Acceptance and utilization of LTER data requires that:
FILE NAME: PRINCIPAL INVESTIGATOR: OTHERS: Peter Doran KEYWORDS: lake, benthic, microbial mat, chlorophyll-a, phaeopigments
ABSTRACT: As part of the Long Term Ecological Research (LTER) project in the
McMurdo Dry Valleys of Antarctica, the growth of benthic cyanobacteria-dominated mats in
the lakes has been monitored. This dataset shows chlorophyll-a levels associated with the
benthic mats. Values are provided for various depths of Lake Hoare during the 1996-97
field season, both with and without correction for phaeopigments.
VARIABLES: location, season, depth (m), total chl-a (µg/cm2), avg chl-a (µg/cm2),
chl-a corrected for phaeopigments (µg/cm2), avg chl-a corrected for phaeopigments (µg/cm2), file name
RESEARCH LOCATION: Samples were obtained from an approximately linear transect stretching
from the Lake Hoare, Taylor Valley, Antarctica laboratory complex towards the lake deepspot.
METHODS: These data are based on analysis of replicated 1.98 cm2 cores of the pigmented
surface layer of benthic microbial mats from Lake Hoare. Parallel experiments in which thicker cores
were sectioned showed that this surface layer contained all chlorophyll-a present in the cores.
They are expressed per unit area of core, units µg/cm2 (micrograms per square centimeter). All depths
refer to depth from the surface and are in meters. Samples were obtained from an approximately linear
transect stretching from the Lake Hoare laboratory complex towards the lake deepspot.
Cores were collected through December 1996 by scuba divers. Initially, cores of 7 cm diameter were collected
using sharpened perspex coring tubes. After retrieval to the surface, these were subsampled using
sharpened, cut-off syringe barrels. Cores were stored at -20°C, in the dark, until processed in
New Zealand some 2-3 months later. Extraction was into 10 ml of 90% acetone (allowing for volume
of water in core), and was aided by grinding with a teflon pestle in a glass tube. Calculations were
based on absorptance of the extract measured at 665, corrected by subtracting that at 750 nm. Correction
for phaeopigments was accomplished by re-measuring absorptance after acidification with dilute HCl.
Equations used for calculating chlorophyll-a in µm/cm2 with (Eq 1) and without (Eq 2) correction for
phaeopigments were:
TIMING: Data collection occurred throughout December 1996.
CITATIONS:
COMMENTS: The data were obtained by Dr. Ian Hawes of the National Institute of Water and
Atmospheric Research, Christchurch New Zealand (i.hawes@niwa.dri.nz), who should be contacted with any
queries. The research was funded by the New Zealand Foundation for Research, Science and Technology,
under grant CO1601. Logistic support was provided by the Taylor Valley Long Term Ecological Research
Program.
STATUS: Restricted Access (Type IV).
VARIABLE DESCRIPTION: LOG:
NOTE: Data contained in these files has been subjected to quality
control standards imposed by the investigator. The user of this data
should be aware that, while efforts have been taken to ensure that these
data are of the highest quality, there is no guarantee of perfection
for the data contained herein and the possibility of errors exists. If
you encounter questionable data, please contact the MCM LTER data manager
(; (303)492-4639) so that the data can be
corrected or qualified. Thus, these data may be modified and future
data will be appended.
where A665(na) and A665(ac) are corrected absorptances (as optical density) before and after acidification,
vol is volume of acetone used (ml) and area is the area of the core (cm2).
VARIABLE TYPE DESCRIPTION UNITS MISSING VALUE INDICATOR MINIMUM MAXIMUM PRECISION
Location Text None Required entry n/a n/a n/a
Season Text DD-MM-SS South Required entry n/a n/a n/a
Depth (m) Number meters Required entry n/a n/a n/a
Total chl-a Number µg/cm2 Null n/a n/a n/a
Avg Chl-a Number µg/cm2 Null n/a n/a n/a
Chl-a corrected Number µg/cm2 Null n/a n/a n/a
for
phaeopigments
Avg chl-a Number µg/cm2 Null n/a n/a n/a
corrected for
phaeopigments
File Name Text None Null n/a n/a n/a