Abstract
Halophila beccarii, listed as ‘Vulnerable’ on the IUCN Red List, aids in seagrass and mangrove succession, acts as a substrate stabilizer and provides feeding grounds for mega-herbivores like dugongs. This species was first recorded from the Andaman & Nicobar Islands in 2015, and its distribution status within the archipelago remains under-investigated. We report a new distribution record of H. beccarii from the North Andamans and shed light on its inter-island distribution. H. beccarii was recorded from a mixed meadow comprising of Cymodocea rotundata (20.5 ± 28.8%, mean seagrass cover), Thalassia hemprichii (16.3 ± 23.3%, mean seagrass cover), and Halodule pinifolia (6.3 ± 12.1%, mean seagrass cover) at Pokkadera, North and Middle Andaman district. H. beccarii had the highest mean seagrass cover (30 ± 34.7%) and shoot density (103.5 ± 68.3 shoots/ m2) among sympatric seagrass species. We also recorded eight seagrass-associated macrofaunal groups (gastropods, bivalves, polychaetes, foraminiferans, nematodes, brachyurans, decapods and asteroids) from the infaunal and epibenthic micro-habitats within the meadow. Infaunal macrobenthos had a much higher density (73.5 ± 129.7 individuals/m2) than the epibenthic macrofauna (0.4 ± 1.5 individuals/m2), possibly influenced by the seagrass canopy structure and biomass. Overall, gastropods were the most dominant macrobenthic faunal group (overall mean 95.0 ± 106.1 individuals/m2). The present findings emphasize the need for more exploratory surveys to understand H. beccarii distribution in the Andaman & Nicobar archipelago to identify priority conservation areas.
Highlights
Seagrasses are ecosystem engineers (Hoegh-Guldberg & Bruno 2010) that stabilize sediments (Ondiviela et al 2014), modify habitats they colonize (Koch 2001) and contribute to coastal protection (Ondiviela et al 2014)
New distribution record of globally threatened Ocean Turf Grass Halophila beccarii Ascherson, 1871 from the North Andaman Islands highlights the importance of seagrass exploratory surveys
We report a new distribution site for Halophila beccarii in the Andaman Islands and update its current distribution status for the Andaman group
Summary
Seagrasses are ecosystem engineers (Hoegh-Guldberg & Bruno 2010) that stabilize sediments (Ondiviela et al 2014), modify habitats they colonize (Koch 2001) and contribute to coastal protection (Ondiviela et al 2014). In India, seagrasses are distributed along the coastlines of Gujarat, Maharashtra, Karnataka, Kerala, Tamil Nadu, and Odisha states, and the Lakshadweep and Andaman & Nicobar archipelagos (Thangaradjou et al 2018). These ecologically valuable and fragile coastal habitats are threatened in Indian waters by high anthropogenic dependency, destructive practices like boat anchorage, extractive fishing, and nutrient enrichment through agricultural run-offs or domestic sewage disposal (Thangaradjou et al 2008; Sridhar et al 2010; Nobi & Thangaradjou 2012). Pan-Island seagrass exploratory surveys by Das (1996) reported Cymodocea serrulata and Halodule pinifolia, followed by a two decadal gap in investigating species distribution status in ANI. Pokkadera is an ecologically diverse site, which supports critical coastal ecosystems like seagrass meadows, mangroves, sandy, and rocky intertidal habitats, along with tropical littoral vegetation
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