Lamborg, C.H., Swarr, G., Hughen, K., Jones, R., Birdwhistell, S., Fuby, K., Murty, S.A., Prouty, N., and Tseng, C-M., 2013 Determination of low-level mercury in coralline aragonite by calcination-isotope dilution-inductively coupled plasma-mass spectrometry and its application to Diploria specimens from Castle Harbour, Bermuda: Geochimica et Cosmochimica Acta, v. 109, pp. 27-37, doi: 10.1016/j.gca.2013.01.026.
Nancy Prouty
Biography
Education
2004: Ph.D., Oceanography, Geological and Environmental Sciences, Stanford University, Stanford, CA
1997: M.S., Climate Change Research Center, Earth Sciences, University of New Hampshire, Durham, NH
1993: B.A., Geology, Whitman College, Walla Walla, WA
Oct. 2009-present - Research Oceanographer, United States Geological Survey, Santa Cruz, CA. Lead PI on groundwater and land-based pollution coral reef ecosystem studies. Design and implement field experiments on geochemical impacts of groundwater and land-based pollution on coral reefs. Lead PI on deep-sea coral paleo-ecology multi-agency project.
July ‘10-Nov.’10 - Science Program Coordinator Advisor, Schmidt Ocean Institute, Palo Alto, CA Served as liaison between the individual scientific researchers and the Institute to implement and execute a scientific strategy. Managed complex, scientific planning efforts involving scientists, engineers, marine operations personnel, technicians, and other support staff.
2007-2009 - Mendenhall Postdoctoral Research Fellow, United States Geological Survey, Santa Cruz, CA. Lead investigator on 2-year Federal scientific research program to investigate the link between sedimentation and coral reef ecosystem health. Collaborated with investigators at multiple Federal agencies and academic institutions.
2004-2007 - Cooperative Institute for Climate and Ocean Research Postdoctoral Scholar, Woods Hole Oceanographic Institution, Woods Hole, MA. Lead investigator on multidisciplinary initiative to develop new tools to assess coral response to environmental stressors from both anthropogenic and natural perturbations.
Summer 2004 - University Instructor, University of California, Berkeley, CA. Developed innovative student centered curriculum for an 8-weeek intensive summer course on oceanography.
2000-2004 - Graduate Research Environmental Fellow, Department of Energy (DOE), Stanford University. Lead investigator of international coral reef project in Kenya and Sumatra.
Science and Products
Date published: April 15, 2021
Status: Active Coral Reef Project
Explore the fascinating undersea world of coral reefs. Learn how we map, monitor, and model coral reefs so we can better understand, protect, and preserve our Nation's reefs.
Date published: March 12, 2021
Status: Active Ecosystems: EXPRESS
The continental shelf and slope offshore California, Oregon, and Washington are home to deep-sea corals, chemosynthetic communities, and other sensitive habitats that could be impacted by the development of energy and mineral resources. The EXPRESS campaign will map and...
Contacts: Danny Brothers, Nancy Prouty
Date published: January 4, 2021
Status: Active Climate Change and Land-use Histories
We are developing new and unique oceanographic and environmental archives from coral skeleton records to better understand the compounding effects of land-use and environmental change on coral reef health.
Contacts: Nancy Prouty
Date published: October 22, 2020
Status: Active EXPRESS: Expanding Pacific Research and Exploration of Submerged Systems
EXPRESS is a multi-year, multi-institution cooperative research campaign in deep sea areas of California, Oregon, and Washington, including the continental shelf and slope. EXPRESS data and information are intended to guide wise use of living marine resources and habitats, inform ocean energy and mineral resource decisions, and improve offshore hazard assessments.
Read the June 11, 2020...
Contacts: Danny Brothers, Nancy Prouty
Date published: September 9, 2020
Status: Active USGS Role in DEEP SEARCH: Deep Sea Exploration to Advance Research on Coral, Canyon, and Cold-seep Habitats
USGS scientists are collaborating with multiple agencies to provide the esssential foundation for understanding these deep-sea environments.
Date published: June 23, 2020
Status: Active Hazards: EXPRESS
Marine geohazards including earthquakes, landslides, and tsunamis lie offshore of densely populated areas of California, Oregon, and Washington. One goal of EXPRESS is to improve assessments of these hazards.
Contacts: Danny Brothers, Nancy Prouty
Date published: June 23, 2020
Status: Active Resources: EXPRESS
Along the U.S. west coast, the Pacific Ocean, ocean floor, and winds above contain potentially vast energy and mineral resources. Developing these resources safely and wisely requires detailed information for each area of interest. One goal of EXPRESS is to inform ocean...
Contacts: Danny Brothers, Nancy Prouty
Date published: August 30, 2019
Status: Active DISCOVRE: Diversity, Systematics and Connectivity of Vulnerable Reef Ecosystems
DISCOVRE (DIversity, Systematics and COnnectivity of Vulnerable Reef Ecosystems) is an integrated, multidisciplinary, international effort investigating the unique and fragile deep-sea coral environments from the microscopic level to the ecosystem level.
Date published: June 19, 2019
Status: Active Seeking the Seeps
From June 12 to July 3, 2019, the USGS sailed onboard Schmidt Ocean Institute’s R/V Falkor with several other partners, seeking methane seeps along the seafloor of several underwater canyons off the coast of Oregon and Washington. On this cruise, USGS scientists will seek to understand how much methane is coming out of these seeps, how it travels through the water column, and its...
Attribution: Ecosystems, Natural Hazards, Coastal and Marine Hazards and Resources Program, Environments Program, Region 1: North Atlantic-Appalachian, Pacific Coastal and Marine Science Center, St. Petersburg Coastal and Marine Science Center, Wetland and Aquatic Research Center, Woods Hole Coastal and Marine Science Center
Date published: August 27, 2018
Status: Completed IMMeRSS- Seafloor Methane Seep Environments
Cold seeps, which are locations where chemicals -- including methane and other hydrocarbons, brine, hydrogen sulfide, and sometimes carbon dioxide--leak from the seafloor, occur worldwide on both passive and tectonically-active continental margins. Cold seeps are distinguished from ...
Contacts: Amanda Demopoulos, Ph.D., Nancy Prouty
Date published: August 27, 2018
Status: Completed IMMeRSS-- Interagency Mission for Methane Research on Seafloor Seeps
From May 3 to May 11, 2017, the U.S. Geological Survey, in collaboration with the British Geological Survey and with support from these two agencies, the National Oceanic and Atmospheric Administration (NOAA) Office of Ocean Exploration and Research, and the U.S. Department of Energy, will lead an...
Date published: December 31, 2020
Geochemistry time series and growth parameters from Tutuila, American Samoa coral record
Geochemical analysis (including radiocarbon, stable carbon isotope, and elemental composition) and growth parameters (including calcification rate, density, and extension information) were measured from a coral core collected from a reef off the southern side of Tutuila, American Samoa. The core was collected near Matautuloa Point on 8 April 2012 in collaboration with the Ecosys
Attribution: Pacific Coastal and Marine Science Center
Date published: November 2, 2020
Radiocarbon dating of deep-sea black corals collected off the southeastern United States
Results of radiocarbon dating of deep-sea (500 m to 700 m) black corals are presented. These corals were collected off the southeastern United States as part of the Southeastern United States Deep-Sea Corals (SEADESC) Initiative.
Date published: August 12, 2020
Water-column environmental variables and accompanying discrete CTD measurements collected off California and Oregon during NOAA Ship Lasker R-19-05 (USGS field activity 2019-672-FA) from October to November 2019
Various water column variables, including salinity, dissolved inorganic nutrients, pH, total alkalinity, dissolved inorganic carbon, radio-carbon isotopes were measured in samples collected using a Niskin-bottle rosette at selected depths from sites offshore of California and Oregon from October to November 2019 during NOAA Ship Lasker R-19-05 (USGS field activity 2019-672-FA). CT
Attribution: Pacific Coastal and Marine Science Center
Date published: June 26, 2020
CTD profiles and discrete water-column measurements collected off California and Oregon during NOAA cruise SH-18-12 (USGS field activity 2018-663-FA) from October to November 2018
Various water column variables, including CTD (Conductivity Temperature Depth) data were measured at selected depths from sites offshore of California and Oregon from October to November 2018 during NOAA cruise SH-18-12 on R/V Bell M. Shimada (USGS field activity 2018-663-FA).
Date published: March 1, 2019
Geochemical analysis of authigenic carbonates and chemosynthetic mussels at Atlantic Margin seeps
Isotopic analyses of authigenic carbonates and methanotrophic deep-sea mussels, Bathymodiolus sp., was performed on samples collected from seep fields in the Baltimore and Norfolk Canyons on the north Atlantic margin. Samples were collected using remotely operated underwater vehicles (ROVs) during three different research cruises in 2012, 2013, and 2015. Analyses were performed by several...
Date published: January 1, 2019
Geochemical analysis of seeps along the Queen Charlotte Fault
Geochemical analyses of authigenic carbonates, bivalves, and pore fluids were performed on samples collected from seep fields along the Queen Charlotte Fault, a right lateral transform boundary that separates the Pacific and North American tectonic plates. Samples were collected using grab samplers and piston cores, and were collected during three different research cruises in 2011, 201
Date published: January 1, 2019
Biomarker analysis of cold seeps along the United States Atlantic Margin
Results of lipid biomarker concentration and compound specific isotopes analyzed from authigenic carbonates and surrounding sediment collected from Baltimore and Norfolk seep fields along the United States Atlantic Margin are presented in csv format. Samples were collected by the U.S. Geological Survey and Duke University between 2012 and 2015 using remotely operated vehicles (ROVs). Geochemi...
Date published: April 25, 2017
Coral growth parameters and seawater chemistry from Kahekili, west Maui, Hawaii
This data release contains time-series of seawater carbonate chemistry variables, including salinity, dissolved inorganic nutrients, pH, total alkalinity, and dissolved inorganic carbon from sites along Kahekili Beach Park, west Maui, Hawai‘i. It also containsdata from coral cores collected from the shallow reef at Kahekili in July 2013 and analyzed for coral growth parameters and geochemical...
Date published: January 1, 2017
Olowalu chronology and geochemistry time-series, West Maui
Chronology and time-series geochemistry data of a coral core collected from Olowalu, West Maui, Hawaii. The chronology is based on density banding, radiocarbon bomb-curve, and uranium thorium dating techniques. The geochemistry time-series data contains major and minor elements over the length of the coral life span, as measured from laser ablation inductively coupled mass spectrometry
Date published: January 1, 2017
Sediment trap and water column chemistry, Baltimore Canyon, U.S. Mid-Atlantic Bight
Time-series of sediment chemistry, including organic biomarker composition and bulk inorganic geochemical analytes, from samples collected over a one-year period in a sediment trap. The sediment traps were deployed at a depth between 603 m to 1318 m, and they were programmed to rotate a 250 mL sample bottle at 30 d intervals, delivering 12 samples during the 1-year deployment between Augu
Date published: January 1, 2016
Geochemical analysis of authigenic carbonates and chemosynthetic mussels at Atlantic Margin seeps (ver. 2.0, March 2019)
Isotopic analyses of authigenic carbonates and methanotrophic deep-sea mussels, Bathymodiolus sp., was performed on samples collected from seep fields in the Baltimore and Norfolk Canyons on the north Atlantic margin. Samples were collected using remotely operated underwater vehicles (ROVs) during three different research cruises in 2012, 2013, and 2015. Analyses were performed by sev
Year Published: 2021
Expanding the repertoire of electron acceptors for the anaerobic oxidation of methane in carbonates in the Atlantic and Pacific Ocean
Authigenic carbonates represent a significant microbial sink for methane, yet little is known about the microbiome responsible for the methane removal. We identify carbonate microbiomes distributed over 21 locations hosted by seven different cold seeps in the Pacific and Atlantic Oceans by carrying out a gene-based survey using 16S rRNA- and ...
Beckmann, Sabrina; Farag, Ibrahim F.; Zhao, Rui; Christman, Glenn; Prouty, Nancy G.; Biddle, Jennifer F.
Year Published: 2020
Focused fluid flow and methane venting along the Queen Charlotte fault, offshore Alaska (USA) and British Columbia (Canada)
Fluid seepage along obliquely deforming plate boundaries can be an important indicator of crustal permeability and influence on fault-zone mechanics and hydrocarbon migration. The ~850-km-long Queen Charlotte fault (QCF) is the dominant structure along the right-lateral transform boundary that separates the Pacific and North American tectonic...
Prouty, Nancy G.; Brothers, Daniel; Kluesner, Jared; Barrie, J. Vaughn; Andrews, Brian D.; Lauer, Rachel; Greene, Gary; Conrad, James E.; Lorenson, Thomas; Law, Michael D.; Sahy, Diana; Conway, Kim; McGann, Mary; Dartnell, PeterAttribution: Pacific Coastal and Marine Science Center
Year Published: 2020
Molecular indicators of methane metabolisms at cold seeps along the United States Atlantic margin
A lipid biomarker study was undertaken to determine the microbial composition and variability in authigenic carbonates and associated soft bottom habitats from the Norfolk and the Baltimore Canyon seep fields along the US mid-Atlantic margin. Results from this study capture a distinct molecular signal from methane oxidizing archaea, including...
Prouty, Nancy G.; Campbell, Pamela L.; Close, Hilary; Biddle, Jennifer F.; Beckmann, SabrinaAttribution: Pacific Coastal and Marine Science Center
Year Published: 2020
Pulse sediment event does not impact the metabolism of a mixed coral reef community
Sedimentation can bury corals, cause physical abrasion, and alter both spectral intensity and quality; however, few studies have quantified the effects of sedimentation on coral reef metabolism in the context of episodic sedimentation events. Here, we present the first study to measure coral community metabolism - calcification and photosynthesis...
Keisha Bahr; Ku'ulei Rodgers; Paul Jokiel; Prouty, Nancy G.; Storlazzi, Curt D.
Year Published: 2019
Coral skeleton δ15N as a tracer of historic nutrient loading to a coral reef in Maui, Hawaii
Excess nutrient loading to nearshore environments has been linked to declining water quality and ecosystem health. Macro-algal blooms, eutrophication, and reduction in coral cover have been observed in West Maui, Hawaii, and linked to nutrient inputs from coastal submarine groundwater seeps. Here, we present a forty-year record of nitrogen...
Murray, Joseph; Prouty, Nancy G.; Peek, Sara E.; Paytan, AdinaAttribution: Pacific Coastal and Marine Science Center
Year Published: 2019
Molecular characterization of Bathymodiolus mussels and gill symbionts associated with chemosynthetic habitats from the U.S. Atlantic margin
Mussels of the genus Bathymodiolus are among the most widespread colonizers of hydrothermal vent and cold seep environments, sustained by endosymbiosis with chemosynthetic bacteria. Presumed species of Bathymodiolus are abundant at newly discovered cold seeps on the Mid-Atlantic continental slope, however morphological taxonomy is challenging, and...
Coykendall, Dolly (Katharine); Cornman, Robert S.; Prouty, Nancy G.; Brooke, Sandra; Demopoulos, Amanda W. J.; Morrison, Cheryl L.Attribution: Leetown Science Center, Eastern Ecological Science Center, Ecosystems, , Region 1: North Atlantic-Appalachian
View Citation
Coykendall, D.K., Cornman, R.S., Prouty, N.G., Brooke, S., Demopoulos, A.W.J., and Morrison, C.L., 2019, Molecular characterization of Bathymodiolus mussels and gill symbionts associated with chemosynthetic habitats from the U.S. Atlantic margin: PLoS ONE, v. 14, no. 3, art. e0211616, https://doi.org/10.1371/journal.pone.0211616.
Year Published: 2019
A 50-year Sr/Ca time series from an enclosed, shallow-water Guam coral: In situ monitoring and extraction of a temperature trend, annual cycle, and ENSO and PDO signals
Located on the northern edge of the West Pacific Warm Pool and having a developed economy and modern infrastructure, Guam is well positioned and equipped for obtaining natural records of the west Pacific maritime paleoclimate. This study was a proof of concept to explore whether useful climate proxy records might be obtained from coral at readily...
Bell, Tomoko; Lander, Mark; Jenson, John; Randall, Richard; Partin, Judson W.; Prouty, Nancy G.Attribution: Pacific Coastal and Marine Science Center
Year Published: 2018
Carbonate system parameters of an algal-dominated reef along west Maui
Constraining coral reef metabolism and carbon chemistry dynamics are fundamental for understanding and predicting reef vulnerability to rising coastal CO2 concentrations and decreasing seawater pH. However, few studies exist along reefs occupying densely inhabited shorelines with known input from land-based sources of pollution. The shallow...
Prouty, Nancy G.; Yates, Kimberly K.; Smiley, Nathan A.; Gallagher, Christopher; Cheriton, Olivia; Storlazzi, Curt D.Attribution: Pacific Coastal and Marine Science Center
View Citation
Prouty, N.G, Yates, K.K., Smiley, N., Gallagher, C., and Storlazzi, C.D., 2018, Carbonate system parameters of an algal-dominated reef along west Maui: Biogeosciences,
https://doi.org/10.5194/bg-2018-35
Year Published: 2018
Uptake and distribution of organo-iodine in deep-sea corals
Understanding iodine concentration, transport, and bioavailability is essential in evaluating iodine's impact to the environment and its effectiveness as an environmental biogeotracer. While iodine and its radionuclides have proven to be important tracers in geologic and biologic studies, little is known about transport of this element to the deep...
Prouty, Nancy G.; Roark, E. Brendan; Mohon, Leslye M.; Chang, Ching-ChihAttribution: Pacific Coastal and Marine Science Center
View Citation
Prouty, N.G., Roark, E.B., Mohon, L.M., and Ching-Chih, C. 2018. Uptake and distribution of organs-iodine in deep-sea corals. Journal of Environmental Radioactivity. https://doi.org/10.1016/j.jenvrad.2018.01.003
Year Published: 2018
Seafloor fluid seeps on Kimki Ridge, offshore southern California: Links to active strike-slip faulting
The Kimki Ridge fluid seeps are located in western Catalina Basin about 60 km southwest of the southern California mainland and at a water depth of approximately 1100 m. Multichannel seismic reflection profiles collected by the U.S. Geological Survey (USGS) in 2014 show acoustic transparency within the Kimki...
Conrad, James E.; Prouty, Nancy G.; Walton, Maureen A. L.; Kluesner, Jared W.; Maier, Katherine L.; McGann, Mary; Brothers, Daniel; Roland, Emily C.; Dartnell, Peter
Year Published: 2017
Deepwater Program: Lophelia II, continuing ecological research on deep-sea corals and deep-reef habitats in the Gulf of Mexico
The deep sea is a rich environment composed of diverse habitat types. While deep-sea coral habitats have been discovered within each ocean basin, knowledge about the ecology of these habitats and associated inhabitants continues to grow. This report presents information and results from the Lophelia II project that examined deep-sea coral habitats...
Demopoulos, Amanda W.J.; Ross, Steve W.; Kellogg, Christina A.; Morrison, Cheryl L.; Nizinski, Martha S.; Prouty, Nancy G.; Bourque, Jill R.; Galkiewicz, Julie P.; Gray, Michael A.; Springmann, Marcus J.; Coykendall, D. Katharine; Miller, Andrew; Rhode, Mike; Quattrini, Andrea; Ames, Cheryl L.; Brooke, Sandra D.; McClain-Counts, Jennifer P.; Roark, E. Brendan; Buster, Noreen A.; Phillips, Ryan M.; Frometa, JanessyAttribution: Wetland and Aquatic Research Center, Ecosystems, Region 2: South Atlantic-Gulf (Includes Puerto Rico and the U.S. Virgin Islands), Region 4: Mississippi Basin
View Citation
Demopoulos, A.W.J., Ross, S.W., Kellogg, C.A., Morrison, C.L., Nizinski, M., Prouty, N.G., Bourque, J.R., Galkiewicz, J.P., Gray, M.A., Springmann, M.J., Coykendall, D.K., Miller, A., Rhode, M., Quattrini, A., Ames, C.L., Brooke, S., McClain-Counts, J., Roark, E.B., Buster, N.A., Phillips, R.M., and Frometa, J., 2017, Deepwater Program: Lophelia II, continuing ecological research on deep-sea corals and deep-reef habitats in the Gulf of Mexico: U.S. Geological Survey Open-File Report 2017–1139, 269 p., https://doi.org/10.3133/ofr20171139.
Year Published: 2017
Vulnerability of coral reefs to bioerosion from land-based sources of pollution
Ocean acidification (OA), the gradual decline in ocean pH and [ ] caused by rising levels of atmospheric CO2, poses a significant threat to coral reef ecosystems, depressing rates of calcium carbonate (CaCO3) production, and enhancing rates of bioerosion and dissolution. As ocean pH and [ ] decline globally, there is increasing emphasis...
Prouty, Nancy G.; Anne Cohen; Yates, Kimberly K.; Storlazzi, Curt D.; Swarzenski, Peter W.; White, DarlaAttribution: Pacific Coastal and Marine Science Center
View Citation
Prouty, N.G, Cohen, A., Yates, K.K., Storlazzi, C.D., Swarzenski,, P.W., and White, D. (2017) Land based pollution exacerbates acidification and bioerosion on coral reefs. Journal of Geophysical Research Letters, DOI: 10.1002/2017JC013264
Pre-USGS Publications
Prouty NG, Roark EB, Andrews A, Robinson L, Hill T, Sherwood O, Willams B, Guilderson T, Fallon S, 2015, Age, Growth Rates, and Paleoclimate Studies of Deep Sea Corals, In: Hourigan TF, Etnoyer PJ, Cairns SD, eds., The State of Deep-Sea Coral and Sponge Ecosystems of the United States: 2015: NOAA Technical Memorandum X, NOAA, Silver Spring, Maryland, p 10-1 – 10-21
Carilli, J., Prouty, N.G., Hughen, K.A., and Norris, R.D., 2009, Century-scale records of land-based activities recorded in Mesoamerican coral cores: Marine Pollution Bulletin, v. 58, i. 12, pp. 1835-1842, doi: 10.1016/j.marpolbul.2009.07.024.
Date published: June 22, 2020
Seafloor Methane Seeps at the Edge of Hydrate Stability
In June 2019, USGS scientists led a 22-day deep-sea research expedition aboard the R/V Falkor to examine methane seep dynamics and processes along the Cascadia Margin offshore of Washington and Oregon.
Date published: June 22, 2020
EXPRESS: Expanding Pacific Research and Exploration of Submerged Systems - Interagency Collaborative Efforts Explore Deep Ocean Areas
As state and national interest in offshore renewable energy development and substantial commercial and recreational fishing activities grows, managing offshore habitats becomes increasingly challenging. In response, USGS and BOEM have joined NOAA and several non-Federal partners to initiate...
Date published: February 4, 2020
USGS collaborates with National Park Service to study threatened coral reefs in American Samoa
USGS scientists from the Pacific Coastal and Marine Science Center and the St. Petersburg Coastal and Marine Science Center are cooperating with the National Park Service to better understand links between coastal groundwater and coral reef health on the island of Ofu in the National Park of American Samoa (NPSA).
Date published: October 30, 2019
WaterWords-Aragonite
Keep up to speed with the latest USGS deep-sea research cruise with this seafloor syntax.
Date published: October 21, 2019
EXPRESS Expedition Team Hosts NOAA, USGS, and BOEM Leadership
Expanding Pacific Research and Exploration of Submerged Systems (EXPRESS) Expedition Team Hosts National Oceanic and Atmospheric Administration (NOAA), USGS, and Bureau of Ocean Energy Management (BOEM) Leadership on October 21, 2019, in San Francisco
Date published: October 16, 2019
WaterWords-Autonomous Underwater Vehicle
Keep up to speed with the latest USGS deep-sea research cruise with this seafloor syntax.
Date published: October 16, 2019
WaterWords-Remotely Operated Vehicle
Keep up to speed with the latest USGS deep-sea research cruise with this seafloor syntax.
Date published: October 16, 2019
WaterWords-Deep Sea
Keep up to speed with the latest USGS deep-sea research cruise with this seafloor syntax.
Date published: October 16, 2019
WaterWords-Telepresence
Keep up to speed with our EXPRESS research cruise with this latest seafloor syntax!
Date published: February 21, 2019
Agencies meet to discuss exploration of deep-water areas off U.S. West Coast
Core players in “Expanding Pacific Research and Exploration of Submerged Systems” (EXPRESS) held a planning workshop at the...
Date published: November 29, 2018
Surveying deep-water habitats off US West Coast
Researchers from the USGS Pacific Coastal and Marine Science Center (PCMSC) participated in a research cruise to survey deep-water coral, sponge, and fish habitats off U.S. West Coast.
Date published: March 30, 2018
Polluted Groundwater Threatens Hawaiian Coral Reefs
According to a study by USGS scientists, polluted, low-pH groundwater discharging onto a shallow coral reef off Kahekili Beach Park in west Maui, Hawai‘i, further increases seawater acidity and exposes corals to nitrate concentrations 50 times higher than normal.