phytwntr English utf8 dataset McMurdo Dry Valleys LTER http://mcmlter.org/ 2014-11-04 ISO 19115-2 Geographic Information - North American Profile Metadata - Data with Biological Extensions ISO 19115-2:2009(E) Winter Phytoplankton Densities during the 1990-1991 season 2014-11-04 publication Diane McKnight University of Colorado Boulder http://www.colorado.edu/ diane.mcknight@colorado.edu pointOfContact documentDigital Using automated overwinter sampling devices, preserved phytoplankton samples were collected from multiple depths in Lake Fryxell, a permanently ice-covered lake in southern Victoria Land, Antarctica. Photosynthetic algae (i.e. algae possessing chloroplasts) are maintained in a stable water column throughout winter darkness. The algal taxa "overwinter" in different ways, in a species specific manner. Typical vegetative cells were the most abundant form for all species found in the water column. Populations of one chlorophyte, Stichococcus sp., and two cryptophyte species increased during winter. We interpret the increase in algal population size as evidence of wintertime heterotrophic growth, and mixotrophic behavior in the context of the entire year. For two chlorophyte species some portion of the population had distinct morphology, e.g. akinetes for Chlamydomonas subcaudata and cells containing a large amount of starch or other storage material for Chlorella sp.. During winter, vegetative cells of the most abundant species of cyanobacteria, Phormidium angustissimum, occurred at the depth of the summertime maximum and at depths below the oxycline, which may represent a "false bottom". Other than this false bottom and the absence of diatoms, settling did not appear to influence the overwinteringalgal community. Name: Inigo San Gil Role: data manager completed McMurdo Dry Valleys LTER http://mcmlter.org/ unknown metadata improved on 2016. population dynamics theme LTER Core Areas English 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): 25.2 163.259582519531 163.048782348633 -77.622711181641 -77.597076416016 ground condition 1990-04-15 1991-09-06 https://mcm.lternet.edu/sites/default/files/phytwntr.csv phytwntr eng; US McMurdo Dry Valleys LTER phytwntr Record Delimiter : \n Number of Header Lines : 1 Number of Footer Lines : 0 Orientation : Column Quote Character : "Field Delimiter : , false LOCATION NAME The name of the lake where samples were acquired DATE_TIME Date on which sample was collected Date Time Format: mm/dd/yyyy DEPTH (m) The lake depth were the sample was collected, relative to the ice surface. Phylum The distinct phylum names corresponding to the measured cell densities Species The distinct species name corresponding to the measured cell densities Species Density (cells/mL) Species Density (cells/mL) Phylum Density (cells/mL) Phylum Density (cells/mL) Phyto Density (cells/mL) Phytoplankton Density (cells/mL) DBF https://mcm.lternet.edu/sites/default/files/phytwntr.csv dataset  Samples were obtained and preserved in situ through the winter season using automated time series samplers. The samplers were composed of an array of syringes suspended at a series of depths on an in situ mooring. Each syringe was hydraulically connected to a manifold and linked to a gear pump. A floating piston in each syringe was hydraulically driven to draw water at prescribed time intervals and introduce Lugol's solution (KI, I and acetic acid) as a preservative.          Algae were identified and enumerated with the use of a Nikon Diaphot inverted microscope under oil immersion at 1000x magnification. Subsamples were allowed to settle in chambers following the method of Utermohl. Strip counts were made with a minimum of 100 individuals of the most common taxa enumerated. Identifications were based primarily upon keys by Prescott, Tikkanen, and Seaburg et al. Cells with intact chloroplasts were counted as "live". Visibly-degraded cells were not counted. We noted qualitatively that few visibly degraded cells were found in the winter samples, which is comparable to the summer samples. Subsamples were also examined at 100x to enumerate protozoans.          In order to  evaluate changes in cell volume between winter and summer, cell volumes were determined by measuring cell dimensions and approximating cell shape to geometric shape. Dimensions of 10 cells of each taxa were measured in four samples from different depths collected in April 1990. In a previous study, 100 cells of each taxa were measured to determine variance in size. Metadata Access Constraints: none Metadata Use Constraints: none annually McMurdo Dry Valleys LTER http://mcmlter.org/ pointOfContact