Aquatic biota in a wetland biotope constructed by excavating fallow field

Abstract

The changes of water environment and aquatic biota were investigated over a three-year period in an artificial wetland biotope (Tebika Biotope) constructed by excavating fallow field. We identified 93 aquatic animal species in 18 orders and 4 submerged plants, so it was thought that this biotope was effective in biodiversity conservation. There was a marked seasonality in the number of aquatic insect species, with an increase in summer (mainly in August) and a decrease in winter (mainly in February). The species number and diversity index (Shannon-Wienerʼs Hʼ) was greater at a site of still water with ecotones. On the other hand, some unique species were found in the monotonous flowing water environment. Almost all the aquatic insects identified in this biotope were found in the ponds within 2 km of the biotope. This suggests that the aquatic biota of an artificial wetland biotope is highly dependent on the surrounding biota, and that ecotones and diverse flow regimes are important for the conservation of biodiversity. The growth of submerged plants and changes in the number of aquatic insect species suggest that the biota of this biotope may have been adversely affected by the invasive alien species, a crayfish Procambarus clarkii, and a snail, Pomacea canaliculata