Frogs as bioindicators - Land and Water Australia

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Contents Acknowledgements…………………………………………………….…….................5 Introduction……………………………………………………….……..........................6 Aims Study sites………………………………………………………...……....................…...8 Survey design Methods………………………………………………………….………......................….9 Tadpole and frog-call surveys Collection of frogs Time-weighted average pesticide concentrations Chytrid fungus pathology Gonadal abnormalities and sex determination Statistical analysis Results…………………………………………………………………....................…....13 Abundance and distribution of species Probability of detection of L. raniformis Pesticide concentrations at the study sites Water quality at the study sites Principal component analysis (PCA) Discriminant Analysis (DA) Chytrid fungus on frogs Histology of frog gonads Discussion………………………………………………………...............................…23 Distribution of frog species across sites L. raniformis distribution and pesticide usage L. raniformis distribution in relation to farm type and water quality Chytrid infection and hermaphroditism Conclusions……………………………………………………………..........................27 References…………………………………………………………..….......................…28 FROGS AS BIOINDICATORS OF CHEMICAL USAGE AND FARM PRACTICES 3
List of figures Figure 1. Map of the Coleambally Irrigation Area and its four regions……...…........…..7 Figure 2. Mean abundance of the four tadpole species assessed using 10 standardised net sweeps in rice bays at the farm study sites in the northern (n = 20) and southern (n = 20) region of the Coleambally Irrigation Area in the 2005 season…………..…..………….............................................…13 Figure 3. Comparison of the estimated probability of non-detection of Litoria raniformis at three groups of farm study sites located in either the northern (#) or southern region (!) of the Coleambally Irrigation Area in relation to the number of site visits………………...........................................….14 Figure 4. Principal components analysis for the 20 study sites during the three site visits in the 2007/07 season (n = 60) as determined by seven pesticides and four water quality variables…………………………………….…….……18 Figure 5. Classification of sites with (solid symbols) or without (empty symbols) L. raniformis on the rice-only or rice and corn farms as determined by the first two canonical functions of a discriminant analysis…………………………………….…19 Figure 6. Gonadal morphology of (A) a pair of ovaries from a Gosner stage 40 Litoria raniformis tadpole with a “string of beads” appearance (arrow); (B) more developed, but still sexually immature, pair of ovaries (arrow) from a recently emerged Litoria raniformis frog; (C) pair of immature testes (arrow) from a recently emerged Litoria raniformis frog; (D) a pair of ovaries with mature oocytes from a recently emerged Limnodynastes tasmaniensis frog; (E) a pair of mature testes from a recently emerged Limnodynastes tasmaniensis frog; and (F) a histological section of testis from a Limnodynastes fletcheri frog with normal morphological appearance, showing intersex with developing oocytes in otherwise normal testicular tissue (bar = 100 μm)………………21 List of tables Table 1. Residues of pesticides (μg/L) detected at the study sites of the Coleambally Irrigation Area during three periods in the 2006/07 season (n = 3 periods x 10 sites of each farm type)………………………………………………………....15 Table 2. Screening for chytridiomycosis in frogs collected from rice farms in the Coleambally Irrigation Area in the spring of 2006……………………………………...20 Table 3. The percentage intersex and sex ratio of 216 metamorph frogs collected from rice farms in the Coleambally Irrigation Area 2005/2006 growing season…………..........................................................................................…...22 FROGS AS BIOINDICATORS OF CHEMICAL USAGE AND FARM PRACTICES 4
Page 1 and 2: Frogs as bioindicators of chemical
Page 3: Frogs as bioindicators of chemical
Page 7 and 8: Introduction Dramatic declines and
Page 9 and 10: Survey design The study farms were
Page 11 and 12: Passive sampling devices offer an e
Page 13 and 14: where n is the number of surveys of
Page 15 and 16: Since the frog distribution data fr
Page 17 and 18: Thiobencarb and molinate were the h
Page 19 and 20: Figure 4. Principal components anal
Page 21 and 22: addition, the results for 19 of the
Page 23 and 24: Table 3. The percentage intersex an
Page 25 and 26: average metolachlor concentrations
Page 27 and 28: Examination of the histological sec
Page 29 and 30: References Abdullah, A.R., Bajet, C
Page 31 and 32: Lacy J, Stevens MM. 2003. Rice Crop

Frogs as bioindicators - Land and Water Australia

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