Impact on Plankton Communities Following Abandonment of Rice Cultivation and Biotope Creation.

The global decline in agricultural land has raised concerns regarding the impact on biodiversity. One effective strategy for preventing a decrease in biodiversity is converting abandoned rice fields into wetland biotopes. However, the impact of these changes on plankton communities remains unclear. The objective of this study was to investigate the diversity and distribution of plankton communities in a single rice field located in Kyoto. The specific objective is to clarify which plankton respond to farmland abandonment. Samples were collected every week from May to July over a two-year period (rice cultivation period in 2022 and post-abandonment biotope creation in 2023) to determine species composition and environmental variation. As a result, no changes in plankton community structure occurred after biotope formation, as evidenced by the absence of statistically significant changes in the biodiversity index (H') or the number of plankton taxa. At the genus level, Trinema, Trachelomonas, and Scenedesmus exhibited a response to fluctuations over the two-year period, despite their low average contribution to community structure. These groups of organisms may be driving subtle changes in community structure and should therefore be considered as indicator species. Subsequent research endeavors will ascertain the true value of biotope formation in abandoned land.