Nicolas Cassar | Scholars@Duke

Nicolas Cassar
Professor of Biogeochemistry in the Division of Earth & Ocean Sciences

Nicolas Cassar's research focuses on environmental biogeochemistry and physiology, with the objective of constraining the mechanisms governing carbon cycling and climate. Current research interests include ocean carbon cycles and productivity; carbon acquisition mechanisms in marine phytoplankton and implications for climate change and paleo-CO2 reconstruction; and global carbon cycle and ocean-atmosphere fluxes. His scientific approach is interdisciplinary, integrating field observations, laboratory experiments, modeling and theory.

Current Appointments & Affiliations

Professor of Biogeochemistry in the Division of Earth & Ocean Sciences, Earth and Ocean Sciences, Nicholas School of the Environment 2019
Sr. Associate Dean for Research and Doctoral Programs, Nicholas School of the Environment, Duke University 2019

Contact Information

Box 90328, Durham, NC 27708
Grainger Hall, 9 Circuit Drive (Gh5119), Nicholas School of the Environment, Durham, NC 27708
nicolas.cassar@duke.edu (919) 681-8865
Cassar Lab

Background
Education, Training, & Certifications
- Ph.D., University of Hawaii, Manoa 2003
- B.S., McGill University (Canada) 1997
Duke Appointment History
- Associate Professor of Biogeochemistry in the Division of Earth & Ocean Sciences, Earth and Ocean Sciences, Nicholas School of the Environment 2014 - 2019
- Assistant Professor, Marine Science and Conservation, Nicholas School of the Environment 2012 - 2015
- Assistant Professor of Biogeochemistry, Earth and Ocean Sciences, Nicholas School of the Environment 2009 - 2014
Recognition
In the News
- NOV 13, 2019 Nicholas School of the Environment
  
  Carbon Isotopes In Tuna Are Changing, Signaling Major Changes in Ocean Life
- JUL 8, 2019
  
  White House Honors Four Faculty for Early Career Research Accomplishments
- FEB 21, 2019 Nicholas School of the Environment
  
  Coastal Waters Are Unexpected Hotspots for Nitrogen Fixation
Awards & Honors
- Faculty Early Career Development (CAREER) Program. National Science Foundation. 2014
Expertise
Subject Headings
Global Scholarship
- Research
  - Australia (Country)
Research
Selected Grants
- Biological and physical drivers of O2 saturation and net community production variability at the Western Antarctic Peninsula awarded by National Science Foundation 2017 - 2022
- Impact of Greenland sea-ice melt on marine biogeochemistry and productivity awarded by University of Basel 2019 - 2021
- CAREER: Method development for high-resolution underway N2 fixation measurements awarded by National Science Foundation 2014 - 2021
- Quantifying the carbon export potential of the marine microbial community: Coupling of biogenic rates and fluxes with genomics at the ocean surface awarded by University of North Carolina - Chapel Hill 2017 - 2020
- The Biogeochemical Compass: Navigating the Flows of Energy and Matter within the Southern Ocean awarded by Antarctic Circumnavigation Expedition 2016 - 2019
- Derivation of a Global Net Community Assessment of Regulating Factors Using in-Situ Measurements & Remotely Sensed Prop. awarded by National Aeronautics and Space Administration 2013 - 2017
- Dynamics of Dissolved Inorganic Carbon (DIC), Biological Oxygen Production and Dinitrogen Fixation in the Coastal Ocean awarded by NC Sea Grant 2016 - 2017
- Physiological and Ecosystem Structure Forcings on Carbon Fluxes in the Southern Ocean Mixed Layer awarded by National Science Foundation 2011 - 2015
- EAGER: Method development for the assessment of spatiotemporal Variablility on Non symbiotic N2 fixation: Acetylene Reduction Assay by CAvity ring-down Spectroscopy (ARACAS) awarded by National Science Foundation 2011 - 2013
External Relationships
- CNRS, Univ Brest, IRD, Ifremer, LEMAR, F-29280 Plouzan¿France
Publications & Artistic Works
Selected Publications
- Academic Articles
  - Gu Y, Katul GG, Cassar N. Mesoscale temporal wind variability biases global air-sea gas transfer velocity of CO2 and other slightly soluble gases. Remote Sensing. 2021 Apr 1;13(7).
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  - Gu Y, Katul GG, Cassar N. The Intensifying Role of High Wind Speeds on Air-Sea Carbon Dioxide Exchange. Geophysical Research Letters. 2021 Mar 16;48(5).
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  - Wang S, Tang W, Delage E, Gifford S, Whitby H, González AG, et al. Investigating the microbial ecology of coastal hotspots of marine nitrogen fixation in the western North Atlantic. Scientific Reports. 2021 Mar 9;11(1):5508.
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  - Berthelot H, Duhamel S, L’Helguen S, Maguer J-F, Wang S, Cetinić I, et al. Correction: NanoSIMS single cell analyses reveal the contrasting nitrogen sources for small phytoplankton. The Isme Journal. 2021 Mar;15(3):938.
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  - Huang Y, Nicholson D, Huang B, Cassar N. Global Estimates of Marine Gross Primary Production Based on Machine Learning Upscaling of Field Observations. Global Biogeochemical Cycles. 2021 Mar 1;35(3).
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  - Tang W, Cerdán-García E, Berthelot H, Polyviou D, Wang S, Baylay A, et al. New insights into the distributions of nitrogen fixation and diazotrophs revealed by high-resolution sensing and sampling methods. The Isme Journal. 2020 Oct;14(10):2514–26.
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  - Landwehr S, Thurnherr I, Cassar N, Gysel-Beer M, Schmale J. Using global reanalysis data to quantify and correct airflow distortion bias in shipborne wind speed measurements. Atmospheric Measurement Techniques. 2020 Jun 30;13(6):3487–506.
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  - Kranz SA, Wang S, Kelly TB, Stukel MR, Goericke R, Landry MR, et al. Lagrangian Studies of Marine Production: A Multimethod Assessment of Productivity Relationships in the California Current Ecosystem Upwelling Region. Journal of Geophysical Research: Oceans. 2020 Jun 1;125(6).
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  - Wang S, Kranz SA, Kelly TB, Song H, Stukel MR, Cassar N. Lagrangian Studies of Net Community Production: The Effect of Diel and Multiday Nonsteady State Factors and Vertical Fluxes on O2/Ar in a Dynamic Upwelling Region. Journal of Geophysical Research: Biogeosciences. 2020 Jun 1;125(6).
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  - Whitby H, Planquette H, Cassar N, Bucciarelli E, Osburn CL, Janssen DJ, et al. A call for refining the role of humic-like substances in the oceanic iron cycle. Scientific Reports. 2020 Apr 9;10(1):6144.
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  - Lorrain A, Pethybridge H, Cassar N, Receveur A, Allain V, Bodin N, et al. Trends in tuna carbon isotopes suggest global changes in pelagic phytoplankton communities. Global Change Biology. 2020 Feb;26(2):458–70.
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  - Gorsky G, Bourdin G, Lombard F, Pedrotti ML, Audrain S, Bin N, et al. Expanding Tara Oceans Protocols for Underway, Ecosystemic Sampling of the Ocean-Atmosphere Interface During Tara Pacific Expedition (2016–2018). Frontiers in Marine Science. 2019 Dec 11;6.
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  - Lampe RH, Wang S, Cassar N, Marchetti A. Strategies among phytoplankton in response to alleviation of nutrient stress in a subtropical gyre. The Isme Journal. 2019 Dec;13(12):2984–97.
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  - Tang W, Cassar N. Data-Driven Modeling of the Distribution of Diazotrophs in the Global Ocean. Geophysical Research Letters. 2019 Nov 16;46(21):12258–69.
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  - Planes S, Allemand D, Agostini S, Banaigs B, Boissin E, Boss E, et al. The Tara Pacific expedition-A pan-ecosystemic approach of the "-omics" complexity of coral reef holobionts across the Pacific Ocean. Plos Biology. 2019 Sep 23;17(9):e3000483.
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  - Berthelot H, Duhamel S, L’Helguen S, Maguer J-F, Wang S, Cetinić I, et al. NanoSIMS single cell analyses reveal the contrasting nitrogen sources for small phytoplankton. The Isme Journal. 2019 Mar;13(3):651–62.
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  - Lin Y, Gifford S, Ducklow H, Schofield O, Cassar N. Towards Quantitative Microbiome Community Profiling Using Internal Standards. Applied and Environmental Microbiology. 2019 Mar;85(5).
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  - Tang W, Li Z, Cassar N. Machine Learning Estimates of Global Marine Nitrogen Fixation. Journal of Geophysical Research: Biogeosciences. 2019 Mar 1;124(3):717–30.
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  - Tang W, Wang S, Fonseca-Batista D, Dehairs F, Gifford S, Gonzalez AG, et al. Revisiting the distribution of oceanic N₂ fixation and estimating diazotrophic contribution to marine production. Nature Communications. 2019 Feb 19;10(1):831.
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  - Li Z, Cassar N. Theoretical Considerations on Factors Confounding the Interpretation of the Oceanic Carbon Export Ratio. Global Biogeochemical Cycles. 2018 Nov 1;32(11):1644–58.
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  - Nevison C, Munro D, Lovenduski N, Cassar N, Keeling R, Krummel P, et al. Net Community Production in the Southern Ocean: Insights From Comparing Atmospheric Potential Oxygen to Satellite Ocean Color Algorithms and Ocean Models. Geophysical Research Letters. 2018 Oct 16;45(19):10–559.
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  - Ducklow HW, Stukel MR, Eveleth R, Doney SC, Jickells T, Schofield O, et al. Spring-summer net community production, new production, particle export and related water column biogeochemical processes in the marginal sea ice zone of the Western Antarctic Peninsula 2012-2014. Philosophical Transactions Series A, Mathematical, Physical, and Engineering Sciences. 2018 Jun;376(2122).
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  - Wang S, Lin Y, Gifford S, Eveleth R, Cassar N. Linking patterns of net community production and marine microbial community structure in the western North Atlantic. The Isme Journal. 2018 May;12(11):2582–95.
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  - Moreno CM, Lin Y, Davies S, Monbureau E, Cassar N, Marchetti A. Examination of gene repertoires and physiological responses to iron and light limitation in Southern Ocean diatoms. Polar Biology. 2018 Apr 1;41(4):679–96.
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  - Cassar N, Tang W, Gabathuler H, Huang K. Method for High Frequency Underway N2 Fixation Measurements: Flow-Through Incubation Acetylene Reduction Assays by Cavity Ring Down Laser Absorption Spectroscopy (FARACAS). Analytical Chemistry. 2018 Feb 6;90(4):2839–51.
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  - Simonin M, Colman BP, Tang W, Judy JD, Anderson SM, Bergemann CM, et al. Plant and Microbial Responses to Repeated Cu(OH)₂ Nanopesticide Exposures Under Different Fertilization Levels in an Agro-Ecosystem. Frontiers in Microbiology. 2018 Jan;9:1769.
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  - Li Z, Cassar N. A mechanistic model of an upper bound on oceanic carbon export as a function of mixed layer depth and temperature. Biogeosciences. 2017 Nov 14;14(22):5015–27.
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  - Lin Y, Cassar N, Marchetti A, Moreno C, Ducklow H, Li Z. Specific eukaryotic plankton are good predictors of net community production in the Western Antarctic Peninsula. Scientific Reports. 2017 Nov;7(1):14845.
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  - Eveleth R, Cassar N, Doney SC, Munro DR, Sweeney C. Biological and physical controls on O2/Ar, Ar and pCO2 variability at the Western Antarctic Peninsula and in the Drake Passage. Deep Sea Research Part Ii: Topical Studies in Oceanography. 2017 May 1;139:77–88.
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  - Eveleth R, Cassar N, Sherrell RM, Ducklow H, Meredith MP, Venables HJ, et al. Ice melt influence on summertime net community production along the Western Antarctic Peninsula. Deep Sea Research Part Ii: Topical Studies in Oceanography. 2017 May 1;139:89–102.
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  - Erickson ZK, Thompson AF, Cassar N, Sprintall J, Mazloff MR. An advective mechanism for deep chlorophyll maxima formation in southern Drake Passage. Geophysical Research Letters. 2016 Oct 28;43(20):10–855.
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  - Li Z, Cassar N, Huang K, Ducklow H, Schofield O. Interannual variability in net community production at the Western Antarctic Peninsula region (1997–2014). Journal of Geophysical Research: Oceans. 2016 Jul 1;121(7):4748–62.
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  - Bender ML, Tilbrook B, Cassar N, Jonsson B, Poisson A, Trull TW. Ocean productivity south of Australia during spring and summer. Deep Sea Research Part I: Oceanographic Research Papers. 2016 Jun 1;112:68–78.
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  - Li Z, Cassar N. Satellite estimates of net community production based on O2/Ar observations and comparison to other estimates. Global Biogeochemical Cycles. 2016 May 1;30(5):735–52.
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  - Huang K, Cassar N, Jonsson B, Cai WJ, Bender ML. An Ultrahigh Precision, High-Frequency Dissolved Inorganic Carbon Analyzer Based on Dual Isotope Dilution and Cavity Ring-Down Spectroscopy. Environmental Science & Technology. 2015 Jul;49(14):8602–10.
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  - Shadwick EH, Tilbrook B, Cassar N, Trull TW, Rintoul SR. Summertime physical and biological controls on O2 and CO2 in the Australian Sector of the Southern Ocean. Journal of Marine Systems. 2015 Jul;147:21–8.
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  - Marchetti A, Catlett D, Hopkinson BM, Ellis K, Cassar N. Marine diatom proteorhodopsins and their potential role in coping with low iron availability. The Isme Journal. 2015 May;
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  - Cassar N, Nevison CD, Manizza M. Correcting oceanic O2/Ar-net community production estimates for vertical mixing using N2O observations. Geophysical Research Letters. 2014 Dec 28;41(24):8961–70.
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  - Eveleth R, Timmermans M-L, Cassar N. Physical and biological controls on oxygen saturation variability in the upper Arctic Ocean. Journal of Geophysical Research: Oceans. 2014 Nov;119(11):7420–32.
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  - Ulfsbo A, Cassar N, Korhonen M, van Heuven S, Hoppema M, Kattner G, et al. Late summer net community production in the central Arctic Ocean using multiple approaches. Global Biogeochemical Cycles. 2014 Oct;28(10):1129–48.
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  - Rutgers van der Loeff MM, Cassar N, Nicolaus M, Rabe B, Stimac I. The influence of sea ice cover on air-sea gas exchange estimated with radon-222 profiles. Journal of Geophysical Research: Oceans. 2014 May;119(5):2735–51.
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  - Chang C-H, Johnson NC, Cassar N. Neural network-based estimates of Southern Ocean net community production from in situ O2/Ar and satellite observation: a methodological study. Biogeosciences. 2014;11:3279–97.
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  - Roedenbeck C, Bakker DCE, Metzl N, Olsen A, Sabine C, Cassar N, et al. Interannual sea-air CO2 flux variability from an observation-driven ocean mixed-layer scheme. Biogeosciences. 2014;11(17):4599–613.
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  - Huang K, Cassar N, Wanninkhof RH, Bender ML. An isotope dilution method for high-frequency measurements of dissolved inorganic carbon concentration in the surface ocean. Limnology and Oceanography: Methods. 2013 Dec 30;11(NOV):572–83.
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  - Castro-Morales K, Cassar N, Shoosmith DR, Kaiser J. Biological production in the Bellingshausen Sea from oxygen-to-argon ratios and oxygen triple isotopes. Biogeosciences. 2013 Apr 5;10(4):2273–91.
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  - Li Z, Li L, Song K, Cassar N. Estimation of phytoplankton size fractions based on spectral features of remote sensing ocean color data. Journal of Geophysical Research: Oceans. 2013;118(3):1445–58.
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  - Jean M-E, Cassar N, Setzer C, Bellenger JP. Short-term N2 fixation kinetics in a moss-associated cyanobacteria. Environmental Science & Technology. 2012 Aug;46(16):8667–71.
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  - Bhattachan A, D’Odorico P, Baddock MC, Zobeck TM, Okin GS, Cassar N. The Southern Kalahari: a potential new dust source in the Southern Hemisphere? Environmental Research Letters. 2012 Apr 10;7(2).
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  - Hamme RC, Cassar N, Lance VP, Vaillancourt RD, Bender ML, Strutton PG, et al. Dissolved O2/Ar and other methods reveal rapid changes in productivity during a Lagrangian experiment in the Southern Ocean. Journal of Geophysical Research: Oceans. 2012 Apr;117(C4).
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  - Huang K, Ducklow H, Vernet M, Cassar N, Bender ML. Export production and its regulating factors in the West Antarctica Peninsula region of the Southern Ocean. Global Biogeochemical Cycles. 2012 Apr;26(2).
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  - Nevison CD, Keeling RF, Kahru M, Manizza M, Mitchell BG, Cassar N. Estimating net community production in the Southern Ocean based on atmospheric potential oxygen and satellite ocean color data. Global Biogeochemical Cycles. 2012 Mar;26(1).
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  - Cassar, Bellenger JP, Jackson RB, Karr J, Barnett BA. N2 fixation estimates in real-time by cavity ring-down laser absorption spectroscopy. Oecologia. 2012;168(2):335–42.
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  - Cassar N, DiFiore PJ, Barnett BA, Bender ML, Bowie AR, Tilbrook B, et al. The influence of iron and light on net community production in the Subantarctic and Polar Frontal Zones. Biogeosciences. 2011 Feb 9;8(2):227–37.
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  - Bender ML, Kinter S, Cassar N, Wanninkhof R. Evaluating gas transfer velocity parameterizations using upper ocean radon distributions. Journal of Geophysical Research: Oceans. 2011 Jan 1;116(2).
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  - Stanley RHR, Kirkpatrick JB, Cassar N, Barnett BA, Bender ML. Net community production and gross primary production rates in the Western Equatorial Pacific. Global Biogeochemical Cycles. 2010 Oct 12;24(4).
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  - Boye M, Achterberg E, Bown J, Bucciarelli E, Cardinal D, Cassar N, et al. A first look at GEOTRACES issues from the IPY BONUS GOODHOPE cruise in the Southern Ocean. Geochimica Et Cosmochimica Acta. 2009 Jun 1;73(13):A152–A152.
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  - Cassar N, Barnett B, Bender ML, Kaiser J, Hamme RC, Tilbrook B. Continuous high-frequency dissolved O2/Ar measurements by Equilibrator Inlet Mass Spectrometry (EIMS). Analytical Chemistry. 2009 Feb 4;81(5):1855–64.
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  - Cassar N, McKinley GA, Bender ML, Mika R, Battle M. An improved comparison of atmospheric Ar/N2 time-series and paired ocean-atmosphere model predictions. Journal of Geophysical Research: Atmospheres. 2008 Nov 16;113(D21).
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  - Nevison CD, Mahowald NM, Doney SC, Lima ID, Cassar N. Impact of variable air-sea O2 and CO2 fluxes on atmospheric potential oxygen (APO) and land-ocean carbon sink partitioning. Biogeosciences. 2008 Jun 2;5:875–89.
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  - Cassar N, Bender ML, Barnett BA, Fan S, Moxim WJ, Levy II H, et al. The Southern Ocean biological response to aeolian iron deposition. Science. 2007 Aug 24;317(5841):1067–70.
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  - Cassar N, Laws EA. Potential contribution of beta-carboxylases to photosynthetic carbon isotope fractionation in a marine diatom. Phycologia. 2007 May;46(3):307–14.
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  - Cassar N, Laws EA, Popp BN. Carbon isotopic fractionation by the marine diatom Phaeodactylum tricornutum under nutrients and light-limited growth conditions. Geochemica Et Cosmochimica Acta. 2006 Nov 1;70(21):5323–35.
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  - Bender ML, Ho DT, Hendricks MB, Mika R, Battle MO, Tans PP, et al. Atmospheric O2/N2 changes, 1993-2002: Implications for the partitioning of fossil fuel CO2 sequestration. Global Biogeochemical Cycles. 2005 Dec 7;19(4).
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  - Cassar N, Laws EA, Bidigare RR, Popp BN. Bicarbonate uptake by Southern Ocean phytoplankton. Global Biogeochemical Cycles. 2004 Jun 1;18(2).
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  - Laws EA, Popp BN, Cassar N, Tanimoto J. C-13 discrimination patterns in oceanic phytoplankton: likely influence of CO2 concentrating mechanisms, and implications for palaeoreconstructions. Functional Plant Biology. 2002 Mar 20;29(3):323–33.
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  - Cassar N, Laws EA, Popp BN, Bidigare RR. Sources of inorganic carbon for photosynthesis in a strain of Phaeodactylum tricornutum. Limnology and Oceanography. 2002;47(4):1192–7.
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  - Laws EA, Popp BN, Cassar N, Tanimoto J. 13C discrimination patterns in oceanic phytoplankton: The likely influence of CCMs and the implications for palaeoreconstructions. Functional Plant Biology. 2002;29:1–11.
  - Berner RA, Petsch ST, Lake JA, Beerling DJ, Popp BN, Lane RS, et al. Isotope fractionation and atmospheric oxygen: Implications for Phanerozoic O2 Evolution. Science. 2000 Mar;287(5458):1630–3.
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  - De Vaugelas J, Meinesz A, Antolic B, Ballesteros E, Belsher T, Cassar N, et al. Standardization proposal for the mapping of Caulerpa taxifolia expansion in the Mediterranean Sea. Oceanologica Acta. 1999 Jan 1;22(1):85–94.
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- Reports
  - Bender ML, Cassar N, Mika R. Atmospheric O2/N2 and Ar/N2 studies at Cape Grim. Baseline 2003-2004 Atmospheric Program Report. 2006.
  - Meinesz A, Cottalorda JM, Chiaverni D, Cassar N, Vaugelas DJ. Suivi de l’invasion de l’algue tropicale Caulerpa taxifolia en Méditerranée: situation au 31.12.1997. Sophia Antipolis, Nice; 1998.
- Conference Papers
  - Thompson AF, Cassar N. Physical-biogeochemical coupling in the southern ocean. In: Eos (United States). 2015. p. 6.
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- Theses and Dissertations
  - Cassar N. Carbon-Concentrating Mechanisms and beta-Carboxylation: their potential contribution to marine photosynthetic carbon isotope fractionation. Laws E, editor. 2003.
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Teaching & Mentoring
Recent Courses
- ENVIRON 593: Independent Studies and Projects 2021
- EOS 393: Research Independent Study 2021
- EOS 394: Research Independent Study 2021
- EOS 791: Independent Study 2021
- ENVIRON 362SA: Changing Oceans 2020
- ENVIRON 593: Independent Studies and Projects 2020
- ENVIRON 790SA: Duke-Administered Study Away: Special Topics 2020
- EOS 364SA: Changing Oceans 2020
- EOS 393: Research Independent Study 2020
- EOS 394: Research Independent Study 2020
- EOS 791: Independent Study 2020
- ENVIRON 362S: Changing Oceans 2019
- EOS 364S: Changing Oceans 2019
- EOS 393: Research Independent Study 2019
- EOS 394: Research Independent Study 2019
- EOS 791: Independent Study 2019

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Education, Training, & Certifications

Duke Appointment History

In the News

Awards & Honors

Subject Headings

Global Scholarship

Research

Selected Grants

External Relationships

Selected Publications

Academic Articles

Reports

Conference Papers

Theses and Dissertations

Recent Courses