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EnvEast: Student Projects


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Diatoms

EnvEast: Student Projects

As mentioned in a past blog post, EnvEast student projects are based around three overarching themes: Climate, Marine and Atmospheric Sciences; Biodiversity, Ecosystem Services and Sustainable Development and Natural Hazards. These themes allow the students of the EnvEast DTP to cover a broad range of science in a fresh and innovative fashion.

Throughout the course of this blog post, I will discuss my own research project, which falls into the category of Climate, Marine and Atmospheric Science.

Working under the title of ’Do diatoms play an important global role in the production of DMS and it’s precursor DMSP?’, my project falls almost too neatly into Climate, Marine and Atmospheric Science. I say this because those three fields coincide within my project. DMS is a climatically active gas, oxidising to form sulphates in the atmosphere which in turn act as cloud condensation nuclei (CCN). These CCN assist in cloud formation, which in turn increases solar reflection and has the overall consequence of global cooling. Combine the climate and atmospheric components from the above, with the fact that DMS is produced in bulk through the release and breakdown of the precursor compound DMSP (http://aem.asm.org/content/68/12/5804.full), which biologically synthesised by marine – and to some extent freshwater – phytoplankton and you’ve covered the marine aspect.

The DMS Cycle

Dimethylsulphide (DMS) forms a key transport pathway of sulphur from sulphur-rich seawater to sulphur-depleted landmasses. Accounting for approximately 50-60% of the total natural reduced sulphur flux to the atmosphere, DMS is a vital component of global biogeochemical cycles. More recent estimates suggest that DMS accounts for 90% of biogenic oceanic sulphur emissions.

Without DMS, global temperatures have been predicted to be 1.6’C higher (Speilmeyer et al. 2012), a temperature rise that has the potential to completely melt the Greenland Ice Sheet (Robinson et al., 2012).

Diatoms

Diatoms are the most diverse group of marine phytoplankton, with greater than 200,000 identified species to date. This diversity is reflected in the sheer amount of weird and wonderful morphologies adopted by different diatom species, which have arisen from the series of endosymbiotic evolutionary events over the past 90 million years. They are incredibly important biogeochemical cyclers not only of sulphur, but also carbon, nitrogen, phosphorus and silicate. Diatoms occur in such great numbers in the oceans, that their photosynthesis alone accounts for every fifth breath that you take, and thus generate as much organic carbon as all of the terrestrial rainforests combined.

It’s this density and diversity that make diatoms an incredibly interesting study species for DMSP production. Where their synthesis levels under conventional ocean conditions do not match those of other marine phytoplankton, such as dinoflagellates, research has shown that synthesis increases under a number of stress conditions. Such conditions include – but are not limited to – nutrient limitation, UV exposure and both temperature and salinity changes.

Diatoms also have comparatively less space available for DMSP production than other groups of marine phytoplankton, making the ’significant’ quantities produce all the more impressive. This is due to the theory that DMSP is produced in the cytoplasm. Diatoms are the only group of marine phytoplankton that possess a vacuole, which drastically lowers the cytoplasm containing volume of the cell.

Research Implications

Since starting my PhD, I’ve struggled with communicating the implications of my research. Where I investigate how DMSP synthesis changes under different environmental conditions, these results will not inherently change the amount of DMS present in the atmosphere.

However, my results can go to improving current global climate models, particularly those that are carbon based. By using stable isotope methodologies, I hope to incorporate a DMSP synthesis rate for diatoms into existing carbon models. This is will help to more accurately predict future temperature, and consequently better combat climate change.

There are many other aspects to my research project that I have no mentioned here. Some, such as creating a catalogue of volatile trace gases produced by diatoms, have been discussed previously.

This is just one of many innovative and inspirational projects occurring under the banner of EnvEast. You can keep up to date with more of these projects over at Science-Envy.

Posted by Seth Thomas on Mon, 30 Oct 2017



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