Phytoplankton growth and microzooplankton grazing dynamics across vertical environmental gradients determined by transplant in situ dilution experiments

TitlePhytoplankton growth and microzooplankton grazing dynamics across vertical environmental gradients determined by transplant in situ dilution experiments
Publication TypeJournal Article
Year of Publication2016
AuthorsGutierrez-Rodriguez A., Selph K.E, Landry MR
JournalJournal of Plankton Research
Volume38
Pagination271-289
Date Published2016/03
Type of ArticleArticle
ISBN Number0142-7873
Accession NumberWOS:000372874300008
Keywordscell-size; central equatorial pacific; chlorophyll maxima; community; community structure; Costa Rica Dome; growth and grazing dynamics; light-limitation; physical perturbation; phytoplankton; prochlorococcus ecotypes; protist plankton; rica upwelling dome; structure; sub-arctic pacific; tropical pacific
Abstract

The Costa Rica Dome (CRD) represents a classic case of the bloom-forming capacity of small phytoplankton. Unlike other upwelling systems, autotrophic biomass in the CRD is dominated by picocyanobacteria and small eukaryotes that outcompete larger diatoms and reach extremely high biomass levels. We investigated responses of the subsurface phytoplankton community of the CRD to changes associated with vertical displacement of water masses, coupling in situ transplanted dilution experiments with flow cytometry and epifluorescence microscopy to assess group-specific dynamics. Growth rates of Synechococcus (SYN) and photosynthetic picoeukaryotes (PEUK) were positively correlated with light (R-pearson_SYN = 0.602 and R-pearson_PEUK = 0.588, P<0.001). Growth rates of Prochlorococcus (PRO), likely affected by photoinhibition, were not light correlated (R-pearson_PRO = 0.101, P = 0.601). Overall, grazing and growth rates were closely coupled in all picophytoplankton groups (R-spearman_PRO = 0.572, R-spearman_SYN = 0.588, R-spearman_PEUK = 0.624), and net growth rates remained close to zero. Conversely, the abundance and biomass of larger phytoplankton, mainly diatoms, increased more than 10-fold in shallower transplant incubations indicating that, in addition to trace-metal chemistry, light also plays a significant role in controlling microphytoplankton populations in the CRD.

DOI10.1093/plankt/fbv074
Student Publication: 
No