Nitrogen is an important nutrient in marine environments and is continually converted from one form to another. One way these processes can be investigated is by looking at the ratio of the ¹⁵N and ¹⁴N stable isotopes of different nitrogen-containing compounds. To date few studies have compared these ratios in seagrass beds, their associated sediments and the porewater NH₄⁺ pool. The strong relationship between these nitrogen pools suggests that nitrogen is tightly recycled within seagrass beds.