Stream Algae Photosynthesis/Light Measurements


As part of the Long Term Ecological Research (LTER) project in the McMurdo Dry Valleys of Antarctica, a systematic sampling program has been undertaken to monitor the abundance and species distribution of algal mats in glacial meltwater streams of the region. This data set includes results from light and dark incubations of algae to calculate net and gross primary productivity versus light curves of algal communities from Green Creek in Fryxell basin during January 1995. This data set constitutes the LTER algal primary productivity data for streams.

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Within each transect, algal mats were visually identified as either orange, red, black, or green. Not all types of algal mats were found within every transect. Algal samples were collected using a cork borer (1.04 cm2) and placed in vials (volume=21.3 mL). Vials of algae were placed in bags to screen sunlight to 0, 0.5, 1.4, 7.7, 16.4, 31.2, 60.7, 67.0, 100 percent of full sunlight for warm temperature incubations and 0, 1.4, 7.7, 31.2, 100 percent of full sunlight for cool temperature incubations. Algae were incubated in the stream for approximately 2.75-4.0 hours typically between 8:50 am and 5:00 pm. Primary productivity was measured as the change in oxygen concentration in the vial using an oxygen microelectrode. Upon completion of incubation, the algae in the vials were taken back to the lab for AFDM processing. Samples were taken in the area of the LTER monumented transect. Samples for ash-free dry mass measurements were filtered through GF/C glass fiber filters and frozen. The samples were dried (100 degrees C) for 24 hours, weighed, ashed (450 degrees C) for 4 hours, rehydrated with water, dried for 24 hours, and reweighed. Net primary productivity (NPP, light bottles) and community respiration (CR, dark bottles) were calculated as follows: NPP or CR (ug C/cm2/hr)=[(((change in mg O2/L x v) x 0.375 C/O2 x 1000 ug/mg)/area/hours incubated], where O2/L = change in oxygen concentration, v = volume of vial (0.0213 L), C/O2 = atom/atom conversion of oxygen to carbon, area = 1.04 cm2.


Data from this table was initially submitted in the ppvsli95.xls file (Microsoft Excel version 5.0). Once submitted to INSTAAR, the file was entered into Microsoft Access and exported in ascii comma delimited and MS-DOS text (table layout) formats. These files are represented in the "strmppvs.dat" and "strmppvs.txt" files used on the web page. In November, 1999, the data manager added a field for stream transect ID code. This assisted in preparing the data for use in Oracle and ArcInfo. In July, 2000, the dataset code field was added in order to simplify generating links between different data and metadata


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