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Tori Harris defends thesis on the impact of sawmill debris on benthic macroinvertebrates

Tori Harris defends thesis on the impact of sawmill debris on benthic macroinvertebrates

On November 21, 2017, Victoria Harris successfully defended her Master’s thesis titled “Determining the impacts of sawmill debris on benthic macroinvertebrate communities within Muskegon Lake, Michigan using traditional and genetic methods of identification”. Her thesis committee members included Drs. Rick Rediske, Charlyn Partridge, and Jim Dunn.

Tori's thesis was to examine the impacts of sawmill debris on Muskegon Lake on the benthic macroinvertebrate communities. Benthic macroinvertebrate samples were collected along transects at sawmill debris and control sites along the northeast shoreline near North Muskegon Water Sports Park at varying in depths. Analyses of the benthic macroinvertebrate communities within Muskegon Lake were conducted using traditional and molecular methods of identification. Traditional analysis of the benthic macroinvertebrate communities indicated sample depths along the control transects were significantly different, while the sawmill debris transects had no differences. Differences between sawmill debris and control macroinvertebrate communities were due largely to differences in Amphipoda, Isopoda, Bivalvia, and Gastropoda densities along with water temperature. NMDS and ANOSIM analyses on average abundance data indicated statistical differences between mill debris and control sites. Analysis of functional trait groups resulted in a similar conclusion, and showed differences in the macroinvertebrate communities between the two site types. Filterer-burrowers, filterer-climber, predators-sprawlers, and shredder-climbers were the most abundant functional trait groups within the control transects, while predator-swimmers were five times greater within the sawmill debris site. Again, a depth gradient was seen with the control transects, while the sawmill debris transects showed no obvious pattern. Molecular methods of identification were done on Chironomidae individuals because they have been considered ideal taxon to be used in ecological metrics. However, the use of this group in ecological metrics is difficult due to problems with traditional species identification. In order to reduce error in identification, we proposed using COI and CytB as molecular markers for chironomid identification. Molecular identifications indicated possible issues with preservation methods of macroinvertebrate specimens, resulting in inconsistently successful extractions, amplification, and sequencing. When DNA barcoding was successful, Chironomidae individuals were sequenced to the correct taxon. We believe these DNA barcoding analyses were another step towards implementing DNA barcoding as the primary method of identifying macroinvertebrates in aquatic investigations to reduce error in identification. As for traditional methods of identification, these analyses do not indicate sawmill debris having a negative effect on the macroinvertebrate communities, but they do show that sawmill debris leads to a difference in community composition.

Since finalizing her thesis submission, Tori has started work as a watershed technician for the Allegan Conservation District.

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