About

William M. Berelson is a Professor in the Department of Earth Sciences and the Environmental Studies Program at the University of Southern California. His research encompasses a wide spectrum of topics aimed at connecting geochemical cycles, budgets, and fluxes through both modern and ancient environments. Much of his work involves studying biogenic material fluxes to the sea floor and across this boundary, utilizing sediment traps, water column profile measurements, and modeling to capture fluxes through the water column. His analysis of the solid phase helps link oceanographic biogeochemistry with the sedimentary rock record, focusing on fluxes and reactions involving elements such as oxygen, carbon, nitrogen, phosphorus, calcium carbonate, biogenic silica, iron, and sulfur, along with their isotopes. Berelson's research includes participation in oceanographic field studies across diverse locations such as the Cocos Ridge in the Tropical Eastern Pacific, the NE Pacific, the Eastern Tropical South Pacific Ocean, the Western Tropical North Atlantic Ocean within the Amazon River plume, the Gulf of Mexico hypoxia zone, and various sites in California including Mono Lake and the Monterey Formation. His lab combines standard geologic and inorganic chemical analytical facilities with novel geochemical instrumentation, supporting a broad range of geochemical and biogeochemical investigations. He teaches graduate courses in carbonate chemistry, sedimentology, and marine sedimentary geochemistry, and has been involved in international training courses that have significantly contributed to the development of the field. Berelson has also served as chairman of the Earth Sciences Department from 2012 to 2018.

Research topics

• Geology
• Chemistry
• Oceanography
• Mineralogy
• Environmental chemistry
• Environmental science
• Ecology
• Earth science
• Biology
• Geochemistry
• Paleontology
• Chemical physics

Selected publications

• Shallow Calcium Carbonate Cycling in the North Pacific Ocean

  Global Biogeochemical Cycles · 2022 · 81 citations

  • Oceanography
  • Geology
  • Mineralogy

  Abstract The cycling of biologically produced calcium carbonate (CaCO 3 ) in the ocean is a fundamental component of the global carbon cycle. Here, we present experimental determinations of in situ coccolith and foraminiferal calcite dissolution rates. We combine these rates with solid phase fluxes, dissolved tracers, and historical data to constrain the alkalinity cycle in the shallow North Pacific Ocean. The in situ dissolution rates of coccolithophores demonstrate a nonlinear dependence on saturation state. Dissolution rates of all three major calcifying groups (coccoliths, foraminifera, and aragonitic pteropods) are too slow to explain the patterns of both CaCO 3 sinking flux and alkalinity regeneration in the North Pacific. Using a combination of dissolved and solid‐phase tracers, we document a significant dissolution signal in seawater supersaturated for calcite. Driving CaCO 3 dissolution with a combination of ambient saturation state and oxygen consumption simultaneously explains solid‐phase CaCO 3 flux profiles and patterns of alkalinity regeneration across the entire N. Pacific basin. We do not need to invoke the presence of carbonate phases with higher solubilities. Instead, biomineralization and metabolic processes intimately associate the acid (CO 2 ) and the base (CaCO 3 ) in the same particles, driving the coupled shallow remineralization of organic carbon and CaCO 3 . The linkage of these processes likely occurs through a combination of dissolution due to zooplankton grazing and microbial aerobic respiration within degrading particle aggregates. The coupling of these cycles acts as a major filter on the export of both organic and inorganic carbon to the deep ocean.

  DOI

• Understanding the isotopic composition of sedimentary sulfide: A multiple sulfur isotope diagenetic model for Aarhus Bay

  American Journal of Science · 2022 · 11 citations

  • Geology
  • Chemistry
  • Mineralogy

  Measurement of the multiple sulfur isotopes (³²S/³³S/³⁴S) enables the calibration of microbial biosignatures and provides a unique diagnosis of S-based metabolic processes: sulfate reduction, disproportionation, and sulfide oxidation. All three metabolisms carry distinct geochemical consequences for S cycling in modern systems, and are particularly powerful for paleoenvironmental interpretations if their respective contributions can be separated. To hone those interpretations and to further develop a quantitative context for understanding early diagenetic sulfur cycling, we constructed a multiple S isotope reactive transport model for the sediments of a geochemically well-characterized system (Aarhus Bay, Denmark). The model reconciles pore water and solid phase concentration profiles of the major species associated with Fe/S/C cycling, and uses multiple S isotope systematics to predict the isotope profiles of the major S species, including pore water sulfate, free sulfide and solid phase pyrite. We note that very large fractionations associated with sulfate reduction (³⁴ε_sr = 70‰) are required to reproduce the observed pore water profiles, and we reconcile these fractionations with low temperature theoretical predictions for isotope equilibrium fractionation. The minor sulfur isotope values (noted as Δ³³S) of sulfate increase at shallow depths within the Aarhus Bay core, and decrease when sulfate drops below 10 mM. Values (Δ³³S) for sulfide decrease nearly monotonically towards seawater sulfate values near the zone of sulfate depletion. Pyrite Δ³³S values are nearly uniform downcore (0.170 ± 0.010‰) despite a ∼10‰ enrichment in surface versus deep pyrite δ³⁴S values. Sulfate reduction is the most important process controlling S isotope pore water distributions, with modest contributions from oxidative S cycling. Further, microbial sulfate reduction demonstrates large fractionations typically not expected for shallow, organic rich (TOC ∼ 4%) continental margin systems.

  PublisherDOI

• Mercury contents and isotope ratios from diverse depositional environments across the Triassic–Jurassic Boundary: Towards a more robust mercury proxy for large igneous province magmatism

  Earth-Science Reviews · 2021 · 47 citations

  • Geology
  • Earth science
  • Geochemistry
  DOI

• Nitrification and Nitrous Oxide Production in the Offshore Waters of the Eastern Tropical South Pacific

  Global Biogeochemical Cycles · 2020 · 77 citations

  • Environmental chemistry
  • Environmental science
  • Oceanography

  Abstract Marine oxygen deficient zones are dynamic areas of microbial nitrogen cycling. Nitrification, the microbial oxidation of ammonia to nitrate, plays multiple roles in the biogeochemistry of these regions, including production of the greenhouse gas nitrous oxide (N 2 O). We present here the results of two oceanographic cruises investigating nitrification, nitrifying microorganisms, and N 2 O production and distribution from the offshore waters of the Eastern Tropical South Pacific. On each cruise, high‐resolution measurements of ammonium ([NH 4 + ]), nitrite ([NO 2 − ]), and N 2 O were combined with 15 N tracer‐based determination of ammonia oxidation, nitrite oxidation, nitrate reduction, and N 2 O production rates. Depth‐integrated inventories of NH 4 + and NO 2 − were positively correlated with one another and with depth‐integrated primary production. Depth‐integrated ammonia oxidation rates were correlated with sinking particulate organic nitrogen flux but not with primary production; ammonia oxidation rates were undetectable in trap‐collected sinking particulate material. Nitrite oxidation rates exceeded ammonia oxidation rates at most mesopelagic depths. We found positive correlations between archaeal amoA genes and ammonia oxidation rates and between Nitrospina ‐like 16S rRNA genes and nitrite oxidation rates. N 2 O concentrations in the upper oxycline reached values of >140 nM, even at the western extent of the cruise track, supporting air‐sea fluxes of up to 1.71 μmol m −2 day −1 . Our results suggest that a source of NO 2 − other than ammonia oxidation may fuel high rates of nitrite oxidation in the offshore Eastern Tropical South Pacific and that air‐sea fluxes of N 2 O from this region may be higher than previously estimated.

  DOI

• The Dissolution Rate of CaCO₃ in the Ocean

  Annual Review of Marine Science · 2020 · 53 citations

  Senior authorCorresponding
  • Mineralogy
  • Geology
  • Chemical physics

  dissolution in key sedimentary environments.

  DOI

Recent grants

• Collaborative Research (OSU, USC, RU): Continental Shelf Diagenesis II: The Importance of Increasing Oceanic Hypoxia to Coastal Iron Supply and the Ocean's Iron Isotope Composition

  NSF · $250k · 2011–2014

• Collaborative Research: New Constraints on Marine Oxygen Cycling

  NSF · $97k · 2014–2017

• Collaborative Proposal: Anoxic Sediment Diagenesis at the Sulfate-Methane Interface: Does a Novel Microbial Syntrophy Result in Enhanced POC Remineralization?

  NSF · $165k · 2004–2008

• Collaborative Research (USC/Caltech): Evaluation of Opal Dissolution Kinetics and Factors That May Regulate Opal Accumulation in Margin Sediments

  NSF · $421k · 2004–2008

• Collaborative Research: CaCO3 Dissolution in the North Pacific Ocean: Comparison of Lab and Field Rates with Biogenic and Abiogenic Carbonates

  NSF · $589k · 2016–2020

Frequent coauthors

• Frank A. Corsetti

  89 shared

• Douglas E. Hammond

  Southern California University for Professional Studies

  84 shared

• Nick E. Rollins

  North Carolina State University

  60 shared

• Jess F. Adkins

  California Institute of Technology

  44 shared

• James McManus

  Bigelow Laboratory for Ocean Sciences

  36 shared

• Victoria A. Petryshyn

  35 shared

• Maria G. Prokopenko

  34 shared

• A. Joshua West

  University of Southern California

  34 shared

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