||Identifier for the sample locality, composed as
YYMsssR where YY is the last two digits of the year,
M is the month (no samples were taken from October
through December, thus one digit suffices), sss is the
site number, and R (literally) is present to indicate
that the site was occupied at an earlier date.
||North latitude of the sample locality.
||Longitude of the sample locality. Negative values are
measured westward from the Prime Meridian, positive
values are measured eastward from the Prime Meridian.
||Calendar date when sample was collected, expressed as
a FIPS date using the form YYYYMMDD where YYYY
signifies the year, MM the month, and DD the day
(month and day beginning with 1).
|Sample depth (m)
||Depth in meters at which water was sampled,
measured from sea-surface.
||Dissolved methane concentration in the water.
|Methane Isotopic Composition (ppt)
||Carbon isotopic composition (delta-13C) relative
|Methane Specific Oxidation
||Rate of microbial oxidation of methane.
This "specific oxidation rate" is really just the
first order rate constant for methane uptake and has
the units (1/day) because the oxidation rate (nM/day)
is divided by the concentration (nM).
|Methane Oxidation Rate (nM/day)
||The first order rate constant for the microbial
oxidation of methane.
We measure methane oxidation by first removing (via
shaking) most of the methane from the collected
samples. We then spike the samples with a known
amount of labeled methane which is somewhere near the
concentration of methane in the natural sample. We
measure the rate of methane oxidation by watching
labeled carbon dioxide grow in. Some methane is
converted to biomass and we get at this part by
filtering and counting the amount of labeled
Once we have these numbers, we calculate what is
called the "specific oxidation rate". This is simply
the measured rate divided by the concentration of
methane in the incubation vials. This "specific
oxidation rate" is really just the first order rate
constant for methane uptake and has the units (1/day)
because the oxidation rate (nM/day) is divided by the
We can then derive what we call the "ambient oxidation
rate" by multipling the "specific oxidation rate" by
the concentration of methane actually measured in the
samples. This obviously only works if first order
kinetics are followed but we have found this to be the
case in all of the environments we have studied.
||Descriptive information about the water samples
or the analyses of them.
||Phosphate concentration in water samples.
||Silica concentration in water sample.
||Nitrate concentration in water samples.
||Ammonium concentration in water samples.