2:00 PM - 2:15 PM
[AOS13-08] Influence of Nori aquaculture-induced change in light environment on phytoplankton dynamics
Keywords:Aquaculture, Ariake Sea, Light environment
We installed a photon meter (DEFI2-L by JFE Advantech Co., Ltd.) and pressure gauge (DEFI2-D10 by JFE Advantech Co., Ltd.) respectively in the sea area just under the Nori aquaculture and in the non-Nori aquaculture area possessed by the Saga Prefecture Fisheries Experiment from January 15 to 25 in 2019. This continuous observation was carried out at 5 second intervals. As a result of the observation, it was revealed that the photon quantum amount decreased by about 75% on average just under Nori aquaculture area. The reduction of this photon (light shielding factor y) was expressed as a function of the leaf length (x unit: cm), and the following equation was obtained.
Next, we developed a numerical ecosystem model that takes this light shielding factor into consideration and examined how it affects phytoplankton dynamics. Calculation was carried out separately into two patterns with and without light shielding factor in Nori aquaculture area. In consideration of the light shielding factor, the phytoplankton biomass was reduced in the vicinity of the Nori aquaculture area in the inner part of Ariake sea, compared to the case without consideration. This indicates that Nori aquaculture suppresses the growth of phytoplankton by deteriorating the light environment in water.