Effects of Experimental Acidification on Phyto‐, Bacterio‐and Zooplankton in Enclosures of a Highly Humic Lake

Abstract

I n situ enclosure experiments were performed in a highlr humic lake to examine the effects of acidification on phyto-, bacterio-and zooplankton. The acidity of three enclosures was adjusted with H 2 S 0 4 to pH 3.5, 4 and 5 and one enclosure and the lake served as controls. The diversity of plankton as well as the mean concentration of chlorophyll a, primary production and respiration of plankton decreased with increasing acidity. Bacterial density was slightly lower in the pH 3.5 enclosure than in the other enclosures and in the lake, but there were no differences in the morphological type or mean volume of the cells between different treatments. In theacidifidenclosures Cryptomonas ozwh and Chlainyclomonas spp. were the dominant phytopisnkters, while Dinobryon and Mallmnonas species seemed t o be most sensitive to acidity. Keratella cochleuris, Kellicoftia longispina and Bosminca. longispina were the most tolerant zooplankton to acidity.

Filamentous algal communities related to pH in streams in The Trossachs, Scotland

“…The results support the findings of Arvola et al (1986), Nalewajko & O'Mahony (1988) and Collier & Winterboum (1990), that a reduction in water pH is accompanied by a decrease in algal standing crop. Since an increased biomass of periphytic algae has been considered a consequence of addification (Stokes, 1981), it is necessary to consider how such diversity of reports could arise.…”

“…Differential sensitivity of algae to Al has been shown previously (Claesson & Tomqvist, 1989) and it is possible that pulses of Al occurring in add episodes may stress more sensitive spedes and eliminate them from the community. A decrease in diversity with addification was also reported by Arvola et al (1986) and Findlay & Kasian (1990). However, Planas et al (1989) found that artifidal addification produced little change in the diversity of periphytic algal communities comprised mainly of diatoms.…”

Effects of acidification on aquatic ecosystems

“…The disappearance of the copepod Cyclops scutifer at pH < 5.0 apparently results from disturbances of normal reproduction and population replenishment, rather than from direct poisoning of adult individuals (Tessier and Horowitz, 1988). An adult Cyclops scutifer can live in highly acidic water (pH 4.0-3.5), but its progeny fails to develop (Arvola et al , 1986). The decrease in reproductive efficiency observed in Daphnia pulex was related to disturbances of its maturation.…”

Tolerance of Ceriodaphnia quadrangula and Diaphanosoma brachyurum(Crustacea: Cladocera) to experimental soft water acidification

“…For example, C. quadrangula is supposed to be a typical faunal element of acidic humic bog lakes. It was reported from soft water lakes with pH values down to 3.9 (Arvola et al, 1990;Flo¨ßner, 2000) and even was present at pH 3.5 in an artificially acidified humic lake in Finland (Arvola et al, 1986). However, C. quadrangula occurred in only a few Swedish lakes below pH 6 (Berzins & Bertilsson, 1990).…”

“…Among others, the plankton assemblage is affected (Arvola et al, 1986(Arvola et al, , 1990Havas & Rosseland, 1995;Edberg et al, 2001). Some cladocerans may occur in a broad range of pH values (Berzins & Bertilsson, 1990), but diversity significantly declines at low pH (Fryer, 1980;Arvola et al, 1986Arvola et al, , 1990.…”