Seasonal growth of Laminaria groenlandica as a function of plant age

Abstract

The seasonal growth of Laminaria groenlandica (Laminariales, Phaeophyta) on the west coast of Vancouver Island, B.C., Canada, was investigated as a function of plant age, using plants maintained at a constant depth on rope structures. First-year plants, which become macroscopically visible in March, had a delayed seasonal peak of maximum blade size relative to the older year classes (April–May) which initiated growth in January. This resulted from the 1st-year plants' lower susceptibility to distal blade erosion and prolonged net growth season. All year classes obtained their greatest wet weight at the same time (July–August). For 1st-year plants, this represented a balance between blade erosion and elongation; for older plants, storage product synthesis and blade thickening and elongation balanced against erosion appeared responsible for determining maximum biomass. The 2nd-year class dominated the other year classes in blade dimensions and few plants survived their 3rd year of growth. The instantaneous growth rates of L. groenlandica were most closely associated with temperature, followed by photon flux density, and changes in growth rates were associated with temperature and salinity.