Glacial influence on the geochemistry of riverine iron fluxes to the Gulf of Alaska and effects of deglaciation

This paper is not subject to U.S. copyright. The definitive version was published in Geophysical Research Letters 38 (2011): L16605, doi:10.1029/2011GL048367.Riverine iron (Fe) derived from glacial weathering is a critical micronutrient source to ecosystems of the Gulf of Alaska (GoA). Here we demonstrate that the source and chemical nature of riverine Fe input to the GoA could change dramatically due to the widespread watershed deglaciation that is underway. We examine Fe size partitioning, speciation, and isotopic composition in tributaries of the Copper River which exemplify a long-term GoA watershed evolution from one strongly influenced by glacial weathering to a boreal-forested watershed. Iron fluxes from glacierized tributaries bear high suspended sediment and colloidal Fe loads of mixed valence silicate species, with low concentrations of dissolved Fe and dissolved organic carbon (DOC). Iron isotopic composition is indicative of mechanical weathering as the Fe source. Conversely, Fe fluxes from boreal-forested systems have higher dissolved Fe concentrations corresponding to higher DOC concentrations. Iron colloids and suspended sediment consist of Fe (hydr)oxides and organic complexes. These watersheds have an iron isotopic composition indicative of an internal chemical processing source. We predict that as the GoA watershed evolves due to deglaciation, so will the source, flux, and chemical nature of riverine Fe loads, which could have significant ramifications for Alaskan marine and freshwater ecosystems.We appreciate support from the USGS CMGP, NCCWSC, and the Mendenhall Postdoctoral Program

Implication of Kir4.1 Channel in Excess Potassium Clearance: An In Vivo Study on Anesthetized Glial-Conditional Kir4.1 Knock-Out Mice

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Iron biogeochemistry across marine systems progress from the past decade

Based on an international workshop (Gothenburg, 14–16 May 2008), this review article aims to combine interdisciplinary knowledge from coastal and open ocean research on iron biogeochemistry. The major scientific findings of the past decade are structured into sections on natural and artificial iron fertilization, iron inputs into coastal and estuarine systems, colloidal iron and organic matter, and biological processes. Potential effects of global climate change, particularly ocean acidification, on iron biogeochemistry are discussed. The findings are synthesized into recommendations for future research areas

Iron biogeochemistry in Antarctic pack ice during SIPEX-2

Our study quantified the spatial and temporal distribution of Fe and ancillary biogeochemical parameters at six stations visited during an interdisciplinary Australian Antarctic marine science voyage (SIPEX-2) within the East Antarctic first-year pack ice zone during September–October 2012. Unlike previous studies in the area, the sea ice Chlorophyll a, Particulate Organic Carbon and Nitrogen (POC and PON) maxima did not occur at the ice/water interface because of the snow loading and dynamic processes under which the sea ice formed. Iron in sea ice ranged from 0.9 to 17.4 nM for the dissolved (<0.2 µm) fraction and 0.04 to 990 nM for the particulate (>0.2 µm) fraction. Our results highlight that the concentration of particulate Fe in sea ice was highest when approaching the continent. The high POC concentration and high particulate iron to aluminium ratio in sea ice samples demonstrate that 71% of the particulate Fe was biogenic in composition. Our estimated Fe flux from melting pack ice to East Antarctic surface waters over a 30 day melting period was 0.2 µmol/m2/d of DFe, 2.7 µmol/m2/d of biogenic PFe and 1.3 µmol/m2/d of lithogenic PFe. These estimates suggest that the fertilization potential of the particulate fraction of Fe may have been previously underestimated due to the assumption that it is primarily lithogenic in composition. Our new measurements and calculated fluxes indicate that a large fraction of the total Fe pool within sea ice may be bioavailable and therefore, effective in promoting primary productivity in the marginal ice zone

Study on control and enforcement rules for geographical indication (GI) protection for non-agricultural products in the EU

This study looks into control and enforcement of geographically rooted non-agricultural products protected by intellectual property mechanisms. Based on desk research, stakeholder interviews and an electronic survey conducted for a research sample of 30 real-life products (from several EU Member States and non-EU countries), six existing protection systems are investigated with regard to their control and enforcement mechanisms, with a case study produced for each system: 1) EU collective marks, 2) EU certification marks, 3) national certification marks, 4) national sui generis geographical indication (GI) protection of non-agricultural products, 5) EU sui generis GI protection of agri-food and drink products, and 6) protection systems in non-EU countries. The six protection systems are then compared and analysed with regard to their effectiveness, cost-efficiency and relevance. Lastly, three models for control and enforcement under a potential EU-wide system for the protection of non-agricultural geographically rooted products are developed. Each model represents a different degree of involvement by public authorities in the control and enforcement process

Iron budgets for three distinct biogeochemical sites around the Kerguelen archipelago (Southern Ocean) during the natural fertilisation experiment KEOPS-2

Iron availability in the Southern Ocean controls phytoplankton growth, community composition and the uptake of atmospheric CO2 by the biological pump. The KEOPS-2 experiment took place around the Kerguelen plateau in the Indian sector of the Southern Ocean, a region naturally fertilised with iron at the scale of hundreds to thousands of square kilometres, producing a mosaic of spring blooms which showed distinct biological and biogeochemical responses to fertilisation. This paper presents biogeochemical iron budgets (incorporating vertical and lateral supply, internal cycling, and sinks) for three contrasting sites: an upstream high-nutrient low-chlorophyll reference, over the plateau, and in the o�shore plume east of Kerguelen Island. These budgets show that distinct regional environments driven by complex circulation and transport pathways are responsible for di�erences in the mode and strength of iron supply, with vertical supply dominant on the plateau and lateral supply dominant in the plume. Iron supply from “new” sources to surface waters of the plume was double that above the plateau and 20 times greater than at the reference site, whilst iron demand (measured by cellular uptake) in the plume was similar to the plateau but 40 times greater than the reference. “Recycled” iron supply by bacterial regeneration and zooplankton grazing was a relative minor component at all sites (< 8% of “new” supply), in contrast to earlier findings from other biogeochemical iron budgets in the Southern Ocean. Over the plateau, a particulate iron dissolution term of 2.5% was invoked to balance the budget; this approximately doubled the standing stock of dissolved iron in the mixed layer. The exchange of iron between dissolved, biogenic and lithogenic particulate pools was highly dynamic in time and space, resulting in a decoupling of iron supply and carbon export and, importantly, controlling the effi�ciency of fertilisation

Potassium Dependent Regulation of Astrocyte Water Permeability Is Mediated by cAMP Signaling

Astrocytes express potassium and water channels to support dynamic regulation of potassium homeostasis. Potassium kinetics can be modulated by aquaporin-4 (AQP4), the essential water channel for astrocyte water permeability regulation. We investigated whether extracellular potassium ([K+]o) can regulate astrocyte water permeability and the mechanisms of such an effect. Studies were performed on rat primary astrocytes and a rat astrocyte cell line transfected with AQP4. We found that 10mM [K+]o caused an immediate, more than 40%, increase in astrocyte water permeability which was sustained in 5min. The water channel AQP4 was a target for this regulation. Potassium induced a significant increase in intracellular cAMP as measured with a FRET based method and with enzyme immunoassay. We found that protein kinase A (PKA) could phosphorylate AQP4 in vitro. Further elevation of [K+]o to 35mM induced a global intracellular calcium response and a transient water permeability increase that was abolished in 5min. When inwardly rectifying potassium (Kir)-channels were blocked, 10mM [K+]o also induced a calcium increase and the water permeability increase no longer persisted. In conclusion, we find that elevation of extracellular potassium regulates AQP4 and astrocyte water permeability via intracellular signaling involving cAMP. A prolonged increase of astrocyte water permeability is Kir-channel dependent and this response can be impeded by intracellular calcium signaling. Our results support the concept of coupling between AQP4 and potassium handling in astrocytes