Distribution of dissolved acidic polysaccharides (dAPS) during cyanobacteria blooms in northern Lake Taihu

Concentrations of dissolved acidic polysaccharides (dAPS) were investigated at four stations zones along Meiliang Bay from the river mouths, to the inner bay, to the outer bay, and further to the lake center in the northern Lake Taihu during the Microcystis blooming periods from June to October 2012. The concentrations of dAPS displayed a decreasing trend from the lakeshore to the open areas. Concentrations of dAPS along Meiliang Bay varied from 1.25 mg gum xanthan equivalents (Xeq)/L to 15.73 mg Xeq/L with an average value of 5.76 mg Xeq/L. High concentrations of dAPS were found at the river mouths [5.44 +/- A 2.32 mg Xeq/L (mean +/- A SD)]. Chlorophyll a (Chl a) was positively related to dAPS in the whole bay (including the river mouths, the inner bay, the outer bay) (p < 0.05), suggesting the algae were the major source of dAPS in the water column. Five-day biological oxygen demand (BOD5) was inversely correlated with the quantities of dAPS, but the mechanism for that should be studied further. On average, dAPS accounted for 42.2 +/- A 20.3 % of dissolved organic carbon (DOC) in the whole bay, and 35.2 +/- A 14.6 % of DOC at the lake center. The abundance of dAPS proved that they were a significant pool of organic carbon in the lake and would further affect the aquatic ecosystems.