title: Does turbidity induced by Carassius carassius limit phytoplankton growth? A mesocosm study.
abstract: It is well established that benthivorous fish in shallow lakes can create turbid conditions that influence phytoplankton growth both positively, as a result of elevated nutrient concentration in the water column, and negatively, due to increased attenuation of light. The net effect depends upon the degree of turbidity induced by the benthivores. Stocked Carassius carassius dominate the benthivorous fish fauna in many nutrient-rich Chinese subtropical and tropical shallow lakes, but the role of the species as a potential limiting factor in phytoplankton growth is ambiguous. Clarification of this relationship will help determine the management strategy and cost of restoring eutrophic lakes in China and elsewhere. Our outdoor mesocosm experiment simulating the effect of high density of crucian carp on phytoplankton growth and community structure in eutrophic shallow lakes suggests that stocking with this species causes resuspension of sediment, thereby increasing light attenuation and elevating nutrient concentrations. However, the effect of light attenuation was insufficient to offset the impact of nutrient enhancement on phytoplankton growth, and significant increases in both phytoplankton biomass and chlorophyll a concentrations were recorded. Crucian carp stocking favored the dominance of diatoms and led to lower percentages (but not biomass) of buoyant cyanobacteria. The dominance of diatoms may be attributed to a competitive advantage of algal cells with high sedimentation velocity in an environment subjected to frequent crucian carp-induced resuspension and entrainment of benthic algae caused by the fish foraging activities. Our study demonstrates that turbidity induced by stocked crucian carp does not limit phytoplankton growth in eutrophic waters. Thus, removal of this species (and presumably other similar taxa) from subtropical or tropical shallow lakes, or suspension of aquaculture, is unlikely to boost phytoplankton growth, despite the resulting improvements in light availability.
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing, 210008, China. hehu@niglas.ac.cn.
authors.forename: Hu
authors.initials: H
authors.lastname: He
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing, 210008, China.
authors.forename: En
authors.initials: E
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing, 210008, China.
authors.forename: Jinlei
authors.initials: J
authors.lastname: Yu
authors.affiliation: College of Animal Science, Inner Mongolia Agricultural University, Hohhot, 010018, China.
authors.forename: Xuguang
authors.initials: X
authors.lastname: Luo
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing, 210008, China.
authors.forename: Kuanyi
authors.initials: K
authors.lastname: Li
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing, 210008, China.|Department of Bioscience, Aarhus University, Aarhus, Denmark.|Sino-Danish Centre for Education and Research, Beijing, 100049, China.
authors.forename: Erik
authors.initials: E
authors.lastname: Jeppesen
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing, 210008, China.|Sino-Danish Centre for Education and Research, Beijing, 100049, China.|Department of Ecology and Institute of Hydrobiology, Jinan University, Guangzhou, 510632, China.
authors.forename: Zhengwen
authors.initials: Z
authors.lastname: Liu
mesh_terms: D000818:Animals; D018533:Biomass; D002347:Carps; D002681:China; D002734:Chlorophyll / Q000031:analogs & derivatives; D000077194:Chlorophyll A; D000458:Cyanobacteria; D017377:Diatoms; D005068:Eutrophication; D019015:Geologic Sediments; D060106:Lakes; D008027:Light; D010758:Phosphorus / Q000032:analysis; D010839:Phytoplankton / Q000254:growth & development*; D014867:Water
chemical_list: D014867:Water; D002734:Chlorophyll; C085815:chlorophyll a'; D010758:Phosphorus; D000077194:Chlorophyll A
keywords: China; Crucian carp; Nutrients; Phytoplankton community; Resuspension; Shallow lakes; Suspended solids