Project: Collaborative Research: Exploring the role of exogenous polyphosphate in the precipitation of calcium phosphate minerals in the marine environment

NSF Award Abstract:
Phosphorous is an important nutrient sustaining all forms of life. In particular, in the ocean, phosphorous is a key limiting nutrient, controlling levels of primary productivity across large swaths of the ocean. Removal of phosphorous occurs largely via formation of stable apatite minerals in ocean sediments. However, average ocean conditions generally inhibit the formation of apatite, thus the abundance of apatite minerals in marine sediments is a mystery. This research aims to determine the mechanisms of apatite formation in the ocean to answer this century-old question. Evaluating these mechanisms will greatly advance current understanding of phosphorous cycling in the ocean. A more detailed understanding of phosphorous cycling can be applied across the disciplines of ocean science, and because of the importance of phosphorous as a nutrient and an element with a variety of interactions with other elements, it will be applicable to a variety of other research questions. The researchers are dedicated to promoting diversity in ocean science and plan to include undergraduate students from underrepresented groups in the study. They will also mentor a postdoc and communicate their science to the public and K-12 teachers via a blog entitled "Britannica Blog", the Atlanta Science Festival, a rock show, and educational material, the latter two to be developed as part of this work.

Marine phosphorous burial via authigenic stable apatite formation in sediments is a major pathway for phosphorous removal in the ocean. However, in most marine environments, under natural conditions, this process is kinetically inhibited. It has been a mystery for more than a century as to how it is therefore possible for apatite to be oversaturated in large areas of marine sediments. A possible mechanism that could explain 95% of the apatite burial flux is that apatite minerals are precipitated as fine-grained particles from exogenous polyphosphate intermediates. Exogenous polyphosphates have been understudied, despite this possible importance as a mechanism for phosphorous removal. As a consequence this research could revolutionize current understanding of phosphorous cycling in the ocean for the major aim is to make a thorough and detailed study of the mechanisms behind marine apatite formation, focusing on the role of exogenous polyphosphate particles. Phosphorous is an element with widespread importance in ocean sciences, and more clearly understanding its burial will have applications across the disciplines.