title: Seasonal patterns of the bacterioplankton community composition in a lake threatened by a pesticide disposal site.
abstract: BACKGROUND AIM AND SCOPE: The objective of the study was to determine the effects of ca. 35 years of pesticide contamination (pesticide dump-PD) of Lake Szeląg Wielki (located in the north-eastern Poland) on changes in the microbial communities of aquatic ecosystems. In the years 2008-2009, analyses were carried out for seasonal changes in the quantity and composition of bacterioplankton in the lake examined, which is of high significance to the tourism and fishing industries and is located in the vicinity of an area subjected to reclamation after a pesticide dump.
  
  
  METHODS
  Bacterioplankton composition was assayed by fluorescence in situ hybridisation technique for the contribution of major groups of the Bacteria domain: ά-, β- and γ-Proteobacteria, Cytophaga-Flavobacterium and Actinobacteria as well as bacteria capable of degrading pesticides in an aquatic environment-Pseudomonas spp. Seasonal patterns of the total number of bacteria were determined by direct counting of 4',6-diamidino-2-phenylindole (DAPI)-stained cells.
  
  
  RESULTS
  The percentage of the detected Eubacteria (EUB 338 probe) relative to all the DAPI-stained bacteria in Lake Szeląg Wielki ranged from 46% to 63%. Bacteria capable of degrading pesticides in an aquatic environment-Pseudomonas spp.-were identified with a highly specific probe PEA 998. The highest mean values of this parameter reached 5.1%. In the spring, Pseudomonas spp. bacteria accounted for up to 80% of all Gamma-Proteobacteria microbes.
  
  
  CONCLUSIONS
  The study showed that the qualitative and quantitative changes in the bacterioplankton of the lake can be characterised by tendencies which are typical of a eutrophic water reservoir. However, a higher contribution of microorganisms capable of degrading sparingly degradable, toxic compounds and pesticides was determined in bacterioplankton from the PD-contaminated lake, as compared to microbial communities of a lake not contaminated with pesticides.
authors.affiliation: Department of Microbiology, Faculty of Biology, University of Warmia and Mazury, Oczapowskiego St. 1a, 10-717, Olsztyn, Poland. sylwia.lew@uwm.edu.pl
authors.forename: Sylwia
authors.initials: S
authors.lastname: Lew
authors.forename: Marcin
authors.initials: M
authors.lastname: Lew
authors.forename: Józef
authors.initials: J
authors.lastname: Szarek
authors.forename: Izabella
authors.initials: I
authors.lastname: Babińska
mesh_terms: D039903:Actinobacteria / Q000145:classification / Q000254:growth & development; D001419:Bacteria / Q000145:classification* / Q000187:drug effects / Q000254:growth & development; D001673:Biodegradation, Environmental; D044822:Biodiversity; D015169:Colony Count, Microbial; D003589:Cytophaga / Q000145:classification / Q000254:growth & development; D017753:Ecosystem; D004784:Environmental Monitoring; D005417:Flavobacterium / Q000145:classification / Q000254:growth & development; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology*; D010575:Pesticides / Q000032:analysis / Q000633:toxicity*; D010933:Plankton / Q000145:classification* / Q000187:drug effects / Q000254:growth & development; D011044:Poland; D020560:Proteobacteria / Q000145:classification / Q000254:growth & development; D012037:Refuse Disposal; D012621:Seasons; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data
chemical_list: D010575:Pesticides; D014874:Water Pollutants, Chemical