Hiking With A Field Microscope

The Big Heat

TABLE OF CONTENTS

Introduction

Secrets of a San Francisco Deck Garden

Giant Bacteria Found in Golden Gate Park Flowers...!

Cryptobiotic Soil Unearthed in Utah

Revealing Films of Life in a Cliff-side Seep

A Hard Life Out in the Salt Flats

Vernal Pool Fantasies

Relax in California Tide Pool

Salt Marsh Mysteries

The Big Heat

Beneath the Tufas in Mono Lake

What is a Field Microscope?

Getting Out Into the Field

Little-known Techniques of Field Photomicrography

Candid Camera

Hot springs have been my most exciting hunting ground since I skied cross-country into Mamouth Hot Springs in Yellowstone Park. That was before I had a digital camera and, although I attempted photomicrographs with a film camera, the results were not publishable. Visions of life comfortable in a steaming kettle, a sort of "outer limits", still fascinate me.

Since then, I have sampled the warm creeks from hot spring run-offs, briefly visited a few warm springs, and spent an afternoon sampling the hot spring source pool and run-off streams at Grover Hot Springs state Park, Markleville, CA.

In the photograph of the source pool shown above, you cannot see the water, but with the exception of the very top of the rock, everything is under water that flows directly out of the source [just off camera to the upper right]. The temperature was billed as 148^oF, but I measured 58.2^oC = 136.8^oF. This is not two surprising, it was winter and water from the melting snow on the slope above the source was trickling in at a steady rate. I could reach into the water for sampling, but it was scalding and I had to be quick.

The water was somewhat acid [pH = 5.5] and very slightly salty [0.8% by my refractometer]. The California State Parks brochure promised a mineral content of almost 2%, mostly sodium chloride, sodium sulfate, and sodium carbonate. The snow-melt water might account for the more dilute salinity, but not for the slight acidity.

If you look back at the photograph, you will notice what appears to be a rusty-red layer of mud on the bottom of the source pool. This red layer covered most of the bottom and it looked like fine silt. Turns out it was not rust and it was not red mud. The first photomicrgraph shows a surprise:

This photomicrograph was taken of a sample lifted by pipette from directly at the surface of the "red mud" and viewed in the bright field at 400X. You can see tiny red particles forming a cloud. This is a cloud of bacteria.

Still, from this photomicrograph, you might doubt my conclusion. After all, it could be very fine particles of red mud. Next, click on the photograph above to view a movie of the "red particles". You need QuickTime to view the movie, but you can download a free QuickTime viewer. When you finish viewing the movie, use the <BACK> button of your browser to return to this page. While you watch the movie, look closely at the tumbling particles. The motion you see might be Brownian motion, some of it probably is. However, you can also see some of the bouncing dot are actually little tumbling "sticks".

So, go to the next photomicrograph, shown below. This photomicrograph was taken at 800X with phase contrast and from the edge of the cloud, there the particles were not so dense. At first it appeared that the bacteria were "cocci" shaped like round balls. Turns out that was an illusion of perspective. Virtually all were large rod-shaped bacteria. Seen from end-on, these bacteria looked like the cocci, but their tumbling quickly revealed them to be much more highly motile rods. You can see a close-up movie of the tumbling by clicking on the photomicrograph below. Return with <BACK> on your browser.

This photomicrograph was take using phase contrast. The phase contrast condenser creates false colors, but has the advantage of shadowing small objects like bacteria so their shape easier to see. Phase contrast also enhances the internal structure of cells and, sometimes, bacteria.

In Hiking With A Field Microscope, you have seen red bacteria in other chapters, particularly in "A Hard Life Out on the Salt Flats". These hot spring red bacteria carry out photosynthesis, just as those salt flat red bacteria did. Identifying bacteria is difficult, under any circumstances. The red bacteria at Grover Hot Springs have, as far as I know, no official taxonomic name. If you search using Google or, better yet, Googal Scholar, on the words "red bacteria hot springs" your will turn up many many articles about red Archeabacteria with such names as Roseiflexus, Rhodothermus, and Chloroflexus. Most of these bacteria turn out to be large rods, from 5-mm to 10-mm, or even 30-mm long. Some are individual, some are colonial, some form mats of gliding bacteria.

So far, I have ignored the much larger filaments of cyanobacteria. In parts of the pond and in the run-off streams, the cyanobacteria formed what appeared to be blue-green "ribbons". Under magnification, these ribbons turned out to be two kinds of cyanobacteria.

Examination of the skinny cyanobacteria showed more detail. In the photomicrograph below, taken with phase contrast at 800X magnification, the very large rod-shaped "barber pole" in the center is probably a skinny cyanobacterial filament showing specialized cells. Such specialized cells along cyanobacteria may be involved in nitrogen metabolism.

In the photomicrograph above, you can also the large rods, although they are dwarfed by the very large "skinny" cyanobacteria.

Very hot springs rarely support higher organisms such as diatoms. In this spring, however, the temperature was "low" enough for a population of diatoms of different species.

These large diatoms were not motile and often showed a green color. It seems unlikely that they had washed into the hot springs source pool with the snow-melt water, since there were many. I also found them even more common in the lower-temperature run-off stream from the hot spring.

Shown in the phase contrast photomicrograph below are the other, smaller diatoms: