EFFECT OF STREAM SIZE ON DENSITY OF A HEADWATER SPECIES OF AQUATIC SNAIL (ELIMIA PROXIMA)
As an abundant scraper, the aquatic snail Elimia proxima has a significant influence on the ecology of headwater streams in the Appalachian Mountains. Because density of organisms strongly influences their roles in their environment, we tested the hypothesis that the density of E. proxima depends on stream size. We chose 13 streams of varying sizes within the Middle Fork of the Broad River System in Banks, Habersham, and Stephens counties, Georgia. We used two methods to determine snail density in each stream. In the first, we took the mean of snails counted in 6 quadrats, each measuring 1 m2, chosen as representative of different stream microhabitats. Secondly, we measured the amount of time required to count 25 snails, referred to herein as snail time). Because this second method is more time efficient, we tested for a potential correlation between the two density measures. We also took mean streambed widths of 6 representative sites along the same stream section where we counted snails in each stream. To test our hypothesis, we regressed snail time against mean streambed width, using log-transformed data. Because we ran two statistical tests on the same data, we tested for significance at a Bonferonni-adjusted alpha level of 0.025. We found a high level of correlation between density measures (r = -0.919, P < 0.0001), indicating that the time-constrained count is an effective, time-efficient method of measuring density. Moreover, we found a significant dependence of snail density (snail time) on stream size (r2 = 0.549, P = 0.0091). Our data support the idea that E. proxima is a headwater species, indicating that this species exerts its greatest ecological influence in the smallest streams.
Ash*, Jenna and Camp, Carlos D.
"EFFECT OF STREAM SIZE ON DENSITY OF A HEADWATER SPECIES OF AQUATIC SNAIL (ELIMIA PROXIMA),"
Georgia Journal of Science, Vol. 81, No. 1, Article 2.
Available at: https://digitalcommons.gaacademy.org/gjs/vol81/iss1/2