title: To increase size or decrease density? Different Microcystis species has different choice to form blooms.
abstract: The buoyancy of Microcystis colonies is a principal factor determining blooms occurrence but the knowledge of seasonal variation in buoyancy is quite poor because of challenge in analysis method. In this study, a method based on the Stokes' Law after researching on the effects of shapes on settling velocity of Microcystis colonies, whose gas vesicles were collapsed, to accurately measure density was established. The method was used in Lake Taihu. From January to May, mean density of Microcystis colonies decreased from 995 kg m-3to 978 kg m-3and then increased to 992 kg m-3in December. The density of colonies in different Microcystis species was in the order M. wesenbergii > M. aeruginosa > M. ichthyoblabe. For all the Microcystis species, the density of colonies with gas vasicles increased significantly along with the increase of colony size. Our results suggested that the main driving factor of Microcystis blooms formation in Lake Taihu was low density for M. ichthyoblabe from May to July but was large colony size for M. wesenbergii and M. aeruginosa from August to October.
authors.affiliation: College of Resources and Environment, Northwest A &F University, Yangling 712100, PR China.
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.affiliation: College of Environment, Hohai University, No. 1 Xikang Road, Nanjing 210098, PR China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhu
authors.affiliation: College of Environment, Hohai University, No. 1 Xikang Road, Nanjing 210098, PR China.
authors.forename: Lili
authors.initials: L
authors.lastname: Guo
authors.affiliation: College of Environment, Hohai University, No. 1 Xikang Road, Nanjing 210098, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Hu
authors.affiliation: College of Environment, Hohai University, No. 1 Xikang Road, Nanjing 210098, PR China.
authors.forename: Huaimin
authors.initials: H
authors.lastname: Chen
authors.affiliation: College of Environment, Hohai University, No. 1 Xikang Road, Nanjing 210098, PR China.
authors.forename: Man
authors.initials: M
authors.lastname: Xiao
mesh_terms: D005068:Eutrophication; D060106:Lakes / Q000382:microbiology*; D046931:Microcystis / Q000254:growth & development*; D014871:Water Microbiology