## 3 Results and Discussion
### Cell Density and Community Composition  
Results from the algal identification services provided by UF/IFAS showed that the most prominent families in the Lake Cochituate cyanoHAB included Bacillariophyta, Charophyta, Chlorophyta, Cryptophyta, Cyanobacteria, Dinophyta, and Euglenophyta. The family that dominated this cyanoHAB was Cyanobacteria. The 5 most prominent species were _Planktolnynybva_ cf. _Iimnetica_, _Raphidiopsis_ spp., _Planktolnyrix agardhi_, _Dolicospermum_ planconicum_, and _Aphanizomenon_ cf. _gracile_, combining for 94.3% of the community composition (60.9%, 17.9%, 10.4%, 2.8%, and 2.4%, respectively), on average throughout the regrowth period. Individual cells in each strand of filament were counted to make comparisons in cell density between filamentous and free-swimming cyanobacterial cells. In general, for total cyanobacteria present (16 species) in the samples, the CyanoS-TUN UV-C treatment suppressed growth for approximately two days, with pre-treatment samples showing a recovery of cell density around Day 1 or 2 of the regrowth period and post-treatment samples showing recovery around Day 4 (Figures 5 and 6). This trend appears to be independent of UV dose; however, the sample for Day 5 for the 45 mJ/cm\({}^{2}\) dose was cracked during shipment and could not be analyzed, so it is unclear whether the cyanobacteria population exposed to the highest treatment dose rebounded after Day 4 or remained suppressed. Additionally, the trend varied slightly at the genus level, with the 2-day suppression appearing most distinctly with _Planktolnybya_ cf. _Iimnetica_, which dominates the community (60.9%) in the samples and likely skews the results for total cyanobacteria. In Figure 5, the initial decrease in cell density in the early timepoints for both the front and rear samples may be attributable to the shock of collection, shipment, and introduction to a growth chamber, all within 24 h.  
Figure 5: Total cyanobacterial cell density (cells/mL) over a 5-day period post-field trial. The “Day 5 Rear (45 mJ/cm\({}^{2}\))” sample was compromised during transport to UF/IFAS and could not be analyzed. Reduction in total cyanobacteria cell density due to the Cyano-STUN UV-C treatment peaked around Day 4 (Figure 7), with the 30 mJ/cm\({}^{2}\) dose yielding the greatest difference (4.11 \(\times\) 10\({}^{5}\) cells/mL;73.9%) of the treatments, followed by the 15 mJ/cm\({}^{2}\) dose (2.90 \(\times\) 10\({}^{5}\) cells/mL; 57.0%), 45 mJ/cm\({}^{2}\) dose (1.72 \(\times\) 10\({}^{5}\) cells/mL; 48.0%) and control (1.70 \(\times\) 10\({}^{5}\) cells/mL; 3.3%). Figure 6: Average of total cyanobacterial cell density (cells/mL) in the front (pre-treatment) vs. the rear (post-treatment samples) over a 5-day period post-field trial (excluding control dose). Figure 7: Reduction in total cyanobacterial cell density due to treatment over a 5-day period post-field trial. The “Day 5 Rear (45 mJ/cm\({}^{2}\))” sample was compromised during transport to UF/IFAS and could not be analyzed. It should be noted that microcstin-producing species were relatively scarce (<15% composition), which explains the relatively low levels of microcstin detected (Figure 2). In addition to growth suppression, the CyanoSTUN UV-C treatment appeared to have some adverse effect on cellular integrity for specific cyanobacteria species. The UF/IFAS laboratory reported distortion of cells where post-treatment samples appeared to be more degraded; filaments on the _Aphanizomenon_, _Raphidiopsis_, and _Dolicospermum_ species showed the most pronounced distortion and fragmentation, whereas _Planktonrix_ showed the least. Non-cyanobacteria were very scarce, comprising only 0.26% of the community, on average. In general, this group of species shows slow but consistent growth in pre-treatment samples over the regrowth period, whereas post-treatment samples show a decline in cell density from Day 0 to Day 1 and then steady maintenance of the population (neither growth nor decline) through Day 5 (Figure 8).