Effects of urban spatial and temporal heterogeneity on benthic macroinvertebrate and diatom communities

Abstract

Water quality, distribution, and flow are often highly altered in rivers in urban watersheds, subjecting aquatic communities in the environment to novel spatial and temporal heterogeneity. An understanding of how novel spatial and temporal heterogeneity impacts aquatic communities is of paramount concern since these taxa are foundational to the urban food web. In this study, we documented the effects of flow perturbations on benthic macroinvertebrate and diatom communities relative to wastewater treatment plant outflows in a transect of an urbanized river in Southern California, USA. In particular, we analyzed trends in the richness and density of diatom and benthic macroinvertebrate communities in relation to novel flow heterogeneity introduced by wastewater treatment plants and urban storm runoff events. We found that diatom density decreased after a disturbance but quickly returned to its pre-disturbance levels, while the benthic macroinvertebrate community showed minimal shifts in composition and density after the disturbance, yet the sites had low richness of predominantly tolerant taxa. The locations of wastewater treatment plant outflows were found to exert a constant negative effect on density and richness in both communities. These results have implications for the conservation of endangered fish species in the urban Santa Ana River that depend on a thriving basal food web for survival.

Evaluation of extinction risk for stream fishes within an urban riverscape using population viability analysis

“…Fish and Wildlife Service, 2017a; U.S. Fish and Wildlife Service, 2017b; Saffarinia et al, 2022), water quality (U.S. Fish and Wildlife Service, 2017a; U.S.…”

“…I G U R E 6 Extinction risk probability projected 100 years by stratum and species within the Santa Ana River, California. Projections include starting values based on abundance estimates by species and strata in 2022 ("Observed") and starting values based on the highest densities for arroyo chub (Gila orcuttii; density = 1.39 fish m À1 ) and Santa Ana sucker (Pantosteus santaanae; density = 1.37 fish m À1 ) estimated from the fitted abundance model ("Highest").2017b;Saffarinia et al, 2022), water quality (U.S. Fish and Wildlife Service, 2017a; U.S.Fish and Wildlife Service, 2017b;Jenkins et al, 2009) and many others.…”

The Intersection of Wastewater Treatment Plants and Threatened and Endangered Species in California, USA Watersheds

“…In an acute example in the Santa Ana River in southern California, periodic treatment plant shutoffs for routine maintenance ceased effluent inputs into the river, leading to rapid and near‐complete flow reductions. The dramatic nature of these shutdowns, unbeknownst to conservation managers and treatment plant operators alike, lead to mortality of federally threatened Santa Ana sucker ( Catostomus santaanae ) and had widespread effects on freshwater community composition (Saffarinia et al., 2022).…”