Assessment of Change in Biotic and Abiotic Factors after Addition of Aligicide (The Thiazolidinedione Derivative Td49): A Manipulated Mesocosm Study

Abstract

We assessed the potential risk for natural application and changes in abiotic and biotic factors the including aquatic micro organism after a novel algicide dosing (thiazolidinedione derivative TD49) that conducted in 1300 L mesocosms inoculated with the harmful algal bloom (HAB) dinoflagellate Heterocapsa circularisquama. A comprehensive set of measurements was made in the mesocosms over a 10 d period, including temporal changes in inorganic nutrients and the phytoplankton community. The NO3- + NO2- and PO42- concentrations rapidly decreased after one day, and remained at limiting levels until day 4 or 5. The daily consumption of NO3- + NO2- in the control and blank (non-TD49 treatments) was higher than in the TD49 treatments until day 2 (t-test, p < 0.05), whereas nutrient consumption in the non-TD49 treatments on day 4 were lower than in the TD49 treatments (t-test, p < 0.05) because of rapid nutrient limitation. Trends in the consumption of PO42- were similar to that for NO3- + NO2-, and coincided with a rapid increase in the phytoplankton biomass. The initial dominance of planktonic diatoms and H. circularisquama clearly shifted to cryptophyte species, and then to periphytic diatoms with increasing culture time, implying that the fate of nutrients may play a key role in the phytoplankton community succession, although this depended on the concentration of TD49. In particular, at ≤ 0.4 μM TD49 there was a correlated with the harmful algal bloom (HAB) dinoflagellate Heterocapsa circularisquama. A comprehensive set of measurements was made in the mesocosms over a 10 d period, including temporal changes in inorganic nutrients and the phytoplankton community. The NO3- + NO2- and PO42- concentrations rapidly decreased after one day, and remained at limiting levels until day 4 or 5. The daily consumption of NO3- + NO2- in the control and blank (non-TD49 treatments) was higher than in the TD49 treatments until day 2 (t-test, p < 0.05), whereas nutrient consumption in the non-TD49 treatments on day 4 were lower than in the TD49 treatments (t-test, p < 0.05) because of rapid nutrient limitation. Trends in the consumption of PO42- were similar to that for NO3- + NO2-, and coincided with a rapid increase in the phytoplankton biomass. The initial dominance of planktonic diatoms and H. circularisquama clearly shifted to cryptophyte species, and then to periphytic diatoms with increasing culture time, implying that the fate of nutrients may play a key role in the phytoplankton community succession, although this depended on the concentration of TD49. In particular, at ≤ 0.4 μM TD49 there was a corre