Diversity and community structure of seagrass at Arrecife Island, Honda Bay, Palawan, Philippines

Abstract

This study assessed the seagrass communities of Arrecife Island, Honda Bay, Palawan, Philippines, focusing on species composition, percent cover, and the diversity and density of associated macroinvertebrates, particularly sea cucumbers. Sampling was done on April 14-15, 2018, at daytime and low tide, using a transect-quadrat method in the established sampling sites. Percent cover was categorized using the dominance classification scheme, and diversity indices were computed to assess community structure. A total of five seagrass species were recorded, namely, Cymodocea rotundata, Enhalus acoroides, Halodule uninervis, Syringodium isoetifolium, and Thalassia hemprichii, as well as notable macroinvertebrates such as Holothuria atra. The results indicated that T. hemprichii was the most dominant species, significantly contributing to overall percent cover (59.73 ± 9.30). However, the overall seagrass bed in the area is classified as “fair” (25.5–50.4%). Seven macroinvertebrate species were recorded, with Holothuria atra exhibiting the highest population density (167 ind./250 m²); diversity indices reflected moderate species diversity and evenness, with H. atra showing a dominant presence among sea cucumbers. These findings highlight the ecological significance of seagrass ecosystems in providing habitat and supporting biodiversity. However, ongoing threats like siltation, pollution, and tourism-related disturbances call for immediate conservation actions. Resort owners and employees are encouraged to participate in habitat protection actively. At the same time, periodic reassessments every five years are recommended to monitor ecological changes and guide conservation strategies. Such initiatives are critical for sustaining biodiversity, protecting ecosystem services, and promoting the well-being of local populations that rely on marine resources.