Microzooplankton : Ciliate Grazing Rates


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. The sample for this micro dataset was gathered at the Lake Fryxell.

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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/microm3. Ciliate ingestion rates were determined using live cryptophytes. Ciliates were incubated in the dark at 2 degrees 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 microm 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.


 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.
On 2006, metadata was standardized to the EML format.  in 2014, metadata was enhanceded with the Drupal Ecological information management system (Inigo San Gil).  Completed in 2016


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