School of Agriculture and Natural Resources Management

Distribution of organochlorine pesticides in macroinvertebrate functional feeding guild (FFG) of predators, Rhagovelia spp. in a tropical estuarine ecosystem

Wed, 01 Jan 2025 00:00:00 GMT

Distribution of organochlorine pesticides in macroinvertebrate functional feeding guild (FFG) of predators, Rhagovelia spp. in a tropical estuarine ecosystem Nyakeya, Kobingi; Onchieku, James; Masese, Frank Onderi; Gichana, Zipporah Moraa; Nyamora, Jane Moraa; Getabu, Albert; Gitonga, Lydiah The current world population stands at approximately 8.5 billion people and this number is likely to shoot up in the coming decades. This increased trend in world population demands for sufficient food, which calls for, improved agricultural production systems. In order to achieve this, a tremendous in- crease in pesticide application of about 30-40% has been documented and this trend is predicted to increase in the coming years. Due to their negative impacts to the environment, some pesticides main- ly those of organochlorines (OCPs) have since been banned, but their residues can still be detected in different media causing deleterious effects on organisms. The aim of this study, therefore, was to assess the distribution of organochlorine pesticides (OCPs) by aquatic macroinvertebrates FFG of Rhagovelia spp. in the tropical estuarine ecosystems of South Coast, Kenya. Twelve sampling stations were purpo- sively identified taking into considerations different hydrological and ecological factors. Rhagovelia spp. were sampled using established methods and analysis for OCPs detection were performed using a TSQ Vantage Triple-Stage Quadrupole Mass Spectrophotometer (Thermo Electron) equipped with a heat- ed electrospray ionization probe (HESI-II). Separation, detection, identification and quantification of tar- get analyses followed the same established methods. Sixteen OCPs were recorded in Rhagovelia spp. samples collected from all the 12 sampling stations. γ-HCH was the lowest (2.74 0.18 ng g-1 dw) recorded concentration value for OCPs from Rhagovelia species samples whereas OCPs Cis_chlordan, mirex, p,p’_DDT, p,p’_DDE, o,p’_DDE and HCH recorded 10.09 0.35 ng g-1 dw, being the highest registered value. Analysis of variance (ANOVA) on the mean concentration residues of OCPs in Rhagovelia spp. samples yielded a significant variation among the sampled stations (F = 77.79, df = 11, p < 2.2e-16). The statistical analysis revealed that each station played a crucial role in determining the levels of OCPs in Rhagove- lia spp. due to environmental factors, early life history strategies of the tested bioassay organism, and different sources of OCPs as influenced by anthropogenic activities. The study recommends for the application of macroinvertebrate FFG of Rhagovelia spp. in biomonitoring of estuarian eco- systems. The study also recommends the use of different FFGs of macroinvertebrates such as grazers, collector-gatherers, filterers and shredders in order to bring out the general behavior of these pesticides along the food web.

Analyzing Spatial-temporal Variation in Water Quality Parameters in South Coast Estuarine Ecosystem, Kenya

Wed, 18 Sep 2024 00:00:00 GMT

Analyzing Spatial-temporal Variation in Water Quality Parameters in South Coast Estuarine Ecosystem, Kenya Nyakeya, Kobingi; Onchieku, James; Masese, Frank; Gichana, Zipporah; Getabu, Albert; Nyamora, Jane Estuarine ecosystems are classified as among the most productive systems on the planet earth supporting an array of biodiversity. However, due to the ever increasing human population, they experience environmental degradation originating from intensive anthropogenic activities hence the need for regular assessment and monitoring to inform its management. The purpose of this study, Original Research Article Nyakeya et al.; Int. J. Environ. Clim. Change, vol. 14, no. 10, pp. 46-57, 2024; Article no.IJECC.121848 47 therefore, was to analyze the spatio-temporal variation in water quality parameters in South Coast estuarine ecosystem, Kenya. Twelve sampling stations were identified based on different hydrological regimes, anthropogenic activities, and accessibility factors. Sampling was done for 12 months taking into account different seasons of the year. Such parameters as temperature, dissolved oxygen, pH, conductivity, salinity and TDS were collected in situ using YSI Multiparameter meter (Professional plus) whereas nutrients (nitrates, phosphates and ammonia) were analyzed in the laboratory using established methods. Two-way analysis of variance (ANOVA) was applied to discriminate any significant differences among stations and between seasons, and where there was a difference, Tukey post hoc test was applied to show which site differed from each other. Principal Component Analysis (PCA) was performed to correlate the environmental factors with sampling sites, and months. There was significant difference in water quality parameters among the sampling stations (P = .05) that was attributed mainly to anthropogenic activities, and both the point and non- point sources of pollution. Conversely, there was no significant difference in most of the water quality attributes in terms of seasons due to unpredictable weather patterns associated with climate change. There is need for long term monitoring strategies in order to generate sufficient data for sound management of South Coast estuary in Kenya. The study further recommends for community sensitization and implementation of relevant policies on the protection and management of riparian land.

Trends in Water Quality in a Tropical Kenyan River-estuary System: Responses to Anthropogenic Activities

Sun, 05 May 2024 00:00:00 GMT

Trends in Water Quality in a Tropical Kenyan River-estuary System: Responses to Anthropogenic Activities Nyakeya, Kobingi; Onchieku, James; Masese, Frank; Gichana, Zipporah; Nyamora, Jane 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. Original Research Article Nyakeya et al.; Asian J. Biol., vol. 20, no. 6, pp. 34-51, 2024; Article no.AJOB.116841 35 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.

Seasonal variations of water quality parameters and their effect on the phytoplankton along a salinity in the Lake Naivasha-Oloiden

Mon, 27 Nov 2023 00:00:00 GMT

Seasonal variations of water quality parameters and their effect on the phytoplankton along a salinity in the Lake Naivasha-Oloiden Guto, Kerubo Carolyne; Njiru, Murithi James; Getabu, Albert; Gichana, Moraa Zipporah Lake Naivasha and Lake Oloiden merged leading to the formation of an estuary. This occurrence may affect the water quality and phytoplankton. A study was conducted with the objective: to investigate seasonal changes in the water quality parameters and their effect on phytoplankton. Depth and secchi depth were measured while some water quality parameters were measured in situ using YSI Multiparameter meter and water samples were collected for laboratory analysis of chlorophyll-a, phosphates, nitrates and total suspended solids. Phytoplankton sample was collected; identification and counting were done under a compound microscope. The nutrients, depth, secchi depth, temperature, dissolved oxygen, salinity, conductivity, total dissolved solids and pH varied monthly. All the water quality parameters positively correlated with Chlorophyceae in Lakes Naivasha and Oloiden except dissolved oxygen, chlorophyll-a, depth and secchi depth that negatively correlated. There were seasonal changes in all the water quality parameters in Lakes Naivasha and Oloiden except the total suspended solids whose effects were in Midlake There were seasonal changes in all the water quality parameters in Lakes Naivasha and Oloiden except the total suspended solids whose effects were only in Midlake and Oloiden ST2. Euglenophyceae, Bacillariophyceae were not affected by water quality except the depth while the other families had varied effects from water quality in Lake Naivasha. All Lake Oloiden's phytoplankton families had varied effects from the water quality. Thus, the prevailing water quality affect phytoplankton.