title: Unusual behaviour of phototrophic picoplankton in turbid waters.
abstract: Autotrophic picoplankton (APP) abundance and contribution to phytoplankton biomass was studied in Hungarian shallow lakes to test the effect of inorganic turbidity determining the size distribution of the phytoplankton. The studied lakes displayed wide turbidity (TSS: 4-2250 mg l-1) and phytoplankton biomass (chlorophyll a: 1-460 μg l-1) range, as well as APP abundance (0 and 100 million cells ml-1) and contribution (0-100%) to total phytoplankton biomass. Inorganic turbidity had a significant effect on the abundance and contribution of APP, resulting in higher values compared to other freshwater lakes with the same phytoplankton biomass. Our analysis has provided empirical evidence for a switching point (50 mg l-1 inorganic turbidity), above which turbidity is the key factor causing APP predominance regardless of phytoplankton biomass in shallow turbid lakes. Our results have shown that turbid shallow lakes are unique waters, where the formerly and widely accepted model (decreasing APP contribution with increasing phytoplankton biomass) is not applicable. We hypothesize that this unusual behaviour of APP in turbid waters is a result of either diminished underwater light intensity or a reduced grazing pressure due to high inorganic turbidity.
authors.affiliation: Department of Hydrobotany, Balaton Limnological Institute, MTA Centre for Ecological Research, Tihany, Hungary.
authors.forename: Boglárka
authors.identifier: http://orcid.org/0000-0003-0900-3315
authors.initials: B
authors.lastname: Somogyi
authors.affiliation: Department of Hydrobotany, Balaton Limnological Institute, MTA Centre for Ecological Research, Tihany, Hungary.
authors.forename: Károly
authors.initials: K
authors.lastname: Pálffy
authors.affiliation: Department of Hydrobotany, Balaton Limnological Institute, MTA Centre for Ecological Research, Tihany, Hungary.
authors.forename: Katalin
authors.initials: K
authors.lastname: V-Balogh
authors.affiliation: Department of Terrestrial Ecology, Institute of Ecology and Botany, MTA Centre for Ecological Research, Vácrátót, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Botta-Dukát
authors.affiliation: Department of Hydrobotany, Balaton Limnological Institute, MTA Centre for Ecological Research, Tihany, Hungary.
authors.forename: Lajos
authors.initials: L
authors.lastname: Vörös
mesh_terms: D018533:Biomass; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D000458:Cyanobacteria / Q000502:physiology*; D005068:Eutrophication; D006814:Hungary; D007287:Inorganic Chemicals / Q000032:analysis; D060106:Lakes / Q000737:chemistry*; D008954:Models, Biological; D009391:Nephelometry and Turbidimetry; D052817:Phototrophic Processes; D010839:Phytoplankton / Q000502:physiology*
chemical_list: D007287:Inorganic Chemicals; D002734:Chlorophyll; D000077194:Chlorophyll A