Recent studies on chemical speciation of trace metals in seawater were reviewed. We introduce a coordination chemistry model to explain the chemical form of trace metals and their concentration levels in open ocean waters. Most of the experimental results determined in the past decade, which were carried out by solution chemistry techniques, have admitted existence of organic metal complexes dissolved in seawater. Apparent discrepancy between metal and ligand titration methods can reasonably be explained by the model containing two strong organic ligands.
Tide and tidal current at the central part of the Seto Inland Sea on 29 March 1185, when the war between Genji and Heisi was carried out, are reproduced. The reproduced tide and tidal current well coincide with the description in "Heike-Monogatari".