Assessment of heavy metals and environmental stress conditions on the production potential of polyunsaturated fatty acids (PUFAs) in indigenous microalgae isolated from the Gulf of Mannar coastal waters

• Published in: Environmental monitoring and assessment 2024-03, Vol.196 (3), p.301, Article 301
• Main Authors: Kadam, Rishikesh Venkatrao, Rani, V., Padmavathy, P., Shalini, R., Selvi, M. J. Thamarai, Narsale, Swapnil Ananda
• Format: Article
• Language: English
• Subjects: Algae; Aquatic microorganisms; Atmospheric Protection/Air Quality Control/Air Pollution; Cadmium; Cadmium - toxicity; Carotenoids; Chlorella; Chlorophyll; Chlorophyll A; Coastal waters; Earth and Environmental Science; Ecology; Ecotoxicology; Environment; Environmental conditions; Environmental Management; Environmental Monitoring; Environmental stress; Exposure; Fatty acids; Heavy metals; Lead; Mercury; Mercury (metal); Mercury - toxicity; Metals, Heavy - analysis; Metals, Heavy - toxicity; Microalgae; Monitoring/Environmental Analysis; Phytoplankton; Polyunsaturated fatty acids; Toxicity
• ISSN: 0167-6369; 1573-2959
• DOI: 10.1007/s10661-024-12447-y

The present study evaluated the effects of heavy metals, viz., lead, mercury, and cadmium, on growth, chlorophyll a, b, c, carotenoids, and PUFA content of marine microalgae Chlorella sp. and Cylindrotheca fusiformis . At 96-h exposure, the IC 50 values for Hg 2+ , Pb 2+ , and Cd 2+ were 0.85 mg/L, 2.4 mg/L, and 5.3 mg/L respectively, in Chlorella sp. In C. fusiformis , IC 50 values for Hg 2+ , Pb 2+ , and Cd 2+ were 0.5 mg/L, 1.2 mg/L, and 3 mg/L respectively. The pigment contents of both microalgae were significantly affected upon heavy metal exposure. In Chlorella sp. and C. fusiformis , the exposed concentrations of Hg 2+ averagely decreased the PUFA content by 76.34% and 78.68%, respectively. Similarly, Pb 2+ -exposed concentrations resulted in 54.50% and 82.64% average reductions in PUFA content of Chlorella sp. and C. fusiformis , respectively. Cd 2+ -exposed concentrations showed 32.58% and 40.54% average reduction in PUFA content of Chlorella sp. and C. fusiformis , respectively. Among the environmental stress conditions, the dark treatment has increased total PUFA content by 6.63% in Chlorella sp. and 3.92% in C. fusiformis. It was observed that the 50% nitrogen starvation (two-stage) significantly improved the PUFA production from 26.47 ± 6.55% to 40.92 ± 10.74% in Chlorella sp. and from 11.23 ± 5.01 to 32.8 ± 14.17% in C. fusiformis . The toxicity for both microalgae was followed in the order Hg 2+  > Pb 2+  > Cd 2+ . Among the two species, Chlorella sp. has shown a high tolerance to heavy metals and can be effectively utilized in PUFA production.