Environmental controls upon picophytoplankton growth and biomass in a eutrophic estuary

Abstract

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 63:133-143 (2011) - DOI: https://doi.org/10.3354/ame01488 Environmental controls upon picophytoplankton growth and biomass in a eutrophic estuary Michael S. Wetz1,*, Hans W. Paerl2, J. Christopher Taylor3, Jeremy A. Leonard2 1Texas A&M University—Corpus Christi, Department of Life Sciences, Corpus Christi, Texas 78412, USA 2Institute of Marine Sciences, The University of North Carolina—Chapel Hill, Morehead City, North Carolina 28557, USA 3NOAA Ocean Service, Center for Coastal Fisheries and Habitat Research, Beaufort, North Carolina 28516, USA *Email: [e-mail] ABSTRACT: We assessed the role of top-down versus bottom-up factors in regulating picophytoplankton (PicoP) growth and overall phytoplankton size structure in a eutrophic estuary. PicoP biomass reached an annual maximum in summer/fall and was positively correlated with temperature. Ephemeral blooms (chlorophyll a > 20 µg l–1) of PicoP were observed in the upper and middle regions of the estuary despite inorganic nitrogen concentrations <1 µmol l–1. Nutrient-amended PicoP growth rates were similar to in situ growth rates in the upper estuary, and PicoP biomass was negatively correlated with river-derived inorganic nitrogen concentrations, indicating that regenerated nutrients are a major source of nitrogen supporting PicoP growth. Microzooplankton grazing rates routinely exceeded PicoP growth rates during summer; therefore, grazing must have become uncoupled from PicoP growth on timescales shorter than the interval between grazing experiments (i.e. 2 to 4 wk) for PicoP to have bloomed. Field data point to the possibility of trophic cascades involving copepods, protistan grazers, and phytoplankton as a mechanism for this growth–grazing uncoupling. These and other recent findings indicate that bottom-up factors alone cannot explain the PicoP blooms observed in some estuarine systems and emphasize the need for grazing control studies to better understand the regulation of primary production. KEY WORDS: Picophytoplankton · Estuary · Microzooplankton · Mesozooplankton · Trophic ­cascade · Nutrients Full text in pdf format PreviousNextCite this article as: Wetz MS, Paerl HW, Taylor JC, Leonard JA (2011) Environmental controls upon picophytoplankton growth and biomass in a eutrophic estuary. Aquat Microb Ecol 63:133-143. https://doi.org/10.3354/ame01488 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 63, No. 2. Online publication date: March 31, 2011 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2011 Inter-Research.