15,735 research outputs found
The Madagascar Bloom – a serendipitous study
No full textThe late austral summer (February-April) phytoplankton bloom that occurs east of Madagascar exhibits significant interannual variability and at its largest extent covers ~1% of the world’s ocean surface area. The bloom raises many intriguing questions about how it begins, is sustained, propagates to the east, exports carbon and ends. It has been observed and studied using satellite ocean color observations, but the lack of in situ data makes it difficult to address these questions. Here we describe observations that were made serendipitously on a cruise in February 2005. These show clearly for the first time the simultaneous existence of a deep chlorophyll maximum at ~70-110 m depths (seen in SeaSoar fluorimeter data) and a surface chlorophyll signature (seen in SeaWiFS satellite ocean color data). The observations also show the modulation of biological signature at the surface by the eddy field, but not of the deep chlorophyll maximum. Trichodesmium dominates the bloom nearer to Madagascar, while the diatom Rhizosolenia clevei (and its symbiont Richelia intracellularis) dominates further from the island. The surface bloom seen in the SeaWiFS data is confined to the shallow (~30 m) mixed layer. It is hypothesized that the interannual variability in bloom intensity may be due to variations in coastal upwelling and thus the supply of iron, which is a micronutrient that can limit diazotroph growth
Physical controls and mesoscale variability in the Labrador Sea spring phytoplankton bloom observed by Seaglider
No full textWe investigated the 2005 spring phytoplankton bloom in the Labrador Sea using Seaglider, an autonomous underwater vehicle equipped with hydrographic, bio-optical and oxygen sensors. The Labrador Sea blooms in distinct phases, two of which were observed by Seaglider: the north bloom and the central Labrador Sea bloom. The dominant north bloom and subsequent zooplankton growth are enabled by the advection of low-salinity water from West Greenland in the strong and eddy-rich separation of the boundary current. The glider observed high fluorescence and oxygen supersaturation within haline-stratified eddy-like features; higher fluorescence was observed at the edges than centers of the eddies. In the central Labrador Sea, the bloom occurred in thermally stratified water. Two regions with elevated subsurface chlorophyll were also observed: a 5 m thin-layer in the southwest Labrador Current, and in the Labrador shelf-break front. The thin layer observations were consistent with vertical shearing of an initially thicker chlorophyll patch. Observations at the front showed high fluorescence down to 100 m depth and aligned with the isopycnals defining the front. The high-resolution Seaglider sampling across the entire Labrador Sea provides first estimates of the scale dependence of coincident biological and physical variables
Bloom-like features in two siblings with an RMI2 gene deletion.
No full text(A) Sibling S1 shows typical café-au-lait macules on torso that are a common feature of Bloom syndrome. (B) UCSC Genome Browser view of the homozygous deleted region that spans the entire RMI2 gene. (C) Immunoblot confirms complete loss of the RMI2 protein in each sib, S1 and S2. Heterozygous parents, P1 and P2, show the presence of RMI2. Anti-α-tubulin was used a protein loading control.</p
Let the Tree Bloom: Scalable Opportunistic Routing with ORPL
No full textRouting in battery-operated wireless networks is challenging, posing a tradeoff between energy and latency. Previous work has shown that opportunistic routing can achieve low-latency data collection in duty-cycled networks. However, applications are now considered where nodes are not only periodic data sources, but rather addressable end points generating traffic with arbitrary patterns.
We present ORPL, an opportunistic routing protocol that supports any-to-any, on-demand traffic. ORPL builds upon RPL, the standard protocol for low-power IPv6 networks. By combining RPL's tree-like topology with opportunistic routing, ORPL forwards data to any destination based on the mere knowledge of the nodes' sub-tree. We use bitmaps and Bloom filters to represent and propagate this information in a space-efficient way, making ORPL scale to large networks of addressable nodes. Our results in a 135-node testbed show that ORPL outperforms a number of state-of-the-art solutions including RPL and CTP, conciliating a sub-second latency and a sub-percent duty cycle. ORPL also increases robustness and scalability, addressing the whole network reliably through a 64-byte Bloom filter, where RPL needs kilobytes of routing tables for the same task
Sequestration efficiency in the iron limited North Atlantic: Implications for iron supply mode to fertilized blooms
No full textEstimates of the amount of carbon sequestered in the ocean interior per unit iron (Fe) supplied, as quantified by the sequestration efficiency (Ceffx), vary widely. Such variability in Ceffx has frequently been attributed to estimate uncertainty rather than intrinsic variability. Here we derive new estimates of Ceffx for the subpolar North Atlantic, where Fe stressed conditions have recently been demonstrated. Derived values of Ceffx from across the region, including areas subject to atypical external Fe fertilization events during the year of sample collection (2010), ranged from 17 - 19 kmol C (mol Fe-1). Comparing these estimates with values from other systems, considered in the context of variable bloom durations in the different oceanographic settings, we suggest that apparent variability in Ceffx may be related to the mode of Fe delivery
Iron biogeochemistry in (sub-) Polar waters
No full textIron represents an important control on primary production in high nutrient low chlorophyll(HNLC) regimes and has received considerably attention during the last two decades. Thiswork has focussed on the biogeochemistry of iron in two oceanic environments; the highlatitude North Atlantic and the Scotia Sea in the Southern Ocean. The mechanisms of ironsupply and the biological response of resident phytoplankton communities to iron wereaddressed in both study areas. Two cruises to the high latitude North Atlantic Ocean (>55 °N)during late July-early September 2007 indicated that nitrate concentrations of 2 to 5 ?Mpersisted in the surface waters. The concentration of dissolved iron (dFe) in the surface waterswas very low, with an average of 0.093 (<0.010-0.218, n=43) nM, and in situ chlorophyllconcentrations were < 0.5 mg m-3. In vitro iron addition experiments demonstrated that theaddition of iron increased photosynthetic efficiencies (Fv/Fm) and resulted in enhancedchlorophyll in treatments amended with iron when compared to controls. A number ofphytoplankton taxa, including the coccolithophore Emiliania huxleyi, were observed toincrease their net growth rates following iron addition. These results provide strong evidencethat iron limitation within the post spring bloom phytoplankton community contributes to theobserved residual macronutrient pool during summer. Low atmospheric iron supply and suboptimalFe:N ratios in winter overturned deep water are suggested as proximal causes for thisseasonal High Nutrient Low Chlorophyll (HNLC) condition, which represents an inefficiencyof the biological (soft tissue) carbon pump. Large areas of the Southern Ocean arecharacterised as HNLC. Satellite chlorophyll data indicate that phytoplankton blooms occurin vicinity to Southern Ocean Island systems. The bloom associated with South Georgia hasthe largest spatial extent and duration (16-20 weeks). Detailed measurements were made onaustral spring and summer cruises to the Scotia Sea during November – early December 2006and January – February 2008. This work presents the first comprehensive study of seasonalvariations in phytoplankton biomass and iron availability in the Scotia Sea. The drawdown ofnitrate between the two seasons in the South Georgia bloom was 16 ?M indicative ofsubstantial new production. Surface water concentrations of dissolved iron (dFe) were slightlyhigher during summer than spring (0.31 nM compared to 0.20 nM, with P>0.05). We suggestthat the South Georgia bloom is sustained by a continuous benthic supply of iron from theSouth Georgia shelf. In addition, enhanced dFe (0.34 nM) was observed in a cryptophytedominated bloom in the southern Scotia Sea in the vicinity of South Orkney Islands. Thedifference in the community composition between the two natural occurring blooms highlightthat Southern Ocean island systems have individual characteristics and should be viewedindependently
Acute Ethanol Administration Rapidly Increases Phosphorylation of Conventional Protein Kinase C in Specific Mammalian Brain Regions in Vivo
No full textBackground
Protein kinase C (PKC) is a family of isoenzymes that regulate a variety of functions in the central nervous system including neurotransmitter release, ion channel activity, and cell differentiation. Growing evidence suggests that specific isoforms of PKC influence a variety of behavioral, biochemical, and physiological effects of ethanol in mammals. The purpose of this study was to determine whether acute ethanol exposure alters phosphorylation of conventional PKC isoforms at a threonine 674 (p-cPKC) site in the hydrophobic domain of the kinase, which is required for its catalytic activity.
Methods
Male rats were administered a dose range of ethanol (0, 0.5, 1, or 2 g/kg, intragastric) and brain tissue was removed 10 minutes later for evaluation of changes in p-cPKC expression using immunohistochemistry and Western blot methods.
Results
Immunohistochemical data show that the highest dose of ethanol (2 g/kg) rapidly increases p-cPKC immunoreactivity specifically in the nucleus accumbens (core and shell), lateral septum, and hippocampus (CA3 and dentate gyrus). Western blot analysis further showed that ethanol (2 g/kg) increased p-cPKC expression in the P2 membrane fraction of tissue from the nucleus accumbens and hippocampus. Although p-cPKC was expressed in numerous other brain regions, including the caudate nucleus, amygdala, and cortex, no changes were observed in response to acute ethanol. Total PKC? immunoreactivity was surveyed throughout the brain and showed no change following acute ethanol injection
Valuation of Marine Ecosystem Threshold Effects : Application of Choice Experiments to Value Algal Bloom in the Black Sea Coast of Bulgaria
No full textAlgal bloom arises in part from anthropogenic emissions of nutrients into the coastal zone. Increased interest in water quality in coastal and marine areas stemming from the Water Framework Directive and the Marine Strategy Framework Directive leads to important questions in terms of policies to address nutrient loadings. This paper presents the results from a choice experiment for the valuation of algal blooms in Varna Bay, Bulgaria. Varna Bay is an important tourist destination and a large port city on the Black Sea coast of Bulgaria. Algal bloom events have been experienced frequently in this area. A choice experiment questionnaire was developed to be applied in Varna Bay. The key attributes used were visibility, duration of bloom and the amount of congestion on the beach. The amount of bloom is found to be important - respondents are willing to pay for a program that entails 1 week of algal bloom about 33 Leva (s.e. 8.09) when there is high visibility; 21 Leva (s.e. 5.75) with medium visibility and 9 Leva (s.e. 3.48) with low visibility. Respondents are willing to pay more for programs that offer shorter duration of algal bloom. The marginal price for one metre of extra space between the respondent and the nearest person is equal to 0.38 Leva.threshold effects; marine ecosystem
China is on the track tackling Enteromorpha spp forming green tide
No full textGreen tide management is supposed to be a long term fight rather than an episode during the 29th Olympic Games for China, since it has been gaining in scale and frequency during the past 3 decades in both marine and estuary environment all over the world. A number of rapid-responding studies including oceanographic comprehensive surveys along the coastline have been conducted during the bloom and post-bloom periods in 2008 by Chinese marine scientists. The preliminary results are as below: (1) phylogenetic analysis indicates that the bloom forming alga forms a clade with representatives of the green seaweed Enteromorpha linza, though, the alga has been identified as E. proliera by means of morphological; (2) the present data suggest that the bloom was originated from south of Yellow Sea, but not the severely affected area near Qingdao City; (3) pathways of reproduction for E. prolifera have approved to be multifarious, including sexual, asexual and vegetative propagation; (4) somatic cells may act as a propagule bank, which is supposed to be a very dangerous transmitting way for its marked movability, adaptability and viability; (5) pyrolysis of the alga showed that three stages appeared during the process, which are dehydration (18–20^o^C), main devolatilization (200–450^o^C) and residual decomposition (450–750^o^C), and activation energy of the alga was determined at 237.23 KJ•mol^-1^. Although the scarce knowlegde on E. prolifera not yet allow a fully understanding of the green tide, some of the results suggests possible directions in further green tide research and management
Stable carbon isotope variations in surface bloom scum and subsurface seston among shallow eutrophic lakes
No full textCarbon stable isotope analysis of surface bloom scum and subsurface seston samples was conducted in shallow eutrophic lakes in China during warm seasons from 2003 to 2004. delta C-13 values of bloom scum were always higher (averaged 5 parts per thousand) than those of seston in this study, and the possible reasons were attributed to (i) direct use of atmospheric CO2 at the air-water interface, (ii) decrease in C-13 fractionation due to higher carbon fixation, (iii) active CO2 transport, and/or (iv) HCO3 accumulation. Negative correlation between delta C-13(scum) - delta C-13(seston) and pH in the test lakes indicated that phytoplankton at the subsurface water column increased isotopic enrichment under the-carbon limitation along with the increase of pH, which might in turn decreased the differences in 313 C between the subsurface seston and the surface scums. Significant positive correlations of seston 8 13C with total concentrations of nitrogen and phosphorus in water column suggested that the increase in delta C-13 of seston with trophic state was depending on nutrient (N or P, or both) supply. Our study showed that delta C-13 of phytoplankton was indicative of carbon utilization, primary productivity, and nutrient supply among the eutrophic lakes. (C) 2007 Elsevier B.V All rights reserved.Carbon stable isotope analysis of surface bloom scum and subsurface seston samples was conducted in shallow eutrophic lakes in China during warm seasons from 2003 to 2004. delta C-13 values of bloom scum were always higher (averaged 5 parts per thousand) than those of seston in this study, and the possible reasons were attributed to (i) direct use of atmospheric CO2 at the air-water interface, (ii) decrease in C-13 fractionation due to higher carbon fixation, (iii) active CO2 transport, and/or (iv) HCO3 accumulation. Negative correlation between delta C-13(scum) - delta C-13(seston) and pH in the test lakes indicated that phytoplankton at the subsurface water column increased isotopic enrichment under the-carbon limitation along with the increase of pH, which might in turn decreased the differences in 313 C between the subsurface seston and the surface scums. Significant positive correlations of seston 8 13C with total concentrations of nitrogen and phosphorus in water column suggested that the increase in delta C-13 of seston with trophic state was depending on nutrient (N or P, or both) supply. Our study showed that delta C-13 of phytoplankton was indicative of carbon utilization, primary productivity, and nutrient supply among the eutrophic lakes. (C) 2007 Elsevier B.V All rights reserved
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