Nitrogen flow and distribution in a northern Michigan dune system

Abstract

While the study of nutrient flow from terrestrial habitats to aquatic habitats is well known, little is known of the nutrient flow from aquatic to terrestrial habitats. The study of nitrogen flow from water to land in a northern Michigan dune system may provide an accurate measure of nutrient transfer. The purpose of this study was to determine the ratios of N-14 to N-15 in American beach grass in transects at various distances from the shore in hopes of explaining how aquatic nitrogen is distributed in a dune system. Samples of Ammophila breviligulata were taken from four transects running parallel to the shoreline at 0, 10, 20 and 30 meters from the shoreline. Washed up algae were also collected at random along the shoreline to act as a control. δ N-15 values, total percent nitrogen, and percentage of nitrogen obtained from aquatic or terrestrial sources were calculated for each distance. Results supported our hypothesis that the proportion of N-15 isotope would decrease as the distance from shore increased. Only samples taken at 0 meters showed a significant amount of aquatic nitrogen in proportion to terrestrial nitrogen. Physical and biological factors may account for the difference in distributions of the two nitrogen isotopes.