Diversity and distribution of seagrasses in Chilika Lagoon: Regional threats and management recommendations

Abstract

Studies examining the spatial distribution and abundance of seagrasses are limited in the Indian coastal lagoons. Chilika (Odisha) is the largest brackish water lagoon in Asia which supports the second-largest seagrass meadows in India. A field survey was conducted from 20 locations (n = 57 sites) across the southern, central, and outer channel sectors of the lagoon. A total of six species: Halophila ovalis, H. ovata, H. beccarii, Halodule pinifolia, H. uninervis, and Ruppia maritima were recorded during the study. Halophila ovalis (31 sites) and H. pinifolia (33 sites) showed wide occurrences in the lagoon. In the southern sector, 46 % of sampled sites demonstrated dense seagrasses (> 70 % cover) with all six species present. In the central sector, 45 % of sites showed medium dense seagrass cover (40 – 70 %) and 4 species were recorded. In the outer channel, 94 % of sampled sites supported dense seagrasses represented by 3 species. Seagrass cover showed a significant positive correlation with salinity (r = 0.489, p-value < 0.01) and plant biomass (r = 0.445, p-value < 0.01). The meadows in the southern and central sectors showed profuse growth of Stuckenia pectinata, Najas indica, Gracilariopsis longissima, and Chaetomorpha with seagrasses. Based on DAPSIR (Drivers-Activities-Pressure-State-Impact-Responses) framework, anthropogenic threats to seagrasses included fishing gears, unsustainable fishing methods, including aquaculture, and boat operations. The framework suggested that management responses must include restrictions on fishing gears, illegal aquaculture, and stricter surveillance on boat traffic and water quality. Besides, promoting ecotourism, framing policy actions, stakeholder awareness and community participation were also recognised as crucial responses for effective conservation and protection of seagrasses.