Pore water studies reef flat sediments, Kaneohe Bay, Oahu, HI (NODC Accession 0000271)

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What does this data set describe?

Pore water studies reef flat sediments, Kaneohe Bay, Oahu, HI (NODC Accession 0000271)
Geochemical behavior of the upper 70 cm of permeable reef flat sediments on Checker Reef, Oahu, Hawaii was examined using spatial and temporal changes in pore water dissolved oxygen, nitrate, nitrite, ammonium, and nitrous oxide. This patch reef was monitored immediately following significant wave events (storm events) between October 1996 and July 1997 to study the hydraulic control of pore water geochemistry within the oxic-suboxic zone of a permeable sediment.
Supplemental_Information: Resource Description: NODC Accession # 0000271
  1. How should this data set be cited?

    Mr. James L. Falter and Dr. Francis J. Sansons of the Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa., 20000914, Pore water studies reef flat sediments, Kaneohe Bay, Oahu, HI (NODC Accession 0000271): University of Hawaii at Manoa, Honolulu, HI.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -157.792
    East_Bounding_Coordinate: -157.791
    North_Bounding_Coordinate: 21.442
    South_Bounding_Coordinate: 21.442
    Description_of_Geographic_Extent: Checker Reef, Oahu, Hawaii

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 01-Oct-1996
    Beginning_Time: Unknown
    Ending_Date: 31-Jul-1997
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: Digital files

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

    2. What coordinate system is used to represent geographic features?

  7. How does the data set describe geographic features?

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

    Mr. James L. Falter and Dr. Francis J. Sansone

  3. To whom should users address questions about the data?

    Patrick Caldwell
    NOAA/NODC/National Coastal Data Development Center
    NOAA/NODC Hawaii/Pacific Liaison
    JIMAR, University of Hawaii at Manoa, 1000 Pope Road
    Honolulu, HI 96822

    808-956-4105 (voice)
    808-956-2352 (FAX)

    Hours_of_Service: 8:00 a.m. to 4:00 p.m. Monday through Friday
    Contact_Instructions: call, write, e-mail, FAX, leave voice mail

Why was the data set created?

The purpose of this study was to examine the behavior of the water composition within these permeable sediments and their relationship to sediment redox structure under varying physical condtions.

How was the data set created?

  1. What methods were used to collect the data?

    Method 0 of 1
    Type: Field

    Well points were fabricated from 1/8 in. diameter schedule 80 PVC pipe and used to sample pore water at depths of 7,15,25,35,50, and 70 cm in the reef. The well points were driven into the reef framework with the aid of a stainless steel installion tool. A set of wells for sampling each of these depths defined an array. The arrangement of wells within a single array was designed to minimize the degree of lateral separation of any two wells within an array while preventing the pore water volume extracted from one well point from overlapping or interfering with the volume extracted from an adjacent well. The sampling volume was estimated to be a sphere ~6 cm in radius, based upond a total extraction volume of ~250 ml per sampling and an estimated sediment porosity of ~0.3. The porosity of modern aragonitic sands is typically ~0.45; however, a more conservative estimate of porosity is used for Checker Reef sediments due to the presence of the larger pieces of broken coral rubble.

    Pore water samples were extracted from the sediment using a battery-powered perstaltic pump. An amount in excess of the dead volume in the tubing that connected the well point to the pump (~270ml) was collected and discarded before taking each 250 ml pore water sample to ensure a pure pore water sample. The mixing of pore water during its passage through the tubing acted to homogenize the samples; however, samples collected from individual well points on and after 1 March 1997 were homogenized in a glass flask free of any head space to ensure uniformity between subsamples intended for different chemical analyses. There did not appear to be any significant change in the relative distribution of pore water species once this deliberate homogenization step was employed. An additional experiment was performed to determine how much pore water composition would change with the volume of water extracted. Four 60 ml pore water samples were sequentially taken from 7-, 25-, and 50-cm well points at each station using 60 ml syringes attached directly to the well points (without using the pump and tubing). These samples showed that nitrate and ammonium concentrations did not change significantly with the amount of pore water extracted, even for the 7-cm well points, suggesting that there was no enhanced movement of pore water along the sides of the well points.

    Two arrays ~1.5 m apart were installed at varying distances from the forereef (Stations S and C) and sampled over a 9-month period. At no point was there a freshwater flow into the bay large enouch to effect surface salinities over the reef. Samples for the determination of dissolved nitrate, nitrite, and ammonium were filtered through glass fiber filters and analysed using standard colorometric techniques. Dissolved oxygen was measured in the field using an Orion model 820 dissolved oxygen meter equipped with a Clark-type electrode. Pore water nitrous oxide concentrations were measured following the method of Pierotti and Rasmussen (1980) with only minor modifications.

    Sediment hydraulic conductivity was estimated for each of the well points using a falling-head permeameter. These estimates assumed that the sediments were homogeneous and extended infinitely around a given well point. These assumptions were made to simplify the required calculations; however, the sensitivity of the calculations to these assumptions at distances greater than 7 cm away from the well point was very small ( less than 5%).

    #INSTRUMENT TYPES: Wells: 1/8 in. diameter schedule 80 PVC pipe

    Water extraction: battery-powered perstaltic pump and 60 ml syringes

    Dissolved oxygen was measured in the field using an Orion model 820 dissolved oxygen meter equipped with a Clark-type electrode.

  2. From what previous works were the data drawn?

  3. How were the data generated, processed, and modified?

    Date: 31-Jul-1997 (process 1 of 1)
    See details under methodogy description in this metadata record and within originator data files.

  4. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

  2. How accurate are the geographic locations?

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    See originator data files and methodolgy description.

  5. How consistent are the relationships among the observations, including topology?

    See originator data files and methodolgy description.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None
Use_Constraints: None

  1. Who distributes the data set? (Distributor 1 of 1)

    NOAA National Oceanographic Data Center
    Attn: NODC User Services
    not applicable
    1315 East-West Highway, SSMC3, 4th Floor
    Silver Spring, MD 20910

    301-713-3277 or 3280 (voice)
    301-713-3302 (FAX)

    Hours_of_Service: 8:30 AM through 6:00 PM, Monday through Friday EST
    Contact_Instructions: Phone/e-mail/FAX/voice mail message
  2. What's the catalog number I need to order this data set?

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    NOAA makes no warranty regarding these data, expressed or implied, nor does the fact of distribution constitute such a warranty. NOAA and NODC cannot assume liability for any damages caused by any errors or omissions in these data, nor as a result of the failure of these data to function on a particular system.

  4. How can I download or order the data?

  5. Is there some other way to get the data?

    Contact the NODC User Services Group via phone/FAX/E-mail: nodc.services@noaa.gov

  6. What hardware or software do I need in order to use the data set?

    Microsoft Excel 97 or higher, or compatible software

Who wrote the metadata?

Last modified: 24-Jan-2017
To be reviewed: 31-Jul-2003
Metadata author:
Sheri Phillips
1315 East-West Highway, E/OC1, SSMC3, 4th Floor
Silver Spring, MD 20910

301-713-3280 x127 (voice)
301-713-3302 (FAX)

Hours_of_Service: 9:30 AM - 6 PM Monday-Thursday
Contact_Instructions: E-mail, phone, FAX, mail
Metadata standard:
FGDC Biological Data Profile of the Content Standard for Digital Geospatial Metadata (FGDC-STD-001.1-1999)

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