Effect of Water Temperature on the Growth of Laminaria japonica (Laminariales, Phaeophyceae) at the Coast of Shiriyazaki, Shimokita Peninsula, Japan

Abstract

Relationship between the standing crop of Laminayia japonica and water temperature was investigated at the coast of Shiriyazaki, Shimokita Peninsula, Aomori Prefecture. Growing densities of the sporophytes of L.japonica were calculated from the number of plants at 53-70 points at depths of 2.5 m, 5 m, 10 m, 15 m, and 20 m from June to July of each year from 1984 to 2002. The water temperature was measured at a depth of 5 m. The significant negative relationship between their densities and the water temperature of January to March by 1% level was accepted. Among those, the growing densities of 1st year and 2nd year sporophytes (L₁ and L₂) indicated a value with the most significant simple correlation of -0.889 and -0.787, for the water temperature of the 5th pentad in January (Tc₅) and of the 3rd pentad in March of the previous year (Tp₁₅), respectively. As a result, applying these relationships to exponential regression equations, can be expressed as follows:
L₁=exp (11.600-1.024×Tc₅) R=0.957
L₂=exp (7.523-0.983×Tp₁₅) R=0.939
The biomass of the 1st year sporophytes and the 2nd year harvestable sporophytes can be predicted from the water temperature of such period.