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Marine Ecology Progress Series

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MEPS 677:17-31 (2021)  -  DOI:

Temporal and spatial variability of phytoplankton and mixotrophs in a temperate estuary

Nicole C. Millette1,2,*, Marcella da Costa2,3, Jordan W. Mora4, Rebecca J. Gast1

1Department of Biology, Woods Hole Oceanographic Institution, 86 Water St, Woods Hole, MA 02543, USA
2Virginia Institute of Marine Science, William & Mary, Gloucester Point, VA 23062, USA
3Department of Biology, Saint Augustine’s University, 1315 Oakwood Ave, Raleigh, NC 27610, USA
4Waquoit Bay National Estuarine Research Reserve, 131 Waquoit Hwy, Waquoit, MA 02536, USA
*Corresponding author:

ABSTRACT: A significant proportion of phototrophic species are known to be mixotrophs: cells that obtain nutrients through a combination of photosynthesis and prey ingestion. Current methods to estimate mixotroph abundance in situ are known to be limited in their ability to help identify conditions that favor mixotrophs over strict autotrophs. For the first time, we combine microscopic analysis of phototrophic taxa with immunoprecipitated bromodeoxyuridine (BrdU)-labeled DNA amplicon sequencing to identify and quantify active and putative mixotrophs at 2 locations in a microtidal temperate estuary. We analyze these data to examine spatial and temporal variability of phytoplankton and mixotrophs. Microscopy-based phototrophic diversity and abundances reveal expected seasonal patterns for our 2 stations, with the start of growth in winter and highest abundances in summer. Diatoms tend to dominate at the site with less stratification, while dinoflagellates and euglenids are usually more prominent at the stratified station. The BrdU-based mixotroph identifications are translated to the microscopy identification and abundances to estimate the proportion of mixotrophs (cells >10 µm in size) at both sites. The average proportion of potential mixotrophs is higher at the station with higher stratification (51%) compared to the station with lower stratification (30%), and potential mixotrophs tend to be higher in summer, although we did not conduct BrdU experiments in any of the other seasons. Combining the identification of active mixotrophs through the uptake of BrdU-labeled bacteria with robust abundance measurements can expand our understanding of mixotrophs across systems.

KEY WORDS: Phytoplankton · Mixotrophs · Estuaries · Chl a

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Cite this article as: Millette NC, da Costa M, Mora JW, Gast RJ (2021) Temporal and spatial variability of phytoplankton and mixotrophs in a temperate estuary. Mar Ecol Prog Ser 677:17-31.

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