Direct and indirect effects of human population density and land use on physical features and invertebrates of Iowa (U.S.A.) streams

Abstract

To improve understanding of human impacts on headwater stream condition, we quantified relationships between human, terrestrial landscape, and stream system variables in 29 central Iowa watersheds. Across study watersheds, between 0 and 100 % of total land area was characterized as Burban^(developed and barren land), whereas cultivated land constituted between 0 and 71 % of watershed area. Several variables were measured for each stream and associated watershed. Strengths of correlative relationships were used to select variables for path analysis, which we used to gain insight into factors affecting stream condition by evaluating direct and indirect effects of human system variables, terrestrial landscape variables, and physical stream variables on stream invertebrates. Results indicated that in predominantly urban watersheds, contaminant inputs to streams (measured by streamwater conductivity) negatively affected invertebrates, including EPT taxa (Ephemeroptera, Plecoptera, Trichoptera), and streamwater contaminant concentrations increased with impervious surface and human population density in the watershed. In rural watersheds, high streamwater nitrogen concentrations associated with cultivated land were related to declines in invertebrate taxon richness. Independent of land use, invertebrate abundance and taxonomic diversity were positively related to coarse substrate abundance on the streambed. Additionally, stream flow (discharge) increased with watershed area, which in turn increased invertebrate taxonomic diversity. Apparently, mechanisms responsible for human impacts on stream condition in central Iowa depend on dominant land use in the watershed. Additionally, stream ecosystems with high quality benthic habitat, and those located in large watersheds with greater flow, appear to be more resilient to land use effects.

Fish Endoparasites from Streams near Paddy Fields in Serian and Padawan, Western Sarawak

“…This might be explained by the presence of a resort at the upstream river, which was constantly occupied with human. Here, human disturbances may play a role in suppressing the aquatic invertebrates, which are the major food sources for the fish and might greatly affect the ecosystem services (Olson, Stewart & Thompson, 2016). This suggested that human interference may directly or indirectly influence the survival of the parasites in freshwater fish as well.…”

Restoration of a pond: monitoring water quality and macroinvertebrate community succession

“…The relatively high biodiversity indices recorded for the new pond during the first sampling period could be due to the new niches available for colonisation after the pond's construction (Lahr et al 1999;Olmo et al 2016). Although successful colonisation and establishment depend on the colonisers' dispersal ability, the habitat must be suitable for survival (Flory and Milner 2000;Olson et al 2016).…”

“…Coloniser organisms must be able to establish successfully in the presence of predators, parasites, and competitors. Finally, the habitat must be suitable for survival and reproduction (Wood et al 2003;Olson et al 2016).…”

Patterns of Aquatic Insect Biodiversity in the Highly Urbanized Bronx River, NY

“…Many of these insects are sensitive to habitat degradation and changes in water chemistry caused by anthropogenic activities, particularly urbanization (Violin et al 2011, Walsh et al 2005). Indeed, high levels of urbanization, often measured as an increase in human population density (Olson et al 2016, Urban et al 2006) and increased impervious surfaces (Paul and Meyer 2001), has been shown to fundamentally change stream hydrology and may even lead to the burial of stream channels for sewage and rainwater drainage (Kaushal and Belt 2012). These hydrological changes can have a profound impact on habitat quantity and quality, thereby reducing aquatic insect biodiversity (Smith et al 2015).…”