Acceptance and utilization of LTER data requires that:
FILE NAME: PRINCIPAL INVESTIGATOR: OTHERS: KEYWORDS: lake, ciliate, grazing, ingestion, cryptophyte, Antarctica, limnology, microzooplankton
ABSTRACT: In conjunction with the Long Term Ecological Research (LTER) project in the
McMurdo Dry Valleys of Antarctica, lakes were monitored for microzooplankton by a team based out of
the University of Nottingham (led by Johanna Laybourn-Parry). This dataset shows grazing rates of
ciliates feeding on cryptophytes between November 1997 and January 1998.
VARIABLES: location, beginning date, ending date, type of organism, min ingestion
rate (cryptophytes/ciliate/h), max ingestion rate (cryptophytes/ciliate/h), min cryptophyte biomass
removed daily (µg C / l), max cryptophyte biomass removed daily (µg C / l)
RESEARCH LOCATION: Samples were drawn from Lake Fryxell, located in the Taylor
Valley, Southern Victoria Land, Antarctica (77°S, 162°E). The lake has a maximum depth of
20m and is a permanently stratified meromictic lake with a conductivity of 1.2 to 2.0 mS/cm in the upper
mixomolimnion and 4.1 to 8.4 mS/cm in the lower anoxic monomolimnion. Water temperatures during the summer
range between 0.01°C and 2.7°C, with temperature increasing with depth. The chemocline is situated at 9.5m.
METHODS: Ciliate samples were collected from Lake Fryxell by drilling a hole through
the thick ice cover (approximately 4m thick) above the deepest point of the lake. A 2.21 Niskin bottle
was used to retrieve duplicate 500 ml water samples from a 9m depth. The water samples were
fixed in Lugol's iodine and concentrated by settling, prior to counting in a
Sedgewick-Rafter counting chamber under phase microscopy at x160.
Cryptophyte biomass was calculated by measuring 50 cells on each preparation. Biovolume was
derived by applying an ellipsoid geometric shape and converted to carbon using a conversion
figure of 220fg C/µm3.
Ciliate ingestion rates were determined using live cryptophytes. Ciliates were incubated in the
dark at 2°C until no autofluorescence from ingested
cryptophytes was visible within the cells. Freshly collected cryptophytes were concentrated by
gravity filtration. The ciliates were then incubated with two concentrations of cryptophytes,
8500/ml and 15000/ml. The former concentration is typical of the deep maximum of
cryptophytes in Lake Fryxell, the latter is close to the highest level ever recorded in Lake Fryxell.
Ingestion rates were measured at 6 intervals over an 8 hour period.
Samples were fixed with ice-cold 2% glutaraldehyde (final concentration), filtered onto 10 µm
polycarbonate filters and viewed under epifluorescence microscopy. Ingested cryptophytes were
visible within the ciliates by their orange autofluorescence. Fifty ciliates were examined on each
preparation.
TIMING: Samples were gathered during the austral summer 1997-1998.
CITATIONS: Roberts, Emily C. and Johanna Laybourn-Parry. 1998. Mixotrophic cryptophytes and their
predators in the Dry Valley lakes of Antarctica. Freshwater Biology. In Press.
COMMENTS:
STATUS: Restricted Access (Type IV).
VARIABLE DESCRIPTION:
VARIABLE TYPE DESCRIPTION UNITS MISSING VALUE INDICATOR MINIMUM MAXIMUM PRECISION Location Text Name of lake where measurement was made none Required entry n/a n/a n/a Beginning Date Date Earliest date on which samples were taken mm/yy Required entry 11/01/97 01/31/98 mm Ending Date Date Latest date on which samples were taken mm/yy Required entry 11/01/97 01/31/98 mm Depth (m) Number Depth at which sample was drawn from lake meters Required entry 0 20 1 Type of Organism Text Category describing species none Required entry n/a n/a n/a Min ingestion rate (cryptophytes/ciliate/h) Number Lowest rate at which cryptophytes were consumed # of cryptophytes/ciliate/hour Required Entry 0 n/a 0.01 Max ingestion rate (cryptophytes/ciliate/h) Number Highest rate at which cryptophytes were consumed # of cryptophytes/ciliate/hour Required Entry 0 n/a 0.01 Min cryptophyte biomass removed daily (µg C / l) Number Lowest amount of cryptophyte biomass consumed in 24 hours Null 0 n/a 1 Max cryptophyte biomass removed daily (µg C / l) Number Highest amount of cryptophyte biomass consumed in 24 hours Null 0 n/a 1 LOG: Data for this file was submitted by Johanna Laybourn-Parry to
the data manager at INSTAAR on October 21, 1998. Files were sent via e-mail as well
as a hard copy. The original version of the file is stored on the Unix system in
"/data1/data/lakes/plankton/laybourn-parry/DV". Upon arrival at INSTAAR, the
data manager reformatted the file to present it in a relational mode. This
was done using Microsoft Access. It was then exported in comma delimited ascii and
MS-DOS text format to present on the web. Links to these files are provided above.
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.
µg of carbon / liter
µg of carbon / liter