BIPHA · Bio-physical processes around marine snow aggregates
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2015-11-01 → 2018-12-18
- EU contribution
- €173,857
- Participants
- 1
- Scheme
- MSCA-IF-EF-ST
Lines connect the coordinator with its partners.
Results in brief
Bio-physical processes around marine snow aggregates
The continuous rise in carbon dioxide levels in the means that it is crucial to better understand the Earth’s carbon cycle. One key aspect is the ocean’s so-called “biological carbon pump” i.e. the biologically driven sequestration of atmospheric carbon to the deep ocean and its sediments. Major vehicles for this transfer of organic matter from the surface to the deep are so-called “marine snow aggregates” and, in particular, aggregates composed of diatoms. Diatoms’ heavy silicified cell walls and long cell chain formation mean that they can form fast-sinking aggregates, and given their abundance as one of the most common types of phytoplankton found in the ocean, can they dominate the particle flux to the ocean floor. Diatom aggregates are like small microbial hotspots as they sink to the seafloor and are frequently glued together by transparent exopolymeric particles (TEP), which is a gel-like transparent sugary substance released by diatoms themselves and bacteria. As the aggregates sink there is an exchange of solutes and they become a food source for microbes and larger organisms such as zooplankton. Despite their importance the small-scale processes occurring around these aggregates as they sink are difficult to study. The key objective of this project was to implement advanced technology to gain a better understanding of the processes, e.g., TEP production, that influence the relative importance of flow and diffusion around and within diatom aggregates and hence the exchange of gases, nutrients and solutes between the aggregate and the surrounding water. We examined the flow around both permeable as well as impermeable aggregates and, further, explored the production of TEP as well as aggregate formation of the cosmopolitan diatom species 'Skeletonema marinoi' in detail. Specifically, we determined how TEP production is affected by dynamic nutrient conditions at a clonal level and if subjected to grazing pressure.
Data: CORDIS, © European Union
Project objective
Advancing our understanding of biologically driven sequestration of carbon is crucial given the rapidly increasing atmospheric CO2 concentrations. Diatoms are the most common type of phytoplankton and, as the ocean’s biological carbon pump, a key component in this process. Diatom aggregates, in particular, comprise a significant fraction of sinking particulate matter drawing down atmospheric carbon to the depths of the ocean. Diatoms produce transparent exopolymeric particles (TEP), a gel-like sticky sugary substance, which plays a significant role in the subsequent coagulation of diatoms into aggregates as their blooms terminate. These sinking aggregates are composed of diatoms, detritus and faecal pellets and are so-called marine snow aggregates. We will use recent innovations in technology to study the role of TEP content for: • Scavenging of particles • Flow and diffusion within and around diatom aggregates We will draw upon the specialized expertise of the applicant and the beneficiary to study diatom aggregates in detail using methods which have greatly profited from technological advances: • Particle image velocimetry, and • digital holographic microscopy, in combination with • microsensors, to study mass transfer at a sub-mm scale. The methods will enable us for the first time to quantify directly any flow inside the aggregates, also called the interstitial fluid flow, and to visualize the aggregate’s structure and particle composition. Targeting these processes with advanced instrumentation will bring European research on aggregates to the forefront in terms of the technology, but more importantly, our understanding of carbon cycling in the ocean and our position on future climate change impacts.
Original text from CORDIS.
Participants
- GOETEBORGS UNIVERSITET · GoeteborgCoordinatorSweden
Links
Data: CORDIS, © European Union