GROWTH CHARACTERISTICS OF MICROALGAE ON MAGNESIA MORTAR CONTAINING SHOCHU DISTILLATION LEES AT THE BEGINNING OF SETTING IN THE SEA

The aim of this study was to confirm the effect of magnesia mortar and Shochu distillation lees on the growth of microalgae in the sea. Cylindrical blocks made of four different materials, namely cement mortar (CM), magnesia mortar (MM), and cement and magnesium mortars containing Shochu distillation lees fermented by lactic acid bacteria (CS, MS) were used for experiments conducted in summer and winter. The blocks were placed in the sea covered with a net to prevent fish from eating the microalgae growing on them. Seawater temperatures were recorded with a temperature meter at 10-min intervals. Ten blocks were collected after three days, one–six weeks in the summer experiment, after one–three weeks in the winter experiment, and placed in an N, N-dimethylformamide solution. The concentrations of chlorophyll a were measured to determine the density of chlorophyll a in the microalgae on the blocks. The seawater temperature was 26–31°C in the summer experiment and 17–21°C in the winter experiment. The density of chlorophyll a increased for one to two weeks after setting in the sea during the summer experiment and decreased gradually from three until six weeks after setting. The density of chlorophyll a in MS was significantly higher than in CM at one, three, and six weeks after setting in the summer experiment and one and two weeks after setting in the winter experiment. Magnesia mortar and Shochu distillation lees contributed to the growth of microalgae in the sea.