Invasive shrub (Lonicera maackii) effects on terrestrial-aquatic linkages in stream ecosystems organic matter processing and macroinvertebrate community colonization

Lonicera maackii, an invasive terrestrial shrub that is dominant in riparian zones, may have substantial impacts on the structure and function of aquatic systems. We investigated linkages between this terrestrial invader and the aquatic community structure in headwater streams by assessing in situ leaf breakdown and the colonization of leaf packs by macroinvertebrates in three 3rd order headwater streams of southwestern Ohio, Possum Run, Fecher Park, and Black Oak Park. Leaf breakdown and colonizing macroinvertebrate taxa richness, density, and functional feeding group relative abundance were assessed using three types of in-stream leaf packs: L. maackii, native (Fraxinus spp., Platanus occidentalus), and a mixture of native and invasive leaves. Invasive leaf breakdown rates were up to 4x faster than native leaves, and significantly less organic matter remained for invasive compared to other leaf types on all sampling days. There were specific macroinvertebrate taxa unique to particular treatments. For instance, invasive leaf packs were dominated by collector-gatherers for the duration of the study and Chironomidae, in particular, was the most important taxon colonizing invasive leaf packs. In contrast, Oligochaeta colonized native leaf packs in greater densities at Possum Run stream and mix leaf packs in Fecher Park stream. Collector-gatherers also dominated mix leaf packs across stream sites and native leaf packs located within Possum Run. In summary, our results demonstrate that L. maackii leaves breakdown significantly faster in headwater streams compared to native leaves, and that macroinvertebrate densities and functional feeding group colonization are influenced by invasive leaf litter input. These results support the hypothesis that L. maackii invasion in riparian zones can have direct and significant impacts on aquatic ecosystems by influencing organic matter processes