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

摘要

The bioaccumulation of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) was examinedin Arthrospira fusiformis algal blooms. The present study was designed to provideinformation on accumulation strategies of the test organism and to verifytwo-compartmenttoxicokinetic models as predictive tools. Heavy metal accumulationin the organisms did occur, and it was possible to estimate significant modelparameters of two-compartmentmodels. The nominal exposure was a metal mixtureof 0.005, 0.03, 0.02 and 0.06 μg/g of Cd, Cu, Pb and Zn, respectively, beingdoubled and tripled in subsequent experiments. The experiment design was a semi-staticsystem comprising five hours for uptake and a similar duration for clearance.The design comprised two replicates and a control. Cd and Cu produced bettermodels (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-valuesfor parameter estimates were ≥2, indicating the estimates were statisticallydifferent from zero. Kinetic bioconcentration factors (BCFs) at theoreticalequilibrium increased with increased exposure doses, especially for Cu. Time-dependentmodel parameters were verified with independent experimental data toassess reproducibility. Cd and Cu models were verifiable, especially when the experimentswere for the same environmental medium/lake. Time-dependentmodelparameters were verified with data from concentration-dependentexposures, indicatingthe models were verifiable, exhibiting better agreement when the model parametersand test data were from the same lake. Specific trace elements accumulationstrategies for the test organism, Arthrospira fusiformis, the main food organism forflamingos in the studied lakes, can be useful in interpreting trophic transfers, notingflamingos in those lakes must be conserved because they are a tourist attraction,thereby being of significant economic benefit to the citizens and government ofKenya.