Morphometric, Physiological, and Environmental Health Assessments of <i>Enhalus acoroides</i> from the Southeast Coast of Bali, Indonesia

Seagrasses function as primary producers and as spawning grounds and shelter for marine biota. Regardless of their relevance, seagrasses are under threat due to anthropogenic impacts and an increasing frequency of extreme climate events. Enhalus acoroides is a species of seagrass that is spread in the east and southeast waters of Bali, from Sanur Beach to Nusa Dua Beach. This study aims to analyze the differences in morphometry and the chlorophyll, proline, and malondialdehyde (MDA) content, a marker for oxidative stress in E. acoroides leaves at Pengastian Beach, Semawang Beach, and Samuh Beach, Bali. Samples were collected using line transect method. Measurements were taken for morphometric traits. Chlorophyll extraction was performed with 80% acetone and measured using a spectrophotometer. Malondialdehyde extraction was done using trichloroacetic acid (TCA) and thiobarbituric acid reactive substances (TBAR) and measured using a spectrophotometer. Proline was extracted using ninhydrin reaction, and the concentration was determined using proline standard curve. The results show that E. acoroides at Semawang Beach had the longest length and largest width of leaves compared to seagrass at Samuh Beach and Pengastian Beach. Enhalus acoroides at Pengastian Beach had the smallest leaf length and width. Similarity analysis using the Gower index showed that E. acoroides at Semawang Beach grouped with E. acoroides at Samuh Beach. Enhalus acoroides leaves at Semawang Beach had the highest chlorophyll content. Malondialdehyde contents were similar between E. acoroides at the three locations while proline concentrations were found higher in E. acoroides at Samuh Beach. Variations in E. acoroides are primarily driven by differences in substrate composition. Semawang and Samuh Beaches are characterized by muddy sand, Pengastian Beach features a coarser rubble sand substrate.