Seasonal acclimatization of eelgrass Zostera marina growth to light

Abstract

Weight loss in the dark increased with temperature whereas the slope of growth versus low light intensities was highest at 15°C. The light compensation point for zero growth was, therefore, lower (18.5 μmol m-2 s-1) for October plants than for March (28.3 μmol m-2 s-1) and August (47.3 μmol m-2 s-1) plants. Biomass allocation from rhizomes to leaves increased with reduced light availability and rhizomes required more light than leaves to maintain the biomass. Leaf weight normalized to area declined at low light, which together with allocation from rhizomes caused sustained leaf elongation for several weeks, despite severe shading and loss of plant weight. Experimental light demands for zero growth for March and October plants were equivalent to 11% of in situ surface irradiance, which is close to estimated light levels at eelgrass depth limits. Eelgrass biomass, however, is expected to increase at the depth limit during summer and to be expended for survival at low light during winter. -from Authors