Macrophyte Diversity and Distribution in Brackish Coastal Lagoons: A Field Survey from Chilika, Odisha

Abstract

AbstractMacrophytes are one of the major components that contribute to the primary production in shallow coastal lagoons. These macroscopic plants play a vital role in maintaining the ecological health of water bodies and also in structuring the biotic communities by providing physical structure for colonization and expanding the habitat complexity and heterogeneity. Chilika, the largest brackish water coastal lagoon of India, is situated on the east coast in the state of Odisha. The lagoon is a biodiversity hotspot with high primary productivity due to a rich and diverse community of aquatic macrophytes and phytoplankton. The present chapter summarized the macrophyte studies from coastal lagoons of India and examined the spatiotemporal distribution, composition, and biomass of macrophytes from Chilika Lagoon based on the data derived from 2 years (2018–2019) of systematic field survey. A total of 22 macrophytes belonging to 14 families were identified from 33 sites which included 4 emergent species (Alternanthera philoxeroides, Ipomoea aquatica, Phragmites karka, and Schoenoplectus litoralis), 11 submerged (Ceratophyllum demersum, Najas indica, Stuckenia pectinata, Potamogeton crispus, Potamogeton nodosus, Hydrilla verticillata, Vallisneria natans, Halophila beccarii, Halophila ovalis, Halodule pinifolia, and Ruppia maritima), 2 rooted with the floating leaves (Nymphaea pubescens and Nymphoides cristata), and 5 free-floating (Azolla pinnata, Eichhornia crassipes, Pistia stratiotes, Salvinia cucullata, and Spirodela polyrhiza). Stuckenia pectinata and Najas indica were found in all sectors except the outer channel. A total of 11 macroalgal taxa comprising 6 species of Chlorophyta and 5 species of Rhodophyta were identified. Gracilaria verrucosa was often associated with seagrasses, whereas Chaetomorpha sp. and Ulva sp. were found growing with hard substratum such as rocks, etc., in the southern and central sectors. The seasonality in total macrophyte biomass revealed that it was the highest in winter (4322.38 g m−2) followed by summer (3056.18 g m−2) and monsoon (1957.14 g m−2). Salicornia brachiata, Sesuvium portulacastrum, and Paspalum distichum were abundant salt marshes in the Nalabana Bird Sanctuary of the lagoon. The occurrence of six seagrasses, namely, Halophila ovata, Halophila ovalis, Halophila beccarii, Halodule pinifolia, Halodule uninervis, and Ruppia maritima, was recorded from southern, central, and outer channel sector. A total of 169.2 km2 area covered by seagrass meadows was mapped through ground survey, which signified the good ecological health of this coastal ecosystem.KeywordsAquatic macrophytesMacroalgaeSeagrassesSalt marshBiomassChilika Lagoon