Comparison of a Wood Sampler for Macroinvertebrate Bioassessment of Non-Wadeable Streams in the Southeastern Coastal Plain

Aquatic macroinvertebrates are often the subject of biomonitoring efforts because they are ubiquitous in most systems and are known to be suitable indicators of water quality. The vast majority of biomonitoring efforts that use macroinvertebrates are tailored towards small, wadeable streams, whereas methods for sampling macroinvertebrates in non-wadeable streams (i.e., large rivers) are often less available. We compared the use of a wood sampler to collect aquatic macroinvertebrates with two more commonly used samplers (Hester-Dendy and leaf packs) to assess its suitability for sampling non-wadeable systems in the Georgia Coastal Plain. All three types of samplers were deployed at three sites on each of the Savannah and Ogeechee River for approximately 30 days during the fall of 2014. Mean, standard deviation, and variance components were examined from 53 common bioassessment metrics and 2 multi-metric indices to assess for potential differences in colonizing macroinvertebrates between the samplers. Only 9 of the metrics examined scored significantly different between sampling devices, however, assemblages colonizing the three sampling devices differed (PERMANOVA; F _14,37 =1.6078, P = 0.001). Results suggest assemblage differences were primarily driven by the proportions of taxa collected by each device, rather than by different taxa colonizing devices altogether. Estimates of variance components attributed a large percentage (i.e., >20%) of the variability encountered to differences between sites, rather than devices. Our study shows that wood samplers are comparable to other devices commonly used for collecting macroinvertebrates from non-wadeable streams in the Georgia Coastal Plain. Furthermore, wood samplers can provide a suitable alternative for bioassessment, although some differences in the proportions of taxa collected with alternative devices should be expected. Determining the precision and overall efficiency of alternative sampling devices is an important step towards developing standard operating procedures for the bioassessment of large coastal plain rivers.