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Decima, M, Landry MR, Stukel MR, Lopez-Lopez L, Krause JW.  2016.  Mesozooplankton biomass and grazing in the Costa Rica Dome: amplifying variability through the plankton food web. Journal of Plankton Research. 38:317-330.   10.1093/plankt/fbv091   AbstractWebsite

We investigated standing stocks and grazing rates of mesozooplankton assemblages in the Costa Rica Dome (CRD), an open-ocean upwelling ecosystem in the eastern tropical Pacific. While phytoplankton biomass in the CRD is dominated by picophytoplankton (<2-mu m cells) with especially high concentrations of Synechococcus spp., we found high mesozooplankton biomass (similar to 5 g dry weight m(-2)) and grazing impact (12-50% integrated water column chlorophyll a), indicative of efficient food web transfer from primary producers to higher levels. In contrast to the relative uniformity in water-column chlorophyll a and mesozooplankton biomass, variability in herbivory was substantial, with lower rates in the central dome region and higher rates in areas offset from the dome center. While grazing rates were unrelated to total phytoplankton, correlations with cyanobacteria (negative) and biogenic SiO2 production (positive) suggest that partitioning of primary production among phytoplankton sizes contributes to the variability observed in mesozooplankton metrics. We propose that advection of upwelled waters away from the dome center is accompanied by changes in mesozooplankton composition and grazing rates, reflecting small changes within the primary producers. Small changes within the phytoplankton community resulting in large changes in the mesozooplankton suggest that the variability in lower trophic level dynamics was effectively amplified through the food web.

Le Borgne, R, Landry MR.  2003.  EBENE: A JGOFS investigation of plankton variability and trophic interactions in the equatorial Pacific (180 degrees). Journal of Geophysical Research-Oceans. 108   10.1029/2001jc001252   AbstractWebsite

[1] The Etude du Broutage en Zone Equatoriale (EBENE) transect (8 degreesS - 8 degreesN) explored the equatorial high-nutrient, low-chlorophyll (HNLC) zone and adjacent oligotrophic areas during a La Nina period (October - November 1996). During this time the passage of a tropical instability wave also influenced the region north of the equator. We present a brief summary of EBENE findings, with an emphasis on phytoplankton utilization by the assemblage of protistan and animal consumers. Despite significant variability over the diel cycle, phytoplankton biomass at the equator was relatively constant on a 24-hour timescale, denoting a dynamic balance between growth and losses. The magnitude of the daily cycle in phytoplankton biomass was well constrained by in situ observations of the diel variability in pigments and suspended particulates, by (14)C uptake rates from in situ incubations, and from experimental determinations of specific growth and grazing rates. The general equilibrium of production and grazing processes is illustrated by applying biomass-specific grazing rates from the equatorial station to measured planktonic biomass along the EBENE transect and comparing them to measured (14)C uptake. Most of the grazing turnover is supported by the production of Prochloroccus (31%) and picoeukaryotic algae (34%). Among the consumers, microzooplankton (< 200 mu m) account for 59 - 98% of the grazing losses. The coherence of the results obtained by independent methods suggests that the essential features of the system have been adequately represented by rate and standing stock assessments from the EBENE study.