Patterning Zooplankton Communities in Accordance with Annual Climatic Conditions in a Regulated River System (Nakdong River, South Korea)

Abstract

In this study, we investigated what environmental factors mainly influence the pattern of zooplankton communities in the regulated Nakdong River. Fifteen years of data (N = 629, 1994 to 2008) were used to analyze the patterns by means of self-organizing map (SOM), that is capable of extracting information through competitive and adaptive properties. A total of 34 variables (18 groups of zooplankton and 16 physicochemical parameters) were patterned onto the SOM, and then each variable was compared in accordance with three different annual rainfall patterns (i.e., dry, moderate, and wet). Finally, seven clusters were categorized according to Euclidian distance between the clusters on the SOM. Clear seasonal features for the variables were interpreted in five major categories, and two more subcategories were partitioned by a specific feature of zooplankton abundance and appearance. In the result, the patterns of zooplankton assemblage were mainly distinguished by water temperature, Secchi transparency, and river flow rate. In particular, the SOM result depicted a clear pattern of zooplankton assemblage clusters partitioned by annual precipitation, which accentuated the prolonged effect of dam regulation on plankton assemblage in a regulated river system.

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

“…In contrast, density of pelagic species such as Brachionus , Keratella , and Polyartha were clearly decreased by rainfall; therefore, their highest densities were found mainly in the spring and autumn. Some studies have reported that pelagic species were strongly affected by flow waves and/or concentrated rainfall (Kingsford, ; Kim et al, ). The decrease of pelagic species by rainfall may increase food availability to epiphytic species in habitat.…”

“…This was because the main goal of this study was to discover a general pattern of rotifer distribution in the wetland system. Typically analyzing ecological data suffers from problems such as non‐linearity, multimodal, many zeros, or multi‐colinearity (Fielding, ), which often hinders discovering general pattern of ecosystem dynamics from the given dataset (Kim et al, ). In this point of view, we focused on the more abundant species in the wetland.…”

“…In particular, rainfall has been seen as a primary factor that determines several physical, chemical, and biological components in freshwater ecosystems (Alexander and Whalen, 1989; Hamilton et al, ). In eastern Asia, rainfall is concentrated in the summer (mainly June–August; Jeong et al, ), and frequently introduces dynamic changes in the spatial and temporal distribution patterns of plankton communities (Ha et al, ; Kim et al, ). In this region, therefore, rainfall attracts much attention in the explanation of short time ecosystem dynamics.…”

“…The impact is often sufficiently strong to change the community structure of rotifers in aquatic environments, determining the seasonality of the rotifer community. In lotic ecosystems such as rivers and streams, increased discharge due to summer concentrated rainfall causes apparent changes in the rotifer community (Kim et al, ), leading to the loss of rotifer density in the autumn (Choi et al, ). This circumstance confines the growth of rotifers in spring seasons when rainfall is relatively scarce.…”

Limnological assessment of the meteo-hydrological and physicochemical factors for summer cyanobacterial blooms in a regulated river system

“…Lake Taihu in China (Duan et al, 2012;Zhang et al, 2012), Lakes Suwa (Yokoyama and Park, 2002) and Kasumigaura (Islam et al, 2012) in Japan, and Han and Nakdong Rivers and Daechung Reservoir in South Korea are representatives of cyanobacterial bloom ecosystems. The Nakdong River is a regulated river system with dams and an estuarine barrage for water resource management during the monsoon season (Jeong et al, 2011;Kim et al, 2012;Hong et al, 2014). This river had a severe cyanobacterial bloom problem in the 1990s (Ha et al, 1998(Ha et al, , 1999.…”