Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Skip to content

M01 SUNA - Nitrate Observations Corrected

Metadata Updated: February 24, 2024

Various nitrate sensors including the SUNA V1, SUNA V2 and ISUS (Sea-Bird Scientific) were deployed on NERACOOS Buoy M (Latitude: 43° 29.44'N and Longitude: 67° 52.79'W) from June 23, 2013 to March 23, 2021. This time period corresponds to University of Maine buoy deployments M0124, M0125, M0126, M0127, M0129, and M130 ( These sensors were placed at the surface, 1m, 50m, 100m, 150m and 250m and programmed to collect nitrate measurements six times per day (0045, 0445, 0845, 1245, 1645 and 2045 GMT) over a fixed sampling window of 30 seconds at approximately 1.4 readings per second. The number of sensors and their depths varied for each deployment depending on the number of available sensors. Five measurements recorded in the middle of the 30 second data stream were transmitted back to the University of Maine Physical Oceanography Group via cell phone. The mean concentration and standard deviation were calculated for each specific sampling time. If the standard deviation for a mean was greater than 2µM, the values were eliminated. Surviving data were then quality controlled (QCed) by removing outliers assessed as values less than -0.5µM and greater than 30µM. Whenever possible at the time of buoy deployment and recovery, a standard CTD cast was conducted with a carousel water sampler equipped with Niskin bottles. Ground truth water samples were collected at the same depth as the nitrate sensors. These samples were analyzed for nitrate concentrations at the University of Maine using a Bran Luebbe AA3 Autoanalyzer and standard techniques. Ground truth corrections were added or subtracted as an offset only if the difference between the nitrate concentration of the water sample collected and the mean nitrate sensor reading at approximately the same time was greater than 2 µM. Upon recovery of the instruments, the data was processed using the software provided by Sea-Bird ( and compared with the real-time measurements as a check for accuracy. In the event that the sensor was not able to transmit in real-time, the processed data was QCed. Please contact David Townsend,, University of Maine, School of Marine Sciences if you have any questions.

Access & Use Information

License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

Downloads & Resources


Metadata Date February 12, 2024
Metadata Created Date May 15, 2021
Metadata Updated Date February 24, 2024
Reference Date(s) February 12, 2024 (creation)
Frequency Of Update

Metadata Source

Harvested from ioos

Additional Metadata

Resource Type Dataset
Metadata Date February 12, 2024
Metadata Created Date May 15, 2021
Metadata Updated Date February 24, 2024
Reference Date(s) February 12, 2024 (creation)
Responsible Party University of Maine School of Marine Sciences (Point of Contact)
Contact Email
Guid M01_corrected_nitrate_csv
Access Constraints
Bbox East Long -67.8798
Bbox North Lat 43.491
Bbox South Lat 43.4907
Bbox West Long -67.88
Coupled Resource [{"title": [], "href": ["#DataIdentification"], "uuid": []}, {"title": [], "href": ["#DataIdentification"], "uuid": []}, {"title": [], "href": ["#DataIdentification"], "uuid": []}]
Frequency Of Update
Harvest Object Id c8ce6788-69a8-4875-994d-be9338dc7993
Harvest Source Id 54e15a6e-6dde-4c9c-a8f0-345cc0dfccfb
Harvest Source Title ioos
Metadata Language eng
Metadata Type geospatial
Old Spatial {"type": "Polygon", "coordinates": [[[-67.88, 43.4907], [-67.8798, 43.4907], [-67.8798, 43.491], [-67.88, 43.491], [-67.88, 43.4907]]]}
Spatial Data Service Type ERDDAP tabledap
Spatial Reference System
Spatial Harvester True
Temporal Extent Begin 2013-06-23T16:45:00Z
Temporal Extent End 2021-03-24T00:45:00Z

Didn't find what you're looking for? Suggest a dataset here.