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Summary Interactions between bacteria and phytoplankton in the phycosphere have impacts at the scale of whole ecosystems, including the development of harmful algal blooms. The cyanobacteriumMicrocystiscauses toxic blooms that threaten freshwater ecosystems and human health globally.Microcystisgrows in colonies that harbour dense assemblages of other bacteria, yet the taxonomic composition of these phycosphere communities and the nature of their interactions withMicrocystisare not well characterized. To identify the taxa and compositional variance withinMicrocystisphycosphere communities, we performed 16S rRNA V4 region amplicon sequencing on individualMicrocystiscolonies collected biweekly via high‐throughput droplet encapsulation during a western Lake Erie cyanobacterial bloom. TheMicrocystisphycosphere communities were distinct from microbial communities in whole water and bulk phytoplankton seston in western Lake Erie but lacked ‘core’ taxa found across all colonies. However, dissimilarity in phycosphere community composition correlated with sampling date and theMicrocystis16S rRNA oligotype. Several taxa in the phycosphere were specific to and conserved withMicrocystisof a single oligotype or sampling date. Together, this suggests that physiological differences betweenMicrocystisstrains, temporal changes in strain phenotypes, and the composition of seeding communities may impact community composition of theMicrocystisphycosphere.
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Sulfolipid substitution ratios of Microcystis aeruginosa and planktonic communities as an indicator of phosphorus limitation in Lake Erie
Abstract Phosphorus (P) availability frequently limits primary production in lakes, influences the physiology of phytoplankton, shapes community structure, and can stimulate or constrain the formation of cyanobacterial blooms. Given the importance of P, numerous methods are available to assess P stress in phytoplankton communities. Marine phytoplankton are known to substitute sulfolipids for phospholipids in response to P limitation. We asked whether sulfolipid substitution might serve as an additional indicator of P stress in freshwater phytoplankton communities. The question was addressed using cultures ofMicrocystis aeruginosa, Lake Erie microcosms, and surveys of lipid profiles in Lake Erie during aMicrocystisspp. bloom. Peak area response ratios of the intact polar lipids sulfoquinovosyldiacylglycerol (SQDG) to phosphatidylglycerol (PG) were used as the metric of lipid substitution. In cultures ofM. aeruginosaNIES‐843, the SQDG : PG ratio increased from ~ 0.9 to ~ 3.3 with decreasing P concentration. In P‐limited communities, the SQDG : PG ratio increased from ~ 6 to ~ 11 after 48 h in microcosm controls, while P amendments reduced the ratio to ~ 3. In Lake Erie surveys, the SQDG : PG ratio ranged from ~ 0.4 to ~ 7.4 and was negatively correlated (Pearsonr = −0.62) with total dissolved P. The SQDG : PG ratio was not correlated with concentrations of chlorophylla, soluble reactive P, or N : P molar ratios. These results demonstrated thatM. aeruginosaandMicrocystis‐dominated communities remodel lipid profiles in response to P scarcity, providing a potential short‐term, time‐integrated biomarker of nutrient history and P stress in fresh waters.
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- Award ID(s):
- 1840715
- PAR ID:
- 10401852
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Limnology and Oceanography
- Volume:
- 68
- Issue:
- 5
- ISSN:
- 0024-3590
- Page Range / eLocation ID:
- p. 1117-1131
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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