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M. L. Delaney

Bio: M. L. Delaney is an academic researcher. The author has contributed to research in topics: Authigenic & Total organic carbon. The author has an hindex of 1, co-authored 1 publications receiving 272 citations.

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TL;DR: In this paper, the authors present an integrated overview of key factors in the oceanic mass balance of dissolved, reactive phosphate, with an emphasis on evaluating the burial sinks for P and defining areas needing further research.
Abstract: Ideas about key factors in the oceanic mass balance of dissolved, reactive phosphate have changed substantially. I present an integrated overview of these here, with an emphasis on evaluating the burial sinks for P and defining areas needing further research. The major source of reactive P to the ocean is river input. Reactive P is delivered to the oceanic sediment-water interface primarily in particulate organic matter. P scavenged by hydrothermal iron-rich oxyhydroxide particles, with uptake in proportion to deep water phosphate concentrations, represents a substantially smaller flux to the sediment-water interface. Diagenetic transformations are important influences on the form of reactive P burial in marine sediments. P burial occurs with organic carbon burial and as P associated with iron-rich oxyhydroxide particles and coatings. Formation of authigenic P-rich phases, presumably apatite, at the expense of organic P and oxide-associated P, is significant in open ocean marine sediments. The authigenic P sink may represent a substantially larger portion of the sedimentary burial than indicated by previous estimates focused on P burial in organic-rich continental margin sediments.

299 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, a comprehensive review of the biogeochemical cycling of P within the oceans is given, with particular attention focused on the composition and recycling rates of P in the water column.

609 citations

Journal ArticleDOI
TL;DR: Research in the Pacific Ocean gyres indicates that biological P uptake rates far surpass the combined input from atmospheric and deep water sources, suggesting that P is efficiently recycled within oligotrophic euphotic zones.
Abstract: Phosphorus (P) is an essential element to all life, being a structural and functional component of all organisms.1-4 P provides the phosphate-ester backbone of DNA and RNA, and it is crucial in the transmission of chemical energy through the ATP molecule (Figure 1). P is also a structural constituent in many cell components such as phosphoproteins, and phospholipids in cell membranes, teeth, and bones (Figure 1). In some organisms it can also be present as intracellular polyphosphate storage granules (Figure 1). Phosphorus availability can impact primary production rates in the ocean as well as species distribution and ecosystem structure.5-8 In some marine and estuarine environments, P availability is considered the proximal macronutrient that limits primary production.8,9 Specifically, in recent years it has been recognized that phosphorus limitation in the ocean may be more prevalent than previously thought. For example, it is generally accepted that orthophosphate (PO4) is the limiting nutrient in the eastern Mediterranean Sea.10-12 In addition, phosphate is suspected to play an important role in limiting production in the Sargasso Sea13 and may also be limiting in bodies of water receiving large freshwater inputs or fertilizer runoff from agriculture, as in the Chesapeake Bay.14,15 Furthermore, research in the Pacific Ocean gyres indicates that biological P uptake rates far surpass the combined input from atmospheric and deep water sources, suggesting that P is efficiently recycled within oligotrophic euphotic zones.16 It has also been suggested that transitions over the last two decades from nitrogen (N) limitation to P limitation have taken place in the North Pacific subtropical gyre and that this may be responsible for the observed succession of prokaryotic picophytoplankton such as Prochlorococcus and Synechococcus in oligotrophic waters.6 In other marine environments, P may only be limiting a subset of organisms within the ecosystem.17-19 Phosphorus, in the form of orthophosphate, plays a key role in photosynthesis (i.e., primary productivity). The chemical equation representing average ocean photosynthesis can be written as

600 citations

Journal ArticleDOI
TL;DR: The resulting budget recognizes significantly higher input and output fluxes and notes that the recycling of silicon occurs mostly at the sediment-water interface and not during the sinking of silica particles through deep waters.
Abstract: Over the past few decades, we have realized that the silica cycle is strongly intertwined with other major biogeochemical cycles, like those of carbon and nitrogen, and as such is intimately related to marine primary production, the efficiency of carbon export to the deep sea, and the inventory of carbon dioxide in the atmosphere. For nearly 20 years, the marine silica budget compiled by Treguer et al. (1995), with its exploration of reservoirs, processes, sources, and sinks in the silica cycle, has provided context and information fundamental to study of the silica cycle. Today, the budget needs revisiting to incorporate advances that have notably changed estimates of river and groundwater inputs to the ocean of dissolved silicon and easily dissolvable amorphous silica, inputs from the dissolution of terrestrial lithogenic silica in ocean margin sediments, reverse weathering removal fluxes, and outputs of biogenic silica (especially on ocean margins and in the form of nondiatomaceous biogenic silica). Th...

569 citations

Journal ArticleDOI
19 Jan 2017-Nature
TL;DR: A compilation of phosphorus abundances in marine sedimentary rocks spanning the past 3.5 billion years is presented and it is found that a combination of enhanced phosphorus scavenging in anoxic, iron-rich oceans and a nutrient-based bistability in atmospheric oxygen levels could have resulted in a stable low-oxygen world.
Abstract: The macronutrient phosphorus is thought to limit primary productivity in the oceans on geological timescales. Although there has been a sustained effort to reconstruct the dynamics of the phosphorus cycle over the past 3.5 billion years, it remains uncertain whether phosphorus limitation persisted throughout Earth’s history and therefore whether the phosphorus cycle has consistently modulated biospheric productivity and ocean–atmosphere oxygen levels over time. Here we present a compilation of phosphorus abundances in marine sedimentary rocks spanning the past 3.5 billion years. We find evidence for relatively low authigenic phosphorus burial in shallow marine environments until about 800 to 700 million years ago. Our interpretation of the database leads us to propose that limited marginal phosphorus burial before that time was linked to phosphorus biolimitation, resulting in elemental stoichiometries in primary producers that diverged strongly from the Redfield ratio (the atomic ratio of carbon, nitrogen and phosphorus found in phytoplankton). We place our phosphorus record in a quantitative biogeochemical model framework and find that a combination of enhanced phosphorus scavenging in anoxic, iron-rich oceans and a nutrient-based bistability in atmospheric oxygen levels could have resulted in a stable low-oxygen world. The combination of these factors may explain the protracted oxygenation of Earth’s surface over the last 3.5 billion years of Earth history. However, our analysis also suggests that a fundamental shift in the phosphorus cycle may have occurred during the late Proterozoic eon (between 800 and 635 million years ago), coincident with a previously inferred shift in marine redox states, severe perturbations to Earth’s climate system, and the emergence of animals.

394 citations

Journal ArticleDOI
TL;DR: In this paper, the accumulation rates of three commonly used proxies for productivity from a set of primarily Quaternary sediment cores at 94 marine sites, compiled from 37 published sources, were evaluated for total organic carbon, organic phosphorus, and biogenic barium (Babio).

365 citations