Microbial food web connections and rates in a subtropical embayment

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 590:19-34 (2018) - DOI: https://doi.org/10.3354/meps12432 Microbial food web connections and rates in a subtropical embayment K. E. Selph1,*, E. Goetze1, M. J. Jungbluth1,3, P. H. Lenz2, G. Kolker1 1Department of Oceanography, University of Hawai‘i at Mānoa, Honolulu, Hawai‘i 96822, USA 2Pacific Biosciences Research Center, University of Hawai‘i at Mānoa, Honolulu, Hawai‘i 96822, USA 3Present address: Romberg Tiburon Center for Environmental Sciences, San Francisco State University, Tiburon, California 94920, USA *Corresponding author: selph@hawaii.edu ABSTRACT: Kāne’ohe Bay, Hawai‘i, USA, an oligotrophic subtropical coastal embayment, is a stable ecosystem dominated by picophytoplankton through most of the year (dry state). After heavy rains, macronutrients from high stream flow result in elevated phytoplankton biomass and change the community to one dominated by diatoms (wet state). However, the effect of this perturbation on the overall productivity of the community, in particular linkages between lower trophic levels and planktonic metazoan consumers, is unknown. Given that microzooplankton are the main intermediaries between phytoplankton and higher trophic levels, this study examined phytoplankton growth and mortality rates using microscopy and flow cytometry, in conjunction with seawater dilution experiments during wet and dry system states. During low stream flow (dry state), Synechococcus dominated the phytoplankton, with growth rates of 1.1 ± 0.4 d-1, and pico- to nano-sized autotrophic eukaryotes were either growing slowly or dying. Growth increased rapidly in experimental bottles with macronutrient (ammonium and phosphorus) addition. Sixty percent of Synechococcus were consumed daily, whereas autotrophic eukaryote mortalities (0.5 d-1) greatly exceeded their growth rates. Microzooplankton were dominated by <30 µm oligotrich ciliates and gymnodinoid dinoflagellates. During the wet state, autotrophic biomass doubled, but microzooplankton biomass increased ~7-fold, including large increases in naupliar and larval stages of metazoans. During wet conditions, the path from primary producers to metazoan consumers had fewer trophic levels and episodically increased the overall productivity of the bay over the dry system state. KEY WORDS: Phytoplankton · Microzooplankton · Grazing rates · Growth rates · Subtropical coastal embayment Full text in pdf format PreviousNextCite this article as: Selph KE, Goetze E, Jungbluth MJ, Lenz PH, Kolker G (2018) Microbial food web connections and rates in a subtropical embayment. Mar Ecol Prog Ser 590:19-34. https://doi.org/10.3354/meps12432 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 590. Online publication date: March 12, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.