@article{DziallasGrossartTangetal.2013,
  author    = {Dziallas, Claudia and Grossart, Hans-Peter and Tang, Kam W. and Nielsen, Torkel Gissel},
  title     = {Distinct Communities of Free-Living and Copepod-Associated Microorganisms along a Salinity Gradient in Godthabsfjord, West Greenland},
  series = {ARCTIC ANTARCTIC AND ALPINE RESEARCH},
  volume    = {45},
  journal   = {ARCTIC ANTARCTIC AND ALPINE RESEARCH},
  number    = {4},
  publisher = {INST ARCTIC ALPINE RES},
  address   = {BOULDER},
  issn      = {1523-0430},
  doi       = {10.1657/1938-4246.45.4.471},
  pages     = {471 -- 480},
  year      = {2013},
  abstract  = {Microorganisms such as Bacteria and Archaea play important roles in the Arctic food web and biogeochemical cycles. Nevertheless, knowledge of microbial community composition in Greenland waters is scarce, and information on microorganisms associated with Arctic zooplankton species is virtually non-existent. We compared free-living microbial communities with those associated with two key copepod species (Calanus finmarchicus and Metridia longa) along a salinity gradient from the deep waters beyond Fyllas Banke to the inner part of Godthabsfjord, West Greenland, in summer 2008. Using genetic fingerprinting we found that free-living Bacteria (in particular Alphaproteobacteria) and Archaea varied with environmental factors and formed different communities along the fjord. Microbial communities associated with the two copepod species were clearly different from those in the ambient water. Surprisingly, Archaea could not be detected on the copepods. Our results show that zooplankton form "microbial islands" in the Arctic pelagic realm with a distinctive community composition and presumably functionality different from the free-living Bacteria. Changes in intensity and timing of meltwater runoff due to global warming are expected to affect these microbial assemblages differently, with potentially significant ramifications for Arctic food webs and biogeochemistry.},
  language  = {en}
}
@article{DziallasGrossart2012,
  author    = {Dziallas, Claudia and Grossart, Hans-Peter},
  title     = {Microbial interactions with the cyanobacterium Microcystis aeruginosa and their dependence on temperature},
  series = {Marine biology : international journal on life in oceans and coastal waters},
  volume    = {159},
  journal   = {Marine biology : international journal on life in oceans and coastal waters},
  number    = {11},
  publisher = {Springer},
  address   = {New York},
  issn      = {0025-3162},
  doi       = {10.1007/s00227-012-1927-4},
  pages     = {2389 -- 2398},
  year      = {2012},
  abstract  = {Associated heterotrophic bacteria alter the microenvironment of cyanobacteria and potentially influence cyanobacterial development. Therefore, we studied interactions of the unicellular freshwater cyanobacterium Microcystis aeruginosa with heterotrophic bacteria. The associated bacterial community was greatly driven by temperature as seen by DNA fingerprinting. However, the associated microbes also closely interacted with the cyanobacteria indicating changing ecological consequence of the associated bacterial community with temperature. Whereas concentration of dissolved organic carbon in cyanobacterial cultures changed in a temperature-dependent manner, its quality greatly varied under the same environmental conditions, but with different associated bacterial communities. Furthermore, temperature affected quantity and quality of cell-bound microcystins, whereby interactions between M. aeruginosa and their associated community often masked this temperature effect. Both macro- and microenvironment of active cyanobacterial strains were characterized by high pH and oxygen values creating a unique habitat that potentially affects microbial diversity and function. For example, archaea including 'anaerobic' methanogens contributed to the associated microbial community. This implies so far uncharacterized interactions between Microcystis aeruginosa and its associated prokaryotic community, which has unknown ecological consequences in a climatically changing world.},
  language  = {en}
}
@article{GrossartFrindteDziallasetal.2011,
  author    = {Grossart, Hans-Peter and Frindte, Katharina and Dziallas, Claudia and Eckert, Werner and Tang, Kam W.},
  title     = {Microbial methane production in oxygenated water column of an oligotrophic lake},
  series = {Proceedings of the National Academy of Sciences of the United States of America},
  volume    = {108},
  journal   = {Proceedings of the National Academy of Sciences of the United States of America},
  number    = {49},
  publisher = {National Acad. of Sciences},
  address   = {Washington},
  issn      = {0027-8424},
  doi       = {10.1073/pnas.1110716108},
  pages     = {19657 -- 19661},
  year      = {2011},
  abstract  = {The prevailing paradigm in aquatic science is that microbial methanogenesis happens primarily in anoxic environments. Here, we used multiple complementary approaches to show that microbial methane production could and did occur in the well-oxygenated water column of an oligotrophic lake (Lake Stechlin, Germany). Oversaturation of methane was repeatedly recorded in the well-oxygenated upper 10 m of the water column, and the methane maxima coincided with oxygen oversaturation at 6 m. Laboratory incubations of unamended epilimnetic lake water and inoculations of photoautotrophs with a lake-enrichment culture both led to methane production even in the presence of oxygen, and the production was not affected by the addition of inorganic phosphate or methylated compounds. Methane production was also detected by in-lake incubations of lake water, and the highest production rate was 1.8-2.4 nM.h(-1) at 6 m, which could explain 33-44\% of the observed ambient methane accumulation in the same month. Temporal and spatial uncoupling between methanogenesis and methanotrophy was supported by field and laboratory measurements, which also helped explain the oversaturation of methane in the upper water column. Potentially methanogenic Archaea were detected in situ in the oxygenated, methane-rich epilimnion, and their attachment to photoautotrophs might allow for anaerobic growth and direct transfer of substrates for methane production. Specific PCR on mRNA of the methyl coenzyme M reductase A gene revealed active methanogenesis. Microbial methane production in oxygenated water represents a hitherto overlooked source of methane and can be important for carbon cycling in the aquatic environments and water to air methane flux.},
  language  = {en}
}