Change Nutrient Concentration Related to the Decrease in Productivity of <i>Monostroma nitidum</i> Farms

MIYAMUKAI Tomoki, ICHIKAWA Tetsuya, AKASHI Yuzou, TASAKI Tomoaki, SUZUKI Teruaki, TANAKA Yoshito

doi:10.57296/jaczs.34.1_15

<p>ABSTRACT : In the inner bays of Japan, the decrease in seaweed aquaculture production due to lack of nutrients has become a problem, and the relationship of nutrients and production of Monostroma nitidum also in the Izonoura of Matoya Bay, which is of this study. The current situation was grasped by comparing the nutrient concentration including the inflowing river with the past. As a result, both DIN* (inorganic nitrogen excluding NH₄-N) and PO₄-P concentrations in the sea decreased from the past (1996-97) to the present (2014-15). DIN* is mainly caused by a decrease in river concentration, which is caused by changes in domestic wastewater treatment methods in the inflow river catchment area, and reduced fertilizer usage on farms. On the other hand, it was suggested that decrease of PO₄-P concentration caused by the decrease of supply from the bottom mud in addition to the decrease in river load. The amount of nutrient regression estimated from the abundance of benthos has decreased by 37 to 67% compared to the past, and the decrease was large compared to the decrease of 39% in river load. Furthermore, the increase in phytoplankton caused by the decrease in the eating pressure of benthos was considered to be one of the factors that decreased the nutrient concentration in the sea.</p>

Change Nutrient Concentration Related to the Decrease in Productivity of <i>Monostroma nitidum</i> Farms

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