22 research outputs found
Reduced airâsea CO2 exchange in the Atlantic Ocean due to biological surfactants
This is the author accepted manuscript. The final version is available from Springer Nature via the DOI in this recordOcean CO2 uptake accounts for 20â40% of the post-industrial sink for anthropogenic CO2. The uptake rate is the product of the CO2 interfacial concentration gradient and its transfer velocity, which is controlled by spatial and temporal variability in near-surface turbulence. This variability complicates CO2 flux estimates and in large part reflects variable sea surface microlayer enrichments in biologically derived surfactants that cause turbulence suppression. Here we present a direct estimate of this surfactant effect on CO2 exchange at the ocean basin scale, with derived relationships between its transfer velocity determined experimentally and total surfactant activity for Atlantic Ocean surface seawaters. We found up to 32% reduction in CO2 exchange relative to surfactant-free water. Applying a relationship between sea surface temperature and total surfactant activity to our results gives monthly estimates of spatially resolved âsurfactant suppressionâ of CO2 exchange. Large areas of reduced CO2 uptake resulted, notably around 20°âN, and the magnitude of the Atlantic Ocean CO2 sink for 2014 was decreased by 9%. This direct quantification of the surfactant effect on CO2 uptake at the ocean basin scale offers a framework for further refining estimates of airâsea gas exchange up to the global scale.This work was supported by grants from the Leverhulme Trust to R.C.U.G. (RPG-303) and the UK Natural Environment Research Council (NERC) to R.C.U.G. (NE/K00252X/1) and J.D.S. (NE/K002511/1). Both NERC grants are components of RAGNARoCC (Radiatively Active Gases from the North Atlantic Region and Climate Change), which contributes to NERC's Greenhouse Gas Emissions and Feedbacks programme (www.nerc.ac.uk/research/funded/programmes/greenhouse). J.D.S. and I.A. acknowledge additional support from the European Space Agency (grant 4000112091/14/I-LG). R.P. acknowledges support from T. Wagner. This study is a contribution to the international IMBeR project and was supported by UK NERC National Capability funding to Plymouth Marine Laboratory and the National Oceanography Centre, Southampton. This is contribution no. 324 of the AMT programme
The Atlantic Ocean surface microlayer from 50°N to 50°S is ubiquitously enriched in surfactants at wind speeds up to 13 m sâ1
We report the first measurements of surfactant activity (SA) in the sea surface microlayer (SML) and in subsurface waters (SSW) at the ocean basin scale, for two Atlantic Meridional Transect from cruises 50°N to 50°S during 2014 and 2015. Northern Hemisphere (NH) SA was significantly higher than Southern Hemisphere (SH) SA in the SML and in the SSW. SA enrichment factors (EFâ=âSASML/SASSW) were also higher in the NH, for wind speeds up to ~13âmâsâ1, questioning a prior assertion that Atlantic Ocean wind speeds >12âmâsâ1 poleward of 30°N and 30°S would preclude high EFs and showing the SML to be self-sustaining with respect to SA. Our results imply that surfactants exert a control on air-sea CO2 exchange across the whole North Atlantic CO2 sink region and that the contribution made by high wind, high latitude oceans to air-sea gas exchange globally should be reexamined
Corrosion evaluation of multi-pass welded nickelâaluminum bronze alloy in 3.5% sodium chloride solution : A restorative application of gas tungsten arc welding process
EXTRACTION OF ASTAXANTHIN ESTERS FROM SHRIMP WASTE BY CHEMICAL AND MICROBIAL METHODS
The carotenoid pigments specifically astaxanthin has many significant
applications in food, pharmaceutical and cosmetic industries. The goal
of this research was the extraction of Astaxanthin from a certain
Persian Gulf shrimp species waste (Penaeus semisulcatus), purification
and identification of the pigment by chemical and microbial methods.
Microbial fermentation was obtained by inoculation of two Lactobacillus
species Lb. plantarum and Lb. acidophilus in the medium culture
containing shrimp waste powder by the intervention of lactose sugar,
yeast extract, the composition of Both and the coolage (-20°C).
The carotenoids were extracted by an organic solvent system. After
purification of astaxanthin with the thin layer chromatography method
by spectrophotometer, NMR and IR analysis the presence of astaxanthin
esters was recognized in this specific species of Persian Gulf shrimp.
Results obtained from this study showed that the coolage at â20
°C not only does not have an amplifying effect on the production
of astaxanthin but also slightly reduces this effect. Also the effect
of intervention of lactose sugar showed more effectiveness in producing
astaxanthin than yeast extract or more than with the presence of both.
The results also indicated that there is not much difference in the
ability of producing the pigment by comparing both Lb. plantarum and
Lb. acidophillus. Also results showed the microbial method of
extraction of astaxanthin is more effective than chemical method. The
pigment extracted from certain amount of shrimp powder, 23.128 mg/g,
was calculated
Meridional and CrossâShelf Variability of N2O and CH4 in the EasternâSouth Atlantic
Upward transport and/or mixing of trace gas-enriched subsurface waters fosters the exchange of nitrous oxide (N2O) and methane (CH4) with the atmosphere in the Eastern-South Atlantic (ESA). To date, it is, however, unclear whether this source is maintained by local production or advection of trace gas-enriched water masses. The meridional and zonal variability of N2O and CH4 in the ESA were investigated to identify the contributions of the major regional water masses to the overall budget of N2O and CH4. The maximal sea surface N2O and CH4 concentrations and the main ESA upwelling cells co-occurred with a strong negative correlation with the sea surface temperature (SST) (p < 0.05). The dominance of the central water masses in the winter and spring seasons and the interplay between shelf topography and wind regime are suggested to determine enhanced gas transfer toward the sea-air interface or âcappingâ at midwater depth. These parameters are supposed to be critical in the local budget of N2O and CH4 in the ESA. Our findings also show that the shape of N2O and CH4 gradients is very similar both meridionally and zonally; however, the extent of the differences between the high-end and low-end members of the concentrations/saturations range is different. This suggests a more pronounced effect of local sources on CH4 than N2O distribution, in particular in the Walvis Bay area. With respect to N2O, however, low-oxygen waters from the poleward undercurrent impinge in the shelf close to Cape Frio and often result in N2O concentrations significantly higher than off LĂŒderitz (p < 0.05