Physiological ecology of a species of the filamentous green alga Mougeotia under acidic conditions: Light and temperature effects on photosynthesis and respiration

Abstract

One of the earliest and most reliable indications of acid precipitation affecting freshwater systems is the development of littoral blooms of the filamentous green alga Mougeotia (Zygnematales, Charophyceae). Field observations of depth distribution and seasonal abundance in Little Rock Lake, an experimentally acidified seepage lake in north-central Wisconsin, suggest that Mougeotia might prefer warmer temperatures and carry out net photosynthesis at fairly low light levels. To test these hypotheses, we measured net photosynthesis and respiration at 56 combinations of irradiance and temperature in a controlled environment facility. Optimum conditions were 25°C and 300-2,300 bmol quanta m-2 s-I. Over this range, net photosynthesis averaged 40.4 mg 0, g-l h-l. Respiration rates increased with both temperature and prior irradiance. Lightenhanced respiration rates were significantly greater than dark respiration rates following irradiance 2 164 pm01 quanta m-* s-l. Mougeotia's photosynthetic response to temperature and irradiance explains aspects of its growth and distribution in acidified lakes but it does not by itself explain the magnitude of this alga's growth at low pH.Since the early 197Os, acidification of freshwater systems by acid precipitation has been increasingly recognized as a widespread and significant environmental problem. One of the earliest and most reliable indications of acid precipitation affecting freshwaters is the development of littoral blooms or mats of filamentous green algae of the family Zygnemataceae. The genus Mougeotia is one of the most common bloom-forming alga in acid waters of Europe and North America. Despite the frequency with which Mougeotia is cited as an indicator of acidification, little is known about its ecology or physiology. Why should Mougeotia rather than some other alga be so frequently associated with acidification? The most Acknowledgments

Palaeoecological reconstruction of the late Oligocene Maar Lake of Enspel, Germany using lacustrine organic walled algae

“…They (depending on the species) are able to live in the cold polar streams of Antartica as well as in hot thermal springs (Kleeberg 2004). But their optimum temperature is about 25°C (Graham et al 1996). Therefore, single species of Zygnemataceae are alternating in lakes depending on the prevailing temperature (Jacob and Kapfer 1999).…”

Terrestrial organic matter support of lake food webs: Evidence from lake metabolism and stable hydrogen isotopes of consumers

“…Autotrophic dark respiration was set to 20% of net primary production (Graham et al 1996). Minimum and maximum values of allochthony, R, were estimated by assuming that 0% or 100% of the net primary production was used for heterotrophic respiration.…”

Growth characteristics of bloom-forming filamentous green algae in the littoral zone of an experimentally acidified lake

“…This phenomenon was first observed in Scandinavia (Hendrey et al 1976;Almer et al 1978) and later seen in culturally and experimentally acidified lakes of North America (Schindler and Turner 198%;Stokes 1986;Howell et al 1990;Brezonik et al 1993;Turner et al 1995b). Yet aside from studies of artificial substrata (Miiller 1980;Fairchild and Everett 1988), preliminary ecological research (Wei et al 1989;Howell et d. 1990; France and W e l b o w 1992), and recent physiological research (Graham et al 1995), relatively little is known about the ecology of FGA growth in acid lakes.…”