Relation between Enzyme Activity of Sediments and Lake Eutrophication in Grass-Type Lakes in North China

In order to discover the biochemistry mechanism of sediments in eutrophic grass-type lakes, this study selected four grass-type lakes in north China to explore the relation between enzyme activities of sediments and lake eutrophication condition. By applying the assessment method of organic nitrogen (ON) and total phosphorus (TP), the nutrition of lake sediments were assessed. As the results show, Hengshui (HS) Lake and Baiyangdian (BY) Lake, suffering severe pollution, have much higher urease activity in comparison with Nansi (NS) Lake and Dongping (DP) Lake. In addition, there is significant positive correlation between the urease activity and the contents of total nitrogen (TN) and organic matter (OM) of sediments (r = 0.805, p < 0.01; r = 0.840, p < 0.01). It's the same case between alkaline phosphatase (APA) activity and TP content (r = 0.876, p < 0.01). The activities of both cellulase and protease in HS Lake and BY Lake are weaker than those of NS Lake and DP Lake. The changes in the activities of polyphenol oxidase and peroxidase tend to be similar and their distributions are closely related to the degree of pollution and disruption caused by human activities. The enzymatic activity of lake sediments can serve as an indicator that reflects how serious lake eutrophication is.