Rainfall as dominant driver of rotifer dynamics in shallow wetlands: Evidence from a long-term data record (Upo Wetlands, South Korea)

In this study, we explain the environmental variables that mainly influence the seasonal pattern of rotifer communities in shallow wetlands (Upo Wetlands, South Korea). Long-term data (n=197, 2006-2013) were used to analyze the patterns by means of a self-organizing map (SOM), which extracts information through competitive and adaptive properties. A total of 32 variables (24 groups of rotifers and 8 environmental variables) were patterned onto the SOM, and then each variable was compared in accordance with four seasonal patterns. Three clusters were categorized according to the Euclidian distance between the clusters on the SOM, and these were interpreted in relation to seasonal features. Using the SOM, the rotifer groups were clearly distinguished by water temperature and rainfall. In particular, pelagic rotifer groups (Brachionus, Keratella, and Polyarthra) were less abundant when high rainfall occurred, but epiphytic rotifers (Lepadella, Leacne, and Monostyla) were strongly associated with high rainfall. Moreover, strong rainfall occurring on several consecutive days increased the rotifer abundance on macrophytes. The SOM results depicted a clear pattern of rotifer density clusters partitioned by rainfall, which determined the seasonal distribution of rotifer groups in a shallow wetland.