Publications

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Sosik, H, Vernet M, Mitchell BG.  1992.  RACER 3: A comparison of particulate absorption properties between high- and mid-latitude surface waters. Antarctic Journal of the United States. 27:162-164. Abstract
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Brody, E, Mitchell BG, Holm-Hansen O, Vernet M.  1992.  RACER 3: Species-dependent variations of the absorption coefficient in the Gerlache Strait. Antarctic Journal of the United States. 27:160-162. Abstract
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Huntlley, ME, Niiler P, Holm-Hansen O, Vernet M, Brinton E, Amos AF, Karl DM.  1990.  RACER: An interdisciplinary study of spring bloom dynamics. Antarctic Journal of the United States. 25:126-128. Abstract
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Holm-Hansen, O, Vernet M.  1992.  RACER: Distribution, abundance, and productivity of phytoplankton in the Gerlache Strait during austral summer. Antarctic Journal of the United States. 27:154-157. Abstract
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Kocmur, SF, Vernet M, Holm-Hansen O.  1990.  RACER: Nutrient depletion by phytoplankton during the 1989 austral spring bloom. Antarctic Journal of the United States. 25:138-141. Abstract
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Vernet, M, Mitchell BG.  1990.  RACER: Phaeopigment photooxidation during the spring bloom in Northern Gerlache Strait. Antarctic Journal of the United States. 25:162-164. Abstract
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Holm-Hansen, O, Vernet M.  1990.  RACER: Phytoplankton distribution and rates of primary production during the austral spring bloom. Antarctic Journal of the United States. 25:141-144. Abstract
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Vernet, M, Karl DM.  1990.  RACER: Phytoplankton growth and zooplankton grazing in the Northern Gerlache Strait. Antarctic Journal of the United States. :164-166. Abstract
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Vernet, M, Letelier R, Karl DM.  1991.  RACER: Phytoplankton growth rates in Northern Gerlache Strait during the spring bloom of 1989. Antarctic Journal of the United States. 26:154-156. Abstract
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Vernet, M.  1992.  RACER: Predominance of cryptomonads and diatoms in the Gerlache Strait. Antarctic Journal of the United States. 27:157-158. Abstract
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Karl, DM, Amos A, Holm-Hansen O, Huntley ME, Vernet M.  1992.  RACER: The Marguerite Bay ice-edge reconnaissance. Antarctic Journal of the United States. 27:175-177. Abstract
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Matrai, P, Vernet M, Wassmann P.  2007.  Relating temporal and spatial patterns of DMSP in the Barents Sea to phytoplankton biomass and productivity. Journal of Marine Systems. 67:83-101.   10.1016/j.jmarsys.2006.10.001   AbstractWebsite

Dimethylsulfoniopropionate (DMSP), produced by many marine phytoplankton, is the main precursor of the climate relevant gas dimethylsulfide (DMS). Currently, it is generally accepted that the relationship between DMSP and phytoplankton biomass (as chlorophyll a), while not representative of the absolute magnitude of the DMSP pool, is a good indicator of ecosystem structure. In this study we test the strength of the relationships between DMSP and various phytoplankton parameters in Arctic shelf waters of the Barents Sea. Our objective is to assess the predictive value that traditional phytoplankton carbon parameters have on DMSP. We discuss C:DMSP-S variability as a function of seasonality, water masses, grazing and nutrient limitation. For this purpose we analyze data from 5 cruises including winter, spring and summer conditions and across the seasonal ice zone at the time of the study. Highest phytoplankton DMSP concentration was usually measured at the ice edge. Marked seasonal variability was observed in phytoplankton carbon biomass and production but not necessarily in the particulate fraction of DMSP (DMSPp), resulting in seasonally varying C:DMSP-S. High winter DMSPp concentrations, when chlorophyll a and primary production were lowest and flagellates dominant, suggest a heterotrophic source. The production of extracellular carbon and the pool of dissolved DMSP (DMSPd) followed similar seasonal trends, with enhanced concentrations in spring, and we suggest that high dissolved primary production induced by nutrient limiting conditions resulted in high DMSPd concentrations. Mesoscale changes in total DMSP (particulate + dissolved) may be modeled from basin-wide total phytoplankton primary production (rather than from phytoplankton biomass) at seasonal and interannual scales. We conclude there is predictive power of DMSP concentrations in the Barents Sea based on seasonality, the position of the ice edge and the distribution of phytoplankton variables. (c) 2006 Elsevier B.V. All rights reserved.

Neori, A, Vernet M, Holmhansen O, Haxo FT.  1986.  Relationship between action spectra for chlorophyll a fluorescence and photosynthetic O2 evolution in algae. Journal of Plankton Research. 8:537-548.   10.1093/plankt/8.3.537   AbstractWebsite

Relative excitation spectra of chlorophyll a fluorescence are shown to be very close to relative action spectra of photosystem II O2 evolution in seven micro- and macro-algae of five phyla. The conditions under which this correspondence should hold, based on theoretical considerations, and the applications of this correspondence to interpretation of fluorescence excitation spectra of chlorophyll a from natural populations are discussed. The spectra presented are interpreted in relation to the light-harvesting pigments and their association with the two photosystems.

Vernet, M, Lorenzen CJ.  1987.  The relative abundance of pheophorbide a and pheophytin a in temperature marine waters. Limnology and Oceanography. 32:352-358.   10.4319/lo.1987.32.2.0352   AbstractWebsite

Pheophytin a and pheophorbide a were measured with reverse-phase, high-performance liquid chromatography (HPLC) in samples from Dabob Bay, a temperate fiord in Puget Sound, Washington. Pheopigment diversity was higher than expected in all samples analyzed (water column, sediment trap material, and fecal pellets of Calanus pacificus): two major forms of pheophytin a and three major forms of pheophorbide a were separated and quantified. These pigments were labeled by their relative polarity al and a2 in the case of pheophytin and al, a2, and a3 in the case of pheophorbide, with a1 being the most polar. Pheophytin a1 and pheophorbide a2 had the same Chromatographic characteristics as the in vitro forms obtained by acidification of Chl a in acetone and chlorophyllide a in methanol. Pheophorbide a1 was present only in the euphotic zone. Pheophorbide a2 showed a maximum at the depth of the Chl a maximum and was least abundant in sediment traps. Pheophorbide a3 was most abundant below the euphotic zone, in sediment traps, and in C. pacificus fecal pellets. Pheophytin forms showed no clear pattern, although pheophytin a2 was more abundant in laboratory experiments than in field samples. The total mass concentration of pheophorbide forms was four times higher, on average, than that of pheophytin forms (n = 64). Because of their field distributions, the more polar may be the more degraded forms of the chlorophyll molecule.

Vernet, M, Whitehead K.  1996.  Release of ultraviolet-absorbing compounds by the red-tide dinoflagellate Lingulodinium polyedra. Marine Biology. 127:35-44.   10.1007/bf00993641   AbstractWebsite

We tested the hypothesis that ultraviolet-absorbing compounds known as mycosporine-like amino acids (MAAs) are not only synthesized but also excreted by marine phytoplankton. An experiment was performed with cultures of the marine dinoflagellate Lingulodinium polyedra (previously known as Gonyaulax polyedra) exposed to visible (photosynthetically available, PAR, 400 to 700 nm) and ultraviolet (UV, 290 to 400 nm) radiation. Absorption properties of both particulate and dissolved organic matter pools (POM and DOM, respectively) showed maxima in ultraviolet absorption at 360 nm. Chromatographic analysis confirmed the presence of MAAs in both pools. Release of organic matter by L. polyedra, as measured spectrophotometrically by changes in UV absorption in the surrounding medium, showed a differential increase at 360 nm in cultures exposed to UV-B + PAR radiation. The changes in absorption in the DOM fraction were inversely proportional to intracellular UV absorption. Photodegradation experiments in which the DOM fraction was exposed to visible and UV-B radiation showed a decrease in absorption with dose. First-order photooxidation decay rates varied between -0.005 and -0.26 m(2) (mol quanta)(-1) and were also a function of the initial optical density (OD). These results indicate that UV-absorbing compounds synthesized by phytoplankton, such as certain dinoflagellates, may be a component of the DOM pool in surface waters of the ocean and contribute to the attenuation of UV radiation in the water column. Photooxidation consumes only 3 to 10% of the daily production of the DOM absorbing between 280 and 390 nm (including MAAs). This suggests that MAAs dissolved in seawater may contribute to the decrease of UV transmission through the water column on a time scale representative of phytoplankton growth (days) and bloom development (weeks).

Wassmann, P, Martinez R, Vernet M.  1994.  Respiration and biochemical-composition of sedimenting organic-matter during summer in the Barents Sea. Continental Shelf Research. 14:79-90.   10.1016/0278-4343(94)90006-x   AbstractWebsite

Sedimentation of particulate carbon and nitrogen, pigments (fluorometric and HPLC analysis) as well as the activity of the respiratory electron transport system in sedimented matter were studied with unpoisoned, short-term deployed sediment traps during June in the central Barents Sea. The vertical flux of sedimenting material and its biochemical composition in the central Barents Sea was different during summer compared to spring with decreased flux of organic matter and decreased relative supplies of particulate nitrogen, but increased phaeopigment concentrations. The summer situation in the Barents Sea is characterized by recycling of the bulk of the suspended matter in the upper layers, a comparatively small loss of suspended biomass, but high sinking rates of some few, large particles, presumed to be faecal pellets. Respiration calculated as a daily loss rate of carbon in the sedimented material was on average only 1.4% day-1. Loss was strongly temperature dependent. At in situ temperatures >5-degrees-C, it is necessary to estimate turnover rates for sedimenting carbon in non-poisoned traps for an accurate elemental budget of a system and for interpretation of estimates from long-term trap deployments.

Vernet, M, Brody EA, Holm-Hansen O, Mitchell GB.  1994.  The response of Antarctic phytoplankton to ultraviolet radiation: absorption, photosynthesis, and taxonomic composition. Antarctic Research Series. 62:143-158. AbstractWebsite
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