Organochlorine pesticides and polychlorinated biphenyls (PCBs) in eggs of red-legged frogs (Rana aurora) and northwestern salamanders (Ambystoma gracile) in an agricultural landscape

Levels of persistent organic pollutants in cane toads (Rhinella marina) differ among sites with varying industrial and agricultural activities

In this study, we captured cane toads (Rhinella marina) in four sites located in different regions affected by anthropogenic activities in Mexico. Subsequently we analyzed liver tissue for the presence of organochlorine pesticides (OCs) and polychlorinated biphenyls (PCBs) The levels of these POPs in the toads' livers ranged from 863.2 to 3109.6 ng/g of lipid weight across all sites. A multivariate statistical analysis highlighted two sites with the highest POPs levels, with the most polluted site displaying a high level of PCBs, suggesting influence of industrial activities. The second most polluted site displayed significant amounts of OCs, linking this location to agricultural activity. Additionally, we found pesticide metabolites and isomers that allowed us to distinguish past and recent exposure events. Our observations indicate that R. marina is suitable bioindicator of sites impacted by anthropogenic activities.

Regional Scale Risk to the Ecological Sustainability and Ecosystem Services of an African Floodplain System

The Phongolo floodplain is one of southern Africa's most important systems. In this study, we carried out a regional scale ecological risk assessment to evaluate the risk of multiple stressors associated with the use of the aquatic resources in the floodplain to selected social and ecological endpoints representing its sustainability. The floodplain has undergone significant changes as a result of the impacts of multiple stressors. This includes high risk of impact and threatened sustainability between the Pongolapoort Dam and the Ndumo Game Reserve (NGR). This compares to relatively low risk to the maintenance of the endpoints within the NGR. The reserve provides a protection and refuge function for regional biodiversity maintenance and ecosystem sustainability processes. In the study a range of scenarios were considered and demonstrate that the system will respond to protection measures and or increased resource use options. Should flood reductions or water quality pollution drivers continue on increasing trajectories, the condition of the Phongolo River and floodplain will probably deteriorate into an unacceptable, unsustainable state. Removal of the protection services of the NGR would result in an unsustainable ecosystem and loss of ecosystem services for regional vulnerable African communities. Additional evidence should be obtained from monitoring and research to refine, validate, and update the assessment in an adaptive management context. The risk assessment framework approach implemented in the Phongolo floodplain can contribute to the management of other floodplains ecosystems and the sustainability management of social and ecological attributes and processes of these important ecosystems.

Investigating Acute and Subchronic Effects of Neonicotinoids on Northwestern Salamander Larvae

This research investigated the adverse effects of neonicotinoids on the Northwestern salamander (Ambystoma gracile; NWS) after acute and subchronic exposures during early aquatic life stages via whole organism (i.e., growth, development) and molecular (i.e., gene expression) level endpoints. In a 96-h exposure, NWS larvae were exposed to four imidacloprid concentrations (250, 750, 2250, 6750 µg/L) and a water control treatment, and no effects on survival, body weight, snout-vent length (SVL), and total body length were observed. However, a significant 1.70- and 2.33-fold decrease in thyroid receptor β (TRβ) mRNA expression levels were detected in the larvae exposed to 750 and 2250 µg/L imidacloprid, respectively, compared with the larvae in the water control. In subsequent subchronic experiments, NWS larvae were exposed for 35 days to imidacloprid alone and an equal part mixture of neonicotinoids (imidacloprid, clothianidin, and thiamethoxam (ICT)) at three concentrations (10, 100 and 1000 µg total neonicotinoids/L) and a water control. In these experiments, there were no effects on larval survival, body weight, SVL, and total body length. However, advanced development of larvae in the 100 µg/L imidacloprid treatment was observed compared with the control after 35-day imidacloprid exposure, providing some evidence of disruption of the thyroid endocrine axis at an environmentally relevant concentration. Ultimately, there is a paucity of studies conducted examining the sensitivity of salamanders to pollutants; thus, this study reports novel findings that will contribute to understanding the sensitivity of a Caudate amphibian model to a common environmental pollutant.

Combined effects of agrochemical contamination and forest loss on anuran diversity in agroecosystems of east-central Argentina

Agricultural expansion and intensification has led globally to a rapid landscape structure change and high agrochemical use resulting in habitat loss and degraded environmental quality. Co-occurrence of landscape change and agrochemical contamination threatens biodiversity and might have interactive effects especially for organisms with complex life-cycles such as amphibians. We evaluated effects of landscape structure and agrochemical contamination at different spatial scales on anurans in Entre Rios, Argentina. We selected 35 independent stream headwaters along an agricultural expansion and intensification gradient. We conducted anuran call surveys from spring 2012 to summer 2013 and obtained detection-non detection data to estimate mean richness and focal species occupancy. We quantified forest area and riparian forest width at two spatial scales (sub-basin and local reach scale). We measured nutrients and pesticides in water and sediment. We evaluated anuran response to landscape and contamination variables using GLMs for richness and single season single-species occupancy models for focal species. Anuran diversity increased with forest area and riparian forest width, and decreased at sites with herbicide and nutrient contamination, particularly glyphosate; 2,4-D and nitrates. Also, most focal frog species responded mainly to basin forest and 2,4-D. Negative effects of agrochemical contamination on anuran diversity was mitigated in areas with larger basin forest cover. Agricultural management should ensure the reduction of herbicide and fertilizer use, the sparing of adequate forested habitat within drainage areas, and preservation of riparian forests around anuran breeding habitat to reduce and mitigate the negative effects of agrochemical contamination on anurans diversity in agroecosystems.

Bioavailability and tissue distribution of Dechloranes in wild frogs (Rana limnocharis) from an e-waste recycling area in Southeast China

Dechlorane Plus (DP), a flame retardant used as an alternative to decabromodiphenylether, has been frequently detected in organisms, indicating its bioaccumulation and biomagnification potential in aquatic and terrestrial species. However, little data is available on the bioaccumulation of DP in amphibians. Dechlorane Plus and its analogs (DPs) were detected in the liver, muscle and brain tissues of wild frogs (Rana limnocharis), which were collected from an e-waste recycling site, Southeast China. DP, Mirex, Dec 602 and a dechlorinated compound of DP (anti-Cl11-DP) varied in the range of 2.01-291, 0.650-179, 0.260-12.4, and not detected (nd)-8.67 ng/g lipid weight, respectively. No difference of tissue distribution was found for syn-DP, Mirex and Dec 602 between the liver and muscle tissue (liver/muscle concentration ratio close to 1, p > 0.05). However, higher retention was observed for anti-DP and anti-Cl11-DP in the frog muscle relative to the liver tissue (liver/muscle concentration ratio < 1, p < 0.05). Additionally, the blood-brain barrier was found to work efficiently to suppress these compounds entering brain tissues in this species (liver/brain concentration ratio > 1, p < 0.05), and the molecular weight was a key factor impacting the extent of the blood-brain barrier. Compared to levels in the muscle and brain tissue, a preferential enrichment of syn-DP was observed in the liver tissue, suggesting the occurrence of stereo-selective bioaccumulation in the wild frog.

DDTs in rice frogs (Rana limnocharis) from an agricultural site, South China: tissue distribution, biomagnification, and potential toxic effects assessment

Contamination with agricultural pesticides such as dichlorodiphenyltrichloroethane (DDT) and its metabolites, dichlorodiphenyldichloroethylene (DDE) and dichlorodiphenyldichloroethane (DDD), is among several proposed stressors contributing to the global declines in amphibian populations and species biodiversity. These chemicals were examined in insects and in the muscle, liver, and eggs of rice frogs (Rana limnocharis) from the paddy fields of an agricultural site in South China. The ΣDDT (sum of DDT, DDE, and DDD) concentrations ranged from 154 to 915, 195 to 1,400, and 165 to 1,930 ng/g lipid weight in the muscle, liver, and eggs, respectively. All the DDTs (DDT, DDE, and DDD) showed higher affinity for the liver relative to muscle tissue and can be maternally transferred to eggs in female frogs. The average biomagnification factors for DDTs ranged from 1.6 to 1.9 and 1.5 to 2.9 in female and male frogs, respectively, providing clear evidence of their biomagnification from insects to frogs. Compared with the reported DDT levels demonstrated to have toxic effects on frogs, DDTs in the present frogs are unlikely to constitute an immediate health risk. However, the adverse impacts of high DDT residues in eggs on the hatching success and their potential toxicity to the newly metamorphosed larval frogs should be assessed further.

PCB accumulation and tissue distribution in cave salamander (Proteus anguinus anguinus, Amphibia, Urodela) in the polluted karstic hinterland of the Krupa River, Slovenia

For over two decades, a manufacturer of electrical capacitors disposed of its waste within the karstic hinterland of the Krupa River (Slovenia) resulting in the surroundings becomming heavily polluted with PCB. Albeit the extent of the contamination has been known since 1983 and the Krupa River has become one of the most PCB polluted river in Europe, the effects on the cave fauna of the region remain unknown. The most famous cave dweller of the Krupa hinterland is the endemic cave salamander Proteus anguinus anguinus. In this study we determine the levels of PCB in the tissues of the Proteus and in river sediments. The total concentration of PCB in individual tissue samples from specimens of the Krupa spring was between 165.59 μg g(-1) and 1560.20 μg g(-1)dry wt, which is at least 28-times higher than those from an unpolluted site. The kidneys contained the lowest concentration, while the highest concentration was in subcutaneous fat and tissues with high lipid contents like visceral fat and liver. Total PCB concentrations in sediment samples from the Krupa River were between 5.47 and 59.20 μg g(-1)dry wt showing that a high burden of PCB still remains in the region. The most abundant PCB congeners in all analyzed samples were di-ortho substituted (PCB #101, #118, #138 and #158), but higher proportion of mono-ortho PCB was present in sediments. The ability of Proteus to survive a high PCB loading in its environment and especially in its tissues is remarkable. Its partial elimination of low chlorinated and mono-ortho substituted congeners is also reported.

The influence of water quality on the embryonic survivorship of the Oregon spotted frog (Rana pretiosa) in British Columbia, Canada

In Canada, the Oregon spotted frog (Rana pretiosa) is a critically endangered species with only three known populations and an estimated breeding population of less than 400 located in isolated sites in the extreme south-west corner of British Columbia. Floating Nitex cages were used to assess embryonic survivorship in two populations of Oregon spotted frogs from 2002-2005. One population, near Aldergrove, BC experienced declines in population size while the other population, at Maria Slough, increased during the period 1997-2001. During embryo development, we measured trace metals, nutrients and physical parameters in the water at each site. These were used to test the hypothesis that water quality parameters were correlated with embryonic survivorship. During the study period in the declining population at Aldergrove R. pretiosa bred at two distinct sub sites (A and B) located 500 m apart within the wetland. Mean embryonic survivorship varied from 9% to 36% at sub site A and from 78% to 88% at sub site B whereas in the population in Maria Slough, the mean embryonic survivorship varied from 77% to 84%. Sulphate was the only water chemistry variable that differed significantly between the two study sites and was the highest at Maria Slough. A weak significant positive correlation was found between chloride and embryonic survivorship and conductivity and embryonic survivorship. A multiple regression model found conductivity was the only significant variable. We concluded that natural water chemistry conditions of low chloride and consequently low conductivity may be contributing to low embryonic survivorship in the population of R. pretiosa at MD Aldergrove, BC.

Polychlorinated biphenyls and organochlorine pesticides bioaccumulated in green frogs, Rana clamitans, from the lower Fraser Valley, British Columbia, Canada

Seven adult green frogs (Rana clamitans) were collected from three sites adjacent to intensive agriculture in the lower Fraser River valley, BC Canada. The highest mean concentrations of chemicals were pp'DDE at 0.313 microg/g lipid wt. and Aroclor 1,254/1,260 at 2.12 microg/g lipid wt. On a lipid weight basis, both pp'DDE and PCB concentrations varied by almost an order of magnitude among sites. Only ortho-substituted PCB congeners were detected. The concentrations of organochlorine pesticides and PCBs measured in these frogs from British Columbia are unlikely to elicit negative effects in frogs.