Screening and Isolation of Microalgae Collected from Tin Mining at Bangka Belitung Province with Remarks on Their UV-C Absorbance and Lead Remediation

Microalgae inhabit mining sites, performing specific adaptations to survive the stress conditions. This study aimed to investigate the effect of growth media on the microalgae isolated from water bodies at abandoned tin mining sites and analyse their sensitivity to ultraviolet-C (UV-C) spectrum and lead resistance. Samples from six locations were enriched in Bold Basal Medium (BBM) (pH 6.8) and Blue Green-11 (BG-11) (pH 7.4) media, and the grown cultures were kept in a cold room at a temperature of 21°C, provided with continuous light (1,600 lux). The UV-C sensitivity of the cultures was observed with spectrophotometry at λ=230 nm, followed by growth rate measurement. The isolate was subjected to lead concentrations of 0, 10, 100, and 200 ppm. The results showed that the diversity of the microalgae in the BBM was higher than in BG-11, with 7 and 3 species, respectively. Most microalgae grown in BBM were coccoid green algae, while diatoms and cyanobacteria were in BG-11. All cultures developed from enrichment step showed UV-C absorption, and the fastest growth was performed by Ulu River (UL) culture. Isolate coccoid green algae UL4 had sensitivity to the UV-C spectrum and survived high lead concentrations up to 200 ppm. This character, plus the capability to survive in high lead concentration, made UL4 a potential candidate for a bioremediation agent. Phylogenetic analysis based on the 18S rRNA gene showed that the strain UL4 is nested within the clade of Chlorococcum spp. It is of interest for future research to investigate the involvement of secondary metabolites as a mechanism for UL4 survival in stress conditions.