Biomass and composition of protistan grazers and heterotrophic bacteria in the Costa Rica Dome during summer 2010

TitleBiomass and composition of protistan grazers and heterotrophic bacteria in the Costa Rica Dome during summer 2010
Publication TypeJournal Article
Year of Publication2016
AuthorsFreibott A., Taylor A.G, Selph K.E, Liu H.B, Zhang W.C, Landry MR
JournalJournal of Plankton Research
Date Published2016/03
Type of ArticleArticle
ISBN Number0142-7873
Accession NumberWOS:000372874300005
Keywordscoastal waters; community; composition; eastern tropical pacific; equatorial pacific; food-web; heterotrophic protists; marine systems; Microzooplankton; nanozooplankton; northern baja-california; phytoplankton growth; temporal dynamics; upwelling dome

We investigated biomass and composition of heterotrophic microbes in the Costa Rica Dome during June-July 2010 as part of a broader study of plankton trophic dynamics. Because picophytoplankton (, 2 mm) are known to dominate in this unique upwelling region, we hypothesized tight biomass relationships between size-determined predator-prey pairs (i.e. picoplankton-nano-grazers, nanoplankton-micro-grazers) within the microbial community. Integrated biomass of heterotrophic bacteria ranged from 180 to 487 mg C m(-2) and was significantly correlated with total autotrophic carbon. Heterotrophic protist (H-protist) biomass ranged more narrowly from 488 to 545 mg C m(-2), and was comprised of 60% dinoflagellates, 30% other flagellates and 11% ciliates. Nano-sized (<20 mu m) protists accounted for the majority (57%) of grazer biomass and were positively correlated with picoplankton, partially supporting our hypothesis, but nanoplankton and micro-grazers (>20 mu m) were not significantly correlated. The relative constancy of H-protist biomass among locations despite clear changes in integrated autotrophic biomass, Chl a, and primary production suggests that mesozooplankton may exert a tight top-down control on micro-grazers. Biomass-specific consumption rates of phytoplankton by protistan grazers suggest an instantaneous growth rate of 0.52 day(-1) for H-protists, similar to the growth rate of phytoplankton and consistent with a trophically balanced ecosystem dominated by piconanoplankton interactions.

Student Publication: