Jm. Graham et al., EFFECTS OF PH AND SELECTED METALS ON GROWTH OF THE FILAMENTOUS GREEN-ALGA MOUGEOTIA UNDER ACIDIC CONDITIONS, Limnology and oceanography, 41(2), 1996, pp. 263-270
When acid precipitation impacts freshwater systems, littoral blooms of
the filamentous green alga Mougeotia (Zygnematales, Charophyceae) fre
quently develop. Field observations of its development in Little Rock
Lake, an experimentally acidified seepage lake in north-central Wiscon
sin, indicated that the species of Mougeotia present there may have an
optimum pH for growth of similar to 5.2. Because a number of metals i
ncrease in concentration in acidified waters, we also proposed that th
is species of Mougeotia may be particularly tolerant of metals. To tes
t these hypotheses, we grew Mougeotia from Little Rock Lake in culture
at eight levels of pH (3 through 10) and measured net photosynthesis
and respiration at each level. We also grew this isolate over a range
of Zn concentrations from 10 to 2,400 mu g liter(-1) and Al concentrat
ions from 10 to 3,600 mu g liter(-1). Little Rock Lake Mougeotia grew
over a broad range of pH levels from 3 to 9 with an optimum at 8, in c
ontrast to our expectation. Mougeotia, however, was tolerant to levels
of Zn and Al considerably higher than the elevated levels to which it
had been exposed in the acidified basin of the lake. Mougeotia may gr
ow luxuriously in acidified waters because of an efficient uptake of C
O2 and dissolved organic C and a lack of grazing pressure.