Identification of Wild Seaweeds at Nipah Beach, Indonesia, and Study of their Antioxidant Potential

Background: The extracts from seaweeds are rich sources of phenolic acids, flavonoids, carotenoids, vitamins, sulphated polysaccharides, and phycobiliproteins, which confer antioxidant, anti-inflammatory, antimicrobial, and bioactive properties. Nipah Beach, Lombok (Indonesia) hosts biodiverse intertidal macroalgae whose functional traits remain under-documented. Objectives: This study aimed to identify prevalent taxa and quantify antioxidant capacity and pigments under in situ conditions. Methods: In May 2025, thalli of Padina australis, Sargassum crassifolium, Chondracanthus sp., and Halimeda opuntia were collected at three intertidal stations; methanolic extracts were assessed for DPPH radical scavenging (% inhibition at 517 nm), chlorophyll-a was derived from A664/A647, and R-phycoerythrin was read at 565 nm with 730 nm turbidity correction by UV–Vis spectrophotometry. Concurrent field measurements (temperature, salinity, pH, dissolved oxygen, illuminance; handheld meters) indicated stable conditions; total dissolved solids were recorded verbatim but not interpreted. Results: Results are descriptive (TEAC/IC50 not computed): Padina australis showed the highest %DPPH inhibition, chlorophyll-a peaked in Sargassum crassifolium, and Chondracanthus sp. exhibited the strongest R-phycoerythrin signal, consistent with lineage-specific pigment architecture. Elevated daytime dissolved oxygen likely reflects wave action and/or photosynthesis. Conclusion: These findings provide an integrated local baseline linking ecology to functional traits and nominate Padina australis as an antioxidant lead, Sargassum crassifolium for chlorophyll-a/fucoxanthin potential, and Chondracanthus sp. as a source of R-phycoerythrin. Priorities include seasonal replication, TEAC/IC50 and ABTS/FRAP/ORAC assays, continuous photosynthetically active radiation (PAR) logging, and strengthened taxonomy, with curated datasets and code planned for release in subsequent project updates.