ALBERT

Description: The erythrocytes of mammals represent a good model to evaluate the cytotoxicity of molecules, organic and inorganic, natural or synthetic, by cellular damage measure. Indeed, before any investigation on the mechanism of action of different molecules, it is important to perform a cytotoxicity assay. Among the different cytotoxicity assays that assess a possible toxicity in the red blood cells is the rate of haemolysis. This essay is based on the evaluation of the alterations of red cell membranes in the presence of an eventual xenobiotic. Red blood cells are the main cells in circulation, and they are responsible for transporting oxygen; in fact, any alterations of this process could be lethal. The plasma membrane of red blood cells is a multi-component structure such as to confer to these cells their characteristic biconcave shape, high flexibility, elasticity and deformability. However, there are clear signs of cellular suffering if there are any alterations to this structure. One method of toxicity assessment is based on measurement of the efflux of haemoglobin from suspended red blood cells. Haemolysis, and therefore the loss of haemoglobin, is the signal stability of the cell membrane of the erythrocytes. In recent years, the discovery of programmed cell death in mammalian red blood cells presented a diversification of the response to injury by these a-nucleated cells. This review shows that mammals' erythrocytes might serve well as a model cell to study on the cellular and molecular mechanisms of many treatments. Copyright © 2015 John Wiley & Sons, Ltd.

Description: Satellite CO 2 retrievals from the Greenhouse gases Observing SATellite (GOSAT), Atmospheric Infrared Sounder (AIRS), and Tropospheric Emission Spectrometer (TES) and in-situ measurements from the Earth System Research Laboratory (NOAA-ESRL) Surface CO 2 and Total Carbon Column Observing Network (TCCON) are utilized to explore the CO 2 variability at different altitudes. A multiple regression method is used to calculate the CO 2 annual cycle and semiannual cycle amplitudes from different data sets. The CO 2 annual cycle and semiannual cycle amplitudes for GOSAT X CO2 and TCCON X CO2 are consistent, but smaller than those seen in the NOAA-ESRL surface data. The CO 2 annual and semiannual cycles are smallest in the AIRS mid-tropospheric CO 2 compared with other data sets in the northern hemisphere. The amplitudes for the CO 2 annual cycle and semiannual cycle from GOSAT, TES, and AIRS CO 2 are small and comparable to each other in the southern hemisphere. Similar regression analysis is applied to the Model for OZone And Related chemical Tracers-2 (MOZART-2) and CarbonTracker model CO 2 . The convolved model CO 2 annual cycle and semiannual cycle amplitudes are similar to those from the satellite CO 2 retrievals, although the models tend to underestimate the CO 2 seasonal cycle amplitudes in the northern hemisphere mid-latitudes and underestimate the CO 2 semi-annual cycle amplitudes in the high latitudes. These results can be used to better understand the vertical structures for the CO 2 annual cycle and semiannual cycle and help identify deficiencies in the models, which are very important for the carbon budget study. This article is protected by copyright. All rights reserved.

Description: Knowledge of the relative contributions of phytoplankton size classes to zooplankton biomass is necessary to understand food-web functioning and response to climate change. During the DEep Water formation EXperiment (DEWEX), conducted in the north-west Mediterranean Sea in winter (February) and spring (April) of 2013, we investigated phytoplankton-zooplankton trophic links in contrasting oligotrophic and eutrophic conditions. Size fractionated particulate matter (pico, nano and micro POM) and zooplankton (64 to 〉 4000 μm) composition and carbon and nitrogen stable isotope ratios were measured inside and outside of the nutrient rich deep convection zone in the central Liguro-Provencal basin. In winter, phytoplankton biomass was low (0.28 mg.m −3 ) and evenly spread among pico, nano and micro phytoplankton. Using an isotope mixing model we estimated average contributions to zooplankton biomass by pico, nano and micro POM of 28, 59 and 15% respectively. In spring, the nutrient poor region outside of the convection zone had low phytoplankton biomass (0.58 mg.m −3 ) and was dominated by pico/nano phytoplankton. Estimated average contributions to zooplankton biomass by pico, nano and micro POM were 64, 28 and 10% respectively, although the model did not differentiate well between pico and nano POM in this region. In the deep convection zone, spring phytoplankton biomass was high (1.34 mg.m −3 ) and dominated by micro/nano phytoplankton. Estimated average contributions to zooplankton biomass by pico, nano and micro POM were 42, 42 and 20% respectively, indicating that a large part of the microphytoplankton biomass may have remained ungrazed.

Description: The effects of declining Arctic sea ice on local ecosystem productivity are not well understood but have been shown to vary inter-specifically, spatially, and temporally. Because marine mammals occupy upper trophic-levels in Arctic food webs, they may be useful indicators for understanding variation in ecosystem productivity. Polar bears ( Ursus maritimus ) are apex predators that primarily consume benthic and pelagic-feeding ice-associated seals. As such, their productivity integrates sea ice conditions and the ecosystem supporting them. Declining sea ice availability has been linked to negative population effects for polar bears but does not fully explain observed population changes. We examined relationships between spring foraging success of polar bears and sea ice conditions, prey productivity, and general patterns of ecosystem productivity in the Beaufort and Chukchi Seas. Fasting status (≥ 7 days) was estimated using serum urea and creatinine levels of 1,448 samples collected from 1,177 adult and subadult bears across three subpopulations. Fasting increased in the Beaufort Sea between 1983-1999 and 2000-2016 and was related to an index of ringed seal body condition. This change was concurrent with declines in body condition of polar bears and observed changes in the diet, condition and/or reproduction of four other vertebrate consumers within the food chain. In contrast, fasting declined in Chukchi Sea polar bears between periods and was less common than in the two Beaufort Sea subpopulations consistent with studies demonstrating higher primary productivity and maintenance or improved body condition in polar bears, ringed seals, and bearded seals despite recent sea ice loss in this region. Consistency between regional and temporal variation in spring polar bear fasting and food web productivity suggest that polar bears may be a useful indicator species. Further, our results suggest that spatial and temporal ecological variation is important in affecting upper trophic level productivity in these marine ecosystems. This article is protected by copyright. All rights reserved.

Description: Evaluating plant community response to atmospheric CO 2 rise is critical to predicting ecosystem level change. Freshwater lakes offer a model system for examining CO 2 effects as submersed macrophyte species differ greatly in their growth responses to CO 2 enrichment, and free CO 2 concentrations among these habitats show a wide range of natural, spatial variation. We determined free CO 2 concentrations in the water column and sediment porewater in littoral zones with pH〈6.0 in Adirondack Mountain (NY, USA) lakes, and derived a community CO 2 responsiveness index (CCRI) based on quantitative sampling of 15 submersed macrophyte communities coupled with greenhouse-derived growth responses to CO 2 enrichment of constituent species to test two hypotheses: (1) CCRI, which is higher for communities dominated by species with greater growth responses to CO 2 enrichment, is positively correlated to free [CO 2 ] in the water column, and (2) in natural communities, the percent of sediment CO 2 -using species, which are relatively unresponsive to CO 2 enrichment, is negatively correlated to free [CO 2 ]. A significant positive correlation (P=0.003) between our physiologically-based CCRI and the concentration of free CO 2 in the water column supported our primary hypothesis that sites with higher levels of free CO 2 are dominated by species with greater growth responses to CO 2 enrichment. Our CCRI is also highly significantly correlated (P〈0.001) to the first axis scores for the same vegetation data from polar ordination. Finally, the relative importance of species that use sediment CO 2 as a photosynthetic carbon source is significantly negatively correlated (P = 0.029) with the concentration of free CO 2 in the water column. Our results indicate that natural variations in CO 2 levels are important determinants of submersed macrophyte community composition. Further, we demonstrate the utility of a physiologically-based index of community composition, our CCRI, as an ecologically valid measure of community response to CO 2 . This article is protected by copyright. All rights reserved.

Description: The Gulf of Lion is an important area of deep convection, where intense winter vertical mixing brings nutrients up from deeper layers, promoting the largest bloom in the Mediterranean at the end of winter/early spring. In DEWEX program conducted cruises in February and April 2013 to investigate the ecosystem level impacts of deep water convection. Zooplankton data were collected through net sampling and imaging with an Underwater Vision Profiler. In winter, low zooplankton abundance and biomass were observed in the Deep Convection Zone ( DCZ) and higher values on its periphery. In spring, this pattern reversed with high biomass in the DCZ and lower values on the periphery. On average for the whole area, the potential grazing impact was estimated to increase by one order of magnitude from winter to spring. In April, all areas except the DCZ incurred top-down control by zooplankton on the phytoplankton stock. In the DCZ, the chlorophyll -a values remained high despite the high zooplankton biomass and carbon demand, indicating a sustained bottom-up control. The zooplankton community composition was comparable for both periods, typified by high copepod dominance, but with some differences between the DCZ and peripheral regions. In spring the DCZ was characterized by a strong increase in herbivorous species such as Centropages typicus and Calanus helgolandicus , and an increase in the number of large zooplankton individuals. Our study indicates that the DCZ is likely an area of both enhanced energy transfer to higher trophic levels and organic matter export in the North Western Mediterranean Sea. This article is protected by copyright. All rights reserved.

Description: Animals can be important in modulating ecosystem-level nutrient cycling, although their importance varies greatly among species and ecosystems. Nutrient cycling rates of individual animals represent valuable data for testing the predictions of important frameworks such as the Metabolic Theory of Ecology (MTE) and ecological stoichiometry (ES). They also represent an important set of functional traits that may reflect both environmental and phylogenetic influences. Over the past two decades, studies of animal-mediated nutrient cycling have increased dramatically, especially in aquatic ecosystems. Here we present a global compilation of aquatic animal nutrient excretion rates. The dataset includes 10,534 observations from freshwater and marine animals of N and/or P excretion rates. These observations represent 491 species, including most aquatic phyla. Coverage varies greatly among phyla and other taxonomic levels. The dataset includes information on animal body size, ambient temperature, taxonomic affiliations, and animal body N:P. This data set was used to test predictions of MTE and ES, as described in Vanni and McIntyre (2016; Ecology DOI: 10.1002/ecy.1582). This article is protected by copyright. All rights reserved.

Description: Spatial and temporal distribution of zooplankton off New Caledonia in the eastern Coral Sea was studied during two multidisciplinary cruises in 2011, during the cool and the hot seasons. Acoustic measurements of zooplankton were made using a shipborne acoustic Doppler current profiler (S-ADCP), a scientific echosounder and a Tracor acoustic profiling system (TAPS). Relative backscatter from ADCP was converted to biomass estimates using zooplankton weights from net-samples collected during the cruises. Zooplankton biomass was estimated using four methods: weighing, digital imaging (ZooScan), ADCP and TAPS. Significant correlations were found between the different biomass estimators and between the backscatters of the ADCP and the echosounder. There was a consistent diel pattern in ADCP derived biomass and echosounder backscatter resulting from the diel vertical migration (DVM) of zooplankton. Higher DVM amplitudes were associated with higher abundance of small zooplankton and cold waters to the south of the study area, while lower DVM amplitudes in the north were associated with warmer waters and higher abundance of large organisms. Zooplankton was largely dominated by copepods (71-73%) among which calanoids prevailed (40-42%), with Paracalanus spp. as the dominant species (16-17%). Overall, zooplankton exhibited low abundance and biomass (mean night dry biomass of 4.7 ± 2.2mg m 3 during the cool season and 2.4 ± 0.4mg m 3 during the hot season) but high richness and diversity (Shannon index ∼4). Substantially enhanced biomass and abundance appeared to be episodically associated with mesoscale features contributing to shape a rather patchy zooplankton distribution. This article is protected by copyright. All rights reserved.

Description: Abstract We evaluate the stability of the radiometric calibration of the Atmospheric Infrared Sounder (AIRS) by analyzing the trend in the time series of the difference between the brightness temperatures measured in the 1231 cm‐1 atmospheric window channel, corrected for atmospheric transmission, relative to the Real‐Time Global Sea Surface Temperature (RTGSST) for oceans between 30S and 30N. The observed bias relative to the RTGSST between 2002 and 2019 was less than 250 mK, with a 2‐3 mK/yr trend. Establishing the stability of the 1231 cm‐1 channel at tropical ocean temperatures at the 2‐3 mK/yr level is a necessary but not sufficient condition of establishing the calibration stability of all AIRS channels over the full dynamic range at a comparable level. Our analysis indirectly establishes the stability of the RTGSST for the 2002‐2017 time period and region at the 2‐3 mK/yr level, with a degradation since 2017.

Description: Zooplankton play a key role in the regeneration of nitrogen and phosphorus in the ocean through grazing and metabolism. This study investigates the role of the organic and inorganic nitrogen and phosphorus compounds released by copepods on biogeochemical processes and on the microbial community composition during the OUTPACE cruise (18 February–3 April 2015) at three long-duration stations (LD). Two LD stations were located in the Melanesian Archipelago region (MA; LD A and LD B) and one in the South Pacific Gyre (SG; LD C), which represent oligotrophic and ultra-oligotrophic regions respectively. At each station, on-board microcosm experiments were performed with locally sampled organisms, comprising a mix of epipelagic copepods fed with their natural food and then incubated along with wild microbial assemblages. In the presence of copepods, ammonium and dissolved organic nitrogen showed a significant increase compared to a control in two situations: in ammonium concentration (rate: 0.29 µmol L−1 h−1 after 4 h of incubation) in LD C and in dissolved organic nitrogen concentration (rate: 2.13 µmol L−1 h−1 after 0.5 h of incubation) in LD A. In addition, during the three experiments, an enhanced remineralization (ammonification and nitrification) was observed when adding copepods compared to the controls. A shift in the composition of the active bacterial community was observed for the experiments in LD A and LD B, which were mainly characterized by an increase in Alteromonadales and SAR11, respectively, and linked with changes in nutrient concentrations. In the experiment performed in LD C, both groups increased but at different periods of incubation. Alteromonadales increased between 1 and 2 h after the beginning of the experiment, and SAR 11 at the end of incubation. Our results in near in situ conditions show that copepods can be a source of organic and inorganic compounds for bacterial communities, which respond to excretion pulses at different timescales, depending on the initial environmental conditions and on their community composition. These processes can significantly contribute to nutrient recycling and regenerated production in the photic zone of ultra-oligotrophic and oligotrophic oceanic regions.