Very Short-Lived Halocarbons have been linked to climate change through their potential to deplete the protective stratospheric ozone layer, influence atmospheric chemistry, and contribute to local weather change and radiative forcing via cloud nuclei formation. Seaweeds are known to be emitters of the short-lived brominated compounds including CHBr₃ and CH₂Br₂ and account to 70% of global bromoform production. The current seaweed industry is expanding globally with doubling in global production in recent year. This could increase the significance of seaweeds in contributing to the regional if not global halocarbon budget. Data from previous small-scale studies on tropical seaweeds in South-East Asia indicates a contribution of 6–224 Mmol Br yr⁻¹. However, variabilities and uncertainties in the current global estimates of oceanic halogen load, derived from top-down and bottom-up modelling, could arise from poor temporal and spatial data coverage, and are commonly attributed to a lack of data for oceanic inputs and under-representation of coastal and extreme emissions. In order to understand how changes in environment could affect the halocarbon emission by farmed seaweed species, we investigated the effect of temperature and the combined effect of varying levels of irradiance and temperature on the halocarbon emission by Kappaphycus alvarezii, a commercially farmed red seaweed in the Coral Triangle. We found that different exposure duration to varying temperature treatments, and the combination of irradiance and temperature affect the halocarbon emissions by K. alvarezii.  

Planktonic picocyanobacterial representatives are abundant and ubiquitous in coastal oceans. The genus Synechococcus is an important player in coastal water by playing a key role in carbon assimilation but its role in mangrove estuaries us not very well understood. In this study, the draft genome of Synechococcus moorigangaii CMS01 has been sequenced which was previously isolated from Sundarbans mangrove ecosystem facing the coastal Bay of Bengal. The genome is approximately 5.5 Mbp in size and contains approximately 0.5 Mbp plasmids. Genome annotation revealed total of 5806 genes out of which 5701 were CDSs. Of these, 5616 coding genes with 5616 protein coding CDSs were identified. Along with genes coding for essential metabolic proteins, transport proteins and other cellular apparatus, genome also codes for proteins involved in flagella and pilus formation which has not been widely reported before in any coastal species of Synechococcus. In silico phenotyping revealed that this species can metabolize growth utilizing carbon sources including sucrose, D-mannose and trehalose. Genome annotation revealed genes involved in photosynthesis including photosystem II reaction centre proteins (psbN, psbH, psbL, psbJ, psbZ, psbQ), photosystem I iron-sulfur centre protein (psaC), photosystem I reaction centre subunits VIII, IX; genes for nitrogen metabolism were also identified. The genome codes for linker polypeptides that are necessary for correct assembly of phycobiliprotein in phycobilisome rods. The presence of many features as identified from the draft genome revealed the adaptative features of this species and its ubiquity in coastal Bay of Bengal including implications for mangrove carbon cycling.

The annual and seasonal changes in the tropical Pacific Walker circulation (PWC) during the Last Glacial Maximum (LGM) are investigated using all available numerical experiments from the Paleoclimate Modelling Intercomparison Project Phases 2 and 3. Compared to the preindustrial period, the annual mean of the PWC intensity weakened by an average of 15%, and both the western edge and center of the PWC cell shifted eastward by an average of 9° and 8°, respectively, as obtained from the ensemble mean of the 16 models used for analysis during the LGM. Those changes were closely linked with an overall weakening of the equatorial Indo-Pacific east–west sea level pressure difference and low-level trade winds over the equatorial west/central Pacific. On the seasonal scale, the LGM PWC generally weakened and shifted eastward throughout the seasons of year. In response to the LGM large ice sheets and lower atmospheric greenhouse gas concentrations, the large-scale uneven surface cooling in the northern hemisphere led to an increased (a decreased) land–sea thermal contrast in boreal cold (warm) seasons. These induced decreases in the North Asian and African monsoon rainfall and hence suppressed a large-scale thermally direct east–west circulation in the two seasons. As a result, the LGM PWC weakened and shifted eastward in both boreal cold and warm seasons, which jointly contributed to the weakening and eastward shift of the annual mean PWC.

Solar Radiation Modification (SRM) has been proposed as a potential option to counteract anthropogenic warming. The underlying idea of SRM is to reduce the amount of sunlight reaching the atmosphere and surface, thus offsetting some amount of global warming. Here we use an Earth system model to investigate the impact of SRM on global carbon cycle and ocean biogeochemistry. We simulate time evolution of global climate and the carbon cycle from pre-industrial to the end of this century following three scenarios: RCP 4.5 CO₂ emission pathway, RCP8.5 CO₂ emission pathway, and RCP 8.5 CO₂ emission pathway with the implementation of SRM to maintain global mean surface temperature at the level of RCP4.5.Our simulations show that SRM, by altering global climate, has a profound effect on the global carbon cycle. Compared to the high-CO₂ (RCP8.5) simulation without SRM, by year 2100, SRM reduces atmospheric CO₂ by 56 ppm mainly as a result of increased CO2 uptake by the terrestrial biosphere. However, SRM-induced change in atmospheric CO₂ and climate has a small effect in mitigating ocean acidification. By year 2100, SRM results in a decrease in hydrogen ion concentration ([H⁺]) by 5%. On the other hand, SRM attenuates the seasonal amplitude of [H⁺] by about 10%. Our simulations also show that SRM slightly reduces global ocean net primary productivity (NPP) relative to the high-CO₂ simulation without SRM. Our offline calculations show that SRM-induced temperature change causes a 8% decrease in NPP and SRM-induced circulation change causes a 6% increase in NPP.