Microbial players and processes involved in phytoplankton bloom utilization in the water column of a fast-flowing, river-dominated estuary
Smith, Maria W.
Fortunato, Caroline S.
Crump, Byron C.
Simon, Holly M.
MetadataShow full item record
Fueled by seasonal phytoplankton blooms, the Columbia River estuary is a natural bioreactor for organic matter transformations. Prior metagenome analyses indicated high abundances of diverse Bacteroidetes taxa in estuarine samples containing phytoplankton. To examine the hypothesis that Bacteroidetes taxa have important roles in phytoplankton turnover, we further analyzed metagenomes from water collected along a salinity gradient at 0, 5, 15, 25, and 33 PSU during bloom events. Size fractions were obtained by using a 3-μm prefilter and 0.2-μm collection filter. Although this approach targeted bacteria by removing comparatively large eukaryotic cells, the metagenome from the ES-5 sample (5 PSU) nevertheless contained an abundance of diatom DNA. Biogeochemical measurements and prior studies indicated that this finding resulted from the leakage of cellular material due to freshwater diatom lysis at low salinity. Relative to the other metagenomes, the bacterial fraction of ES-5 was dramatically depleted of genes annotated as Bacteroidetes and lysogenic bacteriophages, but was overrepresented in DNA of protists and Myxococcales bacterivores. We suggest the following equally plausible scenarios for the microbial response to phytoplankton lysis: (1) Bacteroidetes depletion in the free-living fraction may at least in part be caused by their attachment to fluvial diatoms as the latter are lysed upon contact with low-salinity estuarine waters; (2) diatom particle colonization is likely followed by rapid bacterial growth and lytic phage infection, resulting in depletion of lysogenic bacteriophages and host bacteria; and (3) the subsequent availability of labile organic matter attracted both grazers and predators to feed in this estuarine biogeochemical “hotspot,” which may have additionally depleted Bacteroidetes populations. These results represent the first detailed molecular analysis of the microbial response to phytoplankton lysis at the freshwater–brackish water interface in the fast-flowing Columbia River estuary.
© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in MicrobiologyOpen 6 (2017): e467, doi:10.1002/mbo3.467.
The following license files are associated with this item:
Showing items related by title, author, creator and subject.
Insights into the loss factors of phytoplankton blooms : the role of cell mortality in the decline of two inshore Alexandrium blooms Choi, Chang Jae; Brosnahan, Michael L.; Sehein, Taylor R.; Anderson, Donald M.; Erdner, Deana L. (2017-01)While considerable effort has been devoted to understanding the factors regulating the development of phytoplankton blooms, the mechanisms leading to bloom decline and termination have received less attention. Grazing ...
Annual cycles of ecological disturbance and recovery underlying the subarctic Atlantic spring plankton bloom Behrenfeld, Michael J.; Doney, Scott C.; Lima, Ivan D.; Boss, Emmanuel S.; Siegel, David A. (John Wiley & Sons, 2013-06-20)Satellite measurements allow global assessments of phytoplankton concentrations and, from observed temporal changes in biomass, direct access to net biomass accumulation rates (r). For the subarctic Atlantic basin, analysis ...
The influence of sea ice and snow cover and nutrient availability on the formation of massive under-ice phytoplankton blooms in the Chukchi Sea Zhang, Jinlun; Ashjian, Carin J.; Campbell, Robert G.; Spitz, Yvette H.; Steele, Michael; Hill, Victoria (Elsevier, 2015-03-09)A coupled biophysical model is used to examine the impact of changes in sea ice and snow cover and nutrient availability on the formation of massive under-ice phytoplankton blooms (MUPBs) in the Chukchi Sea of the Arctic ...