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Weeping Beauty

Cris

A week or so ago Wayne Lanier and I took a hike out to Drawbridge. Starting at the Alviso Marina, we stopped in several places where Wayne took microbiological samples and I shot aerial photographs. I headed back down to Drawbridge on Sunday with my son Charlie Benton and this time I collected a few samples to explore under the microscope.

On reviewing my earlier aerial photographs I developed an interest in a series of weeps (small drainages) that channel water from the Southern Pacific railroad embankment. The weeps are colorful and diverse as shown in this set of images ranging from more distant views to photomicrographs.

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Looking down the tracks toward Alviso. The weeps lie between the railroad track to the left and the salt pond levee to the right.

I had not really noticed the weeps very much during our first walk but they sure caught my eye in the aerial photographs. I believe the weeps are fed by standing water on the other side of the railroad tracks. The moist ground of the weeps is covered with various shades of green, brown, and a little red with substantial variation occurring in just a few inches.

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A plan view of the railroad grade and the weeps to its west.

So, while Charlie and I were hiking we paused for a while at the weeps. On close inspection they were quite beautiful. I sampled in two locations. The first was the main drainage channel which was perhaps 30 cm wide and only a few millimeters deep. On sampling,

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First sample site before taking sample

I found that the bottom of the channel was composed of a fine black silt – there may well be interesting micro-community stratification occurring here. The roiled up black silt is evident in the following photograph, taken after I collected the sample.

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View of first sample site after sample collection

The second sample site was just a bit up one of the main lateral feeders that connected the main channel to the railroad embankment. There was a bit of pink froth in the vicinity of this sample and the dark channel bottom was visually evident without disturbing a top layer.

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The second sample site

Charlie and I spent a few minutes admiring the varied colors of this weep and then headed on toward Drawbridge. When we got home I went through the samples we had collected that afternoon and the weep site was the find of the day. The samples collected there had large, healthy Cyanobacteria and a large number of smaller motile filaments that I took to be bacteria. These smaller filaments were reminiscent of Beggiatoa but not quite the same. The samples also had large populations of dinoflagellates at two different sizes and hordes of small motile bacteria. This was a very entertaining sample to watch.

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A ciliate swims through highly motile bacteria

I played around with technique with this sample. The first experiment was a revelation and great fun to boot. I took the video feed from by small Canon Elph and used it to drive a 37” diagonal television monitor. This is a great way to view microscope samples. The resolution is fabulous, the image large (easy viewing for us emerging presbyoptics), and you can use both eyes.

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A clump of Cyanobacteria, small filaments (bacteria?), and debris

I also played around with using sunlight as a source instead of the normal LED flashlight in bright field mode. I guess this is a form of poor man’s dark field photography. It is interesting to compare specimens under transmitted and reflected light.

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A clump of Cyanobacteria under transmitted light.

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The same clump photographed using beam sunlight as a source.

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