A subfossil chironomid-total phosphorus inference model for lakes in the middle and lower reaches of the Yangtze River

Abstract

The results of an investigation into the relationship between surface sediment subfossil chironomid distribution and water quality are presented. Data from 30 lakes in the middle and lower reaches of the Yangtze River indicate that the nutrient gradient was the major factor affecting the distribution of chironomids across these sites. Canonical correspondence analysis (CCA) revealed that of 12 summer water environmental variables, total Phosphorus was most important, accounting for 20.1% of the variance in the chironomid data. This was significant enough to allow the development of quantitative inference models. A TP inference model was developed using weighted averaging (WA), partial least squares (PLS) and weighted averaging partial least squares (WA-PLS). An optimal two-component WA-PLS model provided a high jack-knifed coefficient of prediction for conductivity r 2 jack = 0.76, with a low root mean squared error of prediction (RMSEP jack = 0.13). Using this model it is possible to produce long-term quantitative records of past water quality for lacustrine sites across the middle and lower reaches of the Yangtze River, which has important implications for future lake management and ecological restoration.

Spatial distribution of subfossil Chironomidae in surface sediments of a large, shallow and hypertrophic lake (Taihu, SE China)

“…Nutrient enrichment is generally a key factor affecting the variation of aquatic organisms in freshwater ecosystems Zhang et al, 2006). In Taihu Lake, chironomid distribution was significantly controlled by trophic condition.…”

A 150-year record of recent changes in human activity and eutrophication of Lake Wushan from the middle reach of the Yangze River, China

“…Lake water TP for the Wushan Core was calculated using a chironomid-TP inference model by applying an optimal two-component WA-PLS model which provides a high jack-knifed coefficient of prediction for conductivity r 2 jack = 0.76, with a low root mean squared error of prediction (RMSEP jack = 0.13) (Zhang et al 2006). The water TP reconstruction was undertaken using the program C2 (Juggins 2003).…”

“…A chironomid-inferred record of mean annual lake water TP (CI-TP) for the period 1860s -2007, was calculated for the Wushan Core by applying a WA-PLS model (Zhang et al 2006), to the fossil chironomid assemblage data (Fig. 4).…”

A chironomid-based mean July temperature inference model from the south-east margin of the Tibetan Plateau, China

“…Subfossil chironomids have been successfully used as paleoenvironmental indicators in China for over a decade. These included salinity studies on the Tibetan Plateau (Zhang et al, 2007) and the development of a nutrient-based inference model for eastern China and parts of Yunnan (Zhang et al, 2006(Zhang et al, , 2010(Zhang et al, , 2011(Zhang et al, , 2012. A large database of relatively undisturbed lakes, in which nutrient changes are minimal while temperature gradients are suitably large, is now available from south-western China and this provides the opportunity to develop a summer temperature inference model for this broad region.…”