An Environmental Study Of The Factors Contributing To The Control Of Arthrospira Spp. In East African Soda Lakes (Lake Bogoria, Kenya)

East Africa’s Central Rift Valley has the largest population of lesser flamingos (Phoeniconaias minor) in the world. The lesser flamingos diet consists almost entirely of Arthrospira spp. Occasionally, unexpected crashes in the Arthrospira density occur. The main aim of this study was to investigate whether cyanobacteriophages contribute to this, and if they can regulate Arthrospira spp. biomass in Lake Bogoria. Limnological studies of the lake showed that pH levels were stable, only changing 0.11 units over the study period. All other parameters were lower than previously reported. Conductivity was 41.7 mS cm-1 at the beginning of the study and 63.7 at the end. The total nitrogen concentration explains 14 % of the variance in Chl-a. The analysis of three Arthrospira morphotypes (S, C and H) revealed that the S-morphotype was dominant (47.67%) followed by the C-morphotype (40.65%) and H-morphotype (11.69%). Genetic analysis of these morphotypes found that they are the same Arthrospira species; most likely Arthrospira maxima. A severe collapse in the Arthrospira’s population was observed in July 2016 and this was accompanied by the presence of virus-like particles (VLPs) within Arthrospira samples that were examined following sectioning. There was a strong negative correlation between VLPs concertation and Chl-a content (rs = - 0.629). Cell lysis in the form of trichome fragmentation was only observed once, and occurred in the S-morphotype. The largest increase in VLPs concentration occurred within five days of incubation at an OD560 of ~0.3. Three incomplete prophages were detected; one was integrated into the H-morphotype and two into the S-morphotype genome. Metagenomic analysis revealed no known cyanophages in lake’s waters. The VLPs count using NanoSight was positively associated with their count using epifluorescence microscopy (rs = 0.728). Cyanophages could thus play a vital role in controlling the Arthrospira biomass in such extreme environments.