Rachel Sipler, PhD

Senior Research Scientist
Center for Water Health and Humans Director
Phone: +1 (207) 315-2567, ext. 310
Fax: +1 (207) 315-2329

For media inquiries, please contact sprofaizer@bigelow.org


Ph.D., Oceanography (2009), Rutgers, the State University of New Jersey

B.S., Biology (2003), Salisbury University

B.S., Environmental Science (2003) University of Maryland, Eastern Shore

Research Interests

Rachel Sipler is a marine biogeochemist whose research program combines biogeochemistry, microbial physiology, and phytoplankton ecology to quantify how changes in the physical and chemical environment (temperature, salinity, macro/micro nutrient availability, terrestrial runoff and pollution) impact water quality, elemental cycling, and planktonic community growth, composition, and metabolic rates.

More broadly, Sipler’s work focuses on understanding how changes in the environment will positively or negatively impact organisms at the base of the aquatic food web now and in the future. Past and current research efforts also investigate a broad range of topics including carbon sequestration, nutrient removal and recovery, coastal eutrophication, harmful algal blooms, marine primary productivity, and the response of plankton (including larval fisheries species) to natural and anthropogenic runoff.

Experimental approaches include both laboratory and field studies with research efforts in freshwater, coastal and open ocean waters, from urbanized rivers and wastewater treatment outflow to pristine environments spanning from the Arctic to the Antarctic and many systems in between. She has worked with industry partners to optimize water treatment efforts and to unravel the geochemical drivers of decreased growth efficiency in larval shellfish production. This work is highly collaborative, and often involves working closely with academic, government, non-profit, indigenous communities, working-groups, rights-holders, and industry partners.


  • Goñi, M., L. Juranek, R.E. Sipler, K. Welch. 2021. Particulate Organic Matter Distributions in the Water Column of the Chukchi Sea during Late Summer. Journal of Geophysical Research: Oceans. 126, e2021JC017664. DOI: 10.1029/2021JC017664
  • Jabre, L, A.E. Allen, J. Scott, P. McCain, J.P. McCrow, N. Tenenbaum, J.L. Spackeen, R.E Sipler, B.R. Green, D. A. Bronk, D.A. Hutchins, E.M. Bertrand. 2021. Molecular underpinnings and biogeochemical consequences of enhances diatom growth in a warming Southern Ocean. Proceedings of the National Academy of Sciences. 118(30) DOI:10.1073/pnas.2107238118
  • Büttner, S.H., M. Isaacs, E. Isemonger, D. van Niekerk, R.E. Sipler, R.A. Dorrington. 2021. Living phosphatic stromatolites – a link to Proterozoic microbial communities. Geobiology. 19(1): 35-47 DOI:10.1111/gbi.12415
  • Killberg-Thoreson, L., S.E. Baer, W.G. Reay, Q.N. Roberts, R.E. Sipler, and D.A. Bronk. 2020. Seasonal nitrogen uptake dynamics and harmful algae blooms in the York River, Virginia. Estuaries and Coasts. DOI: 10.1007/s12237-020-00802-4
  • Rogener-Dwitt, M.K., R.E. Sipler, K.S. Hunter, D.A. Bronk, S. Joye. 2019. Pelagic methane oxidation in the northern Chukchi Sea. Limnology & Oceanography. 65(1) 96-110 DOI: 10.1002/lno.11254
  • Yao, X., R. E. Sipler, B.C. Stanley, Q.N. Roberts, M.P. Sanderson, Y. Zhang, C.B. Bott, D.A. Bronk. 2019. Quantifying effluent dissolved organic nitrogen (EDON) uptake by microbial communities along a salinity gradient in the York River. Estuaries & Coasts.42(5) : 1265-1280 DOI: 10.1007/s12237-019-00563-9
  • Harding, K., K. Turk-Kubo, R. Sipler, M.M. Mills, D. Bronk, J. Zehr. 2018. Symbiotic Unicellular Cyanobacteria Fix Nitrogen in the Arctic Ocean. Proceedings of the National Academy of Sciences. 115(52): 13371-13375 DOI 10.1073/pnas. 1813658115
  • Spackeen, J.L., R.E. Sipler, E.M. Bertrand, K. Xu, J.B. McQuaid, N.G. Walworth, D. A. Hutchins, A.E. Allen, D.A Bronk. 2018. Impact of temperature, CO2, and iron on nutrient uptake by a late-season microbial community from the Ross Sea, Antarctica. Aquatic Microbial Ecology. 82:145-159.
  • Spackeen, J.L., D.A. Bronk, R.E. Sipler, E.M. Bertrand, D.A. Hutchins, A.E. Allen. 2018. Stoichiometric N:P ratios, temperature, and iron impact carbon and nitrogen uptake by Ross Sea microbial communities. Journal of Geophysical Research – Biogeosciences. #2017JG004316RR
  • Tatters, A.O., K. Xu, F. Fu, J. Spackeen, N. Walworth, R.E. Sipler, E. Bertrand, J. McQuaid, A. Schnetzer, A.E. Allen, D.A. Bronk, D.A. Caron, J. Sun, K. Gao, D.A. Hutchins. 2018. Interactive Effects of Temperature, CO2, and Nitrogen Source on a Coastal California Diatom Assemblage. Journal of Phytoplankton Research.40 (2): 151-164 DOI: 10.1093/plankt/fbx074.
  • Sipler, R.E., D. Gong, S.E. Baer, M.P. Sanderson, Q.N. Roberts, M. Mulholland, D.A. Bronk. 2017. Preliminary estimate of contribution of Arctic nitrogen fixation to the global nitrogen budget. Limnol Oceanogr Letters.2:159-166. DOI: 10.1002/lol2.10046.
  • Spackeen J.L., R.E. Sipler, K. Xu, A.O. Tatters, N. Walworth, E.M. Bertrand, J.B. McQuaid, D.A. Hutchins, A.E. Allen, D.A. Bronk. 2017. Interactive effects of elevated temperature and CO2 on nitrate, urea, and DIC uptake by a coastal California microbial community. Marine Ecol Prog Ser. 577:49-65. DOI: 10.3354/meps12243.
  • Sipler, R.E., C.T. E. Kellogg, T.L. Connelly, Q.N. Roberts, P.L. Yager, D.A. Bronk. 2017. Microbial Community Response to Terrestrially Derived Dissolved Organic Matter in the Coastal Arctic. Frontiers of Microbiology.8: 1018. DOI: 10.3389/fmicb.2017.01018
  • Baer, S.E., R.E. Sipler, Q.N. Roberts, P.L. Yager, M.E. Frischer and D.A. Bronk. 2017. Seasonal nitrogen uptake and regeneration in the western coastal Arctic. Limnol Oceanogr. DOI: 10.1002/lno.10580
  • Sipler, R.E., S.E. Baer, M.E., Frischer, Q.N. Roberts, T.L. Connelly, P.L. Yager, D.A. Bronk. 2017. Chemical and photophysiological impact of terrestrially-derived dissolved organic matter on nitrate uptake in the coastal western Arctic. Limnol Oceanogr. 62: 1881-1894. DOI: 10.1002/lno.10541
  • Yager, P.L., R.M. Sherrell, S.E. Stammerjohn, H.W. Ducklow, O.M.E. Schofield, E.D. Ingall, S.E. Wilson, K.E. Lowry, C.M. Williams, L. Riemann, S. Bertilsson, A-C. Alderkamp, J. Dinasquet, R. Logares, R.E. Sipler, A.J. Melara, L. Mu, R.G. Newstead, A.F. Post, R. Swalethorp, G.L. van Dijken. 2016. A carbon budget for the Amundsen Sea Polynya, Antarctica; estimating net community production and export in a highly productive polar ecosystem. Elem Sci Anth. 4 (140). DOI: 10.12952/journal.elementa.000140
  • Schofield, O.M., T. Miles, A.C. Alderkamp, S.H. Lee, C. Haskins, E. Rogalsky, R.E. Sipler, R. Sherrell, P.L. Yager. 2015. In situ phytoplankton distributions in the Amundsen Sea polynya measured by autonomous gliders. Elem Sci Anth. 3(73). 3:73. DOI:10.12952/journal.elementa.000073
  • Bertrand, E.M., J.P. McCrow, H. Zheng, A. Moustafa, J. McQuaid, T.O. Delmont, A.F. Post, R.E. Sipler, J.L. Spackeen, K. Xu, D.A. Bronk, D.A. Hutchins, A.E. Allen. 2015. Phytoplankton-bacterial interactions mediate micronutrient colimitation at the coastal Antarctic sea ice edge. Proc. Natl. Acad. Sci. 112(32): 9938-9943. DOI: 10.1073/ pnas.1501615112
  • Sipler, R.E. and T. Connelly. 2015. Bioavailability of surface dissolved organic matter to aphotic bacterial communities in the Amundsen Sea Polynya, Antarctica. Elem Sci Anth. 3(60). DOI: 10.12952/journal.elementa.000060
  • Sipler, R.E. and D.A. Bronk. 2015. Dynamics of Marine Dissolved Organic Nitrogen. In: Hansell D.A. and Carlson, C.A. (Eds) Biogeochemistry of Marine Dissolved Organic Matter 2nd edition. Academic Press. pp.127-232.
  • Baer, S.E., T.L. Connelly, R.E. Sipler, P.L. Yager, D.A. Bronk. 2014. Effect of temperature on rates of ammonium uptake and nitrification in the western coastal Arctic during winter, spring and summer. Global Biogeochemical Cycles. 2013GB004765.
  • Sipler, R.E., L.M. McGuinness, G. J. Kirkpatrick, L. J. Kerkhof, and O. M. Schofield. 2014. Bacteriocidal effects of brevetoxin on natural microbial communities. Harmful Algae. 38: 101-109.
  • Killberg-Thoreson, L., R.E. Sipler, C. A. Heil, M. Garrett, Q.N. Roberts, and D.A. Bronk. 2014. Nutrients released from decaying fish support microbial growth in the eastern Gulf of Mexico. Harmful Algae. 38: 40-49.
  • Bronk, D.A., L. Killberg-Thoreson, M. R. Mulholland, R. E. Sipler, Q. N. Roberts, P. W. Bernhardt, M. Garrett, J. M. O’Neil, C. A. Heil. 2014. Nitrogen uptake and regeneration (ammonium regeneration, nitrification and photoproduction) in waters of the west Florida shelf prone to blooms of Karenia brevis. Harmful Algae. 38: 50-62.
  • Sipler, R.E., D.A. Bronk, S.P. Seitzinger, R.J. Lauck, L.M. McGuinness, G.J. Kirkpatrick, C.A. Heil, and O.M. Schofield. 2013. Trichodesmium-derived dissolved organic matter is a source of nitrogen capable of supporting the growth of toxic red tide Karenia brevis. Mar. Ecol. Prog. Ser.483: 31-45.
  • Killberg-Thoreson, L., R.E. Sipler, and D.A. Bronk. 2013. Anthropogenic nutrient sources supplied to a Chesapeake Bay tributary support algal growth: a bioassay and high resolution mass spectrometry approach. Estuaries and Coasts. 36 (5): 966-980. DOI: 10.1007/s12237-013-9604-5.
  • Osborne, D.M., D.C. Podgorski, Q.N. Roberts, D.A. Bronk, R.E. Sipler, D. Austin, W.T. Cooper. 2013. Characterization of Reactive and Refractory Dissolved Organic Nitrogen Compounds in a Stormwater Treatment Area by Atmospheric Pressure Photoionization Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry. Rapid Communications in Mass Spectrometry. 28: 851-858.
  • Voß, M., D.A. Bronk, B. Deutsch, R. Purvaja, R. Ramesh T. Rixen, R.E. Sipler, and N. Wannicke. 2011. Treatise on estuarine and coastal science: Internal cycling of nitrogen and nitrogen transformations. (Eds) Wolanski, E.and D. McLusky. Elsevier.
  • Sipler, R. E. and S. P. Seitzinger. 2008. Use of electrospray ionization (ESI) mass spectrometry to investigate complex dissolved organic matter (DOM) and its potential applications in phytoplankton research. Harmful Algae. 8:182-187.