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  • Phytoplankton  (5)
  • Elsevier  (5)
  • American Geophysical Union (AGU)
  • Annual Reviews
  • 2020-2023  (1)
  • 2015-2019  (4)
  • 2000-2004
  • 1980-1984
  • 1935-1939
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  • 2020-2023  (1)
  • 2015-2019  (4)
  • 2000-2004
  • 1980-1984
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  • 1
    Publication Date: 2022-05-25
    Description: © The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Remote Sensing of Environment 135 (2013): 77-91, doi:10.1016/j.rse.2013.03.025.
    Description: Photosynthetic production of organic matter by microscopic oceanic phytoplankton fuels ocean ecosystems and contributes roughly half of the Earth's net primary production. For 13 years, the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) mission provided the first consistent, synoptic observations of global ocean ecosystems. Changes in the surface chlorophyll concentration, the primary biological property retrieved from SeaWiFS, have traditionally been used as a metric for phytoplankton abundance and its distribution largely reflects patterns in vertical nutrient transport. On regional to global scales, chlorophyll concentrations covary with sea surface temperature (SST) because SST changes reflect light and nutrient conditions. However, the ocean may be too complex to be well characterized using a single index such as the chlorophyll concentration. A semi-analytical bio-optical algorithm is used to help interpret regional to global SeaWiFS chlorophyll observations from using three independent, well-validated ocean color data products; the chlorophyll a concentration, absorption by CDM and particulate backscattering. First, we show that observed long-term, global-scale trends in standard chlorophyll retrievals are likely compromised by coincident changes in CDM. Second, we partition the chlorophyll signal into a component due to phytoplankton biomass changes and a component caused by physiological adjustments in intracellular chlorophyll concentrations to changes in mixed layer light levels. We show that biomass changes dominate chlorophyll signals for the high latitude seas and where persistent vertical upwelling is known to occur, while physiological processes dominate chlorophyll variability over much of the tropical and subtropical oceans. The SeaWiFS data set demonstrates complexity in the interpretation of changes in regional to global phytoplankton distributions and illustrates limitations for the assessment of phytoplankton dynamics using chlorophyll retrievals alone.
    Description: The authors would like to acknowledge the NASA Ocean Biology and Biogeochemistry program for its long-term support of satellite ocean color research and the Orbital Sciences Corporation and GeoEye who were responsible for the launch, satellite integration and on-orbit management the SeaWiFS mission.
    Keywords: Ocean color ; SeaWiFS ; Phytoplankton ; Colored dissolved organic matter ; Decadal trends
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 118 (2015): 122-135, doi:10.1016/j.dsr2.2015.02.008.
    Description: A coupled biophysical model is used to examine the impact of changes in sea ice and snow cover and nutrient availability on the formation of massive under-ice phytoplankton blooms (MUPBs) in the Chukchi Sea of the Arctic Ocean over the period 1988–2013. The model is able to reproduce the basic features of the ICESCAPE (Impacts of Climate on EcoSystems and Chemistry of the Arctic Pacific Environment) observed MUPB during July 2011. The simulated MUPBs occur every year during 1988–2013, mainly in between mid-June and mid-July. While the simulated under-ice blooms of moderate magnitude are widespread in the Chukchi Sea, MUPBs are less so. On average, the area fraction of MUPBs in the ice-covered areas of the Chukchi Sea during June and July is about 8%, which has been increasing at a rate of 2% yr–1 over 1988–2013. The simulated increase in the area fraction as well as primary productivity and chlorophyll a biomass is linked to an increase in light availability, in response to a decrease in sea ice and snow cover, and an increase in nutrient availability in the upper 100 m of the ocean, in conjunction with an intensification of ocean circulation. Simulated MUPBs are temporally sporadic and spatially patchy because of strong spatiotemporal variations of light and nutrient availability. However, as observed during ICESCAPE, there is a high likelihood that MUPBs may form at the shelf break, where the model simulates enhanced nutrient concentration that is seldom depleted between mid-June and mid-July because of generally robust shelf-break upwelling and other dynamic ocean processes. The occurrence of MUPBs at the shelf break is more frequent in the past decade than in the earlier period because of elevated light availability there. It may be even more frequent in the future if the sea ice and snow cover continues to decline such that light is more available at the shelf break to further boost the formation of MUPBs there.
    Description: This work is supported by the NASA Cryosphere Program and Climate and Biological Response Program and the NSF Office of Polar Programs (Grant Nos. NNX12AB31G; NNX11AO91G; ARC-0901987).
    Keywords: Arctic Ocean ; Chukchi Sea ; Phytoplankton ; Blooms ; Sea ice ; Snow depth ; Light availability ; Nutrient availability
    Repository Name: Woods Hole Open Access Server
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  • 3
    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Remote Sensing of Environment 217 (2018): 126-143, doi:10.1016/j.rse.2018.08.010.
    Description: Diatoms dominate global silica production and export production in the ocean; they form the base of productive food webs and fisheries. Thus, a remote sensing algorithm to identify diatoms has great potential to describe ecological and biogeochemical trends and fluctuations in the surface ocean. Despite the importance of detecting diatoms from remote sensing and the demand for reliable methods of diatom identification, there has not been a systematic evaluation of algorithms that are being applied to this end. The efficacy of these models remains difficult to constrain in part due to limited datasets for validation. In this study, we test a bio-optical algorithm developed by Sathyendranath et al. (2004) to identify diatom dominance from the relationship between ratios of remote sensing reflectance and chlorophyll concentration. We evaluate and refine the original model with data collected at the Martha's Vineyard Coastal Observatory (MVCO), a near-shore location on the New England shelf. We then validated the refined model with data collected in Harpswell Sound, Maine, a site with greater optical complexity than MVCO. At both sites, despite relatively large changes in diatom fraction (0.8–82% of chlorophyll concentration), the magnitude of variability in optical properties due to the dominance or non-dominance of diatoms is less than the variability induced by other absorbing and scattering constituents of the water. While the original model performance was improved through successive re-parameterizations and re-formulations of the absorption and backscattering coefficients, we show that even a model originally parameterized for the Northwest Atlantic and re-parameterized for sites such as MVCO and Harpswell Sound performs poorly in discriminating diatom-dominance from optical properties.
    Description: This work was supported by: a Woods Hole Oceanographic Institution Summer Student Fellowship (NSF REU award #1156952) and a Bowdoin College Grua/O'Connell Research Award to SJK; grants to HMS from NASA (Ocean Biology and Biogeochemistry program and Biodiversity and Ecological Forecasting program), NSF (Ocean Sciences), the Gordon and Betty Moore Foundation, the Simons Foundation, and NOAA through the Cooperative Institute for the North Atlantic Region (CINAR) under Cooperative Agreement NA14OAR4320158; and grants to CSR from NASA (Ocean Biology and Biogeochemistry program).
    Keywords: Phytoplankton ; Community structure ; Ocean color ; Diatoms
    Repository Name: Woods Hole Open Access Server
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  • 4
    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
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  • 5
    Publication Date: 2022-05-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lowenstein, D. P., Mayers, K., Fredricks, H. F., & Van Mooy, B. A. S. Targeted and untargeted lipidomic analysis of haptophyte cultures reveals novel and divergent nutrient-stress adaptations. Organic Geochemistry, 161, (2021): 104315, https://doi.org/10.1016/j.orggeochem.2021.104315.
    Description: Lipids comprise a significant, highly plastic proportion of the biomass in haptophytes, a ubiquitous, globally significant, and genetically diverse clade of photosynthetic microalgae. Recent studies have investigated the cellular lipidomes of disparate, individual species of haptophytes under nutrient-replete and nutrient-limited conditions, but have not investigated how lipidomes vary across the larger evolutionary clade or its ecological functional groups. We cultured eight species of haptophytes, including five strains of Emiliania huxleyi, for analysis via high performance liquid chromatography–high resolution accurate mass–mass spectrometry (HPLC–HRAM–MS), and performed untargeted computational and hierarchical cluster analyses on their lipidomes. We identified similarities and differences in lipidomes along both evolutionary and ecological lines, and identified potential biomarkers for haptophyte sub-clades, including 38 glycosphingolipids, seven betaine-like lipids, and three phosphatidyl-S,S-dimethylpropanethiol (PDPT) sulfo-phospholipids. We also provide the first evidence for the glycolipid, glucuronosyldiacylglycerol, in eukaryotic microalgae. We conducted a more targeted study of four haptophyte species under nitrogen- and phosphorus-limited conditions to investigate their lipidomic responses to nutrient stress. Under N- and P-limitation, the species exhibited disparate lipidomic responses. Uniquely, in response to N-limitation, E. huxleyi CCMP 374 heavily upregulated PDPT from 3.6 ± 0.9% to 10.4 ± 1.5% of quantified polar lipids. These previously uncharacterized lipidomes and responses to nutrient limitation reflect divergent evolutionary strategies and challenge popular phenotypic extrapolations between species.
    Description: This work was funded by a grant to B.A.S.V.M. from the Simons Foundation (#721229) and Gordon and Betty Moore Foundation (#5703). Support was also provided through grants to B.A.S.V.M. from the National Science Foundation (#17562524 and #2022597). Support for K.M. was provided by the U.K. Natural Environment Research Council in the form of a SPITFIRE Doctoral Training Partnership (# NE/L002531/1).
    Keywords: Betaine lipids ; Coccolithophore ; Haptophyte ; Polar lipids ; Nutrient limitation ; Phospholipids ; Phytoplankton ; Triacylglycerols
    Repository Name: Woods Hole Open Access Server
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