PS 1-11
Impacts of Mollusca and Gastropoda shell production and their possible role as ecosystem engineers in Missisquoi Bay
Shell production in aquatic ecosystem has proven to be an important process with many ecological implications especially in benthic communities. Caddisflies and zebra mussels have been shown to facilitate benthic communities because their cases and shells stabilize the substrate, increase habitat heterogeneity, and provide hard substrates in soft sediment habitats. In this study, I looked for relationships between snail shell and mollusk shell accumulation and the abundance and species richness of benthic macroinvertebrates. I hypothesized that a higher number of shells would be associated with increased species richness and total abundance of the benthos. To test these hypotheses we obtained 332 samples from the benthos of Missisquoi Bay in Lake Champlain using a petite ponar sampler. The macroinvertebrates were preserved and later identified to the lowest taxonomic level possible.
Results/Conclusions
There was a subtle but statistically significant increase in species richness with abundance of empty snail shells. There was an average of 1.5 more species found in samples that included 1 or a few mussel shells as compared with samples lacking shells. I rarified the sums of samples in each of 3 categories: zero mussel shells present; 1 or 2 shells present; 3 or more shells present. Both curves for samples with mussels present fell slightly below but within the 95% confidence interval of the zero shells present curve. This result supports the passive-sampling model of succession: mussel shells intercept more individual colonists and so local abundance increases. Because abundance is higher there tend to be more species present at sites with mussel shells. This result expands upon previous marine work and draws important connections between freshwater and marine ecology.