Assessment of the Relationship Between Physico-Chemical Parameters and Phytoplankton Biomass Based on Principal Component Analysis (PCA) and Pearson Correlation Coefficient: A Case of Lake Naivasha, Kenya

Abstract

Physico-chemical parameters play a significant role in determining the limnological and ecological functioning of aquatic spaces. These parameters have the ability to sustain aquatic functions and values as well as support organisms. The study was conducted to determine the relationship between physico-chemical parameters and phytoplankton biomass. Water samples for nutrient and algae biomass were collected in triplicates monthly at seven sampling points in Lake Naivasha and laboratory analyses were conducted following the standard methods described by the American Public Health Association (APHA). Data was organized and analyzed with Single Factor Analysis of Variances (ANOVA). Correlation and PCA was done using Microsoft Excel 2010 and Minitab software and the significant differences considered at p-value ≤ 0.05. Tukey pairwise multiple comparisons were used for post hoc analysis. The results showed the mean temperature of 22.73 ± 1.6 °C, DO 8.51 ± 0.87 mg/L, conductivity 233.85 ± 26.94 μS/cm, pH 8.13 ± 0.3. TN were 471 ± 170.61 µg/L, PO₄ 5.88 ± 2.12 µg/L, TP 97.97 ± 49.06 µg/L, NO₃-N 6.70 ± 3.55 µg/L, NH₄-N 18.93 ± 10.91 µg/L and SiO₂ 3.18 ± 2.99 mg/l. A total of one hundred and twenty-four (124) species belonging to six (6) taxonomic groups were identified. The family Chlorophyceae contributed to 43.84 % of the total phytoplankton biovolume. This was followed by the family Bacillariophyceae with 37.50 % and Cyanophyceae with 8.06 % of the total phytoplankton biovolume. The families Dinophyceae, Euglenophyceae, and Zygnematophyceae recorded lower phytoplankton biovolume of 5.79 %, 2.90 % and 1.91 %, respectively. Pearson correlation showed a positive showed a positive relationship between phytoplankton biomass and key physico-chemical parameter. The results indicate that Lake Naivasha is polluted with pollutants from domestic wastewater, agricultural and/ or surface run off. Sewage discharge point and R. Malewa mouth were identified as the main point sources of pollution. Therefore, there is need for measures to be put in place to reduce water pollution from these points in order to improve the water quality of the lake.