Stream Invertebrate Taxa Qualitative Abundances


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 table contains data showing a qualitative count of invertebrate taxa found in the samples gathered.

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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. A maximum of five algal samples of each color were collected from each transect using a #13 cork borer (diameter = 17 mm, area = 227 square mm). Algal samples were preserved in 10% formalin for laboratory identifications. In all, 141 algal samples were collected from 12 streams. Preserved algal samples were examined in the laboratory to determine species composition and relative abundance using a Nikon Diaphot phase contrast microscope. Samples were well mixed to attain an even (random) sampling of mat (some small "clumps" of algae were still present, but these did not affect the objectives of the study), and then subsamples of 2 ml were withdrawn. Each subsample was placed in a 2-ml settling chamber with a 26 mm diameter and examined at x400 magnification. Invertebrates were estimated by examining the entire slide at low power and assigning a subjective scale of rare (1-2 organisms), moderate (2-10 organisms), and abundant (10-50 organisms). Taxonomic identifications were primarily based on the classical Antarctic literature.


Data from this table was initially included in the raw data files specified under the variable for 'file name'. These are Microsoft Excel version 5.0 files and can be found on the McMurdo LTER data manager's personal computer at INSTAAR. Once submitted to INSTAAR, the data manager combined all of the stream biology files that contained information about invertebrate taxa. The resulting file is represented in the "invrtbrt.dat" file used on the web page. In July, 2000, dataset code and location code (strmtrnsid) fields were added. This would simplify generating links between different data and metadata fields and assist in making the data more relational / useful in Oracle and ArcInfo.


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