{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,24]],"date-time":"2026-01-24T09:40:07Z","timestamp":1769247607826,"version":"3.49.0"},"reference-count":60,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2021,8,24]],"date-time":"2021-08-24T00:00:00Z","timestamp":1629763200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000104","name":"National Aeronautics and Space Administration","doi-asserted-by":"publisher","award":["NNX14AO73G"],"award-info":[{"award-number":["NNX14AO73G"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000104","name":"National Aeronautics and Space Administration","doi-asserted-by":"publisher","award":["80LARC21DA002"],"award-info":[{"award-number":["80LARC21DA002"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000001","name":"National Science Foundation","doi-asserted-by":"publisher","award":["OCE-0752254"],"award-info":[{"award-number":["OCE-0752254"]}],"id":[{"id":"10.13039\/100000001","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>High inflows of freshwater from the Mississippi and Atchafalaya rivers into the northern Gulf of Mexico during spring contribute to strong physical and biogeochemical gradients which, in turn, influence phytoplankton community composition across the river plume\u2013ocean mixing zone. Spectral features representative of bio-optical signatures of phytoplankton size classes (PSCs) were retrieved from underway, shipboard hyperspectral measurements of above-water remote sensing reflectance using the quasi-analytical algorithm (QAA_v6) and validated against in situ pigment data and spectrophotometric analyses of phytoplankton absorption. The results shed new light on sub-km scale variability in PSCs associated with dynamic and spatially heterogeneous environmental processes in river-influenced oceanic waters. Our findings highlight the existence of localized regions of dominant picophytoplankton communities associated with river plume fronts in both the Mississippi and Atchafalaya rivers in an area of the coastal margin that is otherwise characteristically dominated by larger microphytoplankton. This study demonstrates the applicability of underway hyperspectral observations for providing insights about small-scale physical-biological dynamics in optically complex coastal waters. Fine-scale observations of phytoplankton communities in surface waters as shown here and future satellite retrievals of hyperspectral data will provide a novel means of exploring relationships between physical processes of river plume\u2013ocean mixing and frontal dynamics on phytoplankton community composition.<\/jats:p>","DOI":"10.3390\/rs13173346","type":"journal-article","created":{"date-parts":[[2021,8,24]],"date-time":"2021-08-24T22:09:39Z","timestamp":1629842979000},"page":"3346","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Underway Hyperspectral Bio-Optical Assessments of Phytoplankton Size Classes in the River-Influenced Northern Gulf of Mexico"],"prefix":"10.3390","volume":"13","author":[{"given":"Neeharika","family":"Verma","sequence":"first","affiliation":[{"name":"School for Marine Science and Technology, University of Massachusetts Dartmouth, 836 South Rodney French Boulevard, New Bedford, MA 02744, USA"}]},{"given":"Steven","family":"Lohrenz","sequence":"additional","affiliation":[{"name":"School for Marine Science and Technology, University of Massachusetts Dartmouth, 836 South Rodney French Boulevard, New Bedford, MA 02744, USA"}]},{"given":"Sumit","family":"Chakraborty","sequence":"additional","affiliation":[{"name":"Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, FL 34236, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1099-5764","authenticated-orcid":false,"given":"C\u00e9dric G.","family":"Fichot","sequence":"additional","affiliation":[{"name":"Department of Earth and Environment, Boston University, 675 Commonwealth Avenue, Boston, MA 02215, USA"}]}],"member":"1968","published-online":{"date-parts":[[2021,8,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2016","DOI":"10.1111\/j.1365-2486.2005.1004.x","article-title":"Ecosystem dynamics based on plankton functional types for global ocean biogeochemistry models","volume":"11","author":"Harrison","year":"2005","journal-title":"Glob. Chang. Biol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"570","DOI":"10.1002\/lom3.10385","article-title":"Evaluation of diagnostic pigments to estimate phytoplankton size classes","volume":"18","author":"Chase","year":"2020","journal-title":"Limnol. Oceanogr. Methods"},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Smayda, T.J., Borkman, D.G., Beaugrand, G., and Belgrano, A. (2004). Responses of Marine Phytoplankton Populations to Fluctuations in Marine Climate, Oxford Universty Press.","DOI":"10.1093\/acprof:oso\/9780198507499.003.0004"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"204","DOI":"10.4319\/lom.2007.5.204","article-title":"Automated taxonomic classification of phytoplankton sampled with imaging-in-flow cytometry","volume":"5","author":"Sosik","year":"2007","journal-title":"Limnol. Oceanogr. Methods"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"325","DOI":"10.1016\/j.rse.2010.09.004","article-title":"An intercomparison of bio-optical techniques for detecting dominant phytoplankton size class from satellite remote sensing","volume":"115","author":"Brewin","year":"2011","journal-title":"Remote Sens. Environ."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"3153","DOI":"10.1016\/j.rse.2008.03.011","article-title":"An absorption model to determine phytoplankton size classes from satellite ocean colour","volume":"112","author":"Hirata","year":"2008","journal-title":"Remote Sens. Environ."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1029\/2005JC003207","article-title":"Vertical distribution of phytoplankton communities in open ocean: An assessment based on surface chlorophyll","volume":"111","author":"Uitz","year":"2006","journal-title":"J. Geophys. Res. Space Phys."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"404","DOI":"10.4319\/lo.2002.47.2.0404","article-title":"Assessment of the relationships between dominant cell size in natural phytoplankton communities and the spectral shape of the absorption coefficient","volume":"47","author":"Ciotti","year":"2002","journal-title":"Limnol. Oceanogr."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1445","DOI":"10.1002\/jgrc.20137","article-title":"Estimation of phytoplankton size fractions based on spectral features of remote sensing ocean color data","volume":"118","author":"Li","year":"2013","journal-title":"J. Geophys. Res. Ocean."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1029\/2004JC002419","article-title":"Natural variability of phytoplanktonic absorption in oceanic waters: Influence of the size structure of algal populations","volume":"109","author":"Bricaud","year":"2004","journal-title":"J. Geophys. Res. Space Phys."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1093\/plankt\/25.1.35","article-title":"Phytoplankton spectral absorption as influenced by community size structure and pigment composition","volume":"25","author":"Lohrenz","year":"2003","journal-title":"J. Plankton Res."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"31","DOI":"10.3354\/meps11107","article-title":"Phytoplankton community structure in the river-influenced continental margin of the northern Gulf of Mexico","volume":"521","author":"Chakraborty","year":"2015","journal-title":"Mar. Ecol. Prog. Ser."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1881","DOI":"10.5194\/bg-8-1881-2011","article-title":"A coupled physical-biological model of the Northern Gulf of Mexico shelf: Model description, validation and analysis of phytoplankton variability","volume":"8","author":"Fennel","year":"2011","journal-title":"Biogeosciences"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1016\/j.jmarsys.2003.09.002","article-title":"Biological effects of Mississippi River nitrogen on the northern gulf of Mexico\u2014a review and synthesis","volume":"43","author":"Dagg","year":"2003","journal-title":"J. Mar. Syst."},{"key":"ref_15","first-page":"121","article-title":"Phytoplankton blooms at Fronts: Patterns, scales, and physical forcing mechanisms","volume":"6.2","author":"Franks","year":"1992","journal-title":"Rev. Aquat. Sci."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1113","DOI":"10.1016\/S0278-4343(99)00012-6","article-title":"Nutrients, irradiance, and mixing as factors regulating primary production in coastal waters impacted by the Mississippi River plume","volume":"19","author":"Lohrenz","year":"1999","journal-title":"Cont. Shelf Res."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"109","DOI":"10.3354\/meps075109","article-title":"Spatial distribution and abundance of larval and juvenile fish, chlorophyll and macrozooplankton around the Mississippi River discharge plume, and the role of the plume in fish recruitment","volume":"75","author":"Grimes","year":"1991","journal-title":"Mar. Ecol. Prog. Ser."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Falkowski, P.G., Woodhead, A.D., and Vivirito, K. (1992). Phytoplankton size. Primary Productivity and Biogeochemical Cycles in the Sea, Springer.","DOI":"10.1007\/978-1-4899-0762-2"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"4922","DOI":"10.1002\/2016JC012092","article-title":"Photophysiological and light absorption properties of phytoplankton communities in the river-dominated margin of the northern Gulf of Mexico","volume":"122","author":"Chakraborty","year":"2017","journal-title":"J. Geophys. Res. Oceans"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"6763","DOI":"10.1364\/AO.54.006763","article-title":"Correction of pathlength amplification in the filter-pad technique for measurements of particulate absorption coefficient in the visible spectral region","volume":"54","author":"Stramski","year":"2015","journal-title":"Appl. Opt."},{"key":"ref_21","unstructured":"(2021, August 20). Station Home Page\u2013NOAA Tides & Currents, Available online: https:\/\/tidesandcurrents.noaa.gov\/stationhome.html?id=8760922."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"71","DOI":"10.1016\/j.rse.2017.12.039","article-title":"Satellite estimation of coastal pCO2 and air-sea flux of carbon dioxide in the northern Gulf of Mexico","volume":"207","author":"Lohrenz","year":"2018","journal-title":"Remote Sens. Environ."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"486","DOI":"10.1175\/1520-0426(2002)019<0486:AEOAAI>2.0.CO;2","article-title":"An evaluation of above- and in-water methods for determining water-leaving radiances","volume":"19","author":"Hooker","year":"2002","journal-title":"J. Atmos. Ocean. Technol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"187","DOI":"10.1175\/1520-0426(2003)020<0187:PAEEOA>2.0.CO;2","article-title":"Platform and environmental effects on above-water determinations of water-leaving radiances","volume":"20","author":"Hooker","year":"2003","journal-title":"J. Atmos. Ocean. Technol."},{"key":"ref_25","unstructured":"Zibordi, G., Voss, K.J., Johnson, B.C., and Mueller, J.L. (2019). Protocols for Satellite Ocean Colour Data Validation: In Situ Optical Radiometry. IOCCG Protoc. Doc., 3."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"7442","DOI":"10.1364\/AO.38.007442","article-title":"Estimation of the remote-sensing reflectance from above-surface measurements","volume":"38","author":"Mobley","year":"1999","journal-title":"Appl. Opt."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1167","DOI":"10.4319\/lo.2006.51.2.1167","article-title":"Seaborne measurements of near infrared water-leaving reflectance: The similarity spectrum for turbid waters","volume":"51","author":"Ruddick","year":"2006","journal-title":"Limnol. Oceanogr."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"567","DOI":"10.5194\/os-8-567-2012","article-title":"In situ determination of the remote sensing reflectance: An inter-comparison","volume":"8","author":"Zibordi","year":"2012","journal-title":"Ocean Sci."},{"key":"ref_29","unstructured":"(2021, August 20). IOCCG Working Groups\u2014Ocean-Colour Algorithms. Available online: https:\/\/www.ioccg.org\/groups\/software.html."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"937","DOI":"10.5194\/isprs-archives-XLII-3-W10-937-2020","article-title":"Estimation of optical properties using QAA-V6 model based on modis data","volume":"XLII-3\/W10","author":"Zhan","year":"2020","journal-title":"Int. Arch. Photogramm. Remote Sens. Spat. Inf. Sci."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"168","DOI":"10.1016\/j.rse.2013.02.012","article-title":"Uncertainties of SeaWiFS and MODIS remote sensing reflectance: Implications from clear water measurements","volume":"133","author":"Hu","year":"2013","journal-title":"Remote Sens. Environ."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"107","DOI":"10.1016\/j.rse.2016.02.014","article-title":"Uncertainty estimates of remote sensing reflectance derived from comparison of ocean color satellite data sets","volume":"177","author":"Sclep","year":"2016","journal-title":"Remote Sens. Environ."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"41","DOI":"10.3389\/fmars.2017.00041","article-title":"A Consumer\u2019s guide to satellite remote sensing of multiple phytoplankton groups in the global ocean","volume":"4","author":"Mouw","year":"2017","journal-title":"Front. Mar. Sci."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"55","DOI":"10.3389\/fmars.2017.00055","article-title":"Obtaining phytoplankton diversity from ocean color: A scientific roadmap for future development","volume":"4","author":"Bracher","year":"2017","journal-title":"Front. Mar. Sci."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"177","DOI":"10.1007\/BF00121323","article-title":"In-water and remote measurements of ocean color","volume":"18","author":"Morel","year":"1980","journal-title":"Bound. Layer Meteorol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"25682","DOI":"10.1364\/OE.398127","article-title":"Radiometric approach for the detection of picophytoplankton assemblages across oceanic fronts","volume":"28","author":"Lange","year":"2020","journal-title":"Opt. Express"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"123","DOI":"10.1016\/j.pocean.2013.12.008","article-title":"A review of ocean color remote sensing methods and statistical techniques for the detection, mapping and analysis of phytoplankton blooms in coastal and open oceans","volume":"123","author":"Gower","year":"2014","journal-title":"Prog. Oceanogr."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"29714","DOI":"10.1364\/OE.401855","article-title":"Characteristics of water spectrum at ultraviolet wavelengths: Radiative transfer simulations","volume":"28","author":"Bai","year":"2020","journal-title":"Opt. Express"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"202","DOI":"10.3389\/fenvs.2021.647966","article-title":"Detection and sourcing of CDOM in urban coastal waters with UV-visible imaging spectroscopy","volume":"9","author":"Harringmeyer","year":"2021","journal-title":"Front. Environ. Sci."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"3966","DOI":"10.1364\/AO.55.003966","article-title":"Stray light effects in above-water remote-sensing reflectance from hyperspectral radiometers","volume":"55","author":"Talone","year":"2016","journal-title":"Appl. Opt."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"496","DOI":"10.1002\/2014JC010241","article-title":"A new algorithm to retrieve chromophoric dissolved organic matter (CDOM) absorption spectra in the UV from ocean color","volume":"120","author":"Cao","year":"2015","journal-title":"J. Geophys. Res. Ocean."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"00157","DOI":"10.1525\/elementa.2020.00157","article-title":"Satellite detection of dinoflagellate blooms off California by UV reflectance ratios","volume":"9","author":"Kahru","year":"2021","journal-title":"Elem. Sci. Anth."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"5805","DOI":"10.1364\/AO.54.005805","article-title":"Inversion of spectral absorption coefficients to infer phytoplankton size classes, chlorophyll concentration, and detrital matter","volume":"54","author":"Zhang","year":"2015","journal-title":"Appl. Opt."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"2255","DOI":"10.1016\/j.rse.2011.04.025","article-title":"A three component classification of phytoplankton absorption spectra: Application to ocean-color data","volume":"115","author":"Devred","year":"2011","journal-title":"Remote Sens. Environ."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"104","DOI":"10.3389\/fmars.2017.00104","article-title":"Uncertainty in ocean-color estimates of chlorophyll for phytoplankton groups","volume":"4","author":"Brewin","year":"2017","journal-title":"Front. Mar. Sci."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"66","DOI":"10.1016\/j.rse.2013.02.013","article-title":"Deriving phytoplankton size classes from satellite data: Validation along a trophic gradient in the eastern Atlantic Ocean","volume":"134","author":"Brotas","year":"2013","journal-title":"Remote Sens. Environ."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"186","DOI":"10.1016\/j.pocean.2018.01.001","article-title":"An overview of approaches and challenges for retrieving marine inherent optical properties from ocean color remote sensing","volume":"160","author":"Werdell","year":"2018","journal-title":"Prog. Oceanogr."},{"key":"ref_48","unstructured":"Owen, R.W. (1981). Fronts and eddies in the sea: Mechanisms, interactions and biological effects. Anal. Mar. Ecosyst., 197\u2013233."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"109","DOI":"10.1016\/S0924-7963(96)00092-9","article-title":"Property fields in an effluent plume of the Mississippi river","volume":"12","author":"Hitchcock","year":"1997","journal-title":"J. Mar. Syst."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"06005","DOI":"10.1029\/2007JC004594","article-title":"A predictive model for satellite-derived phytoplankton absorption over the Louisiana shelf hypoxic zone: Effects of nutrients and physical forcing","volume":"113","author":"Green","year":"2008","journal-title":"J. Geophys. Res. Space Phys."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"101571","DOI":"10.1016\/j.ocemod.2020.101571","article-title":"River plume source-front connectivity","volume":"150","author":"Cole","year":"2020","journal-title":"Ocean Model."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"147","DOI":"10.1007\/BF02803568","article-title":"Picophytoplankton and bacterioplankton in the Mississippi River plume and its adjacent waters","volume":"27","author":"Liu","year":"2004","journal-title":"Estuaries"},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"185","DOI":"10.3354\/ame035185","article-title":"Phytoplankton community structure and productivity along the axis of the Mississippi River plume in oligotrophic Gulf of Mexico waters","volume":"35","author":"Wawrik","year":"2004","journal-title":"Aquat. Microb. Ecol."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1029\/2005GL022372","article-title":"Observations at the tidal plume front of a high-volume river outflow","volume":"32","author":"Orton","year":"2005","journal-title":"Geophys. Res. Lett."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"C11009","DOI":"10.1029\/2012JC008108","article-title":"A numerical investigation of the Mississippi and Atchafalaya freshwater transport, filling and flushing times on the Texas-Louisiana Shelf","volume":"117","author":"Zhang","year":"2012","journal-title":"J. Geophys. Res. Space Phys."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"C11010","DOI":"10.1029\/2012JC008145","article-title":"A numerical study on convergence of alongshore flows over the Texas-Louisiana shelf","volume":"117","author":"Zhang","year":"2012","journal-title":"J. Geophys. Res. Space Phys."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"1149","DOI":"10.4319\/lo.2012.57.4.1149","article-title":"Floodplain influence on dissolved organic matter composition and export from the Mississippi-Atchafalaya River system to the Gulf of Mexico","volume":"57","author":"Shen","year":"2012","journal-title":"Limnol. Oceanogr."},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"137","DOI":"10.1086\/282171","article-title":"The Paradox of the Plankton","volume":"95","author":"Hutchinson","year":"1961","journal-title":"Am. Nat."},{"key":"ref_59","unstructured":"Cetini\u0107, I., McClain, C.R., Werdell, P.J., Ahmad, Z., Arnone, R., Behrenfeld, M.J., Cairns, B., Cetini, I., and Eplee, R. (2018). E PACE Technical Report Series: Ocean Color Instrument (OCI) Concept Design Studies, NASA."},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"112349","DOI":"10.1016\/j.rse.2021.112349","article-title":"NASA\u2019s surface biology and geology designated observable: A perspective on surface imaging algorithms","volume":"257","author":"Townsend","year":"2021","journal-title":"Remote Sens. Environ."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/17\/3346\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:50:44Z","timestamp":1760165444000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/17\/3346"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,8,24]]},"references-count":60,"journal-issue":{"issue":"17","published-online":{"date-parts":[[2021,9]]}},"alternative-id":["rs13173346"],"URL":"https:\/\/doi.org\/10.3390\/rs13173346","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,8,24]]}}}