First Record of the Seagrass Halophila ovalis and Enhalus acoroides in the Coastal shallow Waters of Kowtharimunai, Poonakary, Sri Lanka: A Preliminary Ecological Assessment

Abstract

Coastal shallow-water ecosystems are renowned for their biodiversity; comprise of diverse faunal and floral components and are of greater ecological significance. This study confirms the first record of the seagrass Halophila ovalis of Family Hydrocharitaceae, in the coastal shallow ecosystem of Kowtharimunai, Poonakary, Northern Province of Sri Lanka. The observation was made during an opportunistic initial discovery, followed by targeted surveys to locate additional patches in the study area. Six field surveys were undertaken periodically from November 2024 to January 2026, alternatively covering the lunar cycles. Species identification was done based on key morphological characteristics including, absence of leaf hairs, paired leaf blades (mean length: 2.3 cm) without serration on tip, attached to the thin rhizome, and distinct reddening along the midrib. H. ovalis was co-occurring with Enhalus acoroides which belongs to same family, in the patches not exceeding a 2m2 in the study area. Preliminary ecological assessment revealed a high coverage of filamentous green algal epiphytes on H. ovalis compared to E. acoroides, and a higher abundance of epifaunal snails on the lower leaf surfaces of both species. The presence of H. ovalis extends its distribution along the Sri Lankan coastal line and establishes a new baseline for the seagrass flora of the Poonakary region. The observed high epiphyte load suggests the influence of environmental conditions/ disturbances and open the scope for further studies. This discovery indicates, the potential for future studies on detailed mapping and the ecology of seagrass meadows in the study area.