Responses of subepilimnetic primary producers to experimental lake acidification

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1991

OSTI ID:5241822

Moffett, M F

Subepilimnetic phytoplankton communities were found to increase in abundance during experimental acidification with sulfuric acid of two Canadian Shield lakes, Lake 223 and Lake 302S, at the Experimental Lakes Area (ELA) in northwestern Ontario. As epilimnetic pH declined in Lake 223, small, edible species of phytoplankton increased more than larger, less edible taxa. Species diversity ultimately decreased when epilimnetic acidity reached the target pH 5.0. In Lake 302S algal populations, Chrysochromulina spp. and Chlamydomonas sp., reached [open quotes]bloom[close quotes] conditions below the epilimnion in the third and fourth summers, respectively, of sulfuric acid additions as pH declined from above pH 6 to pH 5.6 and 5.4. Meta- and hypolimnetic waters of these lakes did not experience similar declines in pH. All responses in Lake 223 and Lake 302S were in contrast to communities in 5-10 ELA lakes not undergoing acidification. Vertical depth profiles of chlorophyll fluorescence were used to follow trends in subepilimnetic communities during the first four years of sulfuric acid additions to Lake 302S. Fluorescence was found to reliably predict chlorophyll a concentrations (r[sup 2] = 0.80-0.94). Characteristics of subepilimnetic communities and the habitats in which they were located were studied at the ELA. Many were mixed with photosynthetic bacteria. Fluorometric techniques with DCMU (3-(3,4-dichlorophenyl-1,1-dimethyl urea)) were used to determine which fluorescence maxima contained viable algal populations. In situ inorganic carbon uptake rates for the algal-dominated communities below the epilimnion were similar to rates by epilimnetic communities. Enclosure experiments demonstrated that growth and inorganic carbon uptake rates of subepilimnetic algal populations were light-limited.

• Research Organization: Kansas Univ., Lawrence, KS (United States)
• OSTI ID: 5241822
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540320* -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (1990-)
550500 -- Metabolism
59 BASIC BIOLOGICAL SCIENCES
ACIDIFICATION
AQUATIC ECOSYSTEMS
AQUATIC ORGANISMS
BIOLOGICAL EFFECTS
ECOSYSTEMS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
LAKES
LIMNOLOGY
PHYTOPLANKTON
PLANKTON
PLANTS
POPULATION DYNAMICS
SPECIES DIVERSITY
SULFURIC ACID
SURFACE WATERS