Combined impact of pesticides and other environmental stressors on animal diversity in irrigation ponds.

Hiroshi C Ito,Hiroaki Shiraishi,Noriko Takamura,Megumi Nakagawa,Michael A Chadwick

doi:10.1371/journal.pone.0229052

Hiroshi C Ito, Hiroaki Shiraishi + Show 3 more

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https://doi.org/10.1371/journal.pone.0229052

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Abstract

Rice paddy irrigation ponds can sustain surprisingly high taxonomic richness and make significant contributions to regional biodiversity. We evaluated the impacts of pesticides and other environmental stressors (including eutrophication, decreased macrophyte coverage, physical habitat destruction, and invasive alien species) on the taxonomic richness of freshwater animals in 21 irrigation ponds in Japan. We sampled a wide range of freshwater animals (reptiles, amphibians, fishes, mollusks, crustaceans, insects, annelids, bryozoans, and sponges) and surveyed environmental variables related to pesticide contamination and other stressors listed above. Statistical analyses comprised contraction of highly correlated environmental variables, best-subset model selection, stepwise model selection, and permutation tests. Results showed that: (i) probenazole (fungicide) was a significant stressor on fish (i.e., contamination with this compound had a significantly negative correlation with fish taxonomic richness), (ii) the interaction of BPMC (insecticide; also known as fenobucarb) and bluegill (invasive alien fish) was a significant stressor on a "large insect" category (Coleoptera, Ephemeroptera, Hemiptera, Lepidoptera, Odonata, and Trichoptera), (iii) the interaction of BPMC and concrete bank protection was a significant stressor on an "invertebrate" category, (iv) the combined impacts of BPMC and the other stressors on the invertebrate and large insect categories resulted in an estimated mean loss of taxonomic richness by 15% and 77%, respectively, in comparison with a hypothetical pond with preferable conditions.

Highlights

Freshwater ecosystems provide a broad variety of services, including disturbance regulation, water regulation, water supply, waste treatment, food production, and recreation [1], some of which are irreplaceable [2]
With regard to the taxonomic richness of the all-sampled category and its 11 subcategories, we found statistically significant effects of BPMC, probenazole, concrete bank, bluegill, F-plant noncoverage, and shallowness, all of which were negative
The relationships between those stressors and the taxonomic richness were intuitively represented in S4 Fig by biplot diagram of redundancy analysis (RDA)

Summary

Introduction

Freshwater ecosystems provide a broad variety of services, including disturbance regulation, water regulation, water supply, waste treatment, food production, and recreation [1], some of which are irreplaceable [2]. These organisms are regulated under the country’s Invasive Alien Species Act, meaning they are regarded to have the potential to harm ecosystems in Japan through predation on and competition with indigenous species (https://www.env.go.jp/ en/nature/as.html) To evaluate their impacts as well as those of other stressors on freshwater animals in the studied ponds, these four invasive species were excluded and were instead treated as environmental variables that can influence biodiversity. Among the environmental variables measured, the declines of floating-leaved plant coverage and that of emergent plant coverage may be stressors on the taxonomic richness of freshwater animals in the studied ponds This is because macrophytes in irrigation ponds in the study area have been decreasing due to urbanization [32], an increase in concrete banks [33], and herbicide contamination. 48 environmental variables were used in the statistical analysis (S5 Table)

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Results

Discussion