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Quetin, LB, Ross RM, Fritsen CH, Vernet M.  2007.  Ecological responses of Antarctic krill to environmental variability: can we predict the future? Antarctic Science. 19:253-266.   10.1017/s0954102007000363   AbstractWebsite

Antarctic krill are a key species in the Southern Ocean ecosystem, and their life cycle appears to be correlated with, and by implication dependent upon, seasonal sea ice dynamics. Moving from correlations with environmental parameters to an understanding of the mechanisms that lead to these correlations may allow predictions of the consequences of climate change on the distribution of favourable habitat for Antarctic krill. During winter cruises in 2001 and 2002 in the region west of the Antarctic Peninsula, one of the most rapidly warming regions on the planet, ice camps were established for periods of 3-9 days. Timing of sea ice advance, chlorophyll a concentrations in ice cores, and growth rates and pigment content of larval krill all differed significantly between winters. Growth rates and pigment content of larval krill from the same ice floe were correlated, suggesting that growth rates in winter are a function of the biomass of the sea ice microbial community. A possible mechanism underlying the correlation between recruitment success and timing of ice advance is proposed. In conjunction with other postulated habitat requirements, this proposed mechanism allows for speculation about future changes in the geographic location of favourable habitat for Antarctic krill.

Thomas, WH, Vernet M, Gibson CH.  1995.  Effects of small-scale turbulence on photosynthesis, pigmentation, cell division, and cell size in the marine dinoflagellate Gonyaulax polyedra (Dinophyceae). Journal of Phycology. 31:50-59.   10.1111/j.0022-3646.1995.00050.x   AbstractWebsite

Several experiments were conducted to understand better the physiological mechanisms underlying growth inhibition of the dinoflagellate Gonyaulax polyedra Stein due to small-scale turbulence shear. To measure photosynthetic C-14 uptake, a ''phytoplankton wheel'' device for rotating cultures in closed bottles was used. Turbulence was quantified biologically in the bottles by comparing growth inhibition with that in cultures with constant shear between a fixed cylinder and an outer concentric rotating cylinder (a stable Couette flow). At saturating irradiances, particulate photosynthesis (P-sat) or photosynthesis per unit chlorophyll (P-sat(B)) were not inhibited completely at the highest turbulence level (26.6 rad(.)s(-1)), and photosynthesis was less sensitive than growth. Photosynthesis per cell (P-sat(C)) was increased by turbulence. In three experiments on the effects of turbulence on photosynthesis versus irradiance curves, the slope of the curve, alpha, for particulate photosynthesis at limiting irradiances did not change. Photosynthesis per unit chlorophyll per unit irradiance (alpha(B)) decreased at high (but not intermediate) turbulence levels. Photosynthesis per cell per unit irradiance, alpha(C), increased with turbulence, suggesting an increase in photosynthetic efficiency in turbulent cultures. In two of the three experiments, respiration rates increased with turbulence, and in one experiment excretion of photosynthetically fixed C-14 was not affected by motion. Ratios of accessory pigments to chlorophyll alpha did not change with turbulence, but pigments per cell and per dry weight increased with turbulence These findings suggest little or no disruption of the photosynthetic apparatus. When turbulence was applied for 1 week, beta-carotene increased while peridinin and diadinoxanthin decreased, suggesting inhibition of synthesis of these latter pigments by prolonged turbulence. Since cell numbers did not increase or decreased during turbulent 72-h incubations, cell division was inhibited and also the cells were very much enlarged. Increases in alpha(C) per cell suggest that, in the sea, photosynthetic metabolism can persist efficiently without cell division during turbulent episodes. After turbulence ceases or reaches low levels again, cells can then divide and blooms may form. Thus, blooms can come or go fairly, rapidly in the ocean depending on the degree of wave- and wind-induced turbulence.

Vernet, M, Smith RC.  1997.  Effects of ultraviolet radiation on the pelagic Antarctic ecosystems. Ozone depletion and aquatic ecosystems. ( H├Ąder D, Ed.).:247-265., Austin, Texas: R. G. Landes Company Bioscience Publishers Abstract
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De Mora, SJ, Demers S, Vernet M.  2000.  The effects of UV radiation in the marine environment. Cambridge environmental chemistry series. :x,324p.., Cambridge ; New York: Cambridge University Press AbstractWebsite
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Vernet, M.  2000.  Effects of UV radiation on the physiology and ecology of marine phytoplankton. The effects of UV radiation in the marine environment. ( De Mora SJ, Demers S, Vernet M, Eds.).:238-278., Cambridge ; New York: Cambridge University Press Abstract
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Vernet, M, Kozlowski W.  2001.  Environmental variability and the net effect of UV radiation in the Antarctic marine ecosystem. Ecosystems and Ultraviolet Radiation. ( Cockwell CS, Blaustein AR, Eds.).:170-194., New York: Springer Verlag Abstract
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Kozlowski, WA, Deutschman D, Garibotti I, Trees C, Vernet M.  2011.  An evaluation of the application of CHEMTAX to Antarctic coastal pigment data. Deep-Sea Research Part I-Oceanographic Research Papers. 58:350-364.   10.1016/j.dsr.2011.01.008   AbstractWebsite

Presented is an evaluation of the application of CHEMTAX (CHEMical TAXonomy) to Antarctic coastal pigments collected along the western Antarctic Peninsula (wAP). Overall analytical error is < 20% for all pigments involved in the analysis. CHEMTAX was stable within a range of input pigment ratios; data were analyzed in three bins based on light depths, with each year's data run independently. Results were validated by comparison to those from CHEMTAX methods that included randomized error, feedback loops and additional diagnostic pigments. Blooms during mid-summer (chlorophyll a concentrations > 5 mu g L(-1)) were dominated primarily by either diatoms or cryptomonads. Mixed flagellates can also be abundant and Pheaocystis spp. and prasinophytes are frequently present in low concentrations. Comparison with microscopy shows CHEMTAX to give superior results in identifying Pheaocystis spp. with favorable results for other groups. This analysis shows CHEMTAX to be a reliable and stable tool for providing estimations of the main phytoplankton taxa in wAP waters based on long-term data collected during a 12-year time series. (C) 2011 Elsevier Ltd. All rights reserved.

Vernet, M, Mitchell BG, Sakshaug E, Johnsen G, Iturriaga R, Wassmann P.  1996.  Evidence for a novel pigment with in vivo absorption maximum at 708 nm associated with Phaeocystis cf pouchetii blooms. Marine Ecology-Progress Series. 133:253-262.   10.3354/meps133253   AbstractWebsite

The presence of a chlorophyll a-like (chi a) pigment, with an in vivo absorption maximum in the near-infrared region at 708 to 712 nm, was observed mainly in sedimenting material and Calanus hyperboreus fecal pellets associated with Phaeocystis cf. pouchetii Harlot blooms. (In vivo absorption is attributed to natural absorption found in naturally occurring particulate matter and seston. In vitro absorption refers to extracts in organic solvents.) This absorption peak was observed in conjunction with the absorption peak at 674 to 676 nm, commonly attributed to chi a and its derivatives. The in vivo absorption maximum in the near infrared, centered around 708 nm, was observed only in particulate matter and not in methanolic and aqueous acetonic extracts. Absorption efficiency (Q(a)) of individual particles measured by microphotometry revealed particles 3 to 4 mu m in diameter with an in vivo absorption maximum at 708 to 713 nm and no in vivo absorption peak at 676 nm, as expected for chlorophylls and its phaeopigments, indicating a different type of particle in the sample. The visible spectrum also had a broad absorption peak in the blue region, between 420 and 450 nm, suggesting a chlorophyll-like spectrum. The main chi degradation product analyzed by high-performance liquid chromatography of sedimenting matter was identified as a phaeophorbide a-like pigment, with absorption maximum in the red at 665 to 666 mn in organic solvents, with no indication of a pigment with in vitro absorption properties in the near infrared. The accumulation of the 708 nm in vivo absorption peak in particles associated with P. cf. pouchetii seems to be a widespread feature as it was observed during 3 different cruises to the Barents Sea, Fram Strait and the Kattegat. We propose 3 different hypotheses on the origin of this novel. peak in in vivo absorption not previously observed in marine environments: (1) P. cf. pouchetii has a chi a breakdown pathway which promotes the accumulation of a known chi degradation product with an in vivo absorption at 708 mn; (2) there is a new chl degradation product produced by grazing of C. hyperboreus on P. cf. pouchetii, as yet to be isolated; and (3) there is a new pigment, synthesized by either P. cf. pouchetii or another organism associated with this alga, during mature blooms of Phaeocystis. These hypotheses are discussed in view of the available evidence.

Huang, K, Ducklow H, Vernet M, Cassar N, Bender ML.  2012.  Export production and its regulating factors in the West Antarctica Peninsula region of the Southern Ocean. Global Biogeochemical Cycles. 26   10.1029/2010gb004028   AbstractWebsite

In connection with the Palmer LTER program, mixed layer water samples were collected during the cruise of the L. M. Gould in Jan., 2008 at 49 stations on a 20 x 100 km grid in the West Antarctica Peninsula (WAP) region of the Southern Ocean. In this study, [O-2]/[Ar] ratios and the triple isotope composition of dissolved O-2 were measured, and were used to estimate net community O-2 production (NCP) and gross primary O-2 production (GPP), respectively. These estimates are further converted to carbon export production, primary production and the f-ratio. Our measurements give NCP ranging from -3 to 76 mmol O-2 m(-2) day(-1) (-25 to 650 mg C m(-2) day(-1)), and GPP from 40 to 220 mmol O-2 m(-2) day(-1) (180 to 1010 mg C m(-2) day(-1)). The O-2 NCP/GPP ratios range from -0.04 to 0.43, corresponding to f-ratios of -0.08 to 0.83. NCP and the NCP/GPP ratio are highest in the northern coastal areas, and decrease to lower values toward the southern coastal area and the open ocean. The inshore-offshore gradient appears to be regulated primarily by iron availability, as supported by the positive correlation between NCP and F-v/F-m ratios (r(2) = 0.22, p < 0.05). Mixed layer depth (MLD) is inversely correlated with NCP (r(2) = 0.21, p < 0.002) and NCP/GPP (r(2) = 0.21, p < 0.02), and highest NCP occurred in the fresh water lenses probably formed from melted coastal glaciers. These results suggest that export production and the f-ratio increase where water stratification is intensified by input of fresh meltwater, and that mixed layer stratification is the major factor regulating NCP in the inner-shelf and coastal regions. Along-shelf variability of phytoplankton community composition is highly correlated with NCP, i.e., NCP increases when the diatom-dominated community in the south transitions to the cryptophyte-dominated one in the north. A high correlation is also observed between NCP and the logarithm of the surface chlorophyll concentration (r(2) = 0.72, p < 0.0001), which makes it possible to estimate carbon export as a function of Chl a concentration in this region.

Massom, RA, Stammerjohn SE, Smith RC, Pook MJ, Iannuzzi RA, Adams N, Martinson DG, Vernet M, Fraser WR, Quetin LB, Ross RM, Massom Y, Krouse HR.  2006.  Extreme anomalous atmospheric circulation in the West Antarctic Peninsula region in Austral Spring and Summer 2001/02, and its profound impact on sea ice and biota. Journal of Climate. 19:3544-3571.   10.1175/jcli3805.1   AbstractWebsite

Exceptional sea ice conditions occurred in the West Antarctic Peninsula (WAP) region from September 2001 to February 2002, resulting from a strongly positive atmospheric pressure anomaly in the South Atlantic coupled with strong negative anomalies in the Bellingshausen - Amundsen and southwest Weddell Seas. This created a strong and persistent north-northwesterly flow of mild and moist air across the WAP. In situ, satellite, and NCEP - NCAR Reanalysis (NNR) data are used to examine the profound and complex impact on regional sea ice, oceanography, and biota. Extensive sea ice melt, leading to an ocean mixed layer freshening and widespread ice surface flooding, snow - ice formation, and phytoplankton growth, coincided with extreme ice deformation and dynamic thickening. Sea ice dynamics were crucial to the development of an unusually early and rapid ( short) retreat season ( negative ice extent anomaly). Strong winds with a dominant northerly component created an unusually compact marginal ice zone and a major increase in ice thickness by deformation and over-rafting. This led to the atypical persistence of highly compact coastal ice through summer. Ecological effects were both positive and negative, the latter including an impact on the growth rate of larval Antarctic krill and the largest recorded between-season breeding population decrease and lowest reproductive success in a 30-yr Adelie penguin demographic time series. The unusual sea ice and snow cover conditions also contributed to the formation of a major phytoplankton bloom. Unexpectedly, the initial bloom occurred within compact sea ice and could not be detected in Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) ocean color data. This analysis demonstrates that sea ice extent alone is an inadequate descriptor of the regional sea ice state/conditions, from both a climatic and ecological perspective; further information is required on thickness and dynamics/deformation.