Document Type



Rappahannock Community College

Publication Date

Spring 2015


In the past century, the world has seen an increase in the amount of carbon dioxide (CO2) in the atmosphere. The rise in CO2 can put stress on aquatic ecosystems due to ocean acidification, an overall decrease in the pH of the ocean’s waters. Freshwater ecosystems, already stressed by pollution and recent increases in the number of invasive species are also showing signs of acidification due to the increase in CO2. The effect of the rise in acidity is known to be harmful to calcifying organisms, but the effect on freshwater submerged aquatic vegetation (SAV) is not well studied. The invasive SAV Hydrilla verticallata (Hydrilla) and native SAV Vallisneria americana (tape grass) often compete for similar environments in the freshwater portions of the Chesapeake Bay. Previous studies on the effects of pH changes on Hydrilla found that the SAV may be experiencing phenotypic plasticity allowing it to continue to produce and respire even at the most acidic treatments. This study looked at the respiration and production rates of Vallisneria americana under differing pH’s. Samples of tape grass were incubated in water with a pH ranging from 8.2 units to 5.7 units in a light gradient box for the production treatments and a dark box for the respiration treatments. It was found that at the pH’s closest to the control 7.2, the 6.7 and 8.2 treatments, tape grass experienced no production. In the 5.7 and 6.2 treatments, tape grass experienced significantly higher production rates. Data was collected and analyzed using a One-Way ANOVA and a Tukey’s HSD test. There was a significant difference found in both the production and respiration rates at the varying pH levels. With the stress of an increase in acidity and invasive species, the results of this study suggest that tape grass will continue to produce and respire as a crucial part of freshwater ecosystems.


Adam Parker received the 2nd place Spring 2015 Student Research Paper Award from Rappahannock Community College Library for this paper.



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