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Figure 1: Lake Magadi, Kenya MapFalse-color Landsat image (bands 7, 4, 2 as RGB) showing sample collection sites. The water in the lake evaporates during the dry season to expose the underlying trona beds (hydrated sodium carbonatebicarbonate; Na3(CO3)(HCO3)•2H2O) shown as bright blue. Water exists as damp ground and lagoons in areas fed directly by hot springs (black). Most samples (A1 through A6) were collected from the southern hot springs area, while sample A7 is from a pond on the eastern shore of Lake Magadi. The inset map shows the location of Lake Magadi within Kenya, with Nairobi and the equator marked for reference. Satellite image of Lake Magadi: http://www.flashearth.com/?lat=-1.944676&lon=36.252237&z=11.5&r=0&src=msa

Figure 2: Oscillatoria-Encrusted Fractures. Lake Magadi, Kenya (A1: 2° 00.122' S, 36° 13.858' E) (Labeled view) (Labeled view)

Figure 3: Micrograph (1,000x) of Encrusted Fractures Showing a Diatom, Oscillatoria, and Pseudanabaena. Lake Magadi, Kenya (A1)Shown are a diatom (unidentified, infrequent in sample), Oscillatoria (a known mat former) which forms the bulk of the sample, and possible Pseudanabaena above the diatom. At lower magnifications, the Oscillatoria trichomes appear as hairy green masses that are sometimes observed to be attached to rock and mineral fragments.

Figure 4: Micrograph (1,000x) of Encrusted Fractures Showing a Diatom, Oscillatoria, and Pseudanabaena. Lake Magadi, Kenya (A1) (Labeled view) (Labeled view)

Figure 5: Synechocystis or Microcystis Biofilm. Lake Magadi, Kenya (A2: 2° 00.183’ S, 36° 13.875’ E)Mucilaginous, bubble-trapping film observed floating on the water’s surface near a hot spring vent. Measured water parameters: 42.8°C, 10.2 pH, 7500 ppm Na+, 86 ppm K+.

Figure 6: Synechocystis or Microcystis Biofilm. Lake Magadi, Kenya (A2: 2 ° 00.183’ S, 36 ° 13.875’ E) (Labeled view) (Labeled view)

Figure 7: Micrograph (640x) of Biofilm Showing Diatom and Synechocystis or Microcystis. Lake Magadi, Kenya (A2)Sample from site A2. Shown are a diatom (unidentified, infrequent in sample) and possible Synechocystis or Microcystis cells that form the bulk of the sample.

Figure 8: Micrograph (640x) of Biofilm Showing Diatom and Synechocystis or Microcystis. Lake Magadi, Kenya (A2) (Labeled view) (Labeled view)

Figure 9: Micrograph (1,000x) Showing Leptolyngbya from a Magenta-Colored Mat. Lake Magadi, Kenya (A3)Sample collected from a magenta-colored mat located near a small hot spring vent at site A3 (not shown). The filamentous organisms shown represent the bulk of this sample and are believed to be Leptolyngbya, which is a mat-forming genus typified by narrow cell width. Synechocystis or Microcystis cells were also prominent in this sample and may be from a green mat found in close proximity. Collected near sites A1 and A2. Measured water parameters: 41.8°C, 10.3 pH, 7500 ppm Na+, 86 ppm K+.

Figure 10: Micrograph (1,000x) Showing Leptolyngbya from a Magenta-Colored Mat. Lake Magadi, Kenya (A3) (Labeled view) (Labeled view)

Figure 11: Synechococcus Mats Encrusting Rocks. Lake Magadi, Kenya (A4)Sample collected from rocks encrusted with purple-colored mats seen near the bottom center of the image. Collected near sites A1 and A2. Measured water parameters: 43.4°C, 10.3 pH, 7500 ppm Na+, 82 ppm K+.

Figure 12: Synechococcus Mats Encrusting Rocks. Lake Magadi, Kenya (A4) (Labeled view) (Labeled view)

Figure 13: Micrograph (1,600x) Showing Synechococcus. Lake Magadi, Kenya (A4) (Labeled view) (Labeled view)

Figure 14: Micrograph (1,600x) Showing Synechococcus. Lake Magadi, Kenya (A4) Organisms from the purple mats at site A4 showing nonfilamentous, unicellular, red ovoid cells that are common in this sample. Possible Synechococcus.

Figure 15: Micrograph (1,000x) Showing Spirulina. Lake Magadi, Kenya (A4)Tight, helically-coiled, Spirulina trichomes, which are also prominent in the sample from site A4. For comparison, contrast with the loosely-spiraled Arthrospira from site A7.

Figure 16: Micrograph (1,000x) Showing Spirulina. Lake Magadi, Kenya (A4) (Labeled view) (Labeled view)

Figure 17: Micrograph (1,600x) Showing Leptolyngbya. Lake Magadi, Kenya (A5)Sample collected from greenish-brown, fibrous, unmineralized (but gritty) microbial columns found in the hottest water sampled at the southern end of the lake (site not shown as columns were difficult to photograph). Structures were located in calm, shallow (<12 cm) water away from active hot spring vents. Micrograph shows translucent segmented trichomes, possibly Leptolyngbya, that comprise the bulk of the sample. Inorganic grit created slide mounting and imaging difficulties as a cover slip could not sit flat on the slide. Collected near sites A1 and A2. Measured water parameters: 44.4°C, 10.2 pH, 7900 ppm Na+, 90 ppm K+.

Figure 18: Micrograph (1,600x) Showing Leptolyngbya. Lake Magadi, Kenya (A5) (Labeled view) (Labeled view)

Figure 19: Oscillatoria-Encrusted Fractures. Lake Magadi, Kenya (A1: 2° 00.122’ S, 36° 13.858’ E)Ridges about 1-inch high and shallowly submerged in the hot springs area at the southern end of the lake. Located away from the vigorous spring vents (those with visible flow), these are likely fractures through which hot spring waters slowly seep. The overall color of the microbial growth around the ridges was green-brown. Measured water parameters: 41.5°C, 10.2 pH, 7900 ppm Na+, 98 ppm K+.

Figure 20: Red Pleurocapsa Mats. Lake Magadi, Kenya (A6: 2° 00.233’ S, 36° 14.010’ E)Image shows the red mat-forming growths often seen at springs with very weak flow (seeps). Often aerially exposed and located where the ground is just barely damp, there are no other macroscale microbial structures nearby, suggesting a lack of competition. The likely harsh environment due to exposure is visualized by the salt crusts seen at the edges of the image. Measured water parameters: 34.6°C, 10.4 pH, 8250 ppm Na+, 100 ppm K+.

Figure 21: Red Pleurocapsa Mats. Lake Magadi, Kenya (A6: 2° 00.233’ S, 36° 14.010’ E) (Labeled view)

Figure 22: Micrograph (1,000x) Showing Pleurocapsa with Baeocytes. Lake Magadi, Kenya (A6)Micrographs of the red mat at site A6 showing a small group of unconstrained cells (A) and the more typical seen-in-sample packed cell pattern (B, lower half). Baeocytes inside enlarged parent cells can also be seen (B). A larger number of baeocytes per parent cell indicates a Pleurocapsa identification rather than Myxosarcina. Note that the cells in these images are not the same color as the macroscopic form seen at site A6. The nongreen pigments may have deteriorated between collection and examination.

Figure 23: Micrograph (1,000x) Showing Pleurocapsa with Baeocytes. Lake Magadi, Kenya (A6) (Labeled view)

Figure 24: Green Arthrospira “Pond Scum.” Lake Magadi, Kenya (A7: 1° 53.482’ S , 36° 18.149’ E)Floating green masses on the surface of one of the deeper ponds on the east boundary of Lake Magadi, located near the salt concentration pools maintained by the Magadi Soda Company. Depth, physically larger Tilapia specimens, and abundant water fowl suggested fresher water than other sites, however, while lower in sodium, this is the most basic and potassic site sampled. Measured water parameters: temperature not measured, ~11 pH, 5100 ppm Na+, 315 ppm K+.

Figure 25: Green Arthrospira "Pond Scum." Lake Magadi, Kenya (A7: 1° 53.482’ S , 36° 18.149’ E) (Labeled view)

Figure 26: Micrograph (250x) Showing Arthrospira. Lake Magadi, Kenya (A7)Image showing loosely spiraled Arthrospira trichomes from site A7. Trichomes show faint cross walls and sections of empty sheaths. Note that Arthrospira species are often referred to as Spirulina on commercial websites and in culture collections. Anabaena and/or Anabaenopsis were also seen in this sample but tended to form coiled, densely pigmented masses that did not image well. Color tone differences from other images in this collection are due to imaging with a petrographic microscope.

Figure 27: Micrograph (250x) Showing Arthrospira. Lake Magadi, Kenya (A7) (Labeled view)