Antarctic mixotrophic protist abundances by microscopy and molecular methods

Gast, Rebecca J.; McKie‐Krisberg, Zaid; Fay, Scott A.; Rose, Julie M.; Sanders, Robert W.

doi:10.1111/1574-6941.12334

Cited by 34 publications

(42 citation statements)

References 42 publications

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“…Italicized stations were sites of sampling for BrdU experiments. *Previously reported in Gast et al (2014).…”

Section: Ingestion Experimentsmentioning

confidence: 90%

“…Filters were later extracted in 90% acetone overnight at −20 • C and fluorescence was determined with a Model TD-700 fluorometer (Turner Designs, Sunnyvale, CA, USA). Nutrient data (soluble reactive phosphate, nitrate, nitrate + nitrite, ammonia, silicate) from these stations is available in the Supplementary Material of Gast et al (2014). In addition to water samples, we collected ice cores from land-fast ice (77 • 43.70 S, 166 • 08.50 E) with a motorized Sipre corer.…”

Section: Sample Collectionmentioning

confidence: 99%

“…Yet the ability to identify which species are mixotrophic is important in understanding their behavior and ecological roles. Phagotrophic phytoplankton species from culture collections have been valuable for determining the variable triggers of feeding, as well as grazing rates and overall impact on bacterial standing stocks (Rothhaupt, 1996;Gast et al, 2014;Johnson, 2015). However, we still miss much of the mixotroph species diversity in field surveys, which is important because feeding by different species may be stimulated by different mechanisms or resource limitations (Maranger et al, 1998;Wilken et al, 2014;Princiotta et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…However, we still miss much of the mixotroph species diversity in field surveys, which is important because feeding by different species may be stimulated by different mechanisms or resource limitations (Maranger et al, 1998;Wilken et al, 2014;Princiotta et al, 2016). Using molecular methods, we recently showed that three known Antarctic mixotroph species usually comprised only a small portion of the total mixotrophic nanoflagellate assemblage identified by tracer methods (Gast et al, 2014), indicating that there are likely a large number of unidentified species present or that the cultured species are not generally abundant in the environment.…”

Section: Introductionmentioning

confidence: 99%

“…First, to assess polar seasonal and regional differences in mixotroph abundance and activity we compared previously reported ingestion results on the impacts of bacterivory, including mixotrophy, during the austral summer in the Ross Sea (Gast et al, 2014) with data from the Ross Sea in austral spring (Moorthi et al, 2009) and from the Arctic in the fall (Sanders and Gast, 2012). Second, we used incubation experiments with bromodeoxyuridine (BrdU) labeled bacteria as food and the subsequent immunoprecipitation of BrdU-labeled DNA followed by amplification of the eukaryotic portion of the labeled DNA and high throughput sequencing.…”

Section: Introductionmentioning

confidence: 99%

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Mixotrophic Activity and Diversity of Antarctic Marine Protists in Austral Summer

2018

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Identifying putative mixotrophic protist species in the environment is important for understanding their behavior, with the recovery of these species in culture essential for determining the triggers of feeding, grazing rates, and overall impact on bacterial standing stocks. In this project, mixotroph abundances determined using tracer ingestion in water and sea ice samples collected in the Ross Sea, Antarctica during the summer of 2011 were compared with data from the spring (Ross Sea) and fall (Arctic) to examine the impacts of bacterivory/mixotrophy. Mixotrophic nanoplankton (MNAN) were usually less abundant than heterotrophs, but consumed more of the bacterial standing stock per day due to relatively higher ingestion rates (1-7 bacteria mixotroph −1 h −1 vs. 0.1-4 bacteria heterotroph −1 h −1 ). Yet, even with these high rates observed in the Antarctic summer, mixotrophs appeared to have a smaller contribution to bacterivory than in the Antarctic spring. Additionally, putative mixotroph taxa were identified through incubation experiments accomplished with bromodeoxyuridine-labeled bacteria as food, immunoprecipitation (IP) of labeled DNA, and amplification and high throughput sequencing of the eukaryotic ribosomal V9 region. Putative mixotroph OTUs were identified in the IP samples by taxonomic similarity to known phototroph taxa. OTUs that had increased abundance in IP samples compared to the non-IP samples from both surface and chlorophyll maximum (CM) depths were considered to represent active mixotrophy and include ones taxonomically similar to Dictyocha, Gymnodinium, Pentapharsodinium, and Symbiodinium. These OTUs represent target taxa for isolation and laboratory experiments on triggers for mixotrophy, to be combined with qPCR to estimate their abundance, seasonal distribution and potential impact.

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“…Italicized stations were sites of sampling for BrdU experiments. *Previously reported in Gast et al (2014).…”

Section: Ingestion Experimentsmentioning

confidence: 90%

Section: Sample Collectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Mixotrophic Activity and Diversity of Antarctic Marine Protists in Austral Summer

2018

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Diversity and spatial distribution of autotrophic communities within and between ice‐covered Antarctic lakes (McMurdo Dry Valleys)

Dolhi

Teufel

Kong

et al. 2015

Limnology & Oceanography

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We compared the spatial distribution and diversity of autotrophic microbial communities among four permanently ice-covered, chemically stratified lakes located in the Taylor (Lakes Bonney-east and west lobes, Fryxell), and Wright (Lake Vanda) Valleys of the McMurdo Dry Valleys (Victoria Land, Antarctica). Clone libraries were constructed for major carbon fixation genes (rbcL isoforms IA/B and ID; cbbM; nifJ). Real time quantitative polymerase chain reaction assays were also developed for each of these markers of autotrophy to assess the influence of lake physicochemical factors on spatial trends in major photosynthetic and chemolithoautotrophic groups. Both lobes of Lake Bonney were dominated by Ribulose-1, 5-bisphosphate carboxylase oxygenase (RubisCO) form ID rbcL (haptophytes and stramenopiles), while Lake Fryxell was dominated by rbcL form ID-harboring cryptophytes. Lake Vanda was the least productive lake and was dominated by form IA/B rbcL (cyanobacteria and chlorophytes) and form ID rbcL (stramenopiles). Autotrophic carbon fixation genes from photosynthetic organisms were generally positively correlated with light availability. Chemolithoautotrophic organisms harboring form II RubisCO were detected in only two of the four lakes (west lobe Lake Bonney and Fryxell) and were associated with the presence of either sulfide (Fryxell) or dimethylated sulfur compounds (west lobe Lake Bonney).

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Heterotrophic and mixotrophic nanoflagellates in a mesotrophic lake: Abundance and grazing impacts across season and depth

Princiotta

Sanders

2016

Limnology & Oceanography

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Nanoflagellates are recognized as fundamental members of the planktonic microbial food web due to their contribution to photosynthetic fixation of carbon and phagotrophic ingestion of bacteria. Although the presence, and often dominance, of mixotrophic nutrition among phytoflagellates has been well documented within a variety of aquatic ecosystems and in a range of taxa, few studies have assessed the abundance and grazing impact of mixotrophs in comparison to their photosynthetic and heterotrophic counterparts across seasons at multiple depths. Abundance and, as appropriate, bacterivory of phototrophic, heterotrophic, and mixotrophic nanoflagellates were quantified at three depths over a 15‐month period in Lake Lacawac (Pocono Mountains, Pennsylvania, U.S.A.) via microscopic analysis of ingested bacterial surrogates. The absolute and relative abundances of all nanoflagellate trophic groups varied with season and depth, likely as a result of differences in physiological tolerance. Whereas the abundance of phototrophic and heterotrophic nanoflagellates varied with depth in both the presence and absence of thermal stratification, mixotrophic protists were evenly distributed throughout the water column during mixis. The abundances of phototrophic and mixotrophic protists were significantly correlated, but only in surface waters during periods of thermal stratification. Grazing rate and consequent impact by bacterivorous nanoflagellates varied with depth across season, particularly during thermal stratification. Mixotrophic bacterivory exceeded that of heterotrophs in the epi‐ and metalimnion during stratification, removing an estimated maximum of 80% of the bacterial standing stock d−1. The relative contribution of heterotrophic nanoflagellates to community bacterivory increased with depth, even during mixis, and dominated the grazing impact in the hypolimnion.

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Antarctic mixotrophic protist abundances by microscopy and molecular methods

Cited by 34 publications

References 42 publications

Mixotrophic Activity and Diversity of Antarctic Marine Protists in Austral Summer

Mixotrophic Activity and Diversity of Antarctic Marine Protists in Austral Summer

Diversity and spatial distribution of autotrophic communities within and between ice‐covered Antarctic lakes (McMurdo Dry Valleys)

Heterotrophic and mixotrophic nanoflagellates in a mesotrophic lake: Abundance and grazing impacts across season and depth

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