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  • 2020-2023  (5)
  • 1
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    WAP-1D-VAR v1.0: development and evaluation of a one-dimensional variational data assimilation model for the marine ecosystem along the West Antarctic Peninsula (2021)
    European Geosciences Union
    Details
    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 Kim, H. H., Luo, Y.-W., Ducklow, H. W., Schofield, O. M., Steinberg, D. K., & Doney, S. C. WAP-1D-VAR v1.0: development and evaluation of a one-dimensional variational data assimilation model for the marine ecosystem along the West Antarctic Peninsula. Geoscientific Model Development, 14(8), (2021): 4939–4975, https://doi.org/10.5194/gmd-14-4939-2021.
    Description: The West Antarctic Peninsula (WAP) is a rapidly warming region, with substantial ecological and biogeochemical responses to the observed change and variability for the past decades, revealed by multi-decadal observations from the Palmer Antarctica Long-Term Ecological Research (LTER) program. The wealth of these long-term observations provides an important resource for ecosystem modeling, but there has been a lack of focus on the development of numerical models that simulate time-evolving plankton dynamics over the austral growth season along the coastal WAP. Here, we introduce a one-dimensional variational data assimilation planktonic ecosystem model (i.e., the WAP-1D-VAR v1.0 model) equipped with a model parameter optimization scheme. We first demonstrate the modified and newly added model schemes to the pre-existing food web and biogeochemical components of the other ecosystem models that WAP-1D-VAR model was adapted from, including diagnostic sea-ice forcing and trophic interactions specific to the WAP region. We then present the results from model experiments where we assimilate 11 different data types from an example Palmer LTER growth season (October 2002–March 2003) directly related to corresponding model state variables and flows between these variables. The iterative data assimilation procedure reduces the misfits between observations and model results by 58 %, compared to before optimization, via an optimized set of 12 parameters out of a total of 72 free parameters. The optimized model results capture key WAP ecological features, such as blooms during seasonal sea-ice retreat, the lack of macronutrient limitation, and modeled variables and flows comparable to other studies in the WAP region, as well as several important ecosystem metrics. One exception is that the model slightly underestimates particle export flux, for which we discuss potential underlying reasons. The data assimilation scheme of the WAP-1D-VAR model enables the available observational data to constrain previously poorly understood processes, including the partitioning of primary production by different phytoplankton groups, the optimal chlorophyll-to-carbon ratio of the WAP phytoplankton community, and the partitioning of dissolved organic carbon pools with different lability. The WAP-1D-VAR model can be successfully employed to link the snapshots collected by the available data sets together to explain and understand the observed dynamics along the coastal WAP.
    Description: Hyewon Heather Kim and Scott C. Doney were supported by the National Aeronautics and Space Administration Ocean Biology and Biogeochemistry Program (grant no. NNX14AL86G) and the US National Science Foundation Office of Polar Programs (grant no. PLR-1440435 to Hugh W. Ducklow at Columbia University; Palmer LTER). Hyewon Heather Kim was additionally supported by the Investment in Science Fund and the Reuben F. and Elizabeth B. Richards Endowed Fund from Woods Hole Oceanographic Institution. Oscar M. Schofield and Deborah K. Steinberg were supported by US NSF grant no. PLR-1440435. Ya-Wei Luo was supported by National Natural Science Foundation of China project no. 41890802.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Decline in plankton diversity and carbon flux with reduced sea ice extent along the Western Antarctic Peninsula (2021)
    Nature Research
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    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 Lin, Y., Moreno, C., Marchetti, A., Ducklow, H., Schofield, O., Delage, E., Meredith, M., Li, Z., Eveillard, D., Chaffron, S., & Cassar, N. Decline in plankton diversity and carbon flux with reduced sea ice extent along the Western Antarctic Peninsula. Nature Communications, 12(1), (2021): 4948, https://doi.org/10.1038/s41467-021-25235-w.
    Description: Since the middle of the past century, the Western Antarctic Peninsula has warmed rapidly with a significant loss of sea ice but the impacts on plankton biodiversity and carbon cycling remain an open question. Here, using a 5-year dataset of eukaryotic plankton DNA metabarcoding, we assess changes in biodiversity and net community production in this region. Our results show that sea-ice extent is a dominant factor influencing eukaryotic plankton community composition, biodiversity, and net community production. Species richness and evenness decline with an increase in sea surface temperature (SST). In regions with low SST and shallow mixed layers, the community was dominated by a diverse assemblage of diatoms and dinoflagellates. Conversely, less diverse plankton assemblages were observed in waters with higher SST and/or deep mixed layers when sea ice extent was lower. A genetic programming machine-learning model explained up to 80% of the net community production variability at the Western Antarctic Peninsula. Among the biological explanatory variables, the sea-ice environment associated plankton assemblage is the best predictor of net community production. We conclude that eukaryotic plankton diversity and carbon cycling at the Western Antarctic Peninsula are strongly linked to sea-ice conditions.
    Description: This work is supported by NSF OPP-1643534 to N.C., NSF OPP-1341479 to A.M., and NSF PLR-1440435 to H.D. and O.S. (Palmer LTER).
    Repository Name: Woods Hole Open Access Server
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  • 3
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    Modeling polar marine ecosystem functions guided by bacterial physiological and taxonomic traits (2022)
    European Geosciences Union
    Details
    Publication Date: 2022-05-27
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kim, H. H., Bowman, J. S., Luo, Y.-W., Ducklow, H. W., Schofield, O. M., Steinberg, D. K., & Doney, S. C. Modeling polar marine ecosystem functions guided by bacterial physiological and taxonomic traits. Biogeosciences, 19(1), (2022): 117–136, https://doi.org/10.5194/bg-19-117-2022.
    Description: Heterotrophic marine bacteria utilize organic carbon for growth and biomass synthesis. Thus, their physiological variability is key to the balance between the production and consumption of organic matter and ultimately particle export in the ocean. Here we investigate a potential link between bacterial traits and ecosystem functions in the rapidly warming West Antarctic Peninsula (WAP) region based on a bacteria-oriented ecosystem model. Using a data assimilation scheme, we utilize the observations of bacterial groups with different physiological traits to constrain the group-specific bacterial ecosystem functions in the model. We then examine the association of the modeled bacterial and other key ecosystem functions with eight recurrent modes representative of different bacterial taxonomic traits. Both taxonomic and physiological traits reflect the variability in bacterial carbon demand, net primary production, and particle sinking flux. Numerical experiments under perturbed climate conditions demonstrate a potential shift from low nucleic acid bacteria to high nucleic acid bacteria-dominated communities in the coastal WAP. Our study suggests that bacterial diversity via different taxonomic and physiological traits can guide the modeling of the polar marine ecosystem functions under climate change.
    Description: This research has been supported by the NASA (grant no. NNX14AL86G) and the NSF (grant no. PLR-1440435).
    Repository Name: Woods Hole Open Access Server
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  • 4
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    Water quality measurements in Buzzards Bay by the Buzzards Bay Coalition Baywatchers Program from 1992 to 2018 (2021)
    Nature Research
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Jakuba, R. W., Williams, T., Neill, C., Costa, J. E., McHorney, R., Scott, L., Howes, B. L., Ducklow, H., Erickson, M., & Rasmussen, M. Water quality measurements in Buzzards Bay by the Buzzards Bay Coalition Baywatchers Program from 1992 to 2018. Scientific Data, 8(1), 2021: 76, https://doi.org/10.1038/s41597-021-00856-4.
    Description: The Buzzards Bay Coalition’s Baywatchers Monitoring Program (Baywatchers) collected summertime water quality information at more than 150 stations around Buzzards Bay, Massachusetts from 1992 to 2018. Baywatchers documents nutrient-related water quality and the effects of nitrogen pollution. The large majority of stations are located in sub-estuaries of the main Bay, although stations in central Buzzards Bay and Vineyard Sound were added beginning in 2007. Measurements include temperature, salinity, Secchi depth and concentrations of dissolved oxygen, ammonium, nitrate + nitrite, total dissolved nitrogen, particulate organic nitrogen, particulate organic carbon, ortho-phosphate, chlorophyll a, pheophytin a, and in lower salinity waters, total phosphorus and dissolved organic carbon. The Baywatchers dataset provides a long-term record of the water quality of Buzzards Bay and its sub-estuaries. The data have been used to identify impaired waters, evaluate discharge permits, support the development of nitrogen total maximum daily loads, develop strategies for reducing nitrogen inputs, and increase public awareness and generate support for management actions to control nutrient pollution and improve water quality.
    Description: We thank the more than 1,500 volunteer Baywatchers citizen monitors who helped collect this information over 27 years. Since its inception, funding for this program has been provided through grants from the Commonwealth of Massachusetts, the U.S. Environmental Protection Agency, Buzzards Bay municipalities, private foundations, and members of the Buzzards Bay Coalition. Thank you to Paul Lefebvre for producing the station map. Amy Costa of the Center for Coastal Studies kindly provided data for comparison. Brian Howes of the School for Marine Science and Technology, University of Massachusetts, Dartmouth kindly provided the data for West Falmouth Harbor collected through the Falmouth Pond Watchers program. We thank the Marine Biological Laboratory and the Woodwell Climate Research Center for support to C. Neill, R. McHorney and L. Scott.
    Repository Name: Woods Hole Open Access Server
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  • 5
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    Whole community metatranscriptomes and lipidomes reveal diverse responses among antarctic phytoplankton to changing ice conditions (2021)
    Frontiers Media
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2021 This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bowman, J. S., Van Mooy, B. A. S., Lowenstein, D. P., Fredricks, H. F., Hansel, C. M., Gast, R., Collins, J. R., Couto, N., & Ducklow, H. W. Whole community metatranscriptomes and lipidomes reveal diverse responses among antarctic phytoplankton to changing ice conditions. Frontiers in Marine Science, 8,(2021): 593566, https://doi.org/10.3389/fmars.2021.593566.
    Description: The transition from winter to spring represents a major shift in the basal energy source for the Antarctic marine ecosystem from lipids and other sources of stored energy to sunlight. Because sea ice imposes a strong control on the transmission of sunlight into the water column during the polar spring, we hypothesized that the timing of the sea ice retreat influences the timing of the transition from stored energy to photosynthesis. To test the influence of sea ice on water column microbial energy utilization we took advantage of unique sea ice conditions in Arthur Harbor, an embayment near Palmer Station on the western Antarctic Peninsula, during the 2015 spring–summer seasonal transition. Over a 5-week period we sampled water from below land-fast sea ice, in the marginal ice zone at nearby Palmer Station B, and conducted an ice removal experiment with incubations of water collected below the land-fast ice. Whole-community metatranscriptomes were paired with lipidomics to better understand how lipid production and utilization was influenced by light conditions. We identified several different phytoplankton taxa that responded similarly to light by the number of genes up-regulated, and in the transcriptional complexity of this response. We applied a principal components analysis to these data to reduce their dimensionality, revealing that each of these taxa exhibited a strikingly different pattern of gene up-regulation. By correlating the changes in lipid concentration to the first principal component of log fold-change for each taxa we could make predictions about which taxa were associated with different changes in the community lipidome. We found that genes coding for the catabolism of triacylglycerol storage lipids were expressed early on in phytoplankton associated with a Fragilariopsis kerguelensis reference transcriptome. Phytoplankton associated with a Corethron pennatum reference transcriptome occupied an adjacent niche, responding favorably to higher light conditions than F. kerguelensis. Other diatom and dinoflagellate taxa had distinct transcriptional profiles and correlations to lipids, suggesting diverse ecological strategies during the polar winter–spring transition.
    Description: JB was supported by NSF-OPP 1641019, NSF-OPP 1846837, and the Simons Foundation Early Career Marine Microbial Investigator program. BV, DL and JC were supported by NSF (OPP-1543328 and OCE-1756254). CH was supported by NSF OCE-1355720. The Palmer LTER project is support by NSF-OPP 1440435. A small-scale Community Sequencing Project (CSP) award from the DOE Joint Genome Institute supported part of the sequencing effort.
    Keywords: Antarctica ; phytoplankton ; lipids ; metatranscriptomics ; Palmer LTER project
    Repository Name: Woods Hole Open Access Server
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