The marine phosphorus cycle

Phosphorus, the 13th element to be discovered on our planet, has a rich and varied history spanning match-making, bombs, fertilizer, and pesticides. Entire islands economies (Nauru) have collapsed in the mad hunt for phosphorus rock (Gowdy and McDaniel, 1999). Mineral reserves of this critical and valuable element are now being so rapidly mined from our Earth’s crust that we are approaching a point where demand exceeds supply (Cordell et al., 2009). Why such a storied element? The answer rests in the fact that phosphorus is an essential ingredient in every known recipe for life: it is integral for energy storage, cell structure, and the very genetic material that encodes all life on the planet. Phosphorus is in fact, the staff of life (Karl, 2000), the scaffolding onwhich all biomass is built. Just as phosphorus fertilizer supports the growth of agricultural crops, phosphorus supply supports the growth of photosynthetic organisms, or phytoplankton, at the base of the marine food web. The biogeochemical cycling of phosphorus in the ocean is thus an important determinant of ecosystem structure and function, which motivated this special research topic in Frontiers in Microbiology entitled “The marine phosphorus cycle.” In total, 10 papers have been included, with 8 original research articles and 2 reviews. Collectively these papers detail new advances, important nuances, and unexpected discoveries related to phosphorus cycling in the marine environment. This e-book begins with a number of papers detailing the production of dissolved organic phosphorus (DOP) in the upper water column. Original research by MacKey et al. (2012) documents the rapid uptake of phosphate by harmful algal bloom forming diatom species in Monterey Bay and the subsequent production of DOP as these blooms decayed. This latter finding is relatively novelsimply because relatively little is known about the rate and control of DOP production in the sea. To address this point, Ruttenberg and Dyhrman (2012) show that changes in the ambient inorganic nitrogen:phosphorus ratio may modulate the rate of DOP production in coastal upwelling regimes. Taken together these papers provide new insights into how DOP is produced in the ocean. Roughly balancing this production is biotic decomposition, which occurs as microbes scavenge organic pools for essential elements. For DOP compounds characterized by a C-O-P bond (esters), hydrolysis is catalyzed by a class of enzymes termed alkaline phosphatases. Organisms with the capacity to build this