Effects of stream diversion on riffle macroinvertebrate communities in a Maui, Hawaii, stream

Abstract

The continual demand for freshwater by industry (e.g. tourism) and agriculture, a growing population, and increasing development over the past 100 years has resulted in the construction of diversions within many streams of Hawaii. The main objective of this study was to evaluate the impact of stream diversions on riffle macroinvertebrate communities. Benthic macroinvertebrate larval populations were compared above and below a diversion in Iao Stream, Maui, Hawaii, from April to August 2000. During this summer approximately 92-97% of daily stream flow was diverted from Iao Stream. Three taxa, Procanace sp. (Diptera: Canacidae), Atyoida bisulcata (Crustacea: Decapoda), and Amphipoda (Crustacea), were only collected above the diversion. However, the most numerous taxa, Chironomidae (63-64% of the total macroinvertebrate community), Hydroptila arctia (Trichoptera: Hydroptilidae; 15%), and Cheumatopsyche pettiti (Trichoptera: Hydropsychidae; 8%), were found both above and below the diversion. The relative percentage abundance of these dominant taxa remained relatively consistent above and below the diversion over the study period. However, the mean total density of individual dominant taxa was greater above the diversion. The mean total macroinvertebrate density above the diversion was 46% greater than below the diversion (Student t-test: df = 30, t = −3.22, p > 0.01). No correlation was found between temperature and density. A positive correlation was detected between Froude number and mean total macroinvertebrate density. Overall, the reduction in macroinvertebrate diversity and in individual and total density below the diversion suggest that trophic interactions, and thus energy flow, could be affected by reduced flow in Hawaiian streams. The information gained from this study will contribute to knowledge on Hawaiian stream ecosystems, help to create minimum instream flow standards for stream restoration, and will provide information for future freshwater management issues on the Hawaiian islands.

Effect of water removal on introduced caddisflies from a tropical mountain stream

“…McIntosh et al (2002) found the absence of three macroinvertebrate groups below the same diversion in Iao Stream and an overall reduction in the densities of all riffle macroinvertebrates. The correlation between stream flow (Froude number) and Trichoptera biomass found in the present study also supports the hypothesis that reduced stream flow negatively affects the extent and characteristics of downstream flow habitat for aquatic insects in Hawaiian streams.…”

“…The most recent studies that have addressed reduced stream flow, due to diversion, and the subsequent effect on macroinvertebrate populations in Hawaii were by McIntosh (2002), Wolff (2001), and Kido (1996). McIntosh et al (2002) found the absence of three macroinvertebrate groups below the same diversion in Iao Stream and an overall reduction in the densities of all riffle macroinvertebrates.…”

“…Downstream reaches below the diversion are characterized by lower flow, infrequent riffles and an increase of shallow pool habitats (McIntosh et al 2002). In general, the substrate of Hawaiian streams can be characterized as a heterogeneous mixture of boulders, cobbles, and rocks (Kinzie et al 1986), indicative of the patchy nature of Hawaiian stream habitats.…”

“…A study by McIntosh et al (2002) found Diptera (native and introduced) to be the dominant taxa (64 %) in riffle habitats; however, the second and third most abundant taxa were two introduced Trichoptera, Hydroptila potosina (Bueno-Soria) (Hydroptilidae) (15 %) and Cheumatopsyche analis (Banks) (Hydropsychidae) (8 %). A similar study by Kido (1993) found C. analis to be the dominant taxa (68 %), succeeded by Diptera (19 %) and H. potosina (9 %).…”

“…Brasher (1996Brasher ( , 1997a and Way et al (1998) have studied diversion effects on the native amphidromous fish, shrimp and snails of Hawaiian streams. However, relatively little published research has focused on the effects of diversions on native and introduced aquatic insect communities, beyond a recent study by McIntosh et al (2002) that found invertebrate communities were negatively impacted by diversions. Kido (1996) and Wolff (2000) found negative diversion impacts on invertebrate and algae communities in Hawaiian streams, but all of these studies mainly addressed density differences.…”