Climate change and diminishing seasonality in Arctic benthic processes

The iconic picture of Arctic marine ecosystems shows an intense pulse of biological productivity around the spring bloom that is sustained while fresh organic matter (OM) is available, after which ecosystem activity declines to basal levels in autumn and winter. We investigated seasonality in benthic biogeochemical cycling at three stations in a high Arctic fjord that has recently lost much of its seasonal ice-cover. Unlike observations from other Arctic locations, we find little seasonality in sediment community respiration and bioturbation rates, although different sediment reworking modes varied through the year. Nutrient fluxes did vary, suggesting that, although OM was processed at similar rates, seasonality in its quality led to spring/summer peaks in inorganic nitrogen and silicate fluxes. These patterns correspond to published information on seasonality in vertical flux at the stations. Largely ice-free Kongsfjorden has a considerable detrital pool in soft sediments which sustain benthic communities over the year. Sources of this include macroalgae and terrestrial runoff. Climate change leading to less ice cover, higher light availability and expanded benthic habitat may lead to more detrital carbon in the system, dampening the quantitative importance of seasonal pulses of phytodetritus to seafloor communities in some areas of the Arctic. This article is part of the theme issue ‘The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning'

A Fair Treatment For All Growers At The Auction

This paper deals with the question, whether the current procedure flowers are auctioned at a major dutch auctioning centre can be considered as fair or not from the growers view. Some growers have stated, that this is not the case. We first introduce a notion of "fairness", which is meant to approximate the real feeling of a fair or unfair treatment. Then we compare the current procedure used at the auctioning centre with other procedures which we developed and present their effect on our approximation of fairness in a simulation environment. We conclude that the auctioning centre should revise their auctioning system, since it shows a significant bias in the growers' chances to sell their products. We show how this drawback can be overcome with. 1 Introduction Flowers Auction is an international trading center with auctioning centers in Naaldwijk and Bleiswijk, the Netherlands. In these auctioning centers a wide range of high quality flowers and plants are traded. The hear..

Direct evidence of a biologically active coastal silicate pump: Ecological implications

International audienceEcological shifts from diatoms to other phytoplankton species have been related to decreasing Si:N and Si:P nutrient ratios. The Bay of Brest is such a perturbated ecosystem where Si has become limiting but where diatoms continue to dominate the phytoplankton throughout the productive period. Several hypothesis have been invoked to account for this dilemma. The most recent combines suspension feeder activity and Si recycling. Suspension feeder activity, stimulated by the proliferation of the invasive species Crepidula fornicata, would be the driving force of a biologically active silicate pump which would (1) retain Si within the Bay during spring and (2) provide the Si necessary for diatoms during summer. During the year 2000, this hypothesis was successfully tested. Direct evidence of silicic acid limitation has been provided, and during summer, benthic fluxes measured at a site with a high density of C. fornicata are one order of magnitude higher than those measured at the site with no C. fornicata. Seasonal budgets of Si inputs and diatom demand demonstrated that diatom production during summer depends strongly on Si recycling at the sediment-water interface. Thus, if C. fornicata decreases benthic biodiversity and perturbates the development of the native Great Scallop (Pecten maximus), it also helps the Bay cope with elevated N inputs. The proposed removal of C. fornicata might be economically desirable from a fisheries economic viewpoint, but it clearly would be associated, in the present context of excessive N inputs, to a potential risk of harmful algal blooms during summer

In vitro evaluation of NA1-115-7-loaded nanoemulsions, an MCL-1-specific inhibitor of natural origin, intended to treat B-cell lymphoproliferative disorders after oral administration

International audienceMCL-1, an anti-apoptotic member of the BCL-2 protein family, is overexpressed in many types of cancer and contributes to chemotherapy resistance. The drimane derivative NA1-115-7 is a natural compound isolated from Zygogynum pancheri that can be considered as a very promising lead for treating MCL-1-dependent hematological malignancies. As this drug suffers from low stability in acidic conditions and poor aqueous solubility, we evaluated the potential oral use of NA1-115-7 by encapsulating it in lipid nanoemulsions (NA-NEs) prepared by spontaneous emulsification. NA-NEs showed a particle size of 41.9 ± 2.2 nm, PDI of 0.131 ± 0.016, zeta potential of-5.8 ± 3.4 mV, encapsulation efficiency of approximately 100 % at a concentration of 24 mM. The stability of NA-1-115-7 was sixfold higher than that of the unencapsulated drug in simulated gastric fluid. NA-NEs significantly restored apoptosis and halved the effective doses of NA1-115-7 on BL2, a Burkitt lymphoma cell line, without toxicity in normal cells. Such a drug-delivery system appears to be particularly interesting for the oral administration of NA1-115-7, as it improves its solubility and stability, as well as efficacy, by reducing the therapeutic dose, making it possible to further consider in-vivo studies of this promising drug in BL2 xenografted mice

NA1—115—7, from Zygogynum pancheri, is a new selective MCL-1 inhibitor inducing the apoptosis of hematological cancer cells but non-toxic to normal blood cells or cardiomyocytes

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