Boron Isotopes in Seaweed
Carrie Wright is a research scientist who was a Marie Curie postdoc in our lab. She uses isotopes to decypher details of diet. In her dissertation work and for her post-doc she worked on Ca isotopes in teeth to learn about weening. Because we had a number of projects on boron, she got interested in the possibility to use this to learn more about diet and trophic levels. We started with seaweed and discovered a significant fractionation from seawater that is consistent with seaweeds selecting for borate only.
Boron speciation and isotope composition
The graph on the right shows the fraction of boric acid and borate for a range of pH values on the top, and the boron isotope composition of these species that results from a preference for the lighter isotope in borate. The isotope value for seaweed is offset from seawater and plots near the expected isotope composition for borate.
Seaweed details
Work published by Miller et al. (2016) used Nuclear Magnetic Resonance (NMR) to determine boron species in seaweed. This work showed differences between the blade and stipe but both contain borate specials complexed with manitol.