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We investigated the distribution, photoproduction, microbial uptake, and air-sea exchange of carbon monoxide (CO), a key photoproduct of chromophoric dissolved organic matter (CDOM), in open waters of the southeastern Beaufort Sea in autumn 2003 and spring 2004. Diurnal cycles of surface water CO concentration ([CO]) occurred in autumn but not in spring. In both seasons [CO] was well above air-equilibrium at most stations (maximum of 12,500% saturation) and dropped with depth to undetectable levels below 50 m. Mean surface water [CO] and CO water-column burdens (0-50 m) were 0.45 nmol L⁻¹ and 5.0 micromol m⁻² in autumn and 4.7 nmol L⁻¹ and 64.8 micromol m⁻² in spring, and the sea-to-air CO flux was 33 times higher in spring. The efficiency of CO photoproduction correlated linearly with CDOM across the Mackenzie River estuary, the Mackenzie Shelf, and the Amundsen Gulf. Modeled water-column CO photoproduction in spring was 15 times that in autumn (45.8 vs. 3.0 micromol m⁻² d⁻¹). Microbial CO uptake followed first-order kinetics in autumn while Hill-type, saturation, and inhibition kinetics were common in surface waters in spring. Bio-oxidation was the dominant CO loss term in autumn while gas exchange was almost equally important in spring. Higher photoproduction and slower bio-uptake in spring resulted in the wide autumn-spring differences in the [CO] distribution pattern and air-sea CO flux. CO cycling in cold northern waters differs both quantitatively and qualitatively from that in warmer seas.

This book, first published in 2000, provides a comprehensive review of UV radiation effects in the marine environment. A multidisciplinary approach is adopted to discuss all aspects from a physical, chemical and biological perspective. The book begins by describing the attenuation of UV radiation in the atmosphere and sea water, outlining the photochemical reactions involved and highlighting the role that such chemistry can play in influencing the biogeochemical cycling of various elements. The deleterious consequences of such radiation on organisms and strategies adopted to mitigate these harmful repercussions are discussed. The organisms considered range from virus and bacteria through phytoplankton and zooplankton to fish and mammals. The book is aimed at researchers and graduate students in photobiology, photochemistry and environmental science. It will also be useful as a supplementary text for courses in oceanography, climatology and ecology.

Spaceborne chlorophyll indices based on red fluorescence (wavelength = 680 nm) and water leaving radiance (Lw) in the visible spectrum (i.e., 400–700 nm) were evaluated in the St Lawrence Estuary (SLE) during September of 2011. Relationships between chlorophyll concentration (chl) and fluorescence were constructed based on fluorescence line height (FLH) measurements derived from a compact laser-based spectrofluorometer developed by ENEA (CASPER) and using spectral bands corresponding to the satellite sensor MERIS (MEdium Resolution Imaging Spectrometer). Chlorophyll concentration as estimated from CASPER (chlCASPER) was relatively high NE of the MTZ (upper Estuary), and nearby areas influenced by fronts or freshwater plumes derived from secondary rivers (lower estuary). These findings agree with historical shipboard measurements. In general, global chl products calculated from Lw had large biases (up to 27-fold overestimation and 50-fold underestimation) with respect to chlCASPER values. This was attributed to the smaller interference of detritus (mineral + organic non-living particulates) and chromophoric dissolved organic matter on chlCASPER estimates. We encourage the use of spectrofluorometry for developing and validating remote sensing models of chl in SLE waters and other coastal environments characterized by relatively low to moderate (<10 g·m−3) concentrations of detritus.

Pelagic–benthic coupling is relatively well studied in the marginal seas of the Arctic Ocean. Responses of meiofauna with regard to seasonal pulses of particulate organic matter are, however, rarely investigated. We examined the dynamics of metazoan meiofauna and assessed the strength of pelagic–benthic coupling in the Southeastern Beaufort Sea, during autumn 2003 and spring–summer 2004. Meiofauna abundance varied largely (range: 2.3 × 105 to 5 × 106 ind m−2), both spatially and temporally, and decreased with increasing depth (range: 24–549 m). Total meiofauna biomass exhibited similar temporal as well as spatial patterns as abundance and varied from 25 to 914 mg C m−2. Significant relationships between sediment photopigments and various representatives of meiofauna in summer and autumn likely indicate the use of sediment phytodetritus as food source for meiofauna. A carbon-based grazing model provided estimates of potential daily ingestion rates ranging from 32 to 723 mg C m−2. Estimated potential ingestion rates showed that meiofauna consumed from 11 to 477% of the sediment phytodetritus and that meiofauna were likely not food-restricted during spring and autumn. These results show that factors governing the distribution and abundance of metazoan meiofauna need to be better elucidated if we are to estimate the benthic carbon fluxes in marginal seas of the Arctic Ocean.

Vertical profiles of ultraviolet radiation (UVR) and photosynthetically available radiation (PAR) were measured under five large ice floes located in the North Water Polynya, northern Baffin Bay, in June 1998. Together with incident irradiance measurements, these profiles were used to assess the irradiance attenuation by the ice and its constituents. We also measured vertical distribution of absorption by colored dissolved organic matter (CDOM) and particulate organic matter (POM) in three melted ice cores. The ice thickness and snow depth varied from 0.5 to 1.3 m and from 1 to 9 cm, respectively. The ice-snow interface was infiltrated by meltwater. About 2-13% of incident UV-B irradiance was transmitted through the snow, ice, and ice algae biomass; transmittance increased to 5-19% for UV-A and to 5-12% for PAR. CDOM and POM contributed significantly to the attenuation of irradiance within the ice. The relatively high UVR transparency found in this study coincided with the seasonal maximum of incident UV irradiance. Hence, the resulting very high UVR:PAR ratio could affect the communities in the sea ice, at the ice-water interface, and in the surface waters underneath the ice cover. In addition, the strong absorption by CDOM found in this high-UVR environment indicates that significant photochemical reactions could occur.

V725 Sgr is a rather peculiar variable that showed a period increase during part of the twentieth century. Its behavior is attributed to rapid stellar evolution. V725 Sgr was monitored in V, R, I and J, H, K with the REM telescope, on la Silla, from 2008 August to 2009 November. Its light variation does not show a well-defined cyclic behavior. Its current [inline image]V[inline image] is similar to what it was 30-40 yrs ago. Its published motion suggests that V725 Sgr is located at a few kiloparsecs from the Sun. This implies that V725 Sgr is a giant rather than a supergiant star. From its mean colors we conclude that V725 Sgr is now an irregular variable of spectral type [inline image]K4 III.

V725 Sgr is a rather peculiar variable that showed a period increase during part of the twentieth century. Its behavior is attributed to rapid stellar evolution. V725 Sgr was monitored in V V , R R , I I and J J , H H , K K with the REM telescope, on La Silla, from 2008 August to 2009 November. Its light variation does not show a well-defined cyclic behavior. Its current〈V〉 〈 V 〉 is similar to what it was 30–40 yrs ago. Its published motion suggests that V725 Sgr is located at a few kiloparsecs from the Sun. This implies that V725 Sgr is a giant rather than a supergiant star. From its mean colors we conclude that V725 Sgr is now an irregular variable of spectral type∼K4 ∼ K 4 III.

The phytoplankton community of the Mackenzie shelf and the Amundsen Gulf (southeastern Beaufort Sea) was characterized (e.g. chlorophyllabiomass, primary production and taxonomy) during autumn 2002 (23 September to 14 October) and 2003 (30 September to 14 November). Spatial differences were evident, particularly in early autumn. Total phytoplankton biomass and the contribution of large cells (>5 μm) to biomass were higher in the Amundsen Gulf than on the Mackenzie shelf. The community of autotrophic cells (>10 μm) was numerically dominated by diatoms in the Amundsen Gulf and by dinoflagellates on the Mackenzie shelf. The abundance of chlorophytes revealed the influence of the Mackenzie River on the Mackenzie shelf. Contrary to 2002, when all measurements were from early October, the phytoplankton community of the Amundsen Gulf in 2003 presented the characteristics of a late bloom, which presumably peaked in late September. In early autumn, however, primary production rates were similar for both years, averaging 75 mg C m–2d–1. High primary production-to-biomass ratios and overall dominance of small cells (<5 μm) suggest that pelagic production in the southeastern Beaufort Sea was sustained by active recycling. During autumn 2003, a temporal decrease in phytoplankton biomass and primary production likely resulted from decreasing light availability. Overall, the autumnal primary production estimated in this study, from mid-September to the end of October, could increase the annual primary production previously estimated for the Beaufort Sea by 15%.

The seasonal development of bacterial abundance in first year bottom ice and underlying seawater were studied at Saroma-ko Lagoon in Hokkaido, Japan, and at Resolute Passage in the High Canadian Arctic during the algal bloom in spring 1992. The aim of this study was to evaluate whether the high algal concentrations reached during the bloom of ice algae have inhibitory effects on bacterial dynamics. Bacterial abundance (measured as total cell count and colony-forming units CFU) increased with the increase of the algal biomass up to 500 µg Chla·L -1 in both locations. Culturable fraction (measured as the percentage of CFU counts versus the total cell counts) was between 7% and 22% at Saroma-ko, and approximately 0.08% at Resolute Passage. When algal biomass exceeded 500 µg of Chla·L -1 , both bacterial abundance and culturable fraction decreased significantly. There was a maximum threshold of algal biomass (between 500 and 800 µg of Chla·L -1 ) after which bacterial dynamics become negatively coupled to the algal biomass. These results suggest that bactericidal and/or bacteriostatic compounds from these extremely high algal concentrations could explain the decrease in bacterial abundance and culturability in bottom ice observed after the ice algae bloom.Key words: bacteria, culturability, algae, inhibitory effects, sea ice, Arctic.

We studied CO₂ and O₂ dynamics in the western Antarctic Peninsula (WAP) waters in relation to (1) phytoplankton biomass, (2) microbial community primary production and respiration, and (3), for the first time, phytoplankton composition, during summer and fall in 3 consecutive years (2002, 2003 and 2004). The areal average of ΔpCO₂ (the difference between surface seawater and atmospheric partial pressure of CO₂) for the 3 yr was significantly negative (–20.04 ± 44.3 μatm, p < 0.01) during the summer to fall period in the region, possibly indicating a CO₂ sink. In the southern WAP (i.e. south of Anvers Island), ΔpCO₂ was significantly negative (–43.60 ± 39.06 μatm) during fall. In the northern WAP (north of Anvers Island), ΔpCO₂ values showed a more complex distribution during summer and fall (–4.96 ± 37.6 and 21.71 ± 22.39 μatm, respectively). Chlorophylla(chla) concentration averaged 1.03 ± 0.25 μg l–1and was higher in the south of the peninsula. Phytoplankton composition influenced chlaconcentration with higher and lower values for diatom- and phytoflagellate-dominated communities, respectively. A significant negative correlation existed between chlaand ΔpCO₂. From incubation experiments performed in the northern WAP, respiration was low (averaging 5.1 mmol O₂ m–3d–1), and the net community production (NCP) correlated negatively with ΔpCO₂ and positively with %O₂ saturation. However, despite the high NCP values measured, ΔpCO₂ was significantly positive in the northern WAP during the summer to fall period. Strong mixing and lower chlaconcentration may explain this result. In contrast, ΔpCO₂ was significantly negative in the southern WAP, possibly because of high surface water chlaconcentration.