Nutrient cycling in lakes

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My research program concerns microbial food webs and nutrient cycles, and in this grant cycle my lab will target four areas. The first area concerns dissolved organic phosphorus (DOP) in lake water. This is the largest dissolved fraction of this limiting nutrient, but our recent work demonstrates that it is mostly derived during the filtration step of sample preparation, probably by cell breakage. Our hypothesis is that truly dissolved organic P is also derived from cell breakage, but due to natural mechanisms such as viral lysis and grazing. To complete this line of research we will test the hypotheses that the high molecular weight fraction of DOP is mostly nucleic acids, and that these become PO4 via low molecular weight DOP that is mostly nucleotides and other substrates available to plankton via cell-membrane associated phosphatases.