Document Type

Technical Report

Publication Date

6-1-1989

Keywords

Algae, bioindicators, data analysis, water quality standards

Abstract

A data base of the algae of Arkansas ecoregions has been established to describe the numerous taxa that occur within the aquatic ecosystems included in these regions. The organisms were identified with the aid of diverse literature from throughout the world. These sources are written in multiple languages and the living organisms had to be compared with outline or silhouette drawings. These illustrations may include shading, but none present the true color of the organism but only the characteristics of the descriptive source. Primary characteristics used to identify algae is based upon pigmentation of the plastid and the number and position of the flagella as well as gross morphology. The focus of this research project was to develop a photographic system which would permit the recording of living organisms with various forms of microscopy with correct color and with arrested flagellar movement. These parameters dictated the use of an electronic flash source with metering and control system after the light has passed through the microscope. Most commercially available systems use preset flash intensities and/or durations. These systems require the use of neutral density filters or other adaptions to attain specified magnifications-illumination method- flash settings. The system for this project uses off-the-shelf components with a modified flashtube holder which positions the tube in the axis of the light beam between the field and iris diaphrams. The light is measured off-the-film so that the combined light from the microscope and flash are included. The flash is quenched and shutter closed based upon the combined reading. This system permits the operator to change magnification and/or illumination technique (brightfield, phase-contrast or Nomarski) without adjusting the flash or camera setting.

Report Number

PUB143

Page

12

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