Benthic community structure and ecosystem functions in above- and below-waterfall pools in Borneo

Kate Baker,Rodzay A Wahab,Michael A Chadwick,Rafhiah Kahar

doi:10.1007/s10750-016-2975-4

Kate Baker, Rodzay A Wahab + Show 2 more

Open Access

https://doi.org/10.1007/s10750-016-2975-4

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Journal: Hydrobiologia	Publication Date: Sep 23, 2016
Citations: 15	License type: open-access

Affiliation: Universiti Brunei Darussalam, King's College London

Abstract

Waterfalls are geomorphic features that often partition streams into discrete zones. Our study examined aquatic communities, litter decomposition and periphyton growth rates for above- and below-waterfall pools in Ulu Temburong National Park, Brunei. We observed higher fish densities in below-waterfall pools (0.24 fish m−2 vs. 0.02 fish m−2 in above-waterfall pools) and higher shrimp abundance in above-waterfall pools (eight shrimp/pool vs. less than one shrimp/pool in below-waterfall pools). However, macroinvertebrate densities (excluding shrimp) were similar among both pool types. Ambient periphyton was higher in below-waterfall pools in 2013 (4.3 vs. 2.8 g m−2 in above-waterfall pools) and 2014 (4.8 vs. 3.4 g m−2 in above-waterfall pools), while periphyton growth rates varied from 0.05 to 0.26 g m−2 days−1 and were significantly higher in below-waterfall pools in 2014. Leaf litter decomposition rates (0.001 to 0.024 days−1) did not differ between pool types, suggesting that neither shrimp nor fish densities had consistent impacts on this ecosystem function. Regardless, this research demonstrates the varied effects of biotic and abiotic factors on community structure and ecosystem function. Our results have highlighted the importance of discontinuities, such as waterfalls, in tropical streams.

Highlights

This study investigated four streams in Ulu Temburong National Park, Brunei Darussalam, all with waterfalls that reduce the upstream dispersal of fish, creating a refuge for shrimp in above-waterfall pools
The non-metric multidimensional scaling (NMDS) showed no clear pattern or difference in macroinvertebrate community structure between aboveand below-waterfall pools, and the analysis of similarities (ANOSIM) procedure revealed no difference between the macroinvertebrate community structure of the above- and below-waterfall pools
Tropical headwater streams in Ulu Temburong National Park contain a large number of shrimp and fish, with waterfalls acting as semi-permeable filters that create different aquatic communities in reaches above and below waterfalls

Summary

Introduction

Tropical streams often support large populations of macroconsumers, such as herbivorous fish, crabs, tadpoles and shrimp (Power, 1984; Flecker, 1992; Rosemond et al, 1998), which can have a significant impact on stream ecosystems via predation and/or competition for food resources like leaf litter and periphyton among a range of other resident animals (Pringle & Hamazaki, 1997; Rosemond et al, 1998). Waterfalls are fast flowing, rocky biotopes with distinct geomorphic structure (e.g. channel slopes and stream channels typically erode down to parent material) These biotopes flow vertically without obstruction and are generally more than 1 m in height (Newson & Newson, 2000). A total of 44 species of fish from 10 families and 30 genera have been identified in the streams and rivers of Ulu Temburong National Park (Choy & Chin, 1994). Three genera of freshwater shrimp live in the streams of Ulu Temburong National Park with the most common being Macrobrachium (Decapoda: Palaemonidae; Wowor, personal communication). A previous study of non-shrimp macroinvertebrates in these streams (Baker et al, in press) identified 14 orders, with Diptera being the most abundant in number of individuals (approximately 40%), followed by Coleoptera (approximately 20%), Ephemeroptera (approximately 20%) and Trichoptera (9%)

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