Using Aquatic Macroinvertebrates as Indicators of Stream Flow ...

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where fast flow and rocky substrate inhibits the establishment of juveniles. Some species ofmussels are also sensitive to pollution and may therefore be absent from impaired waters, orfrom streams that lack the fish hosts required by larval mussels to develop to the juvenile stage.Special considerations for OregonMultiple studies conducted in Oregon streams indicate that whereas sharply delineated perennialobligateor temporary-obligate communities do not exist, certain families of macroinvertebratesare present in higher abundances in perennial vs. intermittent or ephemeral streams. This may bedue in part to the greater predictability of Oregon’s distinct wet and dry seasons, which coulddrive development of a more characteristic faunal community in temporary streams (Dieterich,1992). Many studies have been conducted in the eastern foothills of the Coast Range aroundCorvallis Oregon, in intermittent forested or meadow streams that maintain flow from aboutNovember through May. During the dry season, the meadow channels tended to dry downrapidly and completely, while the forest streams usually dried out more gradually and retainedregions with small pools or seeps, even when dry along much of their length (Dieterich, 1992;Dieterich & Anderson, 1998).Many findings regarding the macroinvertebrate communities of summer-dry streams in Oregonare similar to those reported above in other geographic areas. A great deal of overlap is seen inthe fauna of perennial and temporary streams, but some groups are found more commonly inintermittent or ephemeral sites, and a smaller subset prefer or are restricted to perennial habitats(Dieterich, 1992; Banks, 2005). Some perennial headwater streams in western Oregon had agreater abundance of organisms than intermittent, although the species richness (total number oftaxa) was similar or even greater in intermittent. Ephemeral streams had only about 25-33% asmany species as the other two stream types (Dieterich, 1992). In addition to flow duration, inOregon timber harvest can be a strong driver of macroinvertebrate community composition, aslogging can alter the degree of sunlight reaching the stream and contribute to increasedsedimentation. Differences in adult insect emergence rates, taxa richness, and density have beenobserved in perennial and intermittent streams flowing through logged vs. forested sites inwestern Oregon (Banks, 2005; Banks et al., 2007).Caddisflies often exhibit very high species diversity in Oregon’s summer-dry streams, eventhough they may comprise a small proportion of the overall invertebrate abundance (Dieterich,1992; Anderson & Dieterich, 1992; Anderson 1997); this has also been found in other studies indifferent regions (Mackay & Wiggins, 1979; Smith & Wood, 2002). The Limnephilidae(Northern caddisflies) are the largest caddisfly family in North America; its members exploit awide variety of habitats, from permanent streams to temporary pools to moist terrestrial habitats(Wiggins, 1993). Several genera in this family are known to have adaptations that allow them tosurvive periods of summer dryness, including: synchronizing their growth period to the wetseason; inhabiting moist seeps that persist in intermittent streams; surviving in moist terrestrialhabitats as adults that undergo ovarial diapause, living for 5-7 months and ovipositing whenstream flows resume in fall; or laying desiccation-resistant eggs that persist through the dryseason and hatch when wetted (Clifford, 1966; Tew, 1971; Wiggins, 1973; Mackay & Wiggins,1979; Anderson & Dieterich, 1992). Because of these adaptations, limnephilid caddisflies areoften an abundant and diverse component of intermittent streams. In studies on Trichopteraconducted by Anderson (1997) on intermittent oak savannah streams near Corvallis OR, the vastMacroinvertebrates as indicators of stream flow duration,The Xerces Society for Invertebrate Conservation10
majority of all caddisflies collected were limnephilid species (Pseudostenophylax, Psychoglypha,and Limnephilus). Five species of caddisflies in three families (Limnephilidae, Rhyacophilidae,and Lepidistomatidae) accounted for over three-quarters of the total number of species collectedfrom intermittent streams (Anderson & Dieterich, 1992), with overall species assemblagesdiffering in a characteristic way between forested and meadow streams. Six species in threegenera of Limnephilidae, all of which appeared to have life history adaptations for temporarystreams, were collected from a small second order intermittent stream near Corvallis (Tew,1971).Plecoptera (stoneflies) and Ephemeroptera (mayflies) are more commonly found in fast-flowingperennial waters. An analysis of macroinvertebrate data from 167 small, forested, perennialheadwater streams in three different ecoregions in western Oregon showed that 9 of the 16 mostcommon taxa reported were Ephemeroptera, Trichoptera, or Plecoptera (Herlihy et al., 2005),with an average 55% of all individuals collected at each site being EPT. A comparative study ofsmall headwater streams in a portion of the Central Oregon Coast Range found a heptageniid(flat headed) mayfly (Ironodes) and a hydropsychid (net-spinning) caddisfly (Parapsyche) onlyin the perennial streams (Banks, 2005). However, some EPT taxa in Oregon occur in temporaryhabitats and possess life history characteristics that allow them to survive periods of drought.Lemkuhl (1971) collected stonefly nymphs in the genus Nemoura (Nemouridae; forestflies) andCapnia (Capniidae; small winter stoneflies) from a roadside ditch in Corvallis that dried downregularly for 6 months of the year, and hypothesized that eggs or young nymphs present in thewet spring undergo diapause when the habitat is dry, completing development when flowresumes in the fall. Two species of stonefly from the Nemouridae and Chloroperlidae (greenstonefly) families (Ostrocerca and Sweltsa, respectively) and a philopotamid caddisfly(Wormaldia) were strongly associated with intermittent flow in small headwater streams in theCentral Oregon Coast Range (Banks et al., 2007), although a different philopotamid species(Dolophilodes) was found more commonly in perennial streams in the same study. Two mayflyspecies (Leptophlebiidae and Siphlonuridae family) and four stonefly species (Nemouridae,Chloroperlidae, and Perlodidae families) that accounted for >95% of mayfly and stoneflyemergence from two temporary forested streams in western Oregon were found to exhibit lifehistory strategies that increased the likelihood of survival in temporary habitats, includingasynchronous development, faster development at longer day lengths, and egg diapause duringsummer-dry periods (Dieterich & Anderson, 1995). Tew (1971) reported two species ofBaetidae (small minnow mayflies) as extremely abundant in an intermittent Oregon stream,although these are normally a component of perennial streams, as well as five species ofnemourid and capniid stoneflies, although the precise mechanism of their survival during the dryseason was not elucidated.The variety of ecoregions in Oregon can complicate the designation of flow duration indicatortaxa and community composition. The invertebrate communities in streams in the WillametteValley and Cascade Mountain ecoregions in western Oregon show substantial differences, withtotal taxa richness, diversity, and %EPT composition much higher overall in Cascade streams (Liet al., 2001). Additionally, taxonomic composition of stream communities differs depending onstream elevation, gradient, order, and ecoregion. For example, freshwater mussels, Juga snails,and gomphid dragonfly nymphs rely on permanently flowing water, but are unlikely to be foundin high-gradient forested headwater streams in western Oregon, as substrate, amount of sunlight,Macroinvertebrates as indicators of stream flow duration,The Xerces Society for Invertebrate Conservation11
Page 1 and 2: Using Aquatic Macroinvertebratesas
Page 3 and 4: GoalsThe goal of this project is to
Page 5 and 6: supported different macroinvertebra
Page 7 and 8: that some studies have found simila
Page 9: DispersalAdult invertebrates with s
Page 13 and 14: North CarolinaAquatic macroinverteb
Page 15 and 16: Amphipoda), water mites (subclass H
Page 17 and 18: ScoringThe current Oregon Draft Str
Page 20 and 21: To sample riffle or run/glide habit
Page 22 and 23: However, the degree of dryness in b
Page 24 and 25: Boulton A.J. & Lake P.S. 1992b. Ben
Page 26 and 27: Li, J., Herlihy, A., Gerth, W., Kau
Page 28 and 29: Williams, D. D., 1996. Environmenta
Page 30 and 31: shelter and to filter organic parti
Page 32 and 33: • Dytiscidae (predaceous diving b

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