#TEMPORARY ACCESSION NUMBER:


#ACCESSION NUMBER:


#CONTRIBUTOR:
Mr. James L. Falter
Dr. Francis J. Sansone

#CONTRIBUTOR INSTITUTION:
Department of Oceanography
School of Ocean and Earth Science and Technology
University Of Hawaii at Manoa
Honolulu, Hawaii 96822

#ORIGINATOR:
Mr. James L. Falter 
Dr. Francis J. Sansone 

#ORIGINATOR INSTITUTION:
Department of Oceanography 
School of Ocean and Earth Science and Technology 
University Of Hawaii at Manoa
Honolulu, Hawaii 96822

#TITLE: 
Pore water composition of permeable reef flat sediments
on Checker Reef in Kaneohe Bay, Oahu, Hawaii, 1996-1997

#PROJECT: 
U.S. National Science Foundation grant OCE-9504251

#ABSTRACT:
Geochemical behaviour of the top 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 between October 1996 and July 1997 to study
the hydraulic control of pore water geochemistry within the oxic-
suboxic zone of a permeable sediment.

#PURPOSE: 
The purpose of this study was to examine the behaviour of the
water composition within these permeable sediments and their 
relationsip to sediment redox structure under varying physical 
conditions.

#LOCATION EXTREMES:
SOUTHERNMOST LATITUDE: 21.443
SOUTHERNMOST LATITUDE HEMISPHERE: N
NORTHERNMOST LATITUDE: 21.442
NORTHERNMOST LATITUDE HEMISPHERE: N
WESTERNMOST LONGITUDE: 157.792
WESTERNMOST LONGITUDE HEMISPHERE: W 
EASTERNMOST LONGITUDE: 157.791
EASTERNMOST LONGITUDE HEMISPHERE: W  

#LOCATION KEYWORDS: Checker Reef, Kaneohe Bay, Oahu, coastal Hawaii, 
                    North Pacific Ocean

#SAMPLING STATIONS:
Station C: closest to forereef with two arrays CD and CA
Station S: closest to backreef with two arrays SA and SB

These stations are roughly 75 m apart.  Each well hole
of an array is between 10 and 20 cm apart.

#BEGIN AND END DATES: 
7 October 1996 - 03 July 1997

#SAMPLING PERIODS:
Nutrient samples were collected from all arrays starting
on 7 October 1996.  Dissolved gas samples were collected
from arrays CA and SA starting on 5 December 1996 and from arrays
CD and SB on 1 March 1997.  Nitrous oxide samples were not
collected from array CA due to its very shallow dissolved
oxygen penetration.  All sampling of arrays CA and SA was
concluded on 22 April 1997, and all sampling of arrays
CD and SB were concluded on 3 July 1997.  Sampling intervals
thus ranged from 2 weeks to 2 months.

#PARAMETERS: 
water composition (dissolved oxygen, nitrate, nitrite, 
ammonium, dissolved inorganic nitrogen, dissolved inorganic
phosphorus, silicon, and nitrous oxide)

#METHODOLOGY:
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 (<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.

#REFERENCES: 
Falter, J.L., and F.J. Sansone. 2000. Hydraulic control of pore
    water geochemistry within the oxic-suboxic zone of a permeable
    sediment.  Limnol. Oceanogr., 45(3), 550-557.

Pierrotti, D., and R. A. Rasmussen.  1980.  Nitrous oxide
   measurements in the eastern tropical Pacific Ocean. Tellus
   32: 56-72.

#SUBMITTING MEDIUM:
FTP

#FILE FORMATS: 
Data received in file, appx.xls,  (MS Excel).  Redundant
ASCII text files were made of each individual sheet within
the spreadsheet file.  These files are:

sheetx.prn, where x varies from 1 to 8.

The format is straight-forward with well-defined columns.
The rows are well marked by date and depth.

#DATASET SIZE:
91 Kbytes

#NUMBER OF DATA UNITS:
2 stations, 4 arrays

#MISCELLANEOUS: