Impact of triphenyltin acetate in microcosms simulating floodplain lakes. II. Comparison of species sensitivity distributions between laboratory and semi-field

Abstract

The study objectives were to shed light on the types of freshwater organism that are sensitive to triphenyltin acetate (TPT) and to compare the laboratory and microcosm sensitivities of the invertebrate community. The responses of a wide array of freshwater taxa (including invertebrates, phytoplankton and macrophytes) from acute laboratory Single Species Tests (SST) were compared with the concentration-response relationships of aquatic populations in two types of freshwater microcosms. Representatives of several taxonomic groups of invertebrates, and several phytoplankton and vascular plant species proved to be sensitive to TPT, illustrating its diverse modes of toxic action. Statistically calculated ecological risk thresholds (HC 5 values) based on 96 h laboratory EC 50 values for invertebrates were 1.3 lg/l, while these values on the basis of microcosm-Species Sensitivity Distributions (SSD) for invertebrates in sampling weeks 2-8 after TPT treatment ranged from 0.2 to 0.6 lg/l based on nominal peak concentrations. Responses observed in the microcosms did not differ between system types and sampling dates, indicating that ecological threshold levels are not affected by different community structures including taxa sensitive to TPT. The laboratory-derived invertebrate SSD curve was less sensitive than the curves from the microcosms. Possible explanations for the more sensitive field response are delayed effects and/or additional chronic exposure via the food chain in the microcosms.

Impact of triphenyltin acetate in microcosms simulating floodplain lakes. I. Influence of sediment quality

“…The fact that representatives of Tricladida, Annelida, Mollusca, Crustacea, Insecta and Rotifera all showed a treatment-related decline in abundance suggests that TPT is a compound with a broad biocidal mode of action. These observations in the microcosms are in line with the results of single species toxicity tests with TPT performed in the laboratory (Table 10; for further details see part II, Roessink et al 2006). Indeed, acute laboratory toxicity data show that several invertebrate groups are sensitive to this compound in the concentration range selected in our microcosm experiment (1-100 lg/l).…”

“…This was further substantiated by single species tests performed with Scenedesmus quadricauda. In this species, calculated EC50 values at 48, 72, and 96 h after TPT application were 352.9, 29.1, and 36.0 lg/l, respectively (Roessink et al 2006), suggesting that at even longer periods after TPT application, 10 lg/l could cause toxic (2006) effects which overrule the positive effect of the release from grazing pressure. Similar response patterns have been found for daphnids in insecticide-treated microcosms which were also inhabited by the more sensitive predator Chaoborus obscuripes .…”

“…The observation that overall responses of sensitive populations were rather similar between test system types is further substantiated by the fact that EC 50 values could be calculated for several invertebrate populations sampled in the microcosms, resulting in very similar species sensitivity distribution (SSD) curves between the CS and PS microcosms (for detailed results see part II; Roessink et al 2006). Hazardous concentrations for 5% of the species (HC5) calculated on the basis of these microcosm-SSD curves in sampling weeks 2-8 after TPT treatment ranged from 0.3 to 0.6 lg/l for the CS cosms and from 0.2 to 0.6 lg/l for the PS cosms.…”

“…11; Tables 4 and 5) whereas its sensitivity in 21-day laboratory single species tests was lower. In the laboratory, an EC 50 of 11.8 lg/l was recorded for the relative growth of Elodea nuttallii (Roessink et al 2006). Most populations of algae in the microcosms did not show a clear linear treatment-related decline in abundance.…”

“…A second paper (Part II, Roessink et al 2006) will compare the concentration-response relationships of aquatic populations in the TPTstressed microcosms with the results of acute laboratory single species tests performed with TPT and a wide variety of freshwater species, including algae, macrophytes, zooplankters, and macroinvertebrates.…”