Growth rates and photon yield of growth in natural populations of a marine macroalga Ulva lactuca

Abstract

Examined the photon yield of growth of free-floating Ulva lactuca in a eutrophic Danish estuary (Roskilde Fjord) by exposing discs in mesh cages to 10, 40, and 100% of ambient light in shallow water. Growth per incident or absorbed photon was much higher at 10 than at 100% of ambient light. Growth was linearly related to photon flux density in low light and U. lactuca adapted to the shade by increasing the chlorophyll concentration and thus the photon absorptance in the tissue. Maximum yields at high temperatures in August-September ranged from 16.0 to 21.7 mmol C mol-1 incident photon and 40-61 mmol C mol-1 adsorbed photon at 10% of ambient light. -from Authors