Beavers alter stream macroinvertebrate communities in north‐eastern Utah

Abstract

1. Understanding changes in macroinvertebrate communities is important because they play a large role in stream ecosystem functioning, and they are an important food resource for fish. Beaver-induced changes to stream morphology could alter macroinvertebrate communities, which in turn could affect food webs and ecosystem function. However, studies investigating the effects of North American beaver activities on macroinvertebrates are rare in the inter-mountain west, an area with high potential for beaver-assisted restoration.2. The aim of this study was to quantify differences in the macroinvertebrate community between unaltered segments of streams and within beaver ponds in northeastern Utah, U.S.A. We assessed macroinvertebrate species richness, biomass, density, functional feeding group composition, mobility group composition, and macroinvertebrate habitat characteristics to test the hypothesis that macroinvertebrate communities will differ among habitat types (undammed stream segments and beaver ponds) in beaver-occupied streams.3. Beaver pond communities significantly differed from lotic reach communities in many ways. Beaver ponds were less diverse with 25% fewer species. Although there was variability among streams, in general, beaver ponds had 75% fewer individuals and 90% lower total macroinvertebrate biomass compared to lotic reaches.4. Regarding functional feeding groups, beaver ponds contained more engulfers, while lotic reaches contained more scrapers, filterers, and gatherers. For mobility groups, beaver ponds had more sprawlers, while lotic reaches had more clingers.Swimmers were also more prevalent in lotic reaches, although this is probably due to the abundance of Baetis within lotic reaches. More beaver pond taxa were classified as lentic-dwelling insects, while more lotic reach taxa were categorised as preferring lotic habitats.5. The creation of ponds by beavers fundamentally altered the macroinvertebrate community in north-eastern Utah streams. Such changes to stream macroinvertebrate communities suggest that recolonisation of beavers across North America may be altering stream functioning and food webs. Our study highlights the need to further investigate the effects of beaver recolonisation on stream communities.

Transformation of benthic communities in forest lowland streams colonised by Eurasian beaver Castor fiber (L.)

“…The occurrence of typically rheophilic species at sites with flowing water (group UNS and particularly FSB) and stagnophilic species in ponds seems critical in terms of biodiversity throughout the catchment (Washko et al, 2020). The engineering activities of beavers usually increase taxonomic diversity at the landscape scale (Anderson et al, 2015;Bylak & Kukuła, 2018;Bylak et al, 2014;Clifford et al, 1993;Hood & Larson, 2014;Robinson et al, 2020;Washko et al, 2020). In the present study, the emergence of new habitats, namely ponds, resulted in increased in faunistic diversity at the stream scale.…”

“…The taxa that influenced the Sim in invertebrate fauna of sites from the ponds the most were Oligochaeta and Chironomidae based on their abundance. The dominance of Chironomidae and Oligochaeta in beaver pond complexes has been reported in numerous other streams occupied by beavers and was the primary factor distinguishing ponds from flowing sections (Margolis et al, 2001; McDowell & Naiman, 1986; Naiman et al, 1984; Pliūraitė & Kesminas, 2012; Washko et al, 2020). In the present study, Chironomidae were also relatively abundant in flowing sections, although their density was considerably lower in the flowing sections than in most of the beaver ponds.…”

“…In beaver ponds, rheophilic species decline or exhibit low abundance. It is particularly evident within taxonomic groups such as mayflies, stoneflies, or caddisflies (Pliūraitė & Kesminas, 2012; Sprules, 1941; Washko et al, 2020). Stagnophilic insect species have been frequently observed in beaver ponds (Arndt & Domdei, 2011; Harthun, 1999; Naiman et al, 1984; Smith et al, 1991).…”

“…In the present study, the highest numbers of taxa and levels of taxonomic diversity were observed in flowing sections downstream beaver ponds. The occurrence of typically rheophilic species at sites with flowing water (group UNS and particularly FSB) and stagnophilic species in ponds seems critical in terms of biodiversity throughout the catchment (Washko et al, 2020). The engineering activities of beavers usually increase taxonomic diversity at the landscape scale (Anderson et al, 2015; Bylak & Kukuła, 2018; Bylak et al, 2014; Clifford et al, 1993; Hood & Larson, 2014; Robinson et al, 2020; Washko et al, 2020).…”

Beaver creates early successional hotspots for water beetles

“…25,000 km 2 of new aquatic pond habitat and 550,000 km of riparian interface have been created in boreal and temperate zones (Whitfield et al 2015). Beavers have been proposed as a tool for biodiversity conservation (Law et al 2019;Nummi and Holopainen 2020), and several studies have shown that beavercreated succession can affect aquatic invertebrates in a beaver-modified landscape at a general level (Bush et al 2019;Washko et al 2020). One of the first studies to focus on a specific taxon of aquatic invertebrates found a difference in water beetle abundance in beaver wetlands and non-beaver wetlands (Willby et al 2018).…”