Eco-hydromorphic Classification for Understanding Stream Macroinvertebrate Biodiversity in Brunei Darussalam, Northern Borneo

Abstract

Linking ecology with river geomorphology and hydrology (geomorphic and hydraulic template) plays an important role in the study of macroinvertebrate biodiversity. This understanding and knowledge is crucial in implementing sensible conservation management for ecosystem health monitoring. However, most macroinvertebrate research has been conducted in temperate ecosystems. This study examines the eco-hydrogeomorphology and macroinvertebrate biodiversity of two remote tropical streams in northern Borneo (Bukit Pagon catchment, Brunei Darussalam’s highest mountain - 1850 m) using temperate classification models, more specifically, biotopes. Fast flowing biotopes were defined as bedrock runs and cobble riffles whilst the slow flowing biotopes were deposition pools. Macroinvertebrate size structure associated with biotopes, which can influence overall ecological processes, was also investigated. Forty-three macroinvertebrate taxa were recorded during the study; biodiversity was similar between the study streams. There were differences among biotopes with the lowest diversity occurring in fast flowing biotopes (p = 0.05*). Community structure also varied among the biotopes. Cluster analysis of macroinvertebrate abundance revealed an 0.8 dissimilarity between the fast and slow biotopes. Several taxa were found in multiple biotopes, which is likely linked to the occurrence of moss and leaf litter. Macroinvertebrate size structure distribution between the fast and slow biotopes was statistically different. Our findings suggest biotopes may be an appropriate scale to investigate macroinvertebrate biodiversity in tropical streams. Specifically, we found that biotopes had different macroinvertebrate communities and richness. Further research is required to understand the importance of habitat parameters that are not directly related to flow velocities such as moss. These habitats are important as places of refuge, allowing colonisation that would otherwise be inhospitable during flood periods.