Macroinvertebrate community structure, secondary production and trophic‐level dynamics in urban streams affected by non‐point‐source pollution

Abstract

Summary 1. Despite non‐point‐source (NPS) pollution being perhaps the most ubiquitous stressor affecting urban streams, there is a lack of research assessing how urban NPS pollution affects stream ecosystems. We used a natural experimental design approach to assess how stream macroinvertebrate community structure, secondary production and trophic structure are influenced by urban NPS pollution in six streams. 2. Differences in macroinvertebrate community structure and secondary production among sites were highly correlated with stream‐water specific conductivity and dissolved inorganic phosphorus (DIP) concentrations. Macroinvertebrate richness, the Shannon diversity index and the Shannon evenness index were all negatively correlated with specific conductivity. These patterns were driven by differences in the richness and production of EPT and other intolerant taxa. Production of the five most productive taxa, tolerant taxa, non‐insect taxa and primary consumers were all positively correlated with stream‐water DIP. 3. Despite the positive correlation between primary consumer production and DIP, there was no correlation between macroinvertebrate predator production and either total or primary consumer macroinvertebrate production. This was observed because DIP was positively correlated with the production of non‐insect macroinvertebrate taxa assumed to be relatively unavailable for macroinvertebrate predator consumption. After removing production of these taxa, we observed a strong positive correlation between macroinvertebrate predator production and production of available prey. 4. Our results suggest that urban NPS pollution not only affects macroinvertebrate community structure, but also alters secondary production and trophic‐level dynamics. Differences in taxon production in our study indicate the potential for altered energy flow through stream food webs and potential effects on subsidies of aquatic insect prey to riparian food webs.

Comparison of macroinvertebrate communities of intermittent and perennial streams in the dry forest of Guanacaste, Costa Rica

“…While conductivity in the intermittent streams was constant throughout the study, perennial streams displayed an increasing trend as the wet season progressed. Although taxon richness and diversity of macroinvertebrate communities were negatively correlated with conductivity in Kentucky streams (Johnson et al, 2013), the range of conductivity between stream types in the current study, although significantly different, was well within the range expected for the region, and no significant differences in macroinvertebrate abundance were noted. The results of current study agreed with published differences between intermittent and perennial streams in a number of regards.…”

Influence ofLonicera maackiiInvasion on Leaf Litter Decomposition and Macroinvertebrate Communities in an Urban Stream

“…Similarly, allochthonous inputs of allelopathic litter may support lower fungal colonization as well as directly repel shredders, resulting in reduced abundances of this FFG (Ervin and Wetzel 2003). Predator responses mim- icked these lower trophic level FFGs, most likely through trophic interactions (e.g., Johnson et al 2013). It is notable that the predators were dominated by Planariidae (flatworms).…”

“…It is notable that the predators were dominated by Planariidae (flatworms). In general, predators are lacking in many urban streams due to a lack of small soft-bodied prey items (Johnson et al 2013). However, Planariids are known to feed on snail eggs (e.g., Lombardo et al 2011), and so increases in scrapers could lead to increases in these predators.…”

“…Invertebrates were identified to family (or lowest possible taxon) and assigned to functional feeding groups (FFG) based on Merrit et al (2008) and Thorp and Covich (2001). If a taxon comprised more than one FFG, the FFG that the majority of species in the region belonged to was used (KDOW 2009;Johnson et al 2013). Shannon diversity (H') and taxa richness were calculated for each replicate sample, and values from the three replicates per site per date were averaged for statistical analysis due to the loss of one sample in the lab (making site our experimental unit for these analyses).…”

Ecological responses to contamination: A meta-analysis of experimental marine studies

“…nutrient cycling, productivity), are tested rather than implied through bioindicators, that accurate assessments can be made. In freshwater streams, contamination affects macroinvertebrate community structure but also alters secondary production and energy flows through food webs (Johnson et al, 2013). In a lake ecosystem, fish biomass at contaminated sites were similar to non-contaminated sites, but fish diet and food web dynamics were different, revealing broader impacts at multiple lower trophic levels (Luek et al, 2013).…”