Assessment of selected blue-green and green algae species as potential landscape ecological indicator agent for a sustainable environment

Abstract

Algae have long been recognized as valuable bioindicators in environmental assessments, yet rapid urbanization and increasing industrial activities have intensified the need for innovative ecological monitoring solutions. The escalating carbon emissions and toxic metal contamination in urban environments demand effective biological mitigation strategies. This study investigates the potential of selected algae species Chlorella vulgaris (green algae) and two cyanobacteria species, Phormidium sp. and Synechococcus sp. as ecological indicators for environmental stress and carbon sequestration. The algae were cultured in various media formulations (BBM, BG11, Bristol, Chu-10) under different pH levels (3.0, 5.0, 7.0, 9.0, and 11.0) and photoperiods (24:0, 16:8, 12:12, and 8:16). Growth performance, total chlorophyll content, chromaticity (lightness and chroma stability), and carbon sequestration efficiency were assessed using a UV-Vis spectrophotometer and CIELAB colorimeter, while biomass accumulation was measured by dry weight analysis. To evaluate phycoremediation potential, the algae were exposed to heavy metals (Cr, Cd, and Cu) at concentrations of 1 mg/L, 2 mg/L, and 3 mg/L over four weeks, with weekly spectrophotometric analysis. The results indicate that C. vulgaris achieved the highest absorbance value of 1.45 in BBM medium at pH 9, demonstrating superior growth and adaptability. In terms of carbon sequestration, C. vulgaris recorded a peak sequestration rate of 1.675 g/L CO₂e under BBM at pH 9 with a 16:8 photoperiod, while Synechococcus sp. achieved a higher sequestration rate of 2.006 g/L CO₂e under similar conditions. Phormidium sp. showed a moderate carbon sequestration rate of 1.149 g/L CO₂e in BG11 medium at pH 11. The bioconcentration factor (BCF) analysis revealed varying metal uptake capacities, with C. vulgaris demonstrating the highest affinity for Cu (BCF = 12.1) by week 2, while Synechococcus sp. exhibited significant Cr accumulation (BCF = 7.0) by week 3. These findings highlight the species-dependent efficiency of algae in carbon sequestration and phycoremediation, reinforcing their role as potential landscape ecological indicators in urban environments. The integration of C. vulgaris, Synechococcus and Phormidium into environmental management strategies can enhance carbon capture, improve water quality, and provide real-time ecological monitoring, ultimately contributing to climate mitigation and sustainable urban development. Keywords: Landscape Ecological Indicator, Phycoremediation, Carbon sequestration, Environmental monitoring, Mitigation and Sustainability