Community Structure of Benthic Macroinvertebrates in Jose Abad Santos, Davao Occidental, Philippines

Abstract

Macroinvertebrates play a vital role in energy transfer and nutrient cycling in marine ecosystems and serve as important sources of food and livelihood for coastal communities. However, these critical resources are currently under threat due to uncontrolled harvesting and habitat degradation. This study aimed to provide valuable information on the community structure of benthic macroinvertebrates within the marine protected area (MPA) of Butulan and the open-access area of Balangonan in Jose Abad Santos, Davao Occidental. Sampling was conducted using the belt transect method. A total of 749 individuals, representing 27 species were recorded across the two sites, with gastropods comprising the majority of species. The mean (± SE) population density was significantly higher in Butulan, at 3,540 ± 701.52 ind ha^-1, compared to 1,560 ± 246.36 ind ha^-1 in Balangonan (t = 3.25, P = 0.02). Diversity index results indicated significantly higher species diversity in Butulan (H' = 3.04, H_max = 3.30) than in Balangonan (H' = 2.45, H_max = 2.64) (t = 4.65, P = 0.001), with species evenly distributed and no single species dominating both sites. The higher density and diversity of benthic macroinvertebrates in Butulan may be attributed to the strict protection of the MPA by the local government. In contrast, unregulated collection in the open-access area of Balangonan likely contributed to its lower diversity and density. Regulatory measures such as catch limits, size quotas, restrictions on harvesting juveniles and gravid individuals, and stock enhancement should be implemented to ensure the sustainable use of this important resource.