uid=MCM,o=EDI,dc=edirepository,dc=org all public read flgltgrz Johanna Laybourn-Parry

University Road, Clifton Bristol BS8 1SS Bristol - None - BS8 1S GB

jo.laybourn-parry@bristol.ac.uk McMurdo Dry Valleys LTER http://mcmlter.org/ Inigo San Gil

Department of Biology, MSC03 2020 University of New Mexico Albuquerque NM 87131 US

(505) 277-2625 (505) 277-2541 isangil@lternet.edu data manager 2014-11-10 English

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 heterotrophic and mixotrophic flagellates found in Lakes Hoare and Fryxell at various depths and dates.

bacteria biomass grazing lakes LTER Controlled Vocabulary population dynamics LTER Core Areas

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https://mcm.lternet.edu/content/microzooplankton-flagellate-grazing-lakes-hoare-and-fryxell The Lake Fryxell basin is formed by a moraine depression in a wider portion of the Taylor Valley. It has a number of moraine islands and shallower areas, as well as several relatively well developed deltas. The lake is fed by at least 10 meltwater streams with a total drainage catchment of 230 km2. The lake is dammed to the southwest by the Canada Glacier and is topographically closed. It is perennially ice covered; during summer months, an ice-free moat generally forms around much of the lake margin. Lake levels have risen ~2 m between 1971 and 1996. There are no surface outflows; the only known water loss is through ice ablation (evaporation, sublimation and physical scouring). Valley: Taylor Distance to Sea : 9 Maximum Length (km): 5.8 Maximum Width (km): 2.1 Maximum Depth (m): 20 Surface Area (km^2): 7.08 Ice Thickness Average Surface (m): 3.3 - 4.5 Volume (m^3 * 10^6): 25.2 163.048782348633 163.259582519531 -77.597076416016 -77.622711181641 18 18 meter Lake Hoare occupies a narrower portion of the Taylor Valley, dammed by the Canada Glacier. It would drain almost completely without this dam. There are a number of islands which may be related to an old terminal of Canada Glacier. The lake is fed primarily from direct runoff from the glacier, as well as meltwater streams. (Lake level rose ~1.5 m between 1972 and 1996). There are no surface outflows; the only known water loss is through ice ablation (evaporation, sublimation and physical scouring). Valley: Taylor Distance to Sea : 15 Maximum Length (km): 4.2 Maximum Width (km): 1 Maximum Depth (m): 34 Surface Area (km^2): 1.94 Ice Thickness Average Surface (m): 3.1 - 5.5 Volume (m^3 * 10^6): 17.5 162.784423828125 162.935836791992 -77.623085021973 -77.639259338379 73 73 meter 1997-11-07 1998-01-26 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 using Microsoft Access to present it in a relational mode. 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. McMurdo Dry Valleys LTER http://mcmlter.org/ McMurdo Dry Valleys LTER http://mcmlter.org/ McMurdo Dry Valleys LTER

The water column was sampled at the deepest point in each lake with a 2.21 Niskin bottle, through a hole drilled in thick ice cover (approximately 4m thick). Duplicate 60ml samples from each depth were fixed in buffered glutaraldehyde to a final concentration of 2% and stored in the dark at 4 degrees C prior to being analyzed for bacteria. Fo bacteria counts, 1-2ml samples were stained with DAPI (4', 6-diamindino-2-phenylindole),filtered onto 0.2 microm black polycarbonate membrane filters and then viewed under UV epifluorescence microscopy. Ten Whipple grids were counted on each filter and the mean value determined. For cryptophyte counts, 30-50ml of sample was stained with DAPI, filtered onto a 2.0 microm polycarbonate membrane filter and viewed under epifluorescence. Twenty Whipple grids were counted on each filter to determine mean abundance. Biomass values for bacteria were derived by measuring 100 cells on each preparation using a Patterson graticule at a magnification of x1600. Mean cell volumes were converted to carbon values by applying a conversion factor of 220fg C/microm3. 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. Flagellate ingestion rates were determined using fluorescently labelled bacteria (FLB). FLBs were prepared by labelling bacteria cultured from Lake Fryxell with DTAF [5-(4,6-dichlorotriazin-2-yl) aminofluorscein]. Ingestion rates were measured in flagellates collected from 6m and 12m in Lake Hoare and 6m, 8m, and 9m in Lake Fryxell. Incubations were conducted in situ at the appropriate depths using 60ml acid rinsed Nalgene bottles. Duplicate 50ml samples were fixed with ice-cold 2% phosphate buffered glutaraldehyde (final concentration) after 30 minutes, 1 hour, 2 hours and 3.5 hours. Samples were stained with DAPI filtered onto a 5 microm polycarbonate filter and viewed under epifluorescence microscopy. Four hundred cryptophyte cells were examined on each preparation, and the number of FLB in each cell recorded. Ingestion rates were calculated using the linear portion of the uptake curves.

flgltgrz flgltgrz.csv 1444 1 0 \n column , " https://mcm.lternet.edu/sites/default/files/flgltgrz.csv Location Location Name of lake where measurement was made string Name of lake where measurement was made Date Date Date on which sample was gathered date mm/dd/yyyy Depth (m) Depth (m) Depth at which sample was drawn from lake meter 1 real 6 12 Type of Organism Type of Organism Category describing species string Category describing species Bacteria grazing rate/h/indiv Bacteria grazing rate/h/indiv Rate at which bacteria was consumed #ofbacteria/hour/individual 0.1 real 0 %Bacterial biomass grazed daily %Bacterial biomass grazed daily Proportion of bacterial biomass consumed in 24 hours dimensionless 0.1 real 0 100 Null None given