A NEW APPROACH FOR PREDICTING GREEN TIDES IN THE YATSU TIDAL FLATS USING ARTIFICIAL INTELLIGENCE

Abstract

 The Yatsu tidal flats, located in the inner part of Tokyo Bay, are among the most significant tidal flats remaining in Japan. The tidal flats were registered as a Ramsar site in 1993 because of the numerous migratory birds that visit the wetland annually to breed and feed. In recent years, the occurrence of green tides due to the extraordinary growth of Ulva spp. has become problematic. Since 1995, the green tides have severely impacted the ecology of the area. However, the green tides disappeared suddenly in 2017, and did not occur again until 2020. Although numerous models have been developed to predict the occurrence of green tides, none of these models have been sufficiently robust. In this study, as a follow-up to a previous study examining the causes of extinction in 2017-2018, the reasons underlying the disappearance of green tides from 2019 to 2020 in the Yatsu tidal flats were examined based on field observations. We also constructed a green-tide prediction model using artificial intelligence and a neural network. The results showed that the disappearance of green tides from 2019 to 2020 was due to insufficient illuminance due to a long rainy season as well as high water temperatures. The predicted values for the green tide area generated by the model closely corroborated actual observations in the field. In addition, water temperature, nitrogen, and phosphorus greatly affected the incidence of green tides at the Yatsu tidal flats.