Using Stressor-Response Models to Derive Numeric Nutrient Criteria for Lakes in the Eastern Plain Ecoregion, China

Lakes in the Eastern Plain ecoregion of China are typically shallow, experience large disturbances, and are hydrologically connected to rivers. In recent years, lake eutrophication in this ecoregion has intensified due to human activities. To determine important regional nutrient criteria, the effects of hydrologic features and disturbances should be taken into account. In this paper, annual average data were used to construct stressor-response models for each hydrological lake type identified for lakes in the Eastern Plain ecoregion. In these models, total nitrogen (TN) and total phosphorus (TP) criteria were obtained from a chlorophyll a (Chl-a, response variable) threshold value. A Chl-a concentration of 4.73gL(-1) was identified as this threshold value, which was based on the cyanotoxin limits associated with drinking water supply. The three lake types, which differed in hydrological structure, had significantly different TN and TP criteria. For example, lakes connected to the Yangtze River (T-1) had a TN criterion ranging from 0.594 to 0.838mgL(-1), which was substantially higher than those for lakes that were never connected to the river (T-3, 0.234-0.422mgL(-1)). The exception to this trend occurred for lakes that were historically but not currently connected to the river (T-2) due to P-limitation in this lake type. However, there was little variability in the TP criterion among T-1, T-2, and T-3 lakes, the values of which ranged from 0.021 to 0.037, 0.023 to 0.042, and 0.028 to 0.041mgL(-1), respectively.