In situ production of charophyte communities under reduced light conditions in a brackish-water ecosystem; pp. 28–38

Abstract

There is a lot of circumstantial evidence that light conditions affect the growth and distribution of charophyte communities. In general, limited light availability causes plants to reduce their growth and ultimately disappear from the area. We experimentally evaluated how reduced water transparency affected the photosynthetic production of a charophyte community dominated by Chara aspera and C. canescens in a brackish-water ecosystem of Haapsalu Bay in June–July 2009. Plastic shades were used to manipulate light conditions in the experimental plots. Two types of nets were used so that plants received either 25% or 50% of the natural irradiance relative to the control community (100%). The results clearly demonstrated that light limitation significantly reduced the net photosynthetic production of charophytes, but a considerable effect was observed within the first 24 h only. What is more significant, the charophyte community recovered its photosynthetic production within two weeks of the experiment in spite of the constant reduction of light down to 25% of the natural irradiance. This suggests that charophytes are able to adapt to a low light environment and recover their photosynthetic performance within a short period even under stressful brackish-water conditions.