Algae in Northwest Arkansas

Tailrace of Beaver Lake: Site of Massive Didymosphenia geminata Growths

In early spring of 2003 a massive bloom of Didymosphenia geminata developed in the tailrace area below Beaver Dam.  Trout fisherman had difficult times wading in the area due to the extensive growth that covered rocks and entire stretches of the area, according to local fisherman.  Samples were taken after the large growth was over and still were found remnants of the population.  The growths resembled bryozoan growth, but microscopic analysis showed that the organism is Didymosphenia geminata.  This organism was tentatively misidentified as Gomphonema sp.   In February of 2006 growth of Didymosphenia was observed at the same site and at others.

The bulk of the colony was a cottony white color and texture, while the surface of the colony had a distinctive golden brown color.  Living in the matrix were a variety of invertebrates including scuds (amphipods) and sow bugs (isopods).  Midge larvae were also present.  Since this "bloom" is somewhat unusual, a series of thumbnail images are presented in this note (Table 1).  Larger images can be obtained by clicking on the image. 

Individual cells of Didymosphenia measured 106 microns in valve length and 30 microns at the widest part of the valve.  The thickness at the anterior girdle was 30 microns and 15 microns at the posterior girdle.  There were 3-5 stigmata in the central area. Striae were punctate and were 10 per 10 microns.  Similar growths of Didymosphenia have been reported from Canadian streams (Resource: )

A presentation was made to the Springdale Chapter of Trout Unlimited about Didymosphenia, entitlted "Algae and Trout: Beauty and the Beast"

Several other collections in the same area of the tailrace waters included a variety of algae (Table 2).  Rock scrapings in the same region revealed microscopic colonies of the same Didymosphenia suggesting possible sources for the macro growth that occurred earlier in the spring of 2003 (Table 3).

An experiment of colonizing rate on new surfaces has been started in March, 2006.  Photos of the blocks will be placed in tables for analyses.

Dissection of a Gammarus from the March 28, 2006 collection was completed.  Images of the contents are in Table 7.

Table 1.  Images of macro-colonies of Didymosphenia at both visual and microscopic levels.

Russ Rhodes with a macro-colony of Didymosphenia The same specimen with a 10 centimeter ruler beside it. The same specimen immersed in water with a 10 centimeter ruler beside it.
Microscopic view of Didymosphenia cells attached to stalks (100x) Microscopic view of cells after division and remaining on bifurcating stalks (200x) Individual cell on a stalk (400x)
Valve view of Didymosphenia  (400x) Girdle view of Didymosphenia (400x) Valve view of frustule showing punctate striae and 3 isolated punctae in central region (400x)

Table 2.  Other algae found in samples taken on May 29, 2003 from the tailrace portion below Beaver Dam.

Calothrix (200x) Cladophora (200x) Oscillatoria (200x)
Cocconeis sp.  on Cladophora sp. (400x) Cocconeis sp. (200x) Ulothrix spp.(200x)


Table 3.  Algae from rock scrapings collected May 29, 2003 in tailrace below Beaver Dam.

Diatoma sp. (400x) Microscopic colony of Didymosphenia.(40x) Stephanodiscus sp. (400x)

On another collection date, February 24, 2006, more colonies of Didymosphenia were found at several locations in the tailrace of the White River, Arkansas.  Parker Bend, Station 2, had rocks coated with pingpong sized colonies of Didymosphenia.  Table 4 includes some appearances of colonies.  Bob Britzke and Dick Starr are seen preparing to collect samples and collecting scuds.  Scud intestines were removed, looked at under the microscope, and prepared for diatom identification using the incineration method.

Table 5 includes some algae that were a part of the epilithic flora.  Other algae in the flora included Closterium, Diatoma, Oedogonium, Melosira, Audouniella, Synedra, Stephanodiscus, Didymosphenia, and Navicula.

Table 6 includes some algae that were found in the gut contents of Gammarus, a scud.  These algae were also represented in the flora attached to rocks or epiphytic on other algae. 

Table 4.  Additional collection sites of Didymosphenia in Februrary 24, 2006

Bob Britzke and Dick Starr at Station 1, White River, Arkansas Growth of Didymosphenia at base of rock Colony of Didymosphenia at Station 1, White River, Arkansas Bob Britzke and Dick Starr collecting scud for diet analysis at Station 2, White River Arkansas

Table 5.  Didymosphenia and some associated algae at Station 2, White River, Arkansas collected on February 24, 2006

Didymosphenia cells attached to stalks Didymosphenia cells, large and small Eunotia, cells and stalks epiphytic on stalk of Didymosphenia Audouinella filament. This is a red alga (Rhodophyceae) and found in cold streams.

Table 6.  Gut contents of Gammarus.  The algal cells below were also found on the rock at Station 2, Parker Bend, White River, Arkansas.

Cymbella and Stephanodiscus Diatoma and Eunotia Didymosphenia Audouniella filament
Melosira Oedogonium and Cymbella Forked stalk of Didymosphenia Stalk of Didymosphenia


Table 7.  Gut contents of Gammarus (18 mm) collected on March 28, 2006
Gammarus Sow bug Gammarus bolus under 10.5 dissecting scope conifer pollen 20x
Cymbella 40x Didymosphenia fragment 10x Didymosphenia fragment 20x Didymosphenia fragment 40x
Didymosphenia stalks 10x Eunotia with stalk


Fragilaria 40x millimeter rule under 10.5 dissecting
Mougeotia 20x Oedogonium with apical rings 20x Synedra 40x  

This page is for view only.  Any use of these photos requires the approval of Russell G. Rhodes, Department of Biology, Southwest Missouri State University