Exploring the role of turbulence and biological glue on marine snow formation

Dr Adrian Martin, Dr Chelsey Baker, Dr Christina Vanderwel, Dr John Lawson https://www.southampton.ac.uk/engineering/about/staff/jml1g18.page
Rationale: 

The biological carbon pump transfers a significant amount of carbon dioxide to the deep ocean. The pump is driven by sinking aggregates of organic particles, known as marine snow. The size, shape and structure of particles all influence the rates at which they sink and are remineralised, with fast sinking particles increasing the potential for long-term carbon storage. Transparent exopolymer particles (TEP) are sticky polysaccharides, which act as a biological glue. TEP are produced by certain types of phytoplankton and promotes coagulation of phytoplankton cells to form aggregates [1]. There are several mechanisms by which TEP could promote aggregation, such as stickiness increasing the success rate of particle collisions. Turbulence in the upper water column has also recently been shown to enhance particle aggregation [2]. Turbulence may further promote TEP production in the upper-surface ocean which in turn may increase particle aggregation [3]. Climate change is predicted to suppress turbulence and alter phytoplankton community structure, which may impact TEP production [2]. The aim of this project is to combine analysis of an existing unique dataset, laboratory experiments and modelling to understand how TEP and turbulence impact aggregation with possible implications for the efficiency of the biological carbon pump in the future. 

Methodology: 

The role of turbulence on TEP production and particle transformation in the upper ocean (0-200m) has not previously been explored using in situ observations. Initially, the student will analyse a novel dataset collected during a recent research cruise (https://roses.ac.uk/custard/), which includes observations of turbulence, TEP and particle size profiles collected at three different locations in the Southern Ocean. The student will be encouraged to choose the future direction of the project in line with their interests. There are several exciting avenues that could be explored which would be supported by the supervisor’s expertise. For example, further work could include experiments using a turbulence tank and the advanced digital imaging and laser diagnostic equipment available in the aeronautics group to explore how turbulence influences particle dynamics. A further possible route is for the student to use a simple biogeochemical model to test the influence of turbulence, TEP and particle morphology on particle fluxes and to explore wider consequences for the global carbon cycle.

Location: 
NOC Southampton
Training: 

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the National Oceanography Centre, Southampton. Specific training will include:

The student will be trained in biogeochemical laboratory techniques, such as TEP analysis, by an experienced marine biogeochemist. Training in numerical and statistical techniques needed to analyse the data will be provided. Depending on the student’s interests training in setting up experiments to measure how particles move in turbulent regimes or using a computer model to simulate TEP, particulate and turbulence interactions would be provided. The student will be encouraged to present their work at international conferences. There will also be opportunities to participate on a sea-going research expedition to collect additional data.

Eligibility & Funding Details: 

Please check https://inspire-dtp.ac.uk/how-apply for details.  

 

Background Reading: 

[1] Engel et al., (2020) Marvelous Marine Microgels: On the Distribution and Impact of Gel-Like Particles in the Oceanic Water-Column, Frontiers in Marine Science, 7, 405, doi: 10.3389/fmars.2020.00405.

[2] Takeuchi et al., (2019) Turbulence mediates marine aggregate formation and destruction in the upper ocean, Nature Scientific Reports, 9, 16280, doi.org/10.1038/s41598-019-52470-5.

[3] Beauvais et al., (2006) Effects of turbulence on TEP dynamics under contrasting nutrient conditions: implications for aggregation and sedimentation processes, Marine Ecology Progress Series, 323, 47-57.