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Our current understanding of the Earth's climate is largely based on the predictions of numerical models that simulate the behaviour of, and interaction between, the atmosphere and the ocean. These models are crucially limited in their resolution, however, such that processes within the ocean that have horizontal scales of less than approximately 10 km cannot be explicitly represented and need to be parameterised for their effects to be included within the models. The purpose of this project, Surface Mixed Evolution at Submesoscales (SMILES), is to identify the potentially crucial role played by one variety of these unresolved processes, referred to as submesoscales, in influencing the structure and properties of the upper ocean, and thereby the transformation of surface water masses, within the Southern Ocean. Submesoscales are flows with spatial scales of 1-10 km that occur within the upper ocean where communication and exchange between the ocean and the atmosphere occurs. Previously considered unimportant to climate-scale studies due to their small scale and the presumed insignificance of their dynamics, recent evidence from high resolution regional models and observational studies is now emerging which suggests that submesoscales are actually widespread throughout the upper ocean and play a key role within climate dynamics due to their ability to rapidly restratify the upper ocean and reduce buoyancy loss from the ocean to the atmosphere. The impact of such a process is particularly important to the surface transformation of water masses such as Subantarctic Mode Water (SAMW), which is an important component of the Meridional Overturning Circulation (MOC) that redistributes heat, freshwater and tracers around the globe. Within the MOC, dense water masses such as SAMW are formed and transformed at high latitudes by surface processes before being subducted into the ocean interior. The properties of the subducted water masses and the tracers and dissolved gases such as carbon dioxide contained within them are vitally important to the global climate and geochemical cycles as these water masses remain out of contact with the surface over decennial to centennial timescales. In the light of the recent discoveries concerning the ability of submesoscales to substantially influence the properties of the upper ocean, we will directly study the impacts of submesoscales on SAMW properties within the Scotia Sea. Using an integrated approach, we will both observe and simulate submesoscales within the upper ocean at a range of spatial and temporal scales, spanning from turbulence up to mode water formation. The principal goal of the study is the diagnosis of the role played by submesoscales in water mass transformation so that we can accurately incorporate these effects into climate-scale models which cannot explicitly resolve them. Our methods will entail a cruise approximately 200 miles south of the Falklands Islands at the Subantarctic Front (SAF), to the north of which SAMW is transformed, and a concurrent modelling study using a state-of-the-art global circulation model. During the cruise, we will use towed instruments to measure the length scales of variability in the temperature, salinity and related fields throughout the upper 300 m of the ocean. The data will enable us to identify the intensity and distribution of submesoscales within the vicinity of the SAF, and to ascertain the forcing mechanisms that generate them. In conjunction with the modelling component of the project, which will include both high resolution and coarse-scale simulations with the MITgcm and large eddy simulations (LES), we will assess how submesoscales ultimately impact on the properties of SAMW within the region and the ultimate effect this has on the formation of SAMW.

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Currently producing biofuel from microalgae is commercially prohibited. This is partly due to the high economic costs associated with the nitrogen and phosphorus nutrients required to sustain photosynthetic production. These inorganic nutrients can be found in abundance in industrial wastewater. There are also issues with the requirement of water for cultivating microalgae. Marine microalgae need to be situated near to the coast for utilisation of seawater and freshwater microalgae systems are dependent on large and continuous freshwater supplies, diverting supply away from arable farming etc. Therefore, producing biofuel from microalgae cultivated onwastewater has clear environmental and economic advantages. In any large scale microalgal cultivation system, and particularly when using wastewater, a consortia will be present consisting of a single or several species of algae together with a complement of inherent bacteria; these associated bacteria have been shown to boost lipid production. There are many challenges associated with understanding such a complex and dynamic system. For example, interactions in the system will include metabolic changes occurring both within individual species and between the species. Ultimately the quantity and quality of the biomass suitable for biofuel will be related directly with the growth and the composition of the consortia which will dependent on interactions within it. Currently we have a poor understanding on the composition, development, function and interactions occurring with microalgae consortia. This project will bring the three centres to develop new understanding on developing microalga-bacterial consortia cultivated on industrial water to produce biomass for biofuel. Bharathidasan University (BDU) has expertise on molecular techniques and cultivation of microalgae for bioenergy products. Phycospectrum Environmental Research Centre (PERC) has expertise on robust algal consortia and working with industry on wastewater treatment. Plymouth Marine Laboratory (PML) has expertise on the biology and chemistry to understand microbial community structure and on microbial dynamics. BDU and PERC will focus on optimising strains under industrially relevant conditions and results will be brought together with those from PML who will focus on understanding the microbial dynamics in controlled synthetic wastewater experiments. The project will undertake community composition analysis to obtain understanding on how microalgal consortia change and function at both the cellular and molecular level. We will test the effect that both bacteria and addtional organic carbon have on influencing the growth and composition of the algal biomass as a biofuel feedstock. We will assess both the lipid and carbohydrate content of the algae for potential in biodiesel and bioethanol respectively. Put simplistically we will measure 'who is there? (community/taxonomic analysis), 'how do they compare? (comparative analysis)' and 'what are they doing? (functional analysis)' under the different conditions to optimise the amount and type of biomass suitable for conversion into biofuel. To do this we will use the novel and powerful combination of flow cytometry tools to separate both algal and bacterial populations and genomic tools to characterise the communities. Whilst these tools have recently been applied to study marine microbial ecosystems, they have not been applied to any great extent to understanding wastewater microalgal-bacterial consortia. Knowledge gained will lead to potential to optimise consortia to improve growth rates and the amounts of lipids and/or carbohydrates. This could be achieved through controlling or adding bacteria, the addition of a waste carbon source, or through manipulation of metabolic pathways. The research will contribute to creating solutions to producing biofuel from microalgae grown on wastewater with consideration to both the environment and the economy.