Ecosystem artificiality does not impact aquatic communities
Humans likely construct, transform, and alter aquatic ecosystems often, and on a large scale. These artificial aquatic systems can provide important ecosystem services and disservices. Intrinsic properties, design, setting, management and policy, and time for naturalization may all play a role in how close these systems come to achieving the functionality of equivalent natural systems. Here, we explored whether invertebrate communities differ between natural and artificial streams sharing the same water and watershed, in a web of waterways in Bishop, California. We stratified our sampling by substrate, sand or cobble, and by season, summer 2008 or winter 2010, and collected one Surber sample of benthic macroinvertebrates, later identified to order or family, at each of 52 sites. Then we executed nonparametric multidimensional scaling analyses of the invertebrate assemblages, and PERMANOVAs on the effects of the site variables on the assemblages.
Assemblages varied with substrate and season, but not with artificiality. Cobble and sand assemblages differed significantly (F=5.4285, d.f.=1, p=0.001), as did winter and summer assemblages (F=2.8791, d.f.=1, p=0.015), but artificial and natural assemblages did not (F=1.3357, d.f.=1, p=0.235). This result suggests that in similar settings, artificial and natural ecosystems may function similarly. It raises the question of whether the tendency for policy and management to treat artificial aquatic systems differently stems exclusively from the systems’ function and services, or also from cultural perceptions of artificiality. This distinction matters, because differential treatment, whether as a result of current function and services, perceived artificiality, or both, may in turn impact function. Which drivers of ecosystem function matter in which artificial aquatic systems should inform management and policy options considered in each.