Abundance of macrozoobenthos in seagrass beds in the waters of Tihi-Tihi Village, Bontang City, East Kalimantan

Abstract

Macrozoobenthos are benthic organisms larger than 1.0 mm that live on or within the seabed by crawling, burrowing, attaching, or embedding themselves in the substrate. This study investigated macrozoobenthos abundance and community characteristics in seagrass beds in the waters of Tihi-Tihi Village, Bontang City, East Kalimantan, from November 2024 to January 2025. Sampling was conducted at four stations using 50 × 50 cm quadrats and purposive sampling along transects extending from the lowest tidal level toward the subtidal zone. The analysis included species composition, abundance, Shannon–Wiener diversity, evenness, Simpson dominance, seagrass density, and the relationship between seagrass density and macrozoobenthos abundance. Thirty macrozoobenthos species belonging to five classes (Asteroidea, Bivalvia, Echinoidea, Gastropoda, and Holothuroidea) were recorded. Four seagrass species were identified: Enhalus acoroides, Thalassia hemprichii, Halophila ovalis, and Cymodocea rotundata. Strombus urceus was the most abundant species, with reported values of 228–280 individuals m⁻² across the stations, whereas Cypraea (Erronea) ovum palauensis and Angaria delphinus had the lowest reported abundance, at 4 individuals m⁻² each. Total macrozoobenthos abundance was highest at the southern station (892 individuals m⁻²) and lowest at the northern station (648 individuals m⁻²). The diversity index ranged from 2.132 to 2.231, indicating moderate diversity, while mean evenness was 0.646 and mean dominance was 0.176, indicating moderate evenness and low dominance. Seagrass density showed a very strong positive correlation with macrozoobenthos abundance (r = 0.97).