Abstract
Luxuriant growth of Ulvaceae covering a large area was observed in the lower intertidal and sub-tidal zone on a sander of Uranouchi Inlet, Tosa Bay, southern Japan. Water temperature in the survey area was 15.0-15.9°C in February and attained 29.8°C during summer season. Chlorinity ranged 17-18‰ during autumn to spring and became lower during rainy season to summer. The concentration of NH4-N, NO2-N and NO3-N ranged 0.07-4.9μg at./l, 0.01-0.40μg at./l and 0.07-0.49μg at./l respectively during survey period in 1981. Phosphate-phosphorus was 0.3-2.6μg at./l for the same period.
The Ulva bed was found vertically between-2.0∼1.4m D.L. and 100∼200m horizontally across the sander. Fronds of Ulva sp. on the Ulva bed appeared to be growing from May and attained a mean height of 50cm in July. Maximum biomass of the Ulva bed was 980g w.w./m2 in mid August, with a distinct decrease starting from November.
In the transplant experiments, the optimum depth for maximum growth was within one meter below the surface. The frond area of Ulva in the surface layer was 6.8 times that of the initial after 7 days. Fruiting fronds were observed to appear from May to December, but there were many fruiting fronds on the bed during the period from October to November.
