Search for: All records

Specific activities of long-lived dissolved radium (Ra-226, Ra-228), collected from U.S. Geological Survey small boat operations in the West Florida Shelf from November 2022 to March 2024. Small boat samples include surface water, bottom water, and submarine groundwaters from three well transects along Nature Coast, Indian Rocks Beach, and Venice Headlands. This project investigates how boundary sources, including rivers and submarine groundwater discharge, deliver important nutrients and metals to the coastal ecosystems of the West Florida Shelf. Here, dissolved radium isotopes have been measured to trace boundary sources of nutrients and metals entering the West Florida Shelf. 

This dataset includes the specific activities of dissolved radon-222 collected from grab samples during STING I cruise AE2305 on R/V Atlantic Explorer (February to March 2023) and STING II cruise EN704 on R/V Endeavor in the Gulf of Mexico (June to July 2023). Additional data collected from underway samples during STING II are provided in the related dataset. This project investigates how boundary sources, including rivers and submarine groundwater discharge, deliver important nutrients and metals to the coastal ecosystems of the West Florida Shelf. Here, dissolved radon-222 has been measured to trace boundary sources of nutrients and metals entering the West Florida Shelf, including submarine groundwater discharge. 

Activities of dissolved radium (Ra-223, Ra-224, Ra-226, Ra-228), Th-228, and Ac-227, collected on two cruises in the Gulf of Mexico. STING I cruise AE2305 on R/V Atlantic Explorer was deployed from February to March 2023. STING II consisted of EN704 on R/V Endeavor and U.S. Geological Survey small boat surveys and took place from June to July 2023. This project investigates how boundary sources, including rivers and submarine groundwater discharge, deliver important nutrients and metals to the coastal ecosystems of the West Florida Shelf. Here, dissolved radium and parent isotopes have been measured to trace boundary sources of nutrients and metals entering the West Florida Shelf. 

This dataset includes the concentrations of dissolved inorganic macronutrients (phosphate, nitrate plus nitrite (N+N), silicic acid, and nitrite), chlorophyll a and phaeophytin, dissolved trace metals (iron, manganese, nickel, zinc, copper), and labile dissolved nickel, as well as pH and total alkalinity measurements, from discrete depth profile samples collected on the FeOA cruise SKQ202209S on R/V Sikuliaq in the Northeast Pacific from June to July 2022. This project investigates the effects of ocean acidification on the associations between iron and organic ligands in seawater and on iron bioavailability to marine phytoplankton communities. The project used a combination of shipboard incubation experiments and depth profiles to characterize iron speciation and cycling across coastal upwelling, oligotrophic open ocean, and iron-limited subarctic oceanographic regimes in the NE Pacific. Surface seawater was incubated at pH of 8.1, 7.6, and 7.1 with natural iron and with dissolved iron amendments in order to investigate interactions between pH and iron bioavailability across the different regimes. Understanding how pH influences iron and its relationship with ligands provides important information for assessing the impacts of ocean acidification on primary production and biogeochemical processes. 

This dataset includes trace metal (iron, manganese, cobalt, nickel, copper, zinc, cadmium, lead) and macronutrient (nitrate&nitrite, nitrite, phosphate, silicic acid) concentration data from incubation experiments conducted on board the RRS Discovery during the EXPORTS North Atlantic campaign at the Porcupine Abyssal Plain-Sustained Observatory (PAP-SO) site (DY131). In these experiments, additions of macronutrients (N, P, Si) and Fe were used to assess the level of Si, N, and Fe stress being experienced by the phytoplankton and to contextualize taxa-specific metatranscriptome responses for resolving gene expression profiles in the in-situ communities. This research project focuses on the vertical export of the carbon associated with a major group of phytoplankton, the diatoms in the North Atlantic near the Porcupine Abyssal Plain. The major objective is to understand how diatom community composition and the prevailing nutrient conditions create taxonomic differences in metabolic state that combine to direct diatom taxa to different carbon export pathways. The focus is on diatoms, given their large contribution to global marine primary productivity and carbon export which translates into a significant contribution to the biogeochemical cycling of carbon (C), nitrogen (N), phosphorus (P), iron (Fe) and silicon (Si). It is hypothesized that the type and degree of diatom physiological stress are vital aspects of ecosystem state that drive export. To test this hypothesis, combined investigator expertise in phytoplankton physiology, genomics, and trace element chemistry is used to assess the rates of nutrient use and the genetic composition and response of diatom communities, with measurements of silicon and iron stress to evaluate stress as a predictor of the path of diatom carbon export. The EXPORTS field campaign in the North Atlantic sampled a retentive eddy over nearly a month in May 2021, which coincided with the decline of the North Atlantic Spring Bloom. 

This dataset includes the concentrations of iron (Fe) bound to humic-like substances and total iron-binding capacity of humic-like substances from discrete depth profile and towfish samples collected on the GP17-ANT cruise NBP24-01 on the R/V IB Nathaniel B. Palmer in the Amundsen Sea from 29 November 2023 to 28 January 2024. This project investigates the impact of Fe-binding humic-like substances on Fe biogeochemistry in the Amundsen Sea. The project used a combination of depth profile and surface towfish samples to characterize the contributions of humic-like substances to Fe biogeochemistry across gradients in primary production, water masses, and bathymetric features in the Amundsen Sea. Understanding the distributions of Fe-binding humic-like substances provides insight into the impact of compositional changes of the Fe-binding ligand pool on Fe biogeochemistry and may help elucidate specific sources of these ligands. 

The West Florida Shelf (WFS) in the Gulf of America (formerly the Gulf of Mexico) is oligotrophic, with inorganic nitrogen (N) and phosphorus (P) concentrations typically at or below detection limits, and yet significant rates of primary productivity, including blooms of the harmful algal species Karenia brevis, are observed there. Additionally, multiple clades of the cyanobacterial diazotroph Trichodesmium spp. are endemic on the WFS. Consequently, dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) are thought to be the primary sources of assimilative macro nutrients on the WFS. Here we present results from a multidisciplinary study conducted on spring and summer 2023 cruises that 1) quantified rates of N2 fixation on the WFS; 2) characterized the diazotroph community composition; 3) measured dissolved inorganic and organic and suspended particulate organic nutrient concentrations and isotopic compositions; 4) measured trace element concentrations, speciation, and isotopic composition; 5) characterized dissolved organic matter chemical composition; and, 6) quantified fluxes of these elements from submarine groundwater discharge using a radium isotope mass balance model. Additionally, quarterly sampling of the geochemistry of riverine and submarine groundwater wells defined the chemical composition of margin (i.e., riverine and submarine groundwater) inputs. Together, we use these results to understand whether submarine groundwater discharge is the dominant source of bioavailable DON, DOP, dissolved iron, and iron-binding ligands on the WFS. Additionally, we use the results to ask whether the abundance of Karenia brevis and Trichodesmium spp. are associated with enhanced submarine groundwater inputs, and whether rates of N2 fixation carried out by two different Trichodesmium spp. are associated with enhanced submarine groundwater inputs. 

This dataset includes data from nutrient manipulation experiments aimed at relieving or inducing nutrient stress in phytoplankton and quantifying these responses using metatranscriptomic sequencing. Experiments were conducted by adding key macronutrients (N, P, Si) and Fe in different combinations over different growth periods, simulating potential alleviation of in situ nutrient stress or the induction of nutrient stress. Experiments were conducted on the EXports Processes in the Oceans from RemoTe Sensing (EXPORTS) cruise DY131 in the North Atlantic during May of 2021. 

The GEOTRACES program has greatly expanded measurements of dissolved trace metal concentrations across ocean basins, but to understand the behavior and cycling of metals and their impacts on primary productivity, we must understand the chemical forms in which they are present in the environment. Organic ligands play a central role in the speciation and cycling of trace metals in the marine environment, controlling their chemical reactivity and bioavailability. Here, we present an overview of the contributions the GEOTRACES program has made to understanding ocean metal speciation through advancing our knowledge of the distribution, sources, and sinks of metal-binding organic ligands across the global ocean, particularly for iron. Detailed assessments and intercalibration of the speciation methods most commonly applied have allowed integration of metal-binding ligand measurements across datasets. Work to characterize specific ligand groups within the wider pool of dissolved organic matter, along with their sources and sinks, is starting to unravel the role of metal-binding organic ligands in global biogeochemical cycles. Recent advances in complementary analytical techniques using liquid chromatography and mass spectrometry present a molecular picture of metal speciation and bioavailability—and also pose new questions. Moving forward, we need to address knowledge gaps in our understanding of how metal speciation and complexation relates to bioavailability in order to recognize the impacts of ocean metal distributions and cycling on marine productivity and the global carbon cycle. 

This dataset includes the concentrations and conditional stability constants of iron-binding organic ligands in samples collected during an extension study of the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) project and measured by competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-AdCSV). These samples originated from a spring melt field campaign conducted in Utqiaġvik, Alaska. This campaign was designed when the MOSAiC expedition could no longer accommodate spring melt trace metal work. The melt season was a key period of our effort during MOSAiC and necessary for addressing our proposed hypotheses. Using facilities in Utqiaġvik hosted by Ukpeaǵvik Iñupiat Corporation (UIC), we studied sea ice processes during the spring melt cycle from April – June of 2021. Four UAF Scientists participated in the field campaign. During that time, sea ice, snow and water samples were obtained from homogenous, flat, landfast ice at high (2-3 times a week) temporal resolution.