophyll fl, while gross production from the UST unaffected station was 849.07mglm3 . The result was highly significant (P<0.01). Analysis of variance carried out for the four factors (River water, position, months and chlorophyll .I) showed that there was significant difference for each of the single factors as well as some two- factor interactions and some three-factor levels. A systematic account of the phytoplankton flora consisted mainly of diatoms and which were sparse. Refinery effluent is toxic to natural phytoplankton population. Toxicity was however not reflected In the receiving water, as the levels of the various factors got diluted beyond detection limit. But with the volume of effluent discharge, and possible bioaccumulation process, the environment will pose a threat to the existence of aquatic life, especially as these water bodies areknown to be nursery grounds for fishes and shrimps.

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