Aquatic insect functional diversity and nutrient content in urban streams in a medium‐sized city

Abstract

Citation: Lundquist, M. J., and W. Zhu. 2018. Aquatic insect functional diversity and nutrient content in urban streams in a medium-sized city. Ecosphere 9(5):e02284. 10.1002/ecs2.2284Abstract. Aquatic insects play a large role in the processing of organic matter in headwater streams; however, anthropogenic disturbances associated with watershed urbanization can impact the biodiversity and abundance of these insects. Aquatic insects function on multiple trophic levels (i.e., shredders, collectors, scrapers, and predators) and interact in the nutrient cycling within lotic systems. The degradation or loss of any of these functional groups could disrupt stream biogeochemistry and the flow of energy in stream ecosystems. We used a paired reach site design to assess the insect functional group representation in five streams impacted by urbanization with downstream urban and upstream rural reach sites. We also sampled two non-urban reference streams with rural upstream and rural downstream reach sites. We assessed functional group richness and abundance and measured insect biomass, insect body nitrogen (N) content, phosphorus (P) content, and N:P ratio. We found that collectors were numerically the most abundant and taxonomically the richest insect group in all site types. There were much fewer insects collected from urban sites than rural sites and individual insects were generally smaller in the urban sites. Collectors represented the most insect biomass in urban sites and predators the most insect biomass in rural sites. Insect N and P concentrations were not affected by urban landuse, ranging from 88.45 AE 12.50 to 121.74 AE 15.80 mg/g and 10.60 AE 2.10 to 18.36 AE 7.05 mg/g, respectively; and N:P ratios from 3.48 to 20.97. However, lower total insect biomass, particularly of predators and shredders, led to significantly lower total N and P mass in urban sites. Urbanization had clear effects on the diversity of functional groups, insect biomass, and their nutrient mass in this medium-sized city.

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

“…The sites that have larger insect populations may also be supporting larger populations of other important aquatic fauna. For example, larvae of Hydropsyche are relatively large compared to the other insect taxa collected in the present study and may be an important food source for other organisms in the river (Lundquist and Zhu 2018, Walters et al 2009). The sites with larger insect populations could also act as a source of colonizers for restoration projects of downstream sites that are more urbanized (Sundermann et al 2011).…”

Ecosystem Services, Global Diversity, and Rate of Stonefly Species Descriptions (Insecta: Plecoptera)

“…The ecological consequences of these stonefly species losses are not well understood, but others have hypothesized that it could upset the normal flow of nutrients and energy to downstream areas [25]. Of the 16 stonefly families, 11 are shredders of coarse organic matter and comprise a majority of the species in the order [9].…”

Clean and Green Urban Water Bodies Benefit Nocturnal Flying Insects and Their Predators, Insectivorous Bats

“…In particular, urbanisation can cause various stressors to water bodies via the introduction of sediment pollution [10,11], modification or removal of vegetation and extreme fluctuations in water flow [12,13]. These activities can significantly modify and degrade invertebrate communities [14][15][16], with subsequent implications for their predators [17]. Insectivorous bats (Chiroptera) occur in urban areas globally [18,19] and depend on insect-rich feeding grounds [20]; thus, they are good model organisms for understanding the effects of anthropogenic impacts on urban water bodies and altered prey availability [21,22].…”