Depth distribution of photosynthetic activity in a Myriophyllum, spicatum community in Lake Wingra1

Photosynthetic rates and productivity of Myriophyllum spicatum L. were examined in the littoral by incubating shoot sections at three rooting depths using a 14 C technique. At a rooting depth of 240 cm, the interrelation of biomass and photosynthetic rates resulted in the production of 56% of the total photosynthetic productivity within 100 cm of the water surface in May. In August, 57% of the total productivity occurred within only 20 cm of the surface. Variations in the depth distribution of biomass, due to differing growth and sloughing patterns, resulted in different depth relations of photosynthesis at the other rooting depths. Light extinction and light adaptation of photosynthetic tissues were other factors determining the depth relations of photosynthesis.