Research Fellows Directory
Dr Katharine Hendry
University of Bristol
Despite being microscopic and made from single cells, diatoms are vital for life on earth. Together with other organisms such as sponges, diatoms - photosynthetic algae - make their ornate skeletons from glass-like silica called biogenic opal. Marine diatoms dominate the removal of dissolved silicon (Si) from seawater and contribute to nearly half of the carbon sinking from surface to deep waters, which is a key process responsible for variations in atmospheric carbon dioxide. Diatoms are also used in industry and are a focus of nanotechnology research into optical systems, semiconductors, and for use in medicine.
However, there is much that we still have to learn about how diatoms produce biogenic opal.
My first major aim is to understand how dissolved Si is taken up by diatoms (and sponges) by investigating how these organisms take up different forms or isotopes of Si. There are naturally three Si isotopes with atomic masses of 28, 39 and 30. During growth, diatoms and sponges are selective in the form of Si they take up, preferring the lighter isotope. But the exact processes that control this fractionation are, as yet, unknown.
My second aim is to use the chemistry of biogenic opal to investigate the changes in the marine cycling of silicon at important times of climate change, such as the end of the last ice age around 15 thousand years ago. I was one of the first to show that the Si isotope composition of sponges provides an archive of dissolved Si in the waters in which they grow. This provides us with a unique way of recording marine Si cycling back in time and in waters that can be kilometres deep – the realm of deep sea sponges. I can use these records together with Si isotopes of diatoms, which tells how much of the silicon that reaches the surface is used up by the siliceous algae. This means that, for the first time, we have a handle on the whole silicon cycle - both inputs and outputs - and so on the amount of carbon absorbed.
Interests and expertise (Subject groups)