Open ocean carbon monoxide photo-production

Sunlight-initiated photolysis of chromophoric dissolved organic matter (CDOM) is the dominant source of carbon monoxide (CO) in the open-ocean. A modelling study was conducted to constrain this source. Spectral solar irradiance was obtained from two models (GCSOLAR and SMARTS2). Water-column CDOM and total light absorption were modelled using spectra collected along a Meridional transect of the Atlantic ocean using a 200-cm pathlength liquid waveguide UV-visible spectrophotometer. Apparent quantum yields for the production of CO (AQYCO) from CDOM were obtained from a parameterisation describing the relationship between CDOM light absorption coefficient and AQYCO and the CDOM spectra collected. The sensitivity of predicted rates to variations in model parameters (solar irradiance, cloud cover, surface-water reflectance, CDOM and whole water light absorbance, and AQYCO was assessed. The model\u27s best estimate of open-ocean CO photoproduction was 47 +/- 7 Tg CO-C yr-1, with lower and upper limits of 38 and 84 Tg CO-C yr-1, as indicated by sensitivity analysis considering variations in AQYs, CDOM absorbance, and spectral irradiance. These results represent significant constraint of open-ocean CO photoproduction at the lower limit of previous estimates. Based on these results, and their extrapolation to total photochemical organic carbon mineralisation, we recommend a downsizing of the role of photochemistry in the open-ocean carbon cycle. (c) 2006 Elsevier Ltd. All rights reserved

Photochemical oxidation of dimethylsulphide to dimethylsulphoxide in estuarine and coastal waters

Dimethylsulphide (DMS) photo-oxidation and dimethylsulphoxide (DMSO) photoproduction were estimated in 26 laboratory irradiations of coastal samples from NE England (Tyne estuary) and W Scotland (Loch Linnhe and River Nant at Taynuilt). Pseudo-first order rate constants of DMS photo-oxidation (0.038 h−1 to 0.345 h−1) and DMSO photo-production (0.017 h−1 to 0.283 h−1) varied by one order of magnitude and were lowest in the coastal North Sea. Estuarine samples (salinity S 30) to be most reactive with respect to DMS photo-oxidation. Estimates of water column averaged DMS photo-oxidation rate constants, obtained by scaling to mean daily irradiance (July, NE England) and mid-UV underwater irradiance, were 0.012 d−1, 0.019 d−1, and 0.017 d−1 for upper estuary (S 30), at the lower end of previous observations. Comparing our water column averaged DMS photo-oxidation rate constants with estimated DMS losses via air-sea gas exchange and previously reported biological consumption implies that DMS photochemical removal is of only minor importance in our study area

Ideas and Perspectives: A Strategic Assessment of Methane and Nitrous Oxide Measurements In the Marine Environment

In the current era of rapid climate change, accurate characterization of climate-relevant gas dynamics-namely production, consumption, and net emissions-is required for all biomes, especially those ecosystems most susceptible to the impact of change. Marine environments include regions that act as net sources or sinks for numerous climateactive trace gases including methane (CH4) and nitrous oxide (N2O). The temporal and spatial distributions of CH4 and N2O are controlled by the interaction of complex biogeochemical and physical processes. To evaluate and quantify how these mechanisms affect marine CH4 and N2O cycling requires a combination of traditional scientific disciplines including oceanography, microbiology, and numerical modeling. Fundamental to these efforts is ensuring that the datasets produced by independent scientists are comparable and interoperable. Equally critical is transparent communication within the research community about the technical improvements required to increase our collective understanding of marine CH4 and N2O. A workshop sponsored by Ocean Carbon and Biogeochemistry (OCB) was organized to enhance dialogue and collaborations pertaining to marine CH4 and N2O. Here, we summarize the outcomes from the workshop to describe the challenges and opportunities for near-future CH4 and N2O research in the marine environment

HNF4A and GATA6 loss reveals therapeutically actionable subtypes in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) can be divided into transcriptomic subtypes with two broad lineages referred to as classical (pancreatic) and squamous. We find that these two subtypes are driven by distinct metabolic phenotypes. Loss of genes that drive endodermal lineage specification, HNF4A and GATA6, switch metabolic profiles from classical (pancreatic) to predominantly squamous, with glycogen synthase kinase 3 beta (GSK3β) a key regulator of glycolysis. Pharmacological inhibition of GSK3β results in selective sensitivity in the squamous subtype; however, a subset of these squamous patient-derived cell lines (PDCLs) acquires rapid drug tolerance. Using chromatin accessibility maps, we demonstrate that the squamous subtype can be further classified using chromatin accessibility to predict responsiveness and tolerance to GSK3β inhibitors. Our findings demonstrate that distinct patterns of chromatin accessibility can be used to identify patient subgroups that are indistinguishable by gene expression profiles, highlighting the utility of chromatin-based biomarkers for patient selection in the treatment of PDAC

Ocean acidification induces multi-generational decline in copepod naupliar production with possible conflict for reproductive resource allocation

Climate change, including ocean acidification (OA), presents fundamental challenges to marine biodiversity and sustained ecosystem health. We determined reproductive response (measured as naupliar production), cuticle composition and stage specific growth of the copepod Tisbe battagliai over three generations at four pH conditions (pH 7.67, 7.82, 7.95, and 8.06). Naupliar production increased significantly at pH 7.95 compared with pH 8.06 followed by a decline at pH 7.82. Naupliar production at pH 7.67 was higher than pH 7.82. We attribute the increase at pH 7.95 to an initial stress response which was succeeded by a hormesis-like response at pH 7.67. A multi-generational modelling approach predicted a gradual decline in naupliar production over the next 100 years (equivalent to approximately 2430 generations). There was a significant growth reduction (mean length integrated across developmental stage) relative to controls. There was a significant increase in the proportion of carbon relative to oxygen within the cuticle as seawater pH decreased. Changes in growth, cuticle composition and naupliar production strongly suggest that copepods subjected to OA-induced stress preferentially reallocate resources towards maintaining reproductive output at the expense of somatic growth and cuticle composition. These responses may drive shifts in life history strategies that favour smaller brood sizes, females and perhaps later maturing females, with the potential to profoundly destabilise marine trophodynamics

Targeting DNA Damage Response and Replication Stress in Pancreatic Cancer

Background and aims: Continuing recalcitrance to therapy cements pancreatic cancer (PC) as the most lethal malignancy, which is set to become the second leading cause of cancer death in our society. The study aim was to investigate the association between DNA damage response (DDR), replication stress and novel therapeutic response in PC to develop a biomarker driven therapeutic strategy targeting DDR and replication stress in PC. Methods: We interrogated the transcriptome, genome, proteome and functional characteristics of 61 novel PC patient-derived cell lines to define novel therapeutic strategies targeting DDR and replication stress. Validation was done in patient derived xenografts and human PC organoids. Results: Patient-derived cell lines faithfully recapitulate the epithelial component of pancreatic tumors including previously described molecular subtypes. Biomarkers of DDR deficiency, including a novel signature of homologous recombination deficiency, co-segregates with response to platinum (P < 0.001) and PARP inhibitor therapy (P < 0.001) in vitro and in vivo. We generated a novel signature of replication stress with which predicts response to ATR (P < 0.018) and WEE1 inhibitor (P < 0.029) treatment in both cell lines and human PC organoids. Replication stress was enriched in the squamous subtype of PC (P < 0.001) but not associated with DDR deficiency. Conclusions: Replication stress and DDR deficiency are independent of each other, creating opportunities for therapy in DDR proficient PC, and post-platinum therapy

Microbiology of aquatic surface microlayers

Aquatic surface microlayers are unique microbial ecosystems found at the air-water interface of all open water bodies and are often referred to as the neuston. Unambiguous interpretation of the microbiology of aquatic surface microlayers relies on robust sampling, for which several methods are available. All have particular advantages and disadvantages that make them more or less suited to this task. A key feature of surface microlayers is their role in regulating air-water gas exchange, which affords them a central role in global biogeochemistry that is only now being fully appreciated. The microbial populations in surface microlayers can impact air-water gas exchange through specific biogeochemical processes mediated by particular microbial groups such as methanotrophs or through more general metabolic activity such as the balance of primary production vs. heterotrophy. There have been relatively few studies of surface microlayers that have utilized molecular ecology techniques. The emerging consensus view is that aquatic surface microlayers are aggregate-enriched biofilm environments containing complex microbial communities that are ecologically distinct from those present in the subsurface water immediately below. Future research should focus on unravelling the complex interactions between microbial diversity and the ecosystem function of surface microlayers in order to better understand the important but complex role of microorganisms in Earth system processes