Free-living amoebae population in a caldera lake after a phreatomagmatic eruption

Volcanic eruptions are natural disasters that can change life and the ecosystem. Through molecular testing, this study identified the free-living amoebae (FLA) population in a caldera lake following a phreatomagmatic eruption in 2020 and compared it with pre-established data in 2016 in the same lake. Four sampling sites were identified using purposively sampling, namely: Laurel (T1), Agoncillo (T2), San Nicolas (T3), and Talisay (T4). Water samples were filtered, cultured on NNA lawned with Escherichia coli, and checked microscopically for 14 days. Twelve (12; 30 %) of 40 water samples yielded positive amoebic growth from the water samples. Site T4 had the highest growth. Polymerase chain reaction and sequencing confirmed the presence of Acanthamoeba T4 genotype in two isolates (PP741735 and PP741736). Volcanic eruptions can potentially disrupt the biodiversity of FLA and promote the proliferation of pathogenic forms. This poses health risks to tourists who frequent the area and, more importantly, residents residing along its shores. Local government involvement is necessary in cautioning residents, especially those who have returned from evacuation centers, about using the caldera waters, which is paramount to mitigating future cases.