In situ production of charophyte communities under reduced light conditions in a brackish-water ecosystem

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.

Testing and development of different metrics and indexes describing submerged aquatic vegetation for the assessment of the ecological status of semi-enclosed coastal water bodies in the NE Baltic Sea

“…The two last mentioned bays are under the influence of freshwater inflow from rivers, which affects water transparency and nutrient content; water transparency is also influenced by resuspension of soft sediments. Although resilience to the reduced light availability of the production of charophytes has been detected by different authors before (Marquardt and Schubert, 2009;Kovtun-Kante et al, 2014), the loss or degradation of charophyte communities is detected under severe eutrophication pressure (Schubert and Blindow, 2003;Selig et al, 2007). An example from our study area shows that charophyte communities disappeared from Haapsalu Bay under the influence of sewage inflow during the 1970s (Trei, 1984).…”

Changes in submerged macrophyte colonization in shallow areas of an oligo-mesotrophic lake and the potential role of groundwater

“…Minimum light requirements for charophytes and submerged angiosperms are comparable (Sand-Jensen and Madsen, 1991). In addition, Kovtun-Kante et al (2014) have shown that shallow water C.…”

Ecosystem Services

“…Within two weeks, the charophyte community recovered in spite of a constant reduction of light down to 25% of the natural irradiance, suggesting that charophytes are able to adapt to a low light environment and recover their photosynthetic performance even under stressful brackish conditions (Kovtun-Kante et al 2014).…”

“…Reduced light conditions need however not have long-term effects. Effects of decreased water clarity on production of charophytes was examined by in situ measurements on the Estonian coast (Kovtun-Kante et al 2014), by simulating reduced light conditions. The results showed that net photosynthetic production of charophytes was reduced, but only within the first 24 hours.…”

“…They are highly productive ecosystems that purify the water (c.f. Kautsky 1981, Kufel and Kufel 2002, Kovtun-Kante et al 2014, Rodrigo et al 2014, protect against erosion and storm surges (c.f. Brix 1997, Madsen et al 2001, Horppila and Nurminen 2003, Rönnbäck et al 2007, Costanza et al 2014, fuel marine food webs through the capture, storage and export of carbon (Dayton 1985, Krumhansl andScheibling 2012), as well as being important nursery grounds for many species, including commercial fish species (Norderhaug et al 2005).…”