A research note: Potential importance of N2fixers in the coastal northwestern East/Japan Sea

Biological nitrogen ( N 2 ) fixation, a fundamental step in aquatic and terrestrial N cycles, is an important process through which “new” reactive nitrogen (N) is produced. The role of N 2 fixation in fueling the occurrence of harmful algal blooms (HABs) is one of the major concerns in the present scenario. Since N 2 fixation occurs under highly specific environmental conditions, determining the suitability of various ecosystems for potential N 2 fixation is important. The introduction of 15N2 bubble experiments in 1995 has led to significant N 2 fixation rate estimates from various parts of the world oceans; however, Korean coastal waters, which are prone to HABs, remained unstudied. The present study aimed to construct a research note on N 2 fixation in the Korean coastal waters on the basis of a preliminary data set of N 2 fixation rates (range; 0.31–2.35 nmol N L−1 h−1) obtained from the coastal northwestern East/Japan Sea. The results indicate that N 2 fixation is not currently a significant N source in the northwestern East/Japan Sea. However, the possibility of N 2 fixers being a future significant N source and a fuel for HABs in the East/Japan Sea under favorable environmental conditions cannot be ruled out.