Earth Sciences Commons^™

Marine Anoxia Initiates Giant Sulfur-Bacteria Mat Proliferation And Associated Changes In Benthic Nitrogen, Sulfur, And Iron Cycling In The Santa Barbara Basin, California Borderland, David J. Yousavich, De'marcus Robinson, Xuefeng Peng, Sebastian J.E. Krause, Frank Wenzhoefer, Felix Janßen, Na Liu, Jonathan Tarn, Frank Kinnaman, David L. Valentine, Tina Treude

Faculty Publications

The Santa Barbara Basin naturally experiences transient deoxygenation due to its unique geological setting in the southern California Borderland and seasonal changes in ocean currents. Long-term measurements of the basin showed that anoxic events and subsequent nitrate exhaustion in the bottom waters have been occurring more frequently and lasting longer over the past decade. One characteristic of the Santa Barbara Basin is the seasonal development of extensive mats of benthic nitrate-reducing sulfur-oxidizing bacteria, which are found at the sediment–water interface when the basin's bottom waters reach anoxia but still provide some nitrate. To assess the mat's impact on the benthic …

Ocean-Atmosphere Variability In The Northwest Atlantic Ocean During Active Marine Heatwave Years, Lydia D. Sims, Bulusu Subrahmanyam, Corinne B. Trott

Faculty Publications

The Northwest (NW) Atlantic has experienced extreme ecological impacts from Marine Heatwaves (MHWs) within the past decade. This paper focuses on four MHW active years (2012, 2016, 2017, and 2020) and the relationship between Sea Surface Temperature anomalies (SSTA), Sea Surface Salinity anomalies (SSSA), North Atlantic Oscillation (NAO), Geopotential Height anomalies (ZA), and anomalous Jet Stream positions (JSPA). Multichannel singular spectrum analysis (MSSA) reveals the strongest temporal covariances between SSSA and SSTA, and JSPA and SSTA for all years, particularly for 2020 (SSSA–SSTA: 50%, JSPA–SSTA: 51%) indicating that this active MHW year was more atmospherically driven, followed by 2012, which …

Flood Depth Estimation During Hurricane Harvey Using Sentinel-1 And Uavsar Data, Sananda Kundu, Venkat Lakshmi, Raymond Torres

Faculty Publications

In August 2017, Hurricane Harvey was one of the most destructive storms to make landfall in the Houston area, causing loss of life and property. Temporal and spatial changes in the depth of floodwater and the extent of inundation form an essential part of flood studies. This work estimates the flood extent and depth from LiDAR DEM (light detection and ranging digital elevation model) using data from the Synthetic Aperture Radar (SAR)–Unmanned Aerial Vehicle Synthetic Aperture Radar (UAVSAR) and satellite sensor—Sentinel-1. The flood extent showed a decrease between 29–30 August and 5 September 2017. The flood depths estimated using the …

An Operational Overview Of The Export Processes In The Ocean From Remote Sensing (Exports) Northeast Pacific Field Deployment, David A. Siegel, Ivona Cetinic, Jason R. Graff, Craig M. Lee, Norman Nelson, Mary Jane Perry, Inia Soto Ramos, Deborah K. Steinberg, Ken Buesseler, Roberta Hamme, Andrea J. Fassbender, David Nicholson, Melissa M. Omand, Marie Robert, Andrew Thompson, Vinicius Amaral, Michael Behrenfeld, Claudia R. Benitez-Nelson, Kelsey Bisson, Emmanuel Boss, Et. Al.

Faculty Publications

The goal of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) field campaign is to develop a predictive understanding of the export, fate, and carbon cycle impacts of global ocean net primary production. To accomplish this goal, observations of export flux pathways, plankton community composition, food web processes, and optical, physical, and biogeochemical (BGC) properties are needed over a range of ecosystem states. Here we introduce the first EXPORTS field deployment to Ocean Station Papa in the Northeast Pacific Ocean during summer of 2018, providing context for other papers in this special collection. The experiment was conducted with …

What Is Refractory Organic Matter In The Ocean?, Federico Baltar, Xosé A. Alvarez-Salgado, Javier Arístegui, Ronald Benner, Dennis A. Hansell, Gerhard J. Herndl, Christian Lønborg

Faculty Publications

About 20% of the organic carbon produced in the sunlit surface ocean is transported into the ocean’s interior as dissolved, suspended and sinking particles to be mineralized and sequestered as dissolved inorganic carbon (DIC), sedimentary particulate organic carbon (POC) or “refractory” dissolved organic carbon (rDOC). Recently, the physical and biological mechanisms associated with the particle pumps have been revisited, suggesting that accepted fluxes might be severely underestimated (Boyd et al., 2019; Buesseler et al., 2020). Perhaps even more poorly understood are the mechanisms driving rDOC production and its potential accumulation in the ocean. On the basis of …

What Is Refractory Organic Matter In The Ocean?, Federico Baltar, Xosé A. Alvarez-Salgado, Javier Arístegui, Ronald Benner, Dennis A. Hansell, Gerhard J. Herndl, Christian Lønborg

Faculty Publications

About 20% of the organic carbon produced in the sunlit surface ocean is transported into the ocean’s interior as dissolved, suspended and sinking particles to be mineralized and sequestered as dissolved inorganic carbon (DIC), sedimentary particulate organic carbon (POC) or “refractory” dissolved organic carbon (rDOC). Recently, the physical and biological mechanisms associated with the particle pumps have been revisited, suggesting that accepted fluxes might be severely underestimated (Boyd et al., 2019; Buesseler et al., 2020). Perhaps even more poorly understood are the mechanisms driving rDOC production and its potential accumulation in the ocean. On the basis of recent conflicting evidence …

Volcaniclastic Sandstones Record The Influence Of Subducted Pacific Morb On Magmatism At The Early Izu-Bonin Arc, Anders Mccarthy, Gene M. Yogodzinski, Michael Bizimis, Ivan P. Savov, Rosemary Hickey-Vargas, Richard Arculus, Osamu Ishizuka

Faculty Publications

The remnant rear-arc segment of the early Izu-Bonin arc, known as the Kyushu-Palau Ridge (KPR), is a key location where magmatic outputs can be constrained during the lifetime of an island arc. We present new geochemical data for coarse-grained basaltic to andesitic volcaniclastic sandstones derived from the KPR and deposited in the Amami Sankaku Basin (IODP Site U1438, Unit III rocks) in the time period 40-30 Ma. Bulk disaggregated and cleaned volcaniclastic sandstones of Unit III at Site U1438 retain primary magmatic signatures and can be used to infer the evolution of magmatic sources of the juvenile Izu-Bonin island arc …

Particulate And Dissolved Organic Matter In Stormwater Runoff Influences Oxygen Demand In Urbanized Headwater Catchments, Kelly M. Mccabe, Erik M. Smith, Susan Q. Lang, Claudia Benitez-Nelson

Faculty Publications

Increasing inputs of organic matter (OM) are driving declining dissolved oxygen (DO) concentrations in coastal ecosystems worldwide. The quantity, source, and composition of OM transported to coastal ecosystems via stormwater runoff have been altered by land use changes associated with urbanization and subsequent hydrologic flows that accompany urban stormwater management. To elucidate the role of stormwater in the decline of coastal DO, rain event sampling of biochemical oxygen demand (BOD) in samples collected from the outfall of stormwater ponds and wetlands, as well as samples of largely untreated runoff carried by stormwater ditches, was conducted across a range of urban …

Model And Data, Equilibrium Of Self-Formed, Single-Thread, Sand-Bed Rivers, Enrica Viparelli, Esther C. Eke

Faculty Publications

This submission contains the following files, also uploaded as Supplementary Information for the manuscript Equilibrium of self-formed, single-thread, sand-bed rivers submitted after major revisions to the AGU journal Geophysical Research Letters.

Excel file with embedded macro Equilibrium_calculator.xlxm, contains the solver of the analytical model presented in the manuscript.

Excel file Equilibrium_results.xlxs contains model data used to generate the plots.

Extensive Morphological Variability In Asexually Produced Planktic Foraminifera, Catherine V. Davis, Caitlin M. Livsey, Hannah M. Palmer, Pincelli M. Hull, Ellen Thomas, Tessa M. Hill, Claudia R. Benitez-Nelson

Faculty Publications

Marine protists are integral to the structure and function of pelagic ecosystems and marine carbon cycling, with rhizarian biomass alone accounting for more than half of all mesozooplankton in the oligotrophic oceans. Yet, understanding how their environment shapes diversity within species and across taxa is limited by a paucity of observations of heritability and life history. Here, we present observations of asexual reproduction, morphologic plasticity, and ontogeny in the planktic foraminifer in laboratory culture. Our results demonstrate that planktic foraminifera reproduce both sexually and asexually and demonstrate extensive phenotypic plasticity in response to nonheritable factors. These two processes fundamentally explain …

Multi-Attribute Analysis Using Coherency And Ant-Tracking Techniques For Fault And Fracture Detection In La Florida Anticline, Llanos Foothills, Colombia, Ziyad Albesher, James N. Kellogg, Ibraheem Hafiza, Essam Saeid

Faculty Publications

We present techniques to reduce noise and enhance seismic quality, making possible the first multi-attribute analysis of a 3D seismic volume in the Llanos Foothills (La Florida anticline) of Colombia using coherency and ant-tracking techniques for fault and fracture detection. The results could help reduce risk in models of reservoir fracture porosity and permeability. The dominant fracture strike direction in the studied seismic volume (La Florida anticline) is NE–SW (055 ± 20°), parallel to the structural strike of the adjacent Eastern Cordillera Foothills. The application of the ant-tracking technique also reveals the NE-SW fracture set for the reservoir rocks in …

Green Edge Ice Camp Campaigns: Understanding The Processes Controlling The Under-Ice Arctic Phytoplankton Spring Bloom, Philippe Massicotte, Rémi Amiraux, Marie-Pier Amyot, Philippe Archambault, Mathieu Ardyna, Laurent Arnaud, Lise Artigue, Cyril Aubry, Pierre Ayotte, Guislain Bécu, Simon Bélanger, Ronald Benner, Henry C. Bittig, Annick Bricaud, Éric Brossier, Flavienne Bruyant, Et. Al.

Faculty Publications

The Green Edge initiative was developed to investigate the processes controlling the primary productivity and fate of organic matter produced during the Arctic phytoplankton spring bloom (PSB) and to determine its role in the ecosystem. Two field campaigns were conducted in 2015 and 2016 at an ice camp located on landfast sea ice southeast of Qikiqtarjuaq Island in Baffin Bay (67.4797∘ N, 63.7895∘ W). During both expeditions, a large suite of physical, chemical and biological variables was measured beneath a consolidated sea-ice cover from the surface to the bottom (at 360 m depth) to better understand the factors driving the …

Molecular Properties Are A Primary Control On The Microbial Utilization Of Dissolved Organic Matter In The Ocean, Yuan Shen, Ronald Benner

Faculty Publications

The global ocean sequesters a large amount of reduced carbon in dissolved organic molecules that can persist for centuries to millennia. The persistence of dissolved organic carbon (DOC) in the deep ocean has been attributed to inherently refractory molecules and to low concentrations of molecules, but the relative roles of molecular properties and molecular concentrations remain uncertain. We investigate both of these possibilities using bioassay experiments with unfiltered seawater collected from five depths (50–1500 m) at the Bermuda Atlantic Time-Series Study site. The microbial utilization of compositionally distinct forms of seawater DOC at in situ and elevated concentrations was determined. …

Habitability Of The Oceanic Alkaline Serpentinite Subsurface: A Case Study Of The Lost City Hydrothermal Field, Susan Q. Lang, William J. Brazelton

Faculty Publications

The Lost City hydrothermal field is a dramatic example of the biological potential of serpentinization. Microbial life is prevalent throughout the Lost City chimneys, powered by the hydrogen gas and organic molecules produced by serpentinization and its associated geochemical reactions. Microbial life in the serpentinite subsurface below the Lost City chimneys, however, is unlikely to be as dense or active. The marine serpentinite subsurface poses serious challenges for microbial activity, including low porosities, the combination of stressors of elevated temperature, high pH and a lack of bioavailable ∑CO2. A better understanding of the biological opportunities and challenges in serpentinizing systems …

Mercury Cycling In The North Pacific Subtropical Gyre As Revealed By Mercury Stable Isotope Ratios, Laura C. Motta, Joel D. Blum, Marcus W. Johnson, Blaire P. Umhau, Brian N. Popp, Spencer J. Washburn, Jeffrey C. Drazen, Claudia R. Benitez-Nelson, Cecelia C. S. Hannides, Hilary G. Close, Carl H. Lamborg

Faculty Publications

The oceans are an important global reservoir for mercury (Hg), and marine fish consumption is the dominant human exposure pathway for its toxic methylated form. A more thorough understanding of the global biogeochemical cycle of Hg requires additional information on the mechanisms that control Hg cycling in pelagic marine waters. In this study, Hg isotope ratios and total Hg concentrations are used to explore Hg biogeochemistry in oligotrophic marine environments north of Hawaii. We present the first measurements of the vertical water column distribution of Hg concentrations and the Hg isotopic composition in precipitation, marine particles, and zooplankton near Station …

Short-Term Effect Of Simulated Salt Marsh Restoration By Sand-Amendment On Sediment Bacterial Communities, François Thomas, James T. Morris, Cathleen Wigand, Stefan M. Sievert

Faculty Publications

Coastal climate adaptation strategies are needed to build salt marsh resiliency and maintain critical ecosystem services in response to impacts caused by climate change. Although resident microbial communities perform crucial biogeochemical cycles for salt marsh functioning, their response to restoration practices is still understudied. One promising restoration strategy is the placement of sand or sediment onto the marsh platform to increase marsh resiliency. A previous study examined the above- and below-ground structure, soil carbon dioxide emissions, and pore water constituents in Spartina alterniflora-vegetated natural marsh sediments and sand-amended sediments at varying inundation regimes. Here, we analyzed samples from the …

Growth Kinetics, Carbon Isotope Fractionation, And Gene Expression In The Hyperthermophile Methanocaldococcus Jannaschii During Hydrogen-Limited Growth And Interspecies Hydrogen Transfer, Begüm D. Topçuog˘ Lu, Cem Meydan, Tran B. Nguyen, Susan Q. Lang, James F. Holden

Faculty Publications

Hyperthermophilic methanogens are often H2 limited in hot subseafloor environments, and their survival may be due in part to physiological adaptations to low H2 conditions and interspecies H2 transfer. The hyperthermophilic methanogen Methanocaldococcus jannaschii was grown in monoculture at high (80 to 83 M) and low (15 to 27 M) aqueous H2 concentrations and in coculture with the hyperthermophilic H2 producer Thermococcus paralvinellae. The purpose was to measure changes in growth and CH4 production kinetics, CH4 fractionation, and gene expression in M. jannaschii with changes in H2 flux. Growth and cell-specific CH4 production rates of M. jannaschii decreased with decreasing …

Carbon In The Deep Biosphere: Forms, Fates, And Biogeochemical Cycling, Susan Q. Lang, Magdalena R. Osburn, Andrew D. Steen

Faculty Publications

Building on the synthesis of carbon reservoirs in Earth's subsurface, this chapter focuses on the forms, cycling, and fate of the carbon supporting microbial life in the terrestrial and marine subsurface. As the subsurface is estimated to host a vast reservoir of life on Earth, identifying the carbon compounds that life uses for energy and growth is key to understanding ecosystem functioning in the past and at present, and also for extrapolating these findings to the search for life in the universe. This chapter highlights advances in quantifying small carbon compounds, measuring rates of carbon turnover, and the fate of …

A Time Series Of Water Column Distributions And Sinking Particle Flux Of Pseudo-Nitzschia And Domoic Acid In The Santa Barbara Basin, California, Blaire P. Umhau, Claudia R. Benitez-Nelson, Clarissa R. Anderson, Kelly Mccabe, Christopher Burrell

Faculty Publications

Water column bulk Pseudo-nitzschia abundance and the dissolved and particulate domoic acid (DA) concentrations were measured in the Santa Barbara Basin (SBB), California from 2009–2013 and compared to bulk Pseudo-nitzschia cell abundance and DA concentrations and fluxes in sediment traps moored at 147 m and 509 m. Pseudo-nitzschia abundance throughout the study period was spatially and temporally heterogeneous (L−1 to 3.8 × 106 cells L−1 , avg. 2 × 105 ± 5 × 105 cells L−1 ) and did not correspond with upwelling conditions or the total DA (tDA) concentration, which was also spatially and temporally diverse (1000 cells L−1 …

A Time Series Of Water Column Distributions And Sinking Particle Flux Of Pseudo-Nitzschia And Domoic Acid In The Santa Barbara Basin, California, Blaire P. Umhau, Claudia R. Benitez-Nelson, Clarissa R. Anderson, Kelly Mccabe, Christopher Burrell

Faculty Publications

Water column bulk Pseudo-nitzschia abundance and the dissolved and particulate domoic acid (DA) concentrations were measured in the Santa Barbara Basin (SBB), California from 2009–2013 and compared to bulk Pseudo-nitzschia cell abundance and DA concentrations and fluxes in sediment traps moored at 147 m and 509 m. Pseudo-nitzschia abundance throughout the study period was spatially and temporally heterogeneous (L⁻¹ to 3.8 × 10⁶ cells L⁻¹, avg. 2 × 10⁵ ± 5 × 10⁵ cells L⁻¹) and did not correspond with upwelling conditions or the total DA (tDA) concentration, which was also spatially …

Unveiling The Enigma Of Refractory Carbon In The Ocean, Nianzhi Jiao, Ruanhong Cai, Qiang Zheng, Kai Tang, Jihua Liu, Fangkue Jiao, Douglas Wallace, Feng Chen, Chao Li, Rudolf Amann, Ronald Benner, Farooq Azam

Faculty Publications

No abstract provided.

Deeply-Sourced Formate Fuels Sulfate Reducers But Not Methanogens At Lost City Hydrothermal Field, Susan Q. Lang, Gretchen L. Früh-Green, Stefano M. Bernasconi, William J. Brazelton, Matthew O. Schrenk, Julia M. Mcgonigle

Faculty Publications

Hydrogen produced during water-rock serpentinization reactions can drive the synthesis of organic compounds both biotically and abiotically. We investigated abiotic carbon production and microbial metabolic pathways at the high energy but low diversity serpentinite-hosted Lost City hydrothermal field. Compound-specific 14C data demonstrates that formate is mantle-derived and abiotic in some locations and has an additional, seawater-derived component in others. Lipids produced by the dominant member of the archaeal community, the Lost City Methanosarcinales, largely lack 14C, but metagenomic evidence suggests they cannot use formate for methanogenesis. Instead, sulfate-reducing bacteria may be the primary consumers of formate in Lost City chimneys. …

Hydrothermal Stamp On The Oceans, Susan Q. Lang

Faculty Publications

The composition of the oceans is altered by hydrothermal circulation. These chemical factories sustain microbial life, which in turn alters the chemistry of the fuids that enter the ocean. A decade of research details this complex interchange.

Modeled Co2 Emissions From Coastal Wetland Transitions To Other Land Uses: Tidal Marshes, Mangrove Forests, And Seagrass Beds, Catherine E. Lovelock, James W. Fourqurean, James T. Morris

Faculty Publications

The sediments of coastal wetlands contain large stores of carbon which are vulnerable to oxidation once disturbed, resulting in high levels of CO2 emissions that may be avoided if coastal ecosystems are conserved or restored. We used a simple model to estimate CO2 emissions from mangrove forests, seagrass beds, and tidal marshes based on known decomposition rates for organic matter in these ecosystems under either oxic or anoxic conditions combined with assumptions of the proportion of sediment carbon being deposited in either oxic or anoxic environments following a disturbance of the habitat. Our model found that over 40 years after …

Mineralizing Filamentous Bacteria From The Prony Bay Hydrothermal Field Give New Insights Into The Functioning Of Serpentinization-Based Subseafloor Ecosystems, Céline Pisapia, Emmanuelle Gérard, Martine Gérard, Léna Lecourt, Susan Q. Lang, Bernard Pelletier, Claude E. Payri, Christophe Monnin, Linda Guentas, Anne Postec, Marianne Quéméneur, Gaël Erauso, Bénédicte Ménez

Faculty Publications

Despite their potential importance as analogs of primitive microbial metabolisms, the knowledge of the structure and functioning of the deep ecosystems associated with serpentinizing environments is hampered by the lack of accessibility to relevant systems. These hyperalkaline environments are depleted in dissolved inorganic carbon (DIC), making the carbon sources and assimilation pathways in the associated ecosystems highly enigmatic. The Prony Bay Hydrothermal Field (PHF) is an active serpentinization site where, similar to Lost City (Mid-Atlantic Ridge), high-pH fluids rich in H2 and CH4 are discharged from carbonate chimneys at the seafloor, but in a shallower lagoonal environment. This study aimed …

Metagenomic Identification Of Active Methanogens And Methanotrophs In Serpentinite Springs Of The Voltri Massif, Italy, William J. Brazelton, Christopher N. Thornton, Alex Hyer, Katrina I. Twing, August A. Longino, Susan Q. Lang, Marvin D. Lilley, Gretchen L. Früh-Green, Matthew O. Schrenk

Faculty Publications

The production of hydrogen and methane by geochemical reactions associated with the serpentinization of ultramafic rocks can potentially support subsurface microbial ecosystems independent of the photosynthetic biosphere. Methanogenic and methanotrophic microorganisms are abundant in marine hydrothermal systems heavily influenced by serpentinization, but evidence for methane-cycling archaea and bacteria in continental serpentinite springs has been limited. This report provides metagenomic and experimental evidence for active methanogenesis and methanotrophy by microbial communities in serpentinite springs of the Voltri Massif, Italy. Methanogens belonging to family Methanobacteriaceae and methanotrophic bacteria belonging to family Methylococcaceae were heavily enriched in three ultrabasic springs (pH 12). Metagenomic …

Sources, Distributions, And Dynamics Of Dissolved Organic Matter In The Canada And Makarov Basins, Yuan Shen, Ronald Benner, Lisa Robbins, Jonathan Wynn

Faculty Publications

A comprehensive survey of dissolved organic carbon (DOC) and chromophoric dissolved organic matter (CDOM) was conducted in the Canada and Makarov Basins and adjacent seas during 2010–2012 to investigate the dynamics of dissolved organic matter (DOM) in the Arctic Ocean. Sources and distributions of DOM in polar surface waters were very heterogeneous and closely linked to hydrological conditions. Canada Basin surface waters had relatively low DOC concentrations (69 ± 6 μmol L−1), CDOM absorption (a325: 0.32 ± 0.07 m−1) and CDOM-derived lignin phenols (3 ± 0.4 nmol L−1), and high spectral slope values (S275–295: 31.7 ± …

Calcification Of The Planktonic Foraminiferaglobigerinabulloidesand Carbonate Ion Concentration Resultsfrom The Santa Barbara Basin, Emily B. Osborne, Robert C. Thunell, Brittney J. Marshall, Jessica A. Holm, Eric J. Tappa, Claudia R. Benitez-Nelson, Wei‐Jun Cai, Baoshan Chen

Faculty Publications

Planktonic foraminiferal calcification intensity, reflected by shell wall thickness, has been hypothesized to covary with the carbonate chemistry of seawater. Here we use both sediment trap and box core samples from the Santa Barbara Basin to evaluate the relationship between the calcification intensity of the planktonic foraminifera species Globigerina bulloides, measured by area density (µg/µm2), and the carbonate ion concentration of seawater ([CO32−]). We also evaluate the influence of both temperature and nutrient concentration ([PO43−]) on foraminiferal calcification and growth. The presence of two G. bulloides morphospecies with systematically different calcification properties and offset stable isotopic compositions was identified within …

Prediction Of The Export And Fate Of Global Ocean Net Primary Production: The Exports Science Plan, David A. Siegel, Ken O. Buesseler, Michael J. Behrenfeld, Claudia R. Benitez-Nelson, Emmanuel Boss, Mark A. Brzezinski, Adrian Burd, Craig A. Carlson, Eric A. D'Asaro, Scott C. Doney, Mary J. Perry, Rachel H. R. Stanley, Deborah K. Steinberg

Faculty Publications

Ocean ecosystems play a critical role in the Earth's carbon cycle and the quantification of their impacts for both present conditions and for predictions into the future remains one of the greatest challenges in oceanography. The goal of the EXport Processes in the Ocean from Remote Sensing (EXPORTS) Science Plan is to develop a predictive understanding of the export and fate of global ocean net primary production (NPP) and its implications for present and future climates. The achievement of this goal requires a quantification of the mechanisms that control the export of carbon from the euphotic zone as well as …

Interannual And Subdecadal Variability In The Nutrient Geochemistry Of The Cariaco Basin, Mary I. Scranton, Gordon T. Taylor, Robert Thunell, Claudia R. Benitez-Nelson, Frank Muller-Karger, Kent Fanning, Laura Lorenzoni, Enrique Montes, Ramon Varela, Yrene Astor

Faculty Publications

The CARIACO Ocean Time Series program has made monthly measurements of oxygen, nutrients, and carbon system parameters (∑CO2, alkalinity, pH) in the Cariaco Basin since 1996. At the same time, sediment traps have collected settling particles at four to five depths ranging from 150 to 1,200 m. The depth of the transition from oxic to anoxic conditions has fluctuated dramatically over the time series due to changes in the occurrence of Caribbean water intrusions into the deep basin. Nutrient concentrations in the deep basin have increased steadily with time in a proportion reflective of the elemental ratios in the settling …