Gyttja production by charophytes and its roles in the interaction with other submerged species in an oligotorphic lake

Abstract

Charophyte ecology in Lake Myall, an oligotrophic lake in Australia, was investigated particularly focusing on the interaction with Najas marina and Myriophyllum salsugineum. Chraophytes intensively produces Gyttja, accumulating on the bottom. The Gyttja layer with its soft characteristics and low Redox potential inhibits colonization of submerged species except for Charophytes and Najas, thereby extremely decreasing biodiversity of flora of the lake. In Lake Myall, under high current, where Gyttja is washed away, M. salsugineum can grow on rocky bottom worsens the light climates for Charophytes, while in stagnant water, N. marina, although low in biomass most of the year, vigorously grows in May, suppressing Charophyte communities, although they are tolerant in low light regime. These process was confirmed by measuring light intensity inside the plant canopy, compared with depthwise and biomass distribution in the lake.