Community structure and spatiotemporal patterns of macrozoobenthos in Lake Chaohu (China)

Lake Chaohu, the fifth largest freshwater lake in China, has been subjected to severe eutrophication and cyanobacterial blooms over the past few decades. However, little is known about the macrozoobenthic assemblages in this lake. To characterize the community structure and spatiotemporal patterns of macrozoobenthos in Lake Chaohu and to elucidate the environmental factors that regulate the benthic community, a bimonthly investigation was conducted at 9 stations from September 2002 to July 2003. Principal component analysis suggested that there was a decrease in trophic status from west to east in this lake. A total of 19 taxa were recorded, and the most abundant organisms were members of Oligochaeta and Chironomidae. Two-way ANOSIM indicated significant differences in community structure among stations (R = 0.417, p < 0.001) but not among months (R = 0.058, p = 0.128). Mantel tests showed that spatial changes in macrozoobenthic assemblages were similar across most sampling occasions. A BIO-ENV analysis showed that the concentrations of total nitrogen, total phosphorus, ammonium and dissolved oxygen in the benthic layer were strongly correlated to the community structure of macrozoobenthos in Lake Chaohu. Compared with a study conducted in 1980 to 1981, benthic assemblages shifted from dominance by Corbicula fluminea and gastropods to dominance by oligochaetes and chi-ronomids in the present study. Our results have implications for benthic biodiversity conservation in shallow lakes along the Yangtze River undergoing eutrophication.