Date of Award
Master of Science
Lydy, Michael J.
Whitledge, Gregory W.
The ecological role of chironomids has been described as an abundant and ubiquitous prey item for not only aquatic species, but terrestrial and avian species as well. Global use of pesticides in urban and agricultural applications have introduced a potential threat not only to chironomid populations, but to the individuals that prey on chironomids. Chironomids direct contact with the sediment has resulted in both legacy and current-use pesticides being detected in the individuals throughout their life cycle. The capacity for contaminant uptake and biotransformation among each midge life stage and from larvae to adults, however, is poorly understood. The lipophilic compounds of focus for this thesis include bifenthrin, and p,p’-DDT, along with the biotransformation products, TFP acid, BP alcohol, BP acid, p,p’-DDE and p,p’- DDD. To observe bioaccumulation and biotransformation at each life stage (2nd,3rd,4th, pupae, and adult), month long exposures were run with a subset of individuals being removed at each life stage and processed to quantify total, parent, and biotransformation product concentrations. Exposures at low concentrations (below literature C. dilutus no observable adverse effects concentration) at 25°C produced mean C. dilutus total pesticide concentrations ranging from 36.31 to 896.1 μg/kg dw lipid for bifenthrin and from 41.64 to 877.7 μg/kg dw lipid for DDT through all life stages. The 3rd instar contained the highest parent bifenthrin concentration, though this concentration was not statistically different from the concentration in the pupae. The 3rd instar also contained the highest parent concentration of DDT, though concentrations were not statistically different from concentrations in 2nd to 3rd instar larvae. C. dilutus also displayed subsequent biotransformation of DDT to DDE in each instar. By the 4th instar, 87.10% of the total concentration in the midges was DDE and DDD. The biotransformation of DDT to DDD was also observed to occur in sediments and was likely due to direct reductive dechlorination through chemical processes. Chironomid uptake of DDD increased as the parent DDT was degraded to DDD in the sediments over the testing period. This study provides a greater understanding of the bioaccumulation and biotransformation potential in chironomids at each life stage. Initial spiking concentrations were too low, resulting in low body residues and with no method detection limit or reporting limit defined for the study, so these lower measures have limited certainty. Therefore, the implications of this thesis are limited.
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