Examination of the amount of MAAs in dulse at different time periods

The composition of seaweeds fluctuates greatly depending on the time of year. We investigated the amount of MAAs in the samples from January to May in 2019 and 2020 (Fig. 4), based on the idea that the amount of MAAs may also change depending on the time of year.

The results showed that the amount of MAAs increased from February to March in both years. We also found a gradual decrease after March.

We believe that one of the reasons for this is that the amount of ultraviolet radiation increases as we move toward summer. The sampling site is located near Eruption Bay. Eruption Bay is known to be depleted of nutrients and other substances due to the spring bloom that occurs every year when diatoms proliferate due to ocean currents. Therefore, it was thought that the amount of MAAs might be decreasing due to nutrient depletion despite the increase in UV radiation.

Figure 4. Monthly MAAs amounts and erythema UV intensity for 2019 and 2020, shown in green for 2019 and blue for 2020. Erythema UV intensity was obtained from JMA data. The data were sampled on January 23, February 25, April 2, and May 17 for 2019 and on January 14, February 13, March 18, April 27, and May 27 for 2020.