Halophila hawaiiana is a Native Hawaiian seagrass that creates a habitat relied on by many organisms. H. hawaiiana is labeled as vulnerable to stressors likely due to development, invasive species, and pollution. Low leaf density of seagrass in Maunalua Bay compared to other populations of seagrass on Oahu has been observed this is possibly due to marine pollution. This study will measure the effects of ammonium exposure, simulating marine pollution, on H. hawaiiana.