Structural and functional changes of tropical riffle macroinvertebrate communities associated with stream flow withdrawal

Abstract

Tropical island streams worldwide are threatened by existing or proposed dams and diversions that remove freshwater for human use; yet, there have been few studies that address the effects on aquatic communities. The objective of this study was to quantify changes in tropical macroinvertebrate communities associated with stream flow withdrawal. Benthic macroinvertebrates were collected from riffle habitats located above and below a stream diversion on Maui, Hawaii, from June to August 2000. Native and introduced taxa were identified from both locations. The most dominant taxon was midges (Diptera: Chironomidae) followed by two introduced caddisflies, Cheumatopsyche analis (Banks) (Trichoptera: Hydropsychidae) and Hydroptila potosina (Buenoa-Soria) (Trichoptera: Hydroptilidae). A native shrimp, Atyoida bisulcata, and beach fly, Procanace sp. (Diptera: Canacidae), were either eliminated from or significantly reduced below the diversion. Mean total macroinvertebrate densities were greater above (13 357 individuals/m 2 ) the diversion compared to below (10 360 individuals/m 2 ). Mean total macroinvertebrate biomass was significantly reduced by 60 per cent below the diversion, but specific taxa did not show this effect. These results suggest that diverted stream flow limited macroinvertebrate colonization and growth, expressed as reduced community density and biomass, which may alter the structure and function of other trophic levels within tropical stream food webs.

The challenge of monitoring impacts of water abstraction on macroinvertebrate assemblages in unregulated streams

“…Even with diversion of very large proportions of flow, apparent impacts are not necessarily detected in all assessed attributes of macroinvertebrate assemblages. In a Hawaiian stream where all surface flow was diverted, statistically significant differences were found between upstream and downstream sites for macroinvertebrate biomass density and densities of particular taxa, but not total density over the whole study (McIntosh et al, 2008). In another Hawaiian stream where about 92-97% of summer flow was diverted, total macroinvertebrate density and the densities and biomass densities of some taxa were significantly lower downstream than upstream, but overall composition was little different (McIntosh et al, 2002(McIntosh et al, , 2003.…”

Macroinvertebrate traits distinguish unregulated rivers subject to water abstraction

“…This trait would decrease resilience to unpredictable low flow and drying events and would make taxa susceptible to the conditions caused by water abstraction (Carlisle and Hawkins 2008). Riffle families that appeared to tolerate water abstraction tended to be able to withstand elevated water temperatures, and high water temperatures are often associated with flow reductions and abstraction (Boulton 2003, Miller et al 2007, McIntosh et al 2008.…”

Inter-annual patterns in the stability and persistence of stream macroinvertebrate communities: relationship with water physicochemical parameters

“…In response to increasing population growth and consumption, anthropogenic demands placed on freshwater systems continue to escalate (Mcintosh et al 2008). Recently, anthropogenic river modification has become both widespread and intensive (Bona et al 2008).…”