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Hi all:
I cannot comment on the validity of the various explanations of the
purple sand at the Keji Adjunct, but I would like to point out that
there exists the unrelated phenomenon of purple (or red) rocks. These
rocks are usually quite flat, with depressions temporarily filled with
water. Usually rainwater, sometimes river water, never saltwater. It can
be found in man-made habitats such as bird baths and sagging flat roofs.
The purple or red discoloration is caused by large numbers of the
microscopic unicellular green alga (Chlorophyta) Haematococcus
pluvialis. This alga is highly resistant to drought, and colonies can
persist only in depressions that contain water only occasionally. In
more permanent habitats it is outcompeted by other algae (and other
plants). Today, I visited a large flat rock near Big Indian Lake
(Prospect River, HRM) covered with purple paint-like matter. A
microscopic examination of a sample of the purple matter confirmed the
presence of Haematococcus. It is thriving during the current rainy spell...
See Figure 3 in the link below for a nice colour photo of the alga.
Dusan Soudek
http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artjan99/haem.html
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