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Peloquin, J, Swan C, Gruber N, Vogt M, Claustre H, Ras J, Uitz J, Barlow R, Behrenfeld M, Bidigare R, Dierssen H, Ditullio G, Fernandez E, Gallienne C, Gibb S, Goericke R, Harding L, Head E, Holligan P, Hooker S, Karl D, Landry M, Letelier R, Llewellyn CA, Lomas M, Lucas M, Mannino A, Marty J-C, Mitchell BG, Muller-Karger F, Nelson N, O'Brien C, Prezelin B, Repeta D, Jr. Smith WO, Smythe-Wright D, Stumpf R, Subramaniam A, Suzuki K, Trees C, Vernet M, Wasmund N, Wright S.  2013.  The MAREDAT global database of high performance liquid chromatography marine pigment measurements. 5(1):109-123.: Copernicus Publications AbstractWebsite
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Smith, RC, Ainley D, Baker K, Domack E, Emslie S, Fraser B, Kennett J, Leventer A, Mosley-Thompson E, Stammerjohn S, Vernet M.  1999.  Marine ecosystem sensitivity to climate change. Bioscience. 49:393-404.   10.2307/1313632   AbstractWebsite
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Ducklow, HW, Baker K, Martinson DG, Quetin LB, Ross RM, Smith RC, Stammerjohn SE, Vernet M, Fraser W.  2007.  Marine pelagic ecosystems: The West Antarctic Peninsula. Philosophical Transactions of the Royal Society B-Biological Sciences. 362:67-94.   10.1098/rstb.2006.1955   AbstractWebsite

The marine ecosystem of the West Antarctic Peninsula (WAP) extends from the Bellingshausen Sea to the northern tip of the peninsula and from the mostly glaciated coast across the continental shelf to the shelf break in the west. The glacially sculpted coastline along the peninsula is highly convoluted and characterized by deep embayments that are often interconnected by channels that facilitate transport of heat and nutrients into the shelf domain. The ecosystem is divided into three subregions, the continental slope, shelf and coastal regions, each with unique ocean dynamics, water mass and biological distributions. The WAP shelf lies within the Antarctic Sea Ice Zone (SIZ) and like other SIZs, the WAP system is very productive, supporting large stocks of marine mammals, birds and the Antarctic krill, Euphausia superba. Ecosystem dynamics is dominated by the seasonal and interannual variation in sea ice extent and retreat. The Antarctic Peninsula is one among the most rapidly warming regions on Earth, having experienced a 2 degrees C increase in the annual mean temperature and a 6 degrees C rise in the mean winter temperature since 1950. Delivery of heat from the Antarctic Circumpolar Current has increased significantly in the past decade, sufficient to drive to a 0.6 degrees C warming of the upper 300 m of shelf water. In the past 50 years and continuing in the twenty-first century, the warm, moist maritime climate of the northern WAP has been migrating south, displacing the once dominant cold, dry continental Antarctic climate and causing multi-level responses in the marine ecosystem. Ecosystem responses to the regional warming include increased heat transport, decreased sea ice extent and duration, local declines in ice-dependent Adelie penguins, increase in ice-tolerant gentoo and chinstrap penguins, alterations in phytoplankton and zooplankton community composition and changes in krill recruitment, abundance and availability to predators. The climate/ecological gradients extending along the WAP and the presence of monitoring systems, field stations and long-term research programmes make the region an invaluable observatory of climate change and marine ecosystem response.

Wassmann, P, Vernet M, Mitchell BG, Rey F.  1990.  Mass sedimentation of Phaeocystis pouchetii in the Barents Sea. Marine Ecology-Progress Series. 66:183-195.   10.3354/meps066183   AbstractWebsite

Mass sedimentation of gelatinous colonies of the prymensiophyte Phaeocystis pouchetii were observed in the upper 100 m of Atlantic water in the central Barents Sea. Sedimentation rates of particulate organic carbon and nitrogen as well as pigments were the highest recorded so far from oceanic environments of the North Atlantic or coastal areas of Norway. High relative concentrations of phytoplankton pigments found in the traps are interpreted as a combination of sinlung of intact phytoplankton cells and undegraded pigments present in macrozooplankton faecal pellets. Evldence presented in this study implies that the zooplankton community of the Barents Sea was not able to control this phytoplankton spnng bloom. The suspended and sedimenting organic matter was rlch in carbon and pigments, but poor in nitrogen. This is explained by the presence of large amounts of carbon-rich mucilage which P. pouchetii colonies develop during their development. In addition to diatoms, sedimentation of a gelatinous phytoplankton species like P. pouchetii may contribute signifi- cantly to the formation of marine snow and vertical flux from the euphotic zone. However, degradation of P. pouchetii derived detritus at depths less than 100 m greatly diminishes the likely significance of P. pouchetii blooms in processes such as the carbon flux to the deep ocean and sequestering of CO2.

Vernet, M, Smith RC.  2007.  Measuring and modeling primary production in marine pelagic ecosystems. Principles and standards for measuring primary production. ( Fahey TJ, Knapp AK, Eds.).:142-174., Oxford ; New York: Oxford University Press Abstract
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van den Belt, M, Costanza R, Demers S, Diaz S, Ferreyra GA, Gianesella SMF, Koch EW, Momo FR, Vernet M.  2007.  Mediated modeling for integrating science and stakeholders: impacts of enhanced ultraviolet-B radiation on ecosystem services. Communicating global change science to society : an assessment and case studies. ( Tiessen H, Brklacich M, Breulmann G, Menezes RSC, Eds.)., Washington DC: Island Press Abstract
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van den Belt, M, Bianciotto OA, Costanza R, Demers S, Diaz S, Ferreyra GA, Koch EW, Momo FR, Vernet M.  2006.  Mediated modeling of the impacts of enhanced UV-B radiation on ecosystem services. Photochemistry and Photobiology. 82:865-877.   10.1562/2005-10-19-ir-722   AbstractWebsite

This article describes the use of group model building to facilitate interaction with stakeholders, synthesize research results and assist in the development of hypotheses about climate change at the global level in relation to UV-B radiation and ecosystem service valuation. The objective was to provide a platform for integration of the various research components within a multidisciplinary research project as a basis for interaction with stakeholders with backgrounds in areas other than science. An integrated summary of the scientific findings, along with stakeholder input, was intended to produce a bridge between science and policymaking. We used a mediated modeling approach that was implemented as a pilot project in Ushuaia, Argentina. The investigation was divided into two participatory workshops: data gathering and model evaluation. Scientists and the local stakeholders supported the valuation of ecosystem services as a useful common denominator for integrating the various scientific results. The concept of economic impacts in aquatic and marsh systems was represented by values for ecosystem services altered by UV-B radiation. In addition, direct local socioeconomic impacts of enhanced UV-B radiation were modeled, using data from Ushuaia. We worked with 5 global latitudinal regions, focusing on net primary production and biomass for the marine system and on 3 plant species for the marsh system. Ecosystem service values were calculated for both sectors. The synthesis model reflects the conclusions from the literature and from experimental research at the global level. UV-B is not a significant stress for the marshes, relative to the potential impact of increases in the sea level. Enhanced UV-B favors microbial dynamics in marine systems that could cause a significant shift from primary producers to bacteria at the community level. In addition, synergetic effects of UV-B and certain pollutants potentiate the shift to heterotrophs. This may impact the oceanic carbon cycle by increasing the ratio of respiratory to photosynthetic organisms in surface waters and, thus, the role of the ocean as a carbon sink for atmospheric CO2. In summary, although changes in the marine sector due to anthropogenic influences may affect global climate change, marshes are expected to primarily be affected by climate change.

Garcia-Munoz, C, Lubian LM, Garcia CM, Marrero-Diaz A, Sangra P, Vernet M.  2013.  A mesoscale study of phytoplankton assemblages around the South Shetland Islands (Antarctica). Polar Biology. 36:1107-1123.   10.1007/s00300-013-1333-5   AbstractWebsite

Phytoplankton assemblages around the South Shetland Islands (SSI) were closely related to mesoscale physical features, based on high spatial resolution sampling performed during the summer of 2010. Sampling was done in 8 transects with stations 9 km apart. Phytoplankton groups were described using flow cytometry, FlowCAM and HPLC/CHEMTAX pigment analysis. Nanophytoplankton (2-20 mu m) was predominant throughout the study area, which was dominated by small diatoms. They were distributed along the stratified waters of the SSI shelf and in the centre of the Bransfield Strait where an anticyclonic eddy was detected, established between two frontal structures [Bransfield Front and Peninsula Front (PF)]. The highest concentrations correlated with mid-to-high temperatures (1.07 A degrees C) and mid-salinities (34.03) corresponding with Transitional Bellinghausen Water stations. Haptophytes distribution co-varied with small diatoms but also appeared in those vertical mixed stations with Transitional Zonal Water with Weddell Sea influence. A shift from smaller to larger diatoms was detected at the ice edge in the Antarctic Sound. Cryptophytes were restricted to stratified stations of the SSI shelf and those associated with the PF, while small prasinophytes were the only group occupying deeper and colder waters of the Drake Passage, beneath the Antarctic Surface Water, north of a narrow frontal region described here for the first time (Shetland Front). Phytoplankton assemblages around the SSI were strongly connected with the Bransfield Current System, supporting a clockwise circulation around the archipelago. The Bransfield Current System components are permanent structures during the austral summer suggesting that the distribution of phytoplankton, which responds to these structures, must also be a quasi-permanent feature.

Cary, SC, Lovette JT, Perl PJ, Huntley ME.  1992.  A microencapsulation technique for introducing pure compounds in zooplankton diets. Limnology and Oceanography. 37:404-413.   10.4319/lo.1992.37.2.0404   AbstractWebsite

Sodium alginate microcapsules have low permeability, high digestibility, and are specifically suited as artificial food particles for zooplankton. The microcapsules may be used to introduce pure compounds into zooplankton diets and to study the biochemical fate of those compounds. We encapsulated a highly labile molecule, Chl a, and traced it and its principal degradation products in zooplankton grazing experiments. Chlorophyll was not degraded or lost during the encapsulation procedure and remained stable for at least 6 d at 4-degrees-C in the dark. The microcapsules were ingestible and digestible by female Calanus pacific, and fecal pellets were formed at normal rates, 40-60 min after ingestion. Two quantitative feeding experiments were conducted with pure chlorophyll. The mean loss of ingested pigment was 85.9% (+/-7.2%) and 76.1% (+/-6.1%). In the second experiment, we analyzed the medium to determine if any chlorophyll may have gone into solution; <2% of the total "lost" chlorophyll went into solution. We conclude that a significant amount of ingested Chl a is degraded into non-fluorescent compounds during passage through copepod guts.

Verity, PG, Vernet M.  1992.  Microzooplankton grazing, pigments, and composition of plankton communities during late spring in two Norwegian fjords. Sarsia. 77:263-274. AbstractWebsite

The coupling between primary and secondary production, and its impact upon vertical flux of organic matter, was studied in a fjord and a poll in late spring. We report here the abundance and vertical distribution of phototrophic and heterotrophic plankton; their growth rates and grazing by microzooplankton; and the degradation products of chlorophyll a due to grazing. Both fjord and poll contained abundant nano- and microplankton communities. Typical peak concentrations were 2-4 x 10(3) cells ml-1 of photosynthetic nanoplankton, 1-3 x 10(3) cells . ml-1 of heterotrophic (aplastidic) nanoplankton, 4-8 x 10(4) cells . ml-1 of cyanobacteria, and 4-9 ciliates . ml-1. Maximum abundances occurred within the euphotic zone. The dominant phytoplankton were chlorophyll c-containing taxa, principally prymnesiophytes and chrysophytes. Grazing by < 200 mum microzooplankton generally removed 50-100 % and 20-100 % of daily production by < 10 mum and < 2 mum cells, respectively, including autotrophic and heterotrophic taxa. Planktonic ciliates were numerically important microzooplankton. Phaeophorbides were the dominant form of phaeopigments. The three main phaeophorbide forms decreased in concentration during experimental incubations, while phaeophytins and chlorophyllide a were differentially produced by microzooplankton grazing. When corrected for losses not related to grazing, grazing rates estimated from pigments were similar to those derived from cell enumerations. Based upon measured primary production and sedimentation rates, little newly formed particulate organic matter was apparently available for export to depth. The key attribute to explain the close coupling between production and consumption was the small cell size of phototrophs and the accompanying importance of microzooplankton.

Sakshaug, E, Johnsen G, Andresen K, Vernet M.  1991.  Modeling of light-dependent algal photosynthesis and growth: experiments with the Barents Sea diatoms Thalassiosira nordenskioeldii and Chaetoceros furcellatus. Deep-Sea Research Part a-Oceanographic Research Papers. 38:415-430.   10.1016/0198-0149(91)90044-g   AbstractWebsite

The models by SAKSHAUG et al. (1989, Limnology and Oceanography, 34, 198-205) and WEBB et al. (1974, Oecologia, 17, 281-291), for prediction of the gross growth rate of phytoplankton and short-term photosynthesis, respectively, have been modified on the basis of experiments with cultures of the centric diatoms Thalassiosira nordenskioeldii and Chaetoceros furcellatus grown at 0.5-degrees-C at combinations of two irradiances (25 and 400-mu-mol m-2 s-1) and two day-lengths (12 and 24 h). The models have one spectrum, degrees-sigma, which represents chlorophyll a (Chla) specific absorption of photosynthetically usable light, and introduces a factor q which represents Chla per PSU, functionally defined. The models describe phytoplankton growth in terms of physiologically relevant coefficients. A properly scaled fluorescence excitation spectrum (degrees-F) represents a more appropriate estimate for degrees-sigma than the Chla-specific absorption spectrum degrees-a(c) judging from calculations of PHI-max (= alpha-B/degrees-sigma). On the basis of degrees-F, PHI-max is 0.04 g-at C(mol photons)-1 for gross growth and about 0.05-0.08 for short-term carbon uptake (unfiltered samples). Calculations based on degrees-a(c) yield values for PHI-max which on average are 44% lower. P vs I (photosynthesis vs irradiance) parameters are relatively independent of day-length and highly dependent on growth irradiance. The product of q [mg Chla (mol PSU)-1] and tau (the minimum turnover time of the photosynthetic unit, h) increases 2-3-fold from high to low irradiance, thus P(m)B (= PHI-max/q-tau) and I(k) (= 1/q-tau-degrees-sigma) decreased. degrees-F decreases from high to low irradiance. Carbon-specific dark respiration rates are < 0.09 day-1. Pigment ratios vary inversely with irradiance and day-length. The Chla:C ratio is particularly low under high, strong continuous light; Chlc:Chla ratios are higher for shade- than for light-adapted cells, while the converse is true for the ratio of the sum of the photoprotective pigments diadinoxanthin and diatoxanthin to Chla. The fucoxanthin:Chla ratio is virtually independent of the light regime. The two species are similar with respect to variations in growth rate (0.09-0.33 day-1) and I(k) (31-36 vs 49-100-mu-mol m-2 s-1 at low and high irradiance respectively). P(m)B and alpha-B for growth as well as degrees-F are systematically higher for C. furcellatus than for T. nordenskioeldii, while the product q-tau is lower. C. furcellatus is considerably more plastic than T. nordenskioeldii with respect to pigment composition.

Gabric, AJ, Matrai PA, Vernet M.  1999.  Modelling the production and cycling of dimethylsulphide during the vernal bloom in the Barents Sea. Tellus Series B-Chemical and Physical Meteorology. 51:919-937.   10.1034/j.1600-0889.1999.t01-4-00005.x   AbstractWebsite

Recent field work suggests an important role for the Arctic Ocean in the global budget of dimethylsulphide (DMS), a climatically active volatile sulphur compound. Here, we have used an existing DMS production model and local field data to examine the temporal dynamics of the DMS cycle during the spring bloom in the Arctic shelf of the Barents Sea. The timing and duration of the spring phytoplankton bloom has been shown to be a key determinant of the flux of DMS to the atmosphere. Particular oceanic conditions due to the retreating ice-edge (e.g., a shallow mixed layer) can have an important effect on the timing of the phytoplankton bloom and thus the efflux of DMS in this region. Model simulations support the view that algal taxonomy is not the most important factor determining DMS production in these waters. The mean vernal DMS flux is predicted to be 0.063 mg S m(-2) d(-1) which is in general agreement with previous summer season averages in the Arctic.

Diaz, S, Booth CR, Armstrong R, Brunat C, Cabrera S, Camilion C, Casiccia C, Deferrari G, Fuenzalida H, Lovengreen C, Paladini A, Pedroni J, Rosales A, Zagarese H, Vernet M.  2005.  Multichannel radiometer calibration: a new approach. Applied Optics. 44:5374-5380.   10.1364/ao.44.005374   AbstractWebsite

The error in irradiance measured with Sun-calibrated multichannel radiometers may be large when the solar zenith angle (SZA) increases. This could be particularly detrimental in radiometers installed at mid and high latitudes, where SZAs at noon are larger than 50 degrees during part of the year. When a multi-regressive methodology, including the total ozone column and SZA, was applied in the calculation of the calibration constant, an important improvement was observed. By combining two different equations, an improvement was obtained at almost all the SZAs in the calibration. An independent test that compared the irradiance of a multichannel instrument and a spectroradiometer installed in Ushuaia, Argentina, was used to confirm the results. (c) 2005 Optical Society of America.

Ducklow, HW, Schofield O, Vernet M, Stammerjohn S, Erickson M.  2012.  Multiscale control of bacterial production by phytoplankton dynamics and sea ice along the western Antarctic Peninsula: A regional and decadal investigation. Journal of Marine Systems. 98-99:26-39.   10.1016/j.jmarsys.2012.03.003   AbstractWebsite

We present results on phytoplankton and bacterial production and related hydrographic properties collected on nine annual summer cruises along the western Antarctic Peninsula. This region is strongly influenced by inter-annual variations in the duration and extent of sea ice cover, necessitating a decade-scale study. Our study area transitions from a nearshore region influenced by summer runoff from glaciers to an offshore, slope region dominated by the Antarctic Circumpolar Current. The summer bacterial assemblage is the product of seasonal warming and freshening following spring sea ice retreat and the plankton succession occurring in that evolving water mass. Bacterial production rates averaged 20 mg C m(-2) d(-1) and were a low (5%) fraction of the primary production (PP). There was significant variation in BP between regions and years, reflecting the variability in sea ice, chlorophyll and PP. Leucine incorporation was significantly correlated (r(2) ranging 0.2-0.7, p<0.001) with both chlorophyll and PP across depths, regions and years indicating strong phytoplankton-bacteria coupling. Relationships with temperature were variable, including positive, negative and insignificant relationships (r(2)<0.2 for regressions with p<0.05). Bacterial production is regulated indirectly by variations in sea ice cover within regions and over years, setting the levels of phytoplankton biomass accumulation and PP rates; these in turn fuel BP, to which PP is coupled via direct release from phytoplankton or other less direct pathways. (C) 2012 Elsevier B.V. All rights reserved.