Nutrient and microbial water quality of the upper Ganga river, India: identification of pollution sources

The Ganga River is facing mounting environmental pressures due to rapidly increasing human population, urbanisation, industrialisation and agricultural intensification, resulting in worsening water quality, ecological status and impacts on human health. A combined inorganic chemical, algal and bacterial survey (using flow cytometry and 16S rRNA gene sequencing) along the upper and middle Ganga (from the Himalayan foothills to Kanpur) was conducted under pre-monsoon conditions. The upper Ganga had total phosphorus (TP) and total dissolved nitrogen concentrations of less than 100 μg l−1 and 1.0 mg l−1, but water quality declined at Kannauj (TP = 420 μg l−1) due to major nutrient pollution inputs from human-impacted tributaries (principally the Ramganga and Kali Rivers). The phosphorus and nitrogen loads in these two tributaries and the Yamuna were dominated by soluble reactive phosphorus and ammonium, with high bacterial loads and large numbers of taxa indicative of pathogen and faecal organisms, strongly suggesting sewage pollution sources. The high nutrient concentrations, low flows, warm water and high solar radiation resulted in major algal blooms in the Kali and Ramganga, which greatly impacted the Ganga. Microbial communities were dominated by members of the Phylum Proteobacteria, Bacteriodetes and Cyanobacteria, with communities showing a clear upstream to downstream transition in community composition. To improve the water quality of the middle Ganga, and decrease ecological and human health risks, future mitigation must reduce urban wastewater inputs in the urbanised tributaries of the Ramganga, Kali and Yamuna Rivers

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

Fill, flush, or shuffle: how is sediment carried through submarine channels to build lobes?

Submarine channels are the primary conduits for land-derived material, including organic carbon, pollutants, and nutrients, into the deep-sea. The flows (turbidity currents) that traverse these systems can pose hazards to seafloor infrastructure such as cables and pipelines. Here we use a novel combination of repeat seafloor surveys and turbidity current monitoring along a 50 km-long submarine channel in Bute Inlet, British Columbia, and discharge measurements from the main feeding river. These source-to-sink observations provide the most detailed information yet on magnitude-frequency-distance relationships for turbidity currents, and the spatial-temporal patterns of sediment transport within a submarine channel-lobe system. This analysis provides new insights into mass redistribution, and particle residence times in submarine channels, as well as where particles are eventually buried and how that is recorded in the deposits. We observe stepwise sediment transport down the channel, with turbidity currents becoming progressively less frequent with distance. Most flows dissipate and deposit within the proximal (&lt; 11 km) part of the system, whilst longer run-out flows then pick up this sediment, ‘shuffling’ it further downstream along the channel. This shuffling occurs mainly through upstream migration of knickpoints, which can generate sediment bypass along the channel over timescales of 10–100 yrs. Infrequent large events flush the channel and ultimately transport sediment onto the lobe. These flushing events can occur without obvious triggers, and thus might be internally generated. We then present the first ever sediment budget analysis of an entire submarine channel system, which shows that the river input and lobe aggradation can approximately balance over decadal timescales. We conclude by discussing the implication of this sediment shuffling for seafloor geohazards and particle burial.</p

Differential Regulation of Secretory Compartments Containing the Insulin-responsive Glucose Transporter 4 in 3T3-L1 Adipocytes

Insulin and guanosine-5′-O-(3-thiotriphosphate) (GTPγS) both stimulate glucose transport and translocation of the insulin-responsive glucose transporter 4 (GLUT4) to the plasma membrane in adipocytes. Previous studies suggest that these effects may be mediated by different mechanisms. In this study we have tested the hypothesis that these agonists recruit GLUT4 by distinct trafficking mechanisms, possibly involving mobilization of distinct intracellular compartments. We show that ablation of the endosomal system using transferrin-HRP causes a modest inhibition (∼30%) of insulin-stimulated GLUT4 translocation. In contrast, the GTPγS response was significantly attenuated (∼85%) under the same conditions. Introduction of a GST fusion protein encompassing the cytosolic tail of the v-SNARE cellubrevin inhibited GTPγS-stimulated GLUT4 translocation by ∼40% but had no effect on the insulin response. Conversely, a fusion protein encompassing the cytosolic tail of vesicle-associated membrane protein-2 had no significant effect on GTPγS-stimulated GLUT4 translocation but inhibited the insulin response by ∼40%. GTPγS- and insulin-stimulated GLUT1 translocation were both partially inhibited by GST-cellubrevin (∼50%) but not by GST-vesicle-associated membrane protein-2. Incubation of streptolysin O-permeabilized 3T3-L1 adipocytes with GTPγS caused a marked accumulation of Rab4 and Rab5 at the cell surface, whereas other Rab proteins (Rab7 and Rab11) were unaffected. These data are consistent with the localization of GLUT4 to two distinct intracellular compartments from which it can move to the cell surface independently using distinct sets of trafficking molecules