Saturday, March 8, 2014

It all comes back to silica

After Emma and David left, we hosted two colleagues from Antwerp University, Belgium, in the Mara. Jonas Schoelynck and Eric Struyf study silica cycling and are particularly interested in the role animals might play in the silica cycle. 

What is silica? It's commonly found in nature as quartz, but it can also be found in living organisms like grass (it gives grass the sharpness that can cut you). Silica is taken up by diatoms in the ocean, that are at the base of the food web, and it is often limiting to their growth. That it, the more silica there is, the more diatoms there are, and the more overall productivity in that region of the ocean. A lot of the silica in the ocean is brought in by rivers, and it has generally been assumed that all of that silica originated from weathering of rocks. But recent advances in the last decade have shown that animals can actually contribute a great deal of silica by eating grass and defecating it out, and the silica defecated by animals is more reactive than that simply eroded form rocks. If it involves animals eating and defecating grass, we have the perfect animal to study...

Hippos basking in the Mara River

Jonas and Eric came to the Mara to work with us to investigate the role hippos might be playing in the silica cycle. To study this, they collected water and sediment samples from multiple reaches of the river with varying densities of hippos.

Eric collecting a pore water sample from the Mara

Jonas and Eric collecting a sediment core from the riverbank
We did this throughout a 100 km reach of the Mara, which was a great opportunity to see some beautiful places, and to learn a lot about silica.

Jonas and Eric on the banks of the Mara

They also took sediment samples in the middle of the grasslands for comparison.

Jonas and Eric collecting a sediment core in the savanna
These guys are super passionate about their subject and a lot of fun to work with, and after a week in the field together, they pretty much convinced me that everything comes back to silica cycling! Best of all, they took a system and an animal about which we have thought a lot, and introduced a whole new component to think about that we hadn't considered before. It will be really exciting to see what these new analyses can teach us about the Mara.
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