Constructed wetlands as potential breeding sites for amphibians in agricultural landscapes: A case study

Constructed wetlands are used as an effective measure to improve water quality and reduce nutrient runoff from agriculture. However, their role as alternative breeding sites for different amphibian species is rarely explored. We studied amphibians' colonization and breeding success in two in-stream free surface water wetlands in intensively managed agricultural landscape in south-eastern Estonia. Additionally, the sedimentation pond and a nearby farm pond were observed. The observations started a year after the establishment of the constructed wetlands in 2015 and lasted for four years. In Vanda constructed wetlands, breeding of five amphibian species were observed, all of which were common to the area: smooth newt (Lissotriton vulgaris L.), common toad (Bufo bufo L.), common frog (Rana temporaria L.), moor frog (Rana arvalis Nilsson) and pool frog (Pelophylax lessonae Camerano). Threatened species, such as the common spadefoot toad (Pelobates fuscus Wagler) or the northern crested newt (Triturus cristatus Laur.), also present in this region, were not found in the study sites. Unlike the sedimentation and farm ponds, constructed wetlands with their shallow rapidly warming water and absence of fish, provided breeding habitat for amphibians, especially for common frog and moor frog. In addition, chemical analyses of the water showed that nutrient concentration in the surface water was relatively low, which should not impair the reproduction of amphibians, at least in the short-term.