Development of multivariate health index for tropical seagrass meadows: a case study from Pulicat Lagoon, India

Seagrasses are critical coastal ecosystems that provide multiple ecosystem services but are increasingly threatened worldwide. Effective monitoring is essential for detecting habitat change and supporting conservation efforts. Although multi-metric indices offer holistic ecosystem assessment, such tools remain limited for tropical multispecies seagrass meadows. This study developed a Seagrass Health Index (SHI) to assess seagrass health in Pulicat Lagoon. From 37 initial variables, 12 key indicators were selected and grouped into six sub-indices: ecosystem structure, soil characteristics, sediment heavy metals, sediment nutrients, water nutrients, and water quality. The SHI was validated through sensitivity analysis, internal consistency testing, and correlation with seagrass cover. Results indicated overall excellent seagrass health in the lagoon (SHI = 2.04), with the north zone classified as excellent (SHI = 2.69) and the south zone as good (SHI = 0.58). The study demonstrates the value of field-based ecological assessments for dynamic coastal systems and provides a baseline framework that could be adaptable for other tropical seagrass ecosystems following further validation across diverse environmental settings.