Bioaccumulation of trace elements in Arthrospira fusiformis algal blooms in Lakes Bogoria and Sonachi, Kenya: Evaluation and verification of toxicokinetic models

The bioaccumulation of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) was examined in Arthrospira fusiformis algal blooms. The present study was designed to provide information on accumulation strategies of the test organism and to verify two‐compartment toxicokinetic models as predictive tools. Heavy metal accumulation in the organisms did occur, and it was possible to estimate significant model parameters of two‐compartment models. The nominal exposure was a metal mixture of 0.005, 0.03, 0.02 and 0.06 μg/g of Cd, Cu, Pb and Zn, respectively, being doubled and tripled in subsequent experiments. The experiment design was a semi‐static system comprising five hours for uptake and a similar duration for clearance. The design comprised two replicates and a control. Cd and Cu produced better models (R² > 0.5), compared to Pb and Zn. Concurrent uptake rate constants (k₁) were higher than the elimination rate constants (k₂), leading to net accumulation. The t‐values for parameter estimates were ≥2, indicating the estimates were statistically different from zero. Kinetic bioconcentration factors (BCFs) at theoretical equilibrium increased with increased exposure doses, especially for Cu. Time‐dependent model parameters were verified with independent experimental data to assess reproducibility. Cd and Cu models were verifiable, especially when the experiments were for the same environmental medium/lake. Time‐dependent model parameters were verified with data from concentration‐dependent exposures, indicating the models were verifiable, exhibiting better agreement when the model parameters and test data were from the same lake. Specific trace elements accumulation strategies for the test organism, Arthrospira fusiformis, the main food organism for flamingos in the studied lakes, can be useful in interpreting trophic transfers, noting flamingos in those lakes must be conserved because they are a tourist attraction, thereby being of significant economic benefit to the citizens and government of Kenya.