07 May 2004

The Strange Red Film on Fish Lake

Ted Clarke

Photography by the author.

Note: I hope all of you will take the time to read this article carefully; Ted has presented some wonderful ideas, especially his construction of a universal microscope. Now, I'd like to issue a challenge to our members to find ways to build one on a tight budget.
--Shawn Carlson

I am a retired materials engineer living on a small lake in northeastern Indiana. I have a home machine shop that I have used to build optical imaging systems, especially for my specialty of photomacrography.

My wife, Trudy, and I attended meetings of the State Microscopical Society of Illinois before retirement. My artistic wife took great interest in the polarized light photomicrographs of crystals shown for their artistic quality by Anna Teetsov of McCrone Associates. Some of Anna's images are seen on the Modern Microscopy web page at http://www.modernmicroscopy.com/main.asp

Trudy and I wanted her to have her own polarized light microscope so she could make colorful photomicrographs of crystals. Such imaging requires a real polarized light microscope with compensators and a precise rotating stage with a bright illumination system. This type of transmitted light microscope is rarely seen on the used market, and a new polarized light microscope was too costly.

Trudy took good care of me while I was recovering from spinal surgery, so I decided to use this convalescing time to design a polarized light microscope for her that I could build using materials and components I already owned. I designed this microscope system so it would also have vertical illumination capability for my profession of metallurgical engineering. The combination of both transmitted and reflected light capability is found in universal microscopes, which are more costly even than polarized light microscopes. This universal student microscope was built by repairing and upgrading my brother's Monolux student microscope from the 1960's. I am told that I "made a silk purse out of a sows ear."

A summary article about this universal microscope was published in Microscopy Today. More details are given in Theodore M. Clarke, Building an Affordable Universal Student Microscope, The Microscope 48, 19-39, 2000. I used this microscope to examine live organisms from our lake home, a fascinating experience I was denied as a young student, because I was required to take physics and chemistry without biology in high school.

My wife is very ecology oriented and was disturbed to see a red film on the shore of our lake just after the ice melted in 1999. I had noticed a much thinner film the previous December, just before the ice formed, and examined the source of the film with the student microscope without photographing it. My professional career was spent using microscopy to solve problems, so it was only natural to examine a sample of this red film with the microscope to determine its cause, which is the subject of this article.

The red film at the shore of Fish Lake in March of 1999 is shown in Figure 1. The universal microscope system I initially used to study the red film is shown in Figure 2. This microscope is now equipped with Edmund Scientific JIS objectives and not those from the original Monolux.

I found that the red film was entirely due to a straight filament organism 5 micrometers wide. Figures 3 and 4 show this reddish brown organism. These photomicrographs were recorded on Kodachrome film using the 60X 0.85 NA Edmund objective and Koehler bright field illumination.

I also studied this organism with crossed polarized light and found it to be birefringent. The insertion of the first order red compensator with the crossed polarizers showed the filaments to have a positive sign of elongation, as do most synthetic fibers. The filaments are blue in the 1:30-7:30 orientation and yellow in the 10:30-4:30 orientation, as shown in Figures 5 and 6.

The red compensator plate has its slow (high index) direction in the 1:30-7:30 orientation. So the blue color of the filament in this orientation indicates increased retardation to give a second order blue interference color. These observations with polarized light were the same as I had made of the organism causing the faint film on the water the previous December. The photographs with the red compensator were taken at a later time, after the water had dried from under the cover slip and the specimen was remounted with Canada balsam. These photomicrographs with the first order red compensator were taken using my second student microscope, a modified Lomo Biolam microscope shown in Figure 7, using the 90X oil immersion objective.

My mentor in microscopy is John Delly, author of Kodak's "Photography through the Microscope." He was very helpful in my attempts to identify the red film organism. He found this organism described as Oscillatoria rubescens De Candolle in G. W. Prescott, Algae of the Western Great Lakes Area . Prescott noted that the red film organism was found in hard water lakes of southern Michigan causing blooms in late winter just after melting of the ice. He noted differences with Oscillatoria rubescens, such as lack tapering ends on the filaments and "lack of capita apical cells."

The drawing of the red filament organism in Prescott's book resembles the filament organism from Fish Lake, which is also a hard water lake just South of the border with Michigan. I was fortunate to find a photomicrograph of Oscillatoria rubescens on the AYMA web site at http://personal.telefonica.terra.es/web/ayma/atlas.htm (Spanish). This reference image, shown in Figure 8, does not match the images I recorded of the red film causing filament organism from Fish Lake.

According to my friend John Delly, it has been known for 150 years that algae are commonly birefringent. It is unfortunate that polarized light microscopes are not used for microscopy of algae by modern researchers. Lacking such data to compare with my findings for the red film organism, I decided to use polarized light to examine the organisms associated with noxious green films that form occasionally on Fish Lake hoping to find the common Oscillatoria.

Figure 9 shows Oscillatoria from one of the green film events. I now usually use the modified Biolam shown in Figure 7 for transmitted light microscopy using a Nikon Coolpix 995 digital camera instead of film for photomicroscopy. (Further information on my use of digital imaging can be found by searching for my articles in the online journal Modern Microscopy.) This common Oscillatoria is birefringent between crossed polarizers, as shown in Figure 10.

Figure 11 shows this

organism between crossed polarizers with the first order red compensator. Figure 11, with the filament oriented in the 1:30-7:30 orientation, shows yellow instead of the blue for the red film organism in Figure 5. The molecular structures giving rise to the birefringence are evidently quite different between the two organisms.

I hope this article has demonstrated that it is possible to build an affordable, high performance student microscope for serious amateurs and high school science teachers. Further details, such as imaging the complete field in transmitted dark field or bright field with a draw tube mounted objective and metallographic imaging in reflected light, can be found by searching for my articles in the online magazine Micscape at www.microscopy-uk.net/mag/indexmag.html