Publication: Trends in Water Quality in a Tropical Kenyan River-estuary System: Responses to Anthropogenic Activities
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2024-05-11
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Funder
National Research Fund
Publisher
Asian Journal of Biology
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Abstract
Aims: To determine the spatial variation in physico-chemical water quality attributes in estuarine
ecosystems of South Coast Kenya to inform its management.
Study Design: We employed diagnostic research design where such factors as anthropogenic
activities, hydrology, and accessibility were considered in choosing 12 sampling stations. A mixed
sampling design (probability and non-probability) was used to sample.
Place and Duration of Study: Four discharging rivers into estuarine system with a reference point
were identified. 12 sampling points were earmarked and sampled for 12 months.
Methodology: Nine selected water quality parameters were collected in triplicates monthly for 12
months. Temperature, dissolved oxygen, pH, conductivity, salinity and TDS were collected in situ
using YSI Multiparameter meter (Professional plus) while nutrients were analyzed in the laboratory
calorimetrically. Data was tested for normality and homogeneity of variances using Levene's and
Shapiro-Wilk tests. Two-way analysis of variance (ANOVA), and Principal Component Analysis
(PCA) were done using the 64-bit R Software version 4.3.0 to test for significant differences and
correlate the parameters among the sampling sites respectively. Observed differences were
considered statistically significant at P < 0.05.
Results: The measured environmental variables differed significantly among the sampling stations
(P < 0.05). temperature and salinity exhibited moderate to strong effect on water quality, while pH
and nutrients (phosphates, nitrates, and ammonia) exhibited mixed effects with both negative and
positive loadings on the Principal Components. It is demonstrated that the south coast estuary,
Kenya is affected by two gradients: mineralization from the sea and the organic matter gradient at
the upstream stations dominated by the fluvial inflows from the respective rivers.
Conclusion: The south coast of Kenya estuary is impacted by natural processes and
anthropogenic activities. we recommend for continued regular water quality assessment and
monitoring to acquire sufficient data to shape policy frameworks towards its sustainable
management.