Manganese Oxides as Localized Drivers of Benthic Invertebrate Density and Community Structure
Oxidized manganese (Mn) forms tightly bound, dark precipitates on exposed rock surfaces in rivers, which could impact benthic communities. We combined a field survey with two experiments to identify patterns in benthic invertebrate community structure and potential mechanisms creating these patterns on substrates coated with Mn oxides and on ‘uncoated’ substrates in a large gravel-bed river. Uncoated substrate had roughly seven times higher densities of benthic macroinvertebrates, particularly fixed retreat filter feeders such as Brachycentrus, Rheotanytarsus, and Hydropsyche, while clinger taxa had similar densities between coated and uncoated substrates. In a substrate preference experiment conducted in laboratory microcosms, nymphs of a swimming mayfly (Isonychia bicolor) were more likely to
avoid Mn-coated than uncoated substrate, while nymphs of a clinger mayfly family (Heptageniidae) showed no significant substrate preference or avoidance. In a field colonization experiment, invertebrate communities established on Mn-coated substrate had significantly higher variability in taxonomic composition but similar densities to communities on uncoated rocks. Combined, these results demonstrate a large difference in biological communities and describe patterns that occur during community assembly on Mn-coated substrate. While established communities responded negatively to Mn oxides, our results indicated coated substrate might also create community heterogeneity within large river riffle habitats.
Wilson, Matthew J.; McTammany, Matthew; and Bohr, Hannah. "Manganese Oxides as Localized Drivers of Benthic Invertebrate Density and Community Structure." (2019) : 85-98.