Constraining nitrogen sources to a seagrass-dominated coastal embayment by using an isotope mass balance approach

Nitrogen (N) is often the key nutrient limiting primary production in coastal waters. Quantifying sources and sinks of N therefore critical to understanding factors that underpin productivity ecosystems. Constraining nitrogen inputs can be difficult for some terms such as fixation marine exchange a consequence uncertainties associated with scaling stochasticity. To help overcome these issues, we undertook budget incorporating an isotope mass balance constrain large oligotrophic embayment (Western Port, Australia). The total input Western Port was calculated 1400 Mg year−1, which remarkably consistent previous estimates sedimentation rates within system. Catchment inputs, fixation, atmospheric deposition comprised 44, 28, 28 13% respectively. Retention marine-derived equated ~3 ~10% NOx flushed through system from end-member. relatively high contribution compared studies most likely due proportion nutrient-limited intertidal sediments where mediated by seagrasses sediment cyanobacteria.