Master of Science
Robert B. Gillespie
Date of Award
Out of the nearly 300 species of freshwater mussels (Family: Unionidae) represented in North America, most have exhibited declines in abundance and distribution largely due to anthropogenic impacts. I compared community composition, abundance and richness of mussels in Cedar Creek, Indiana in 2015 with published data from 1988 and 2005. In 2015, five sites in Cedar Creek and seven sites in agricultural headwater streams were surveyed. Additionally, one headwater stream in Hillsdale County, Michigan was surveyed as a high-quality reference site. At each 200 m long site, mussels were sampled with quadrats (sixteen per site) and visual searches. From each quadrat, a quart of sediment was retained for sediment analysis. Physicochemical measurements, habitat analyses, and water chemistry data were collected concurrently with surveys. Fishes were sampled using electrofishing to document the presence of fish host species. Out of thirteen sites sampled in 2015, only six had live mussels. Ten species and 84 individuals were identified and measured from these six sites. The reference and two Cedar Creek sites comprised almost 90% of the individuals found, with the furthest upstream Cedar Creek site having the greatest abundance (28). Only two agricultural headwater streams that were located close to the main stem of Cedar Creek had mussels and only six individuals were found. Lampsilis siliquoidea occurred at four sites in 2015 and was the most abundant and widespread species comprising 31% of the individuals found. The abundance of live mussels within four Cedar Creek main stem sites exhibited a decrease in individuals from 168 in 1988 to 110 in 2005 to 56 in 2015. Additionally, since 1988, no live mussels have been recorded in Cedar Creek between Waterloo and Auburn, Indiana. To assess which factors explain the variation in mussel parameters, I evaluated the relationships of instream habitat, physicochemical, and water chemistry variables with mussel abundance and species richness. Generalized linear regression models revealed a significant positive correlation between dominant riparian vegetation and mussel richness (p<0.01) as well as mussel abundance (p<0.001). A positive relationship with water temperature (p<0.01) and a negative relationship with host fish abundance (p<0.05) also significantly explained mussel abundance. In the CEAP analysis, both mussel richness and abundance were significantly negatively correlated with ammonia and total phosphorous (p<0.05).
Ashley D. Taylor (2016).
Temporal Trends and Influence of Habitat on Freshwater Mussel Communities within Cedar Creek, Indiana.