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This chapter describes the stoneflies located in the Glacier National Park and Flathead River basin in Montana. It explains that 58 species were documented in the Flathead River, 58 from Glacier Park, and 95 and 74 species respectively from west and east of the continental divide. The chapter stresses the need to conduct more studies on the number of Lentic stoneflies in this region and on hyporheic stonefly fauna.

The idea that there are many subterranean habitats close to the surface that are little known and do not fit comfortably into any habitat classification scheme is introduced. Four of these shallow subterranean habitats (SSHs) are unique (strict sense shallow subterranean habitats)—hypotelminorheic and seepage springs, milieu souterrain superficiel (including talus and scree), epikarst, and calcrete aquifers—and have intermediate sized habitat spaces, no light, and close connections to the surface. Broad sense shallow subterranean habitats include habitats with large (lava tubes) or small (aquatic interstitial and soil) spaces. SSHs are generally broadly but patchily distributed across the landscape although some have restricted physical requirements, such as the presence of a shallow clay layer for hypotelminorheic habitats. Close surface connections have impacts on environmental conditions, nutrient fluxes, and movement of animals through SSHs. While SSHs can be ecotones, they are habitats in their own right, and not necessarily connected with deeper subterranean habitats. They are of general biological interest because of the presence of eyeless, depigmented species, their possible role as stepping stones to adaptation to deeper subterranean environments, their geographic pattern, and conservation issues raised by them. Brief examples of each type of SSH are discussed.

The interstitial habitats along rivers and streams are generally small-pore SSHs, ones where the dissolution of bedrock plays little if any role. The best-studied and most ubiquitous of these habitats is the hyporheic, the underflow of rivers and streams. The hyporheic is an ecotone between surface and subsurface habitats, and is a filter in three ways—a photic filter, a mechanical filter, and a biochemical filter. Transfers occur in both directions, and a characteristic feature of the hyporheic is that there are series of upwellings of groundwater and downwellings of surface water. Oxygen concentrations are among the most critical parameters of the hyporheic and some species are only found in areas of low oxygen concentrations. Organic carbon is typically higher than in other SSHs, and particulate organic matter (POM), in addition to dissolved organic matter (DOM), may be an important organic carbon source. Little is known about large-scale patterns of species richness in spite of the possibility of quantitative, comparative sampling. At the local level, species richness can be quite high, typically with up to a hundred species and perhaps ten to twenty stygobionts. From a short-term ecological perspective, the hyporheos may serve as a refuge from flooding, from drying, and from competition and predation. Based on detailed studies of the phylogeography of the amphipod Niphargus rhenorhodanensis, Lefébure et al. (2007) concluded that subterranean dispersal of hyporheic species along river corridors did occur, but it was limited in extent, on the order of 200–300 km.

This chapter is devoted to the groundwater dependencies of riverine corridors, and the methods available to assess those dependencies and to protect and manage groundwater resources as part of frameworks for managing surface stream flows and catchment water resources. Classification schemes capture different types of groundwater-surface water interactions. Several methods identify hyporheic flow paths in streams (e.g., natural tracers such as temperature and chloride, injection of conservative tracers, modeling of subsurface flow based on the distribution of hydraulic heads and aquifer properties). There is growing understanding of how various factors govern the diversity, heterogeneity, and distribution of groundwater fauna, and how best to assess groundwater ecosystem health. An ecohydrogeological framework presents a broad vision of groundwater dependencies and challenging opportunities for management.

This chapter examines the basic ecology of streams in the Toolik Region. It provides information gathered from monitoring year-to-year variability and to identify long-term changes in the ecology of streams. It looks into the importance of understanding the role nutrients have in limiting and structuring stream ecosystems. It describes the ecological characteristics of the five types of arctic streams in the Toolik region, including biogeochemistry, primary producers, microheterotrophs, and secondary producers. It enumerates details of three stream-fertilization experiments that provide the basis of past and current research. It combines the research results under six themes: resource limitation; recovery from nutrient enrichment; trophic cascades; hyporheic processes; disturbance as a driver; and how warming leads to changes in permafrost and thermokarst.