An investigation into the effects of pesticide application on the distribution and larval development of frogs in the rice bays of the Coleambally Irrigation Area, NSW Australia

University of Technology, Sydney. Faculty of Science.NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material. The hardcopy may be available for consultation at the UTS Library.NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material

Morphological abnormalities in frogs from a rice-growing region in NSW, Australia, with investigations into pesticide exposure

Three frog species were surveyed in rice bays of the Coleambally Irrigation Area (CIA) NSW during the rice-growing season. A total external morphological abnormality index of 7% was observed. No conclusive evidence was found of unnaturally high rates of intersex, gonadal maldevelopment or unbalanced sex ratios in any species. Rice bay surface waters differed significantly in mean pesticide concentration of atrazine and metolachlor on farms growing rice and corn compared to farms growing rice only. However, the similar abnormality indices observed in recent metamorphs emerging from these two farm types provided no evidence to suggest a link between larval exposure to the measured pesticides and developmental malformations

Growth, development and sex ratios of spotted marsh frog (Limnodynastes tasmaniensis) larvae exposed to atrazine and a herbicide mixture

Exposures of Limnodynastes tasmaniensis tadpoles to atrazine (0.1, 1, 3 and 30 μg L−1), metolachlor (0.1, 1 and 10 μg L−1) and thiobencarb (90, 180 and 360 μg L−1) from Gosner stage 28 to 42 under controlled laboratory conditions gave no significant effects on tadpole growth, development and sex ratios. A binary mixture of atrazine and thiobencarb as well as a ternary mixture of all three herbicides also had no significant effects on the developing larvae to show no evidence of interactive toxicity. Abnormal gonad morphology was observed on two occasions; both from 0.1 μg L−1 atrazine treatments with one tadpole observed with testicular ovarian follicles. The low frequencies of abnormal gonadal morphology and testicular ovarian follicles did not indicate a concentration associated response to herbicide exposure. No significantly unbalanced sex ratios were observed to suggest any evidence of chemically induced feminisation. These observations suggest that environmentally relevant concentrations of atrazine, metolachlor and thiobencarb do not present a significant threat to the normal development of L. tasmaniensis larvae in surface waters of irrigated agricultural areas

Distribution of frogs in rice bays within an irrigated agricultural area : links to pesticide usage and farm practices

The occurrence of four frog species in rice bays of the Coleambally Irrigation Area (NSW, Australia) was studied over two seasons. The mean abundance of Litoria raniformis tadpoles was significantly lower in the northern sites compared to the southern sites. In contrast, tadpoles of the three other species had a uniform distribution across all study sites. A discriminant analysis showed low concentrations of the corn herbicide metolachlor and increased pH were the main variables studied that determined site occupation by L. ranifromis. We concluded that farm practices associated with increased corn cropping in the northern region, rather than any direct effect of corn herbicides, determine the reduced species presence of L. raniformis in the northern region