REVIEW: Potential roles of soil fauna in improving the efficiency of rain gardens used as natural stormwater treatment systems

Abstract

1. Natural treatment systems such as rain gardens aim to overcome the negative effects of urbanization on water quality, availability, and freshwater and marine ecosystem integrity by mimicking the natural water cycle in urban planning and design. While soils in these systems are inhabited by a diverse array of invertebrates, the soil macrofauna is ignored in the vast majority of studies on new or existing rain gardens. 2. Here, we review the functional roles of invertebrates commonly found within soils of rain gardens. Soil fauna have the potential to substantially alter plant growth, water infiltration rates, and the retention and removal of pathogens, nutrients, heavy metals and other contaminants. Their lack of inclusion in controlled laboratory or greenhouse studies may contribute to differences in observed function in field and laboratory settings. 3. Promising future research directions include the following: (i) the use of controlled experiments to study invertebrate effects on rain garden function; (ii) determining the factors affecting variability in organismal abundance among and within sites; and (iii) the design of rain gardens to facilitate development of fauna that promote desired functions. 4. Synthesis and applications. Soil fauna may substantially alter the function of rain gardens as natural stormwater treatment systems in urban areas. Therefore, incorporating animal effects into design and testing may better enable managers and researchers to understand and optimize rain garden functioning, and forecast the longevity of rain gardens.

Indicator and Pathogen Removal by Low Impact Development Best Management Practices

“…To date, few studies (five since 1990) have evaluated the composition and/or role of meso-or macro-invertebrate infauna (hereafter referred to as invertebrates) in stormwater biofilters [93]. Those that have suggest that the most common taxa include earthworms, potworms, springtails, mites, fly larvae, beetles, millipedes, centipedes, isopods, ants, spiders, and snails [94,95].…”

“…Indeed, infiltration and plant growth are on the list, suggesting that invertebrates could affect microbial removal indirectly by impacting biofilter residence time and/or plant root architecture (see mechanisms discussed above). Earthworms in particular are organisms of interest from a microbial removal perspective, as they are abundant in biofilters, burrow extensively (in some cases increasing soil infiltration rates 2-15-fold), increase plant growth and vertical and lateral spread of plant roots, and have significant but sometimes contradictory effects on pathogen and viral persistence when used for vermicomposting of biosolids or sludge (being variously associated with reduced levels of fecal coliforms, Salmonella, enteric viruses, and parasitic worm eggs; increased microbial diversity/activity; and enhanced pathogen transport through soils) [12,93,96].…”

Optimization of bioretention systems through application of ecological theory

“…Common plant forms include rushes, sedges, grasses, and shrubs . Characteristic soil biota include oligochaetes (earthworms), millipedes, collembolans (spring tails), beetles, isopods, mites, spiders, and centipedes . These systems, also called rain gardens, biofilters or bioswales, have become a common tool for stormwater management.…”

“…They integrate knowledge from engineering, hydrology, soil science, horticulture, and landscape architecture . Design criteria focus largely on hydrodynamics, filtration media including soils, and to a lesser extent on selection of plants, with limited to no attention to associated fauna …”

Nematode Community Response to Green Infrastructure Design in a Semiarid City

“…The balance of soil microbial communities (e.g., bacteria vs. fungi) can affect decomposition, carbon (C) balance, and nutrient mineralization rates due to differences in life histories, environmental tolerances, and stoichiometric demands (Wardle et al, 2004). Soil invertebrates play critical roles in regulating ecosystem processes through direct regulation of microbial populations and physical effects on soil properties and decomposition substrates (Wolters, 2001; Mehring and Levin, 2015). Soil nematodes are used as an indicator of soil food web responses to environmental change and management because they have broad functional diversity, exhibit predictable responses to stress and disturbance, span a range of trophic levels, and bridge processes of detritivory, microbivery, and predation in soils (Bongers, 1990, 1999; Bongers and Ferris, 1999).…”