Dynamics of arsenic speciation in surface waters: As(III) production by algae

Algae reduce and methylate arsenate [As(V)]. The end product of the overall transformation reaction can be arsenite [As(III)] or methylated arsenic. Field and laboratory data suggest a strong correlation between the end product of the reaction and the growth rate of the algae, with As(III) only produced during log (exponential, fast) growth. The result is a peak in As(III) concentration preceding or coincident with the algal bloom. This paper analyzes data from 18 different water bodies (five lakes, one river, six estuary/marine sites, six experimental sites). Algal blooms, As(III) peaks and algal blooms with preceding or coincident As(III) peaks were identified. In total, 80 algal blooms were identified, 49 (61%) of which were associated with As(III) peaks. In 78% of water bodies algal blooms were typically (>50%) associated with As(III) peaks. The average time lag between As(III) peaks and algal blooms was 20 days (standard deviation 18 days). Copyright © 2005 John Wiley & Sons, Ltd.