Influences of aTsuga canadensis(L.) Carriere (Eastern Hemlock) Riparian Habitat on a Lotic Benthic Community

Abstract

Tsuga canadensis (Eastern Hemlock) forests provide unique riparian zones that can influence adjacent streams, but increasing mortality from the invasive Adelges tsugae (Hemlock Woolly Adelgid) is eliminating this distinctive landscape component in some regions. The objective of this study was to determine if a stream section within a hemlock ravine harbored a unique benthic community as compared to other sections of the stream that could be threatened in the event of a Hemlock Woolly Adelgid outbreak. We sampled benthic algae and macroinvertebrates in an unnamed tributary of Sugar Creek within Beach City Wildlife Area, OH, in April and September 2015. The stream flows through 3 riparian habitats: beech—maple upland forest, hemlock ravine, and lowland forest dominated by Acer saccharinum (Silver Maple), A. negundo (Box Elder), and Platanus occidentalis (American Sycamore). Our results show that Chironomidae, Navicula, Caloneis, and Nitzschia were the dominant taxa across all 3 stream sections, but that benthic macroinvertebrate richness and density were significantly lower in the hemlock ravine when compared to the lowland habitat. Periphyton community metrics were not significantly affected by riparian habitat. Overall, seasonality was more influential than riparian habitat on benthic community composition; specific taxa were indicative of either the spring or summer season. Connectivity between stream sites and/or the abundance of sandstone bedrock substrate at many sample locations might account for the similarity in benthic communities across these 3 habitats.