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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Oxford University Press for personal use, not for redistribution. The definitive version was published in Journal of Plankton Research (2015), doi:10.1093/plankt/fbv081.
    Description: Microzooplankton are the main consumers of marine phytoplankton. Intrinsic traits of phytoplankton can reduce grazing mortality, directly influencing phytoplankton population dynamics, food web ecology, and biogeochemical cycling. We examined the impact of calcification in mediating the functional grazing response of three heterotrophic dinoflagellates, on the coccolithophore, Emilania huxleyi. A variety of parameters, including predator grazing and growth rates, were examined over a 24-48 h period, at 1-5 prey concentrations for five isolates of E. huxleyi that fell along a gradient of calcification states. Significant differences in ingestion and clearance rate were strain-specific, and no apparent trends were observed in relation to calcification. However, predators had, on average, a had a 60% slower growth rate on calcified strains relative to naked strains; furthermore, gross growth efficiency was reduced when ingesting calcified strains. A growth rate model demonstrated a positive feedback from grazing interactions whereby decreased predator growth rate on calcified strains resulted in the accumulation of E. huxleyi. This study highlights the complexity involved in understanding the role of prey phenotype on grazing rates, and emphasizes the importance in considering morphological traits when deciphering predator-prey interactions in the plankton.
    Description: This research was funded by the Gordon and Betty Moore Foundation through Grant GBMF3301 to MDJ and KDB.
    Description: 2016-09-30
    Keywords: Grazing ; Microzooplankton ; Emiliania huxleyi ; Intra-specific variability
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 2
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Protist 167 (2016): 106–120, doi:10.1016/j.protis.2016.01.003.
    Description: Arranging organisms into functional groups aids ecological research by grouping organisms (irrespective of phylogenetic origin) that interact with environmental factors in similar ways. Planktonic protists traditionally have been split between photoautotrophic “phytoplankton” and phagotrophic “microzooplankton”. However, there is a growing recognition of the importance of mixotrophy in euphotic aquatic systems, where many protists often combine photoautotrophic and phagotrophic modes of nutrition. Such organisms do not align with the traditional dichotomy of phytoplankton and microzooplankton. To reflect this understanding, we propose a new functional grouping of planktonic protists in an eco-physiological context: (i) phagoheterotrophs lacking phototrophic capacity, (ii) photoautotrophs lacking phagotrophic capacity, (iii) constitutive mixotrophs (CMs) as phagotrophs with an inherent capacity for phototrophy, and (iv) non-constitutive mixotrophs (NCMs) that acquire their phototrophic capacity by ingesting specific (SNCM) or general non-specific (GNCM) prey. For the first time, we incorporate these functional groups within a foodweb structure and show, using model outputs, that there is scope for significant changes in trophic dynamics depending on the protist functional type description. Accordingly, to better reflect the role of mixotrophy, we recommend that as important tools for explanatory and predictive research, aquatic food-web and biogeochemical models need to redefine the protist groups within their frameworks.
    Description: This work was funded by grants to KJF and AM from the Leverhulme Trust (International Network Grant F00391 V) and NERC (UK) through its iMARNET programme NE/K001345/1.
    Keywords: Plankton functional types (PFTs) ; Phagotroph ; Phototroph ; Mixotroph ; Phytoplankton ; Microzooplankton
    Repository Name: Woods Hole Open Access Server
    Type: Article
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