Oceanography The Official Magazine of
The Oceanography Society
Volume 30 Issue 04

View Issue TOC
Volume 30, No. 4
Pages 114 - 127

Hourly In Situ Nitrate on a Coastal Mooring: A 15-Year Record and Insights into New Production

Carole M. Sakamoto Kenneth S. JohnsonLuke J. ColettiTanya L. MaurerGene MassionJ. Timothy PenningtonJoshua N. PlantHans W. JannaschFrancisco P. Chavez
Article Abstract

Chemical sensor development has been a focus for the Monterey Bay Aquarium Research Institute (MBARI) from its inception. Progress in chemical analyzers benefited from technological advances in many fields. MBARI’s development of a low power, reagent-free, in situ ultraviolet spectrophotometer (ISUS) for measuring dissolved nitrate has been transformative. These ultraviolet optical nitrate sensors have been deployed on remotely operated vehicles, autonomous underwater vehicles, benthic flux chambers, profiling floats, and moorings. This paper focuses on a 15+ year time series of nitrate observations on MBARI’s M1 mooring in Monterey Bay, California. The resulting data set captures seasonal and interannual variability from El Niño and La Niña, and water mass anomalies on the eastern boundary of the Pacific Ocean. The high temporal resolution (hourly) nitrate measurements additionally quantify diel cycles of nitrate uptake as a proxy for new production. The calculated f-ratio varies seasonally with relatively higher values during the lower productivity winter season. The physical supply and uptake of nitrate are dominated by upwelling in this coastal environment. An expanding number of ultraviolet optical nitrate sensor deployments on moorings and autonomous platforms such as profiling floats will provide ever-​broadening coverage of the world ocean, resulting in enhanced spatial and temporal resolution of nitrate measurements and, ultimately, improved insight into the dynamics of nitrogen cycling and phytoplankton ecology throughout a changing global ocean.


Sakamoto, C.M., K.S. Johnson, L.J. Coletti, T.L. Maurer, G. Massion, J.T. Pennington, J.N. Plant, H.W. Jannasch, and F.P. Chavez. 2017. Hourly in situ nitrate on a coastal mooring: A 15-year record and insights into new production. Oceanography 30(4):114–127, https://doi.org/10.5670/oceanog.2017.428.


Aubert, A.H., and L. Breuer. 2016. New seasonal shift in in-stream diurnal nitrate cycles identified by mining high-frequency data. PloS ONE 11(4):e0153138, https://doi.org/10.1371/journal.pone.0153138.

Bakun, A. 1973. Coastal Upwelling Indices, West Coast of North America, 1946–1971. US Department of Commerce, NOAA Technical Report NMFS-SSRF-​671, 103 pp.

Bakun, A. 1975. Daily and Weekly Upwelling Indices, West Coast of North America, 1967–1973. US Department of Commerce, NOAA Technical Report NMFS-SSRF-693, 114 pp.

Bastin, R., R. Weberling, and F. Palilla. 1957. Ultraviolet spectrophotometric determination of nitrate…Application to analysis of alkaline earth carbonates. Analytical Chemistry 29:1,795–1,797, https://doi.org/​10.1021/ac60132a038.

Bence, J.R. 1995. Analysis of short time series: Correcting for autocorrelation. Ecology 76(2):628–639, https://doi.org/​10.2307/1941218.

Betteridge, D., E.L. Dagless, B. Fields, and N.F. Graves. 1978. A highly sensitive flow-through phototransducer for unsegmented continuous-​flow analysis demonstrating high-speed spectrophotometry at the parts per 109 level and a new method of refractometric determinations. Analyst 1230:897–908, https://doi.org/10.1039/AN9780300897.

Bond, N.A., M.F. Cronin, H. Freeland, and N. Mantua. 2015. Causes and impacts of the 2014 warm anomaly in the NE Pacific. Geophysical Research Letters 42:3,414–3,420, https://doi.org/​10.1002/​2015GL063306.

Burns, D.A., M.P. Miller, B.A. Pellersin, and P.D. Capel. 2016. Patterns of diel variation in nitrate concentrations in the Potomac River. Freshwater Science 35:1,117–1,132, https://doi.org/​10.1086/​688777.

Chapin, T.P., H.W. Jannasch, and K.S. Johnson. 2002. In situ osmotic analyzer for the year-long continuous determination of Fe in hydrothermal systems. Analytica Chimica Acta 463:265–274, https://doi.org/​10.1016/​S0003-2670(02)00423-3.

Chavez, F.P., J.T. Pennington, R.A. Herlien, H.W. Jannasch, G. Thurmond, and G.E. Friederich. 1997. Moorings and drifters for real-time interdisciplinary oceanography. Journal of Atmospheric and Oceanic Technology 14:1,199–1,211, https://doi.org/​10.1175/​1520-0426​(1997)​014​<1199:MADFRT>​2.0.CO;2.

Chavez, F.P., J.T. Pennington, R.P. Michisaki, M. Blum, G.M. Chavez, J. Friederich, B. Jones, R. Herlien, B. Kieft, B. Hobson, and others. 2017. Climate variability and change: Response of a coastal ocean ecosystem. Oceanography 30(4):128–145, https://doi.org/10.5670/oceanog.2017.429.

Chavez, F.P., J. Sevadjian, C. Wahl, J. Friederich, and G.E. Friederich. 2017b. Measurements of pCO2 and pH from an autonomous surface vehicle in a coastal upwelling system. Deep Sea Research Part II, https://doi.org/10.1016/j.dsr2.2017.01.001.

Clayson, C.H. 2000. Sensing of nitrate concentration by UV absorption spectrophotometry. Pp. 107–121 in Chemical Sensors in Oceanography. M.S. Varney, ed., Gordon and Breach.

Cochlan, W.P., P.J. Harrison, and K.L. Denman. 1991. Diel periodicity of nitrogen uptake by marine phytoplankton in nitrate-rich environments. Limnology and Oceanography 36:1,689–1,700, https://doi.org/​10.4319/lo.1991.36.8.1689.

Collins, C.A., J.T. Pennington, C.G. Castro, T.A. Rago, and F.P. Chavez. 2003. The California Current System off Monterey, California: Physical and biological coupling. Deep Sea Research Part II 50:2,389–2,404, https://doi.org/10.1016/S0967-0645(03)00134-6.

Collins, J.R., P.A. Raymond, W.F. Bohlen, and M.M. Howard-Strobel. 2013. Estimates of new and total productivity in central Long Island Sound from in situ measurements of nitrate and dissolved oxygen. Estuaries and Coasts 36:74–97, https://doi.org/​10.1007/​s12237-012-9560-5.

Collos, Y., F. Mornet, A. Sciandra, N. Waser, A. Larson, and P.J. Harrison. 1999. An optical method for the rapid measurement of micromolar concentrations of nitrate in marine phytoplankton cultures. Journal of Applied Phycology 11:179–184, https://doi.org/10.1023/A:1008046023487.

D’Ortenzio, F., H. Lavigne, F. Besson, H. Claustre, L. Coppola, N. Garcia, A. Laës-Huon, S. Le Reste, D. Malardé, C. Migon, and others. 2014. Observing mixed layer depth, nitrate and chlorophyll concentrations in the northwestern Mediterranean: A combined satellite and NO3 profiling floats experiment. Geophysical Research Letters 41:6,443–6,451, https://doi.org/10.1002/2014GL061020.

Dugdale, R.C., and J.J. Goering. 1967. Uptake of new and regenerated forms of nitrogen in primary productivity. Limnology and Oceanography 12:196–206, https://doi.org/10.4319/lo.1967.12.2.0196.

Elrod, V.A., K.S. Johnson, S.E. Fitzwater, and J.N. Plant. 2008. A long-term, high-resolution record of surface water iron concentrations in the upwelling-driven central California region. Journal of Geophysical Research 113, C11021, https://doi.org/​10.1029/2007JC004610.

Eppley, R.W., and B.J. Peterson. 1979. Particulate organic matter flux and planktonic new production in the deep ocean. Nature 282:677–680, https://doi.org/10.1038/282677a0.

Falkowski, P.G., R.T. Barber, and V. Smetacek. 1998. Biogeochemical controls and feedbacks on ocean primary production. Science 281:200–206, https://doi.org/10.1126/science.281.5374.200.

Finch, M.S., D.J. Hydes, C.H. Clayson, B. Weigl, J. Dakin, and P. Gwillam. 1998. A low power ultra violet spectrophotometer for measurement of nitrate in seawater: Introduction, calibration and initial sea trials. Analytica Chimica Acta 377:167–177, https://doi.org/10.1016/S0003-2670(98)00616-3.

Fischer, A.M., J.P. Ryan, and E.V. Rienecker. 2017. Fine scale mapping of the structure and composition of the Elkhorn Slough (California, USA) tidal plume. Estuarine, Coastal and Shelf Science 184:10–20, https://doi.org/10.1016/j.ecss.2016.10.035.

Friederich, G.E., L.A. Codispoti, and C.M. Sakamoto. 1991. An Easy-to-Construct Automated Winkler Titration System. MBARI Technical Report No 91-6.

Friederich, G.E., P.G. Brewer, R. Herlien, F.P. Chavez. 1995. Measurement of sea surface partial pressure of CO2 from a moored buoy. Deep Sea Research Part I 42:1,175–1,186, https://doi.org/​10.1016/0967-0637(95)00044-7.

Hansen, H.P, and K. Grasshoff. 1983. Methods of Seawater Analysis, 2nd ed. K. Grasshoff, M. Ehrhardt, and K. Kremling, eds, Verlag Chemie, Weinheim, 347 pp.

Harris, F.J. 1978. On the use of windows for harmonic analysis with the discrete Fourier transform. Proceedings of the IEEE. 66:51–83, https://doi.org/​10.1109/PROC.1978.10837.

Hartz, T., R. Smith, M. Cahn, T. Bottoms, S.C. Bustamante, L. Tourte, K. Johnson, and L. Coletti. 2017. Wood chip denitrification bioreactors can reduce nitrate in tile drainage. California Agriculture 71:41–47, https://doi.org/10.3733/ca.2017a0007.

Harvey, J., Y. Zhang, and J. Ryan. 2012. AUVs for ecological studies of marine plankton communities. Sea Technology 53:51–54.

Hensley, R.T., and M.J. Cohen. 2016. On the emergence of diel solute signals in flowing waters. Water Resources Research 52:759–772, https://doi.org/10.1002/2015WR017895.

Jannasch, H.W., L.J. Coletti, K.S. Johnson, S.E. Fitzwater, J.A. Needoba, and J.N. Plant. 2008. The Land/Ocean Biogeochemical Observatory: A robust networked mooring system for continuously monitoring complex biogeochemical cycles in estuaries. Limnology and Oceanography: Methods 6:263–276, https://doi.org/10.4319/lom.2008.6.263.

Jannasch, H.W., K.S. Johnson, and C.M. Sakamoto. 1994. Submersible, osmotically pumped analyzers for continuous determination of nitrate in situ. Analytical Chemistry 66:3,352–3,361, https://doi.org/​10.1021/ac00092a011.

Johnson, K.S. 2010. Simultaneous measurements of nitrate, oxygen, and carbon dioxide on oceanographic moorings: Observing the Redfield ratio in real time. Limnology and Oceanography 55:615–627, https://doi.org/​10.4319/lo.2010.55.2.0615.

Johnson, K.S., C.L. Beehler, and C.M. Sakamoto-Arnold. 1986a. A submersible flow analysis system. Analytica Chimica Acta 179:245–257, https://doi.org/​10.1016/S0003-2670(00)84469-4.

Johnson, K.S., C.L. Beehler, C.M. Sakamoto-Arnold, and J.J. Childress. 1986b. In situ measurements of chemical distributions in a deep-sea hydrothermal vent field. Science 231:1,139–1,141, https://doi.org/​10.1126/science.231.4742.1139.

Johnson, K.S., J.J. Childress, R.R. Hessler, C.M. Sakamoto-Arnold, and C.L. Beehler. 1988. Chemical and biological interactions in the Rose Garden hydrothermal vent field, Galapagos spreading center. Deep Sea Research Part A 35:1,723–1,744, https://doi.org/​10.1016/​0198-0149(88)90046-5.

Johnson, K.S., and H. Claustre. 2016. Bringing biogeochemistry into the Argo age. Eos 97, https://doi.org/​10.1029/2016EO062427.

Johnson, K.S., and L.J. Coletti. 2002. In situ ultraviolet spectrophotometry for high resolution and long-term monitoring of nitrate, bromide and bisulfide in the ocean. Deep Sea Research Part I 49:1,291–1,305, https://doi.org/10.1016/S0967-0637(02)00020-1.

Johnson, K.S., L.J. Coletti, and F.P. Chavez. 2006. Diel nitrate cycles observed with in situ sensors predict monthly and annual new production. Deep Sea Research Part I 53:561–573, https://doi.org/​10.1016/j.dsr.2005.12.004.

Johnson, K.S., L.J. Coletti, H.W. Jannasch, C.M. Sakamoto, D.D. Swift, and S.C. Riser. 2013. Long-term nitrate measurements in the ocean using the In Situ Ultraviolet Spectrophotometer: Sensor integration into the APEX profiling float. Journal of Atmospheric and Oceanic Technology 30:1,854–1,866, https://doi.org/10.1175/JTECH-D-12-00221.1.

Johnson, K.S., H.W. Jannasch, L.J. Coletti, V.A. Elrod, T.R. Martz, Y. Takeshita, R.J. Carlson, and J.G. Connery. 2016. Deep-Sea DuraFET: A pressure tolerant pH sensor designed for global sensor networks. Analytical Chemistry 88:3,249–3,256. https://doi.org/10.1021/acs.analchem.5b04653.

Johnson, K.S., and J.A. Needoba. 2008. Mapping the spatial variability of plankton metabolism using nitrate and oxygen sensors on an autonomous underwater vehicle. Limnology and Oceanography 53:2,237–2,250, https://doi.org/​10.4319/lo.2008.53.5_part_2.2237.

Johnson, K.S., J.N. Plant, L.J. Coletti, H.W. Jannasch, C.M. Sakamoto, S.C. Riser, D.D. Swift, N.L. Williams, E. Boss, N. Haëntjens, and others. 2017a. Biogeochemical sensor performance in the SOCCOM profiling float array. Journal of Geophysical Research 122:6,416–6,436, https://doi.org/​10.1002/​2017JC012838.

Johnson, K.S., J.N. Plant, J.P. Dunne, L.D. Talley, and J.L. Sarmiento. 2017b. Annual nitrate drawdown observed by SOCCOM profiling floats and the relationship to annual net community production. Journal of Geophysical Research 122:6,668–6,683, https://doi.org/10.1002/2017JC012839.

Johnson, K.S., S.C. Riser, and D.M. Karl. 2010. Nitrate supply from deep to near-surface waters of the North Pacific subtropical gyre. Nature 465:1,062–1,065, https://doi.org/10.1038/nature09170.

Johnson, K.S., C.M. Sakamoto-Arnold, and C.L. Beehler. 1989. Continuous determination of nitrate concentrations in situ. Deep Sea Research Part A 36:1,407–1,413, https://doi.org/​10.1016/​0198-0149(89)90091-5.

Karstensen, J., F. Schütte, A. Pietri, G. Krahmann, B. Fiedler, D. Grundle, H. Hauss, A. Körtzinger, C.R. Löscher, P. Testor, and others. 2017. Upwelling and isolation in oxygen-depleted anticyclonic modewater eddies and implications for nitrate cycling. Biogeosciences 14:2,167–2,181, https://doi.org/​10.5194/​bg-14-2167-2017.

Kudela, R.M., W.P. Cochlan, and R.C. Dugdale. 1997. Carbon and nitrogen uptake response to light by phytoplankton during an upwelling event. Journal of Plankton Research 19:609–630, https://doi.org/​10.1093/plankt/19.5.609.

Kudela, R.M., and R.C. Dugdale. 2000. Nutrient regulation of phytoplankton productivity in Monterey Bay, California. Deep Sea Research Part II 47:1,023–1,053, https://doi.org/10.1016/S0967-0645(99)00135-6.

Le Moigne, F.A.C., S.A. Henson, E. Cavan, C. Georges, K. Pabortsava, E.P. Achterberg, E. Ceballos-Romero, M. Zubkov, and R.J. Sanders. 2016. What causes the inverse relationship between primary production and export efficiency in the Southern Ocean. Geophysical Research Letters 43:4,457–4,466, https://doi.org/10.1002/2016GL068480.

MacCready, P., and P. Quay. 2001. Biological export flux in the Southern Ocean estimated from a climatological nitrate budget. Deep Sea Research Part II 48:4,299–4,322, https://doi.org/10.1016/S0967-0645(01)00090-X.

Maiti, K., M.A. Charette, K.O. Buesseler, and M. Kahru. 2013. An inverse relationship between production and export efficiency in the Southern Ocean. Geophysical Research Letters 40:1,557–1,561, https://doi.org/10.1002/grl.50219.

Manning, C.C., R.H.R. Stanley, D.P. Nicholson, J.M. Smith, J.T. Pennington, M.R. Fewings, M.E. Squibb, and F.P. Chavez. 2017. Impact of recently upwelled water on productivity investigated using in situ and incubation-based methods in Monterey Bay. Journal of Geophysical Research 122:1,901–1,926, https://doi.org/​10.1002/2016JC012306.

Marra, J. 2009. Net and gross productivity: Weighing in with 14C. Aquatic Microbial Ecology 56:123–131, https://doi.org/10.3354/ame01306.

Martz, T.R., J.G. Connery, and K.S. Johnson. 2010. Testing the Honeywell Durafet for seawater pH applications. Limnology and Oceanography: Methods 8:172–184, https://doi.org/10.4319/lom.2010.8.172.

Martz, T., U. Send, M.D. Ohman, Y. Takeshita, P. Bresnahan, H.-J. Kim, and S. Nam. 2014. Dynamic variability of biogeochemical ratios in the Southern California Current System. Geophysical Research Letters 41:2,496–2,501, https://doi.org/​10.1002/​2014GL059332.

McCabe, R.M., B.M. Hickey, R.M. Kudela, K.A. Lefebvre, N.G. Adams, B.D. Bill, F.M.D. Gulland, R.E. Thomson, W.P. Cochlan, and V.L. Trainer. 2016. An unprecedented coastwide toxic algal bloom linked to anomalous ocean conditions. Geophysical Research Letters 43:10,366–10,376, https://doi.org/10.1002/2016GL070023.

McNeil, J.D., H.W. Jannasch, T. Dickey, D. McGillicuddy, M. Brzezinski, and C.M. Sakamoto. 1999. New chemical, bio-optical and physical observations of upper ocean response to the passage of a mesoscale eddy off Bermuda. Journal of Geophysical Research 104:15,537–15,548, https://doi.org/10.1029/1999JC900137.

Olivieri, R.A., and F.P. Chavez. 2000. A model of plankton dynamics for the coastal upwelling system of Monterey Bay, California. Deep Sea Research Part II 47:1,077–1,106, https://doi.org/10.1016/S0967-​0645(99)00137-X.

Packard, D. 1989. Welcoming remarks to The Oceanography Society at its inaugural meeting. Oceanography 2(2):46–47, https://doi.org/10.5670/oceanog.1989.15.

Pasqueron de Fommervault, O., F. D’Ortenzio, A. Mangin, R. Serra, C. Migon, H. Claustre, H. Lavigna, M. Ribera d’Alcala, L. Prieur, V. Taillandier, and others. 2015. Seasonal variability of nutrient concentrations in the Mediterranean Sea: Contribution of Bio-Argo floats. Journal of Geophysical Research 120:8,528–8,550, https://doi.org/10.1002/2015JC011103.

Pellerin, B.A., B.D. Downing, C. Kendall, R.A. Dahlgren, T.E.C. Kraus, J. Saraceno, R.G.M. Spencer, and B.A. Bergamaschi. 2009. Assessing the sources and magnitude of diurnal nitrate variability in the San Joaquin River (California) with an in situ optical nitrate sensor and dual nitrate isotopes. Freshwater Biology 54:376–387, https://doi.org/​10.1111/j.1365-2427.2008.02111.x.

Pennington, J.T., M. Blum, and F.P. Chavez. 2016. Seawater sampling by an autonomous underwater vehicle: “Gulper” sample validation for nitrate, chlorophyll, phytoplankton, and primary production. Limnology and Oceanography: Methods 14:14–23, https://doi.org/10.1002/lom3.10065.

Pennington, J.T., and F.P. Chavez. 2000. Seasonal fluctuations of temperature, salinity, nitrate, chlorophyll, and primary production at station H3/M1 over 1989–1996 in Monterey Bay, California. Deep Sea Research Part II 47:947–973, https://doi.org/10.1016/S0967-0645(99)00132-0.

Pennington, J.T., and F.P. Chavez. 2017. Decade-scale oceanographic fluctuation in Monterey Bay, California, 1989–2011. Deep Sea Research Part II, https://doi.org/10.1016/j.dsr2.2017.07.005.

Pennington, J.T., G.E. Friederich, C.G. Castro, C.A. Collins, W.W. Evans, and F.P. Chavez. 2010. The northern and central California coastal upwelling system. Pp. 29–44 in Carbon and Nutrient Fluxes in Continental Margins. K.-K. Liu, ed., Springer-Verlag, Berlin Heidelberg.

Pilskaln, C.H., J.B. Paduan, F.P. Chavez, R.Y. Anderson, and W.M. Berelson. 1996. Carbon export and regeneration in the coastal upwelling system of Monterey Bay, central California. Journal of Marine Research 54:1,149–1,178, https://doi.org/​10.1357/0022240963213772.

Plant, J.N., K.S. Johnson, J.A. Needoba, and L.J. Coletti. 2009. NH4-Digiscan: An in situ and laboratory ammonium analyzer for estuarine, coastal, and shelf waters. Limnology and Oceanography: Methods 7:144–156, https://doi.org/10.4319/lom.2009.7.144.

Plant, J.N., K.S. Johnson, C.M. Sakamoto, H.W. Jannasch, L.J. Coletti, S.C. Riser, and D.D. Swift. 2016. Net community production at Ocean Station Papa observed with nitrate and oxygen sensors on profiling floats. Global Biogeochemical Cycles 30(6):859–879, https://doi.org/​10.1002/​2015GB005349.

Prestigiacomo, A.R., S.W. Effler, D.A. Matthews, and L.J. Coletti. 2009. Nitrate and bisulfide: Monitoring and patterns in Onondaga Lake, New York, following implementation of nitrification treatment. Water Environment Research 81:466–475, https://doi.org/​10.2175/106143008X357156.

Ramp, S.R., J.D. Paduan, I. Shulman, J. Kindle, F.L. Bahr, and F. Chavez. 2005. Observations of upwelling and relaxation events in the northern Monterey Bay during August 2000. Journal of Geophysical Research 110, C07013, https://doi.org/​10.1029/2004JC002538.

Rode, M., S. Halbedel née Angelstein, M.R. Anis, D. Borchardt, and M. Weitere. 2016. Continuous in-stream assimilatory nitrate uptake from high-​frequency sensor measurements. Environmental Science and Technology 50:5,685–5,694, https://doi.org/10.1021/acs.est.6b00943.

Rosenfeld, L.K., F.B. Schwing, N. Garfield, and D.E. Tracy. 1994. Bifurcated flow from an upwelling center: A cold water source for Monterey Bay. Continental Shelf Research 14:931–964, https://doi.org/​10.1016/0278-4343(94)90058-2.

Růžička, J., and E.H. Hansen. 1975. Flow injection analyses: Part I. A new concept of fast continuous flow analysis. Analytica Chimica Acta 78:145–157, https://doi.org/10.1016/S0003-2670(01)84761-9.

Ryan, J.P., R.M. Kudela, J.M. Birch, M. Blum, H.A. Bowers, F.P. Chavez, G.J. Doucette, K. Hayashi, R. Marin III, C.M. Mikulski, and others. 2017. Causality of an extreme harmful algal bloom in Monterey Bay, California, during the 2014–2016 northeast Pacific warm anomaly. Geophysical Research Letters 44:5,571–5,579, https://doi.org/​10.1002/2017GL072637.

Ryan, J.P., M.A. McManus, and J.M. Sullivan. 2010. Interacting physical, chemical and biological forcing of phytoplankton thin-layer variability in Monterey Bay, California. Continental Shelf Research 30:7–16, https://doi.org/10.1016/​j.csr.2009.10.017.

Sakamoto, C.M., K.S. Coletti, and L.J. Coletti. 2009. Improved algorithm for the computation of nitrate concentrations in seawater using an in situ ultraviolet spectrophotometer. Limnology and Oceanography: Methods 7:132–143, https://doi.org/​10.4319/lom.2009.7.132.

Sakamoto, C.M., G.E. Friederich, S.K. Service, and F.P. Chavez. 1996. Development of automated surface seawater nitrate mapping systems for use in open ocean and coastal waters. Deep Sea Research Part I 43:1,763–1,775, https://doi.org/​10.1016/S0967-0637(96)00070-2.

Sakamoto, C.M., D.M. Karl, H.W. Jannasch, R.R. Bidigare, R.M. Letelier, P.M. Walz, J.P. Ryan, P.S. Polito, and K.S. Johnson. 2004. Influence of Rossby waves on nutrient dynamics and the plankton community structure in the North Pacific subtropical gyre. Journal of Geophysical Research 109, C05032, https://doi.org/10.1029/2003JC001976.

Santus, G., and R.W. Baker. 1995. Osmotic drug delivery: A review of the patent literature. Journal of Controlled Release 35:1–21, https://doi.org/​10.1016/​0168-3659(95)00013-X.

Smith, J.M., K.L. Casciotti, F.P. Chavez, and C.A. Francis. 2014. Differential contributions of archaeal ammonia oxidizer ecotypes to nitrification in coastal surface waters. The ISME Journal 8:1,704–1,714, https://doi.org/10.1038/ismej.2014.11.

Welch, P.D. 1967. The use of fast Fourier transform for the estimation of power spectra: A method based on time averaging over short, modified periodograms. IEEE Transactions on Audio and Electroacoustics 15:70–73, https://doi.org/10.1109/TAU.1967.1161901.

Wong, C.S., N.A.D. Waser, Y. Nojiri, W.K. Johnson, F.A. Whitney, J.S.C. Page, and J. Zeng. 2002. Seasonal and interannual variability in the distribution of surface nutrients and dissolved inorganic carbon in the northern North Pacific: Influence of El Niño. Journal of Oceanography 58:227–243, https://doi.org/10.1023/A:1015897323653.

Wong, C.S., F.A. Whitney, R.J. Matear, and K. Iseki. 1998. Enhancement of new production in the northeast subarctic Pacific Ocean during negative North Pacific index events. Limnology and Oceanography 43:1,418–1,426, https://doi.org/​10.4319/​lo.1998.43.7.1418.

Wulff, T., E. Bauerfeind, and W.-J. von Appen. 2016. Physical and ecological processes at a moving ice edge in the Fram Strait as observed with an AUV. Deep Sea Research Part I 115:253–264, https://doi.org/​10.1016/​j.dsr.2016.07.001.

Zhang, Y., J.G. Bellingham, J.P. Ryan, M.A. Godin. 2015. Evolution of a physical and biological front from upwelling to relaxation. Continental Shelf Research 108:55–64, https://doi.org/10.1016/​j.csr.2015.08.005.