Spatial and Temporal Distribution of Dissolved Inorganic Nutrients and Phytoplankton in Mida Creek,Kenya |
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Authors: | Email author" target="_blank">B?M?MwashoteEmail author B?O?Ohowa P?O?Wawiye |
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Institution: | (1) Kenya Marine and Fisheries Research Institute, P.O. Box 81651, Mombasa, Kenya |
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Abstract: | The spatial and temporal distributions of dissolved inorganic nutrients were investigated between May 1996 and April 1997
in Mida Creek, a mangrove area along the north coast region of Kenya. The nutrient levels of pore water from boreholes/wells
within the surrounding area of the creek were also investigated for comparison. In addition, phytoplankton distribution in
Mida Creek was assessed in three stations within the creek in order to determine the structure and succession stages of the
phytoplankton community and to provide an indication of the status of primary productivity of the creek.
Measurements carried out within the creek revealed that the mean concentration ranges for NH4+ –N, (NO
2− + NO3−)−N, PO43− −P and SiO32− −Si were: 0.002–5.45; 0.12–5.63; 0.10–0.58 and 1.31–81.36 μM, respectively. For the case of boreholes/wells found in the
surrounding area, their respective nutrient levels were found to lie in the ranges 0.4–907.0; 16.7–4897.0; 1.09–22.39 and
83.9–596.0 μM. A total of 295 species of phytoplankton belonging to 78 genera were identified with great temporal variability
in abundance in all the stations sampled. The most dominant algal members in the Creek included Chaetoceros spp., Chroococcus
limneticus and Oscillatoria spp. The diversity values recorded were indicative of mesotrophic conditions. The highest nutrient
concentration levels within the creek were measured during the wet season as compared to dry season and this trend closely
corresponded with that of the phytoplankton productivity. However, no significant variation ( p > 0.05) was found in all cases
with respect to the tidal cycles. On the contrary, diurnal nutrient concentrations especially in areas with high flooding
duration (>12 h) were found to be highest during the dry season as opposed to wet season for all nutrients except for SiO32−. The relatively high nutrient laden groundwater outflow into the creek water, coupled with surface runoff events during wet
season, are the two main factors responsible for the elevated nutrients in the creek waters in the absence of river inflow
into the creek. |
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Keywords: | Distribution Kenya Mida creek Nutrients Phytoplankton Spatial Temporal |
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