Evaluation of Whole-Lake Nitrogen Fertilization for Controlling Blue-Green Algal Blooms in a Hypereutrophic Lake

Abstract

Indian Lake, a shallow hypereutrophic lake in southern Wisconsin, was treated with ammonium nitrate to test whether high dissolved inorganic nitrogen (DIN) concentrations or high total nitrogen to phosphorus (N:P) ratios could prevent the development of summer blue-green algal blooms (predominately Microcystis aeruginosa). The fertilizer was applied weekly from late April to early July 1981–82 in annual amounts of 14 and 23 g N/m2, respectively. In 1981, a dense summer blue-green algal bloom developed, although both dissolved inorganic phosphorus (DIP) and algal P (particulate P/chlorophyll a) were lower than in summers without fertilizer treatments. In 1982, unusually clear water in May allowed aquatic macrophytes and associated filamentous algae to become very dense in June. The increase in water clarity and macrophytes was probably a response to a fishkill the previous winter. Later in the summer the macrophyte community disappeared and a blue-green algal bloom developed. After each fertilization in both treatment years, the NH4+ and NO3− decreased rapidly, suggesting nitrification/denitrification in the lake sediments. Whole-lake N fertilization did not prevent the summer blue-green algal blooms in Indian Lake. Low DIN apparently does not trigger the bloom development or cause the vernal nonblue-green algae to decline. Also, Sow total N:P ratios (<11 by weight) during the blooms occur partly because of high DIP and because of high algal P levels resulting from luxury P consumption. The Indian Lake data suggest that low total N:P ratios are only predictive of (or resultant from) blue-green algal blooms rather than causative.

Comparative effects of urea, ammonium, and nitrate on phytoplankton abundance, community composition, and toxicity in hypereutrophic freshwaters

“…As suggested previously (Downing et al 2005), added N also increased the concentration of MCs by two-to 13-fold in late summer, although the magnitude of response varied with the chemical form of N and the relative importance of Planktothrix or Microcystis spp. Combined with insights from prior laboratory (Turpin et al 1985;Berman and Chava 1999), mesocosm (Barica et al 1980;Levine and Schindler 1999;Finlay et al 2010), whole-lake (Barica et al 1980;Lathrop 1988), and catchment analyses Bunting et al 2007), these findings show that pollution with N can further increase algal abundance and toxicity in highly eutrophic lakes, but suggest that the magnitude of effect may depend on the chemical form of N influx.…”

Responses of a eutrophic pond community to separate and combined effects of N:P supply and planktivorous fish: a mesocosm experiment

“…Although phosphorus is the nutrient most often positively correlated with plankton biomass (Smith & Shapiro, 1981 ;McQueen et al, 1986), nitrogen can also affect plankton communities (Lathrop, 1988). Algal species have taxa specific requirements for supply ratios of nitrogen : phosphorus (N : P) ranging from 7 : 1 to 45 : 1 (by atoms) (Suttle & Harrison, 1988) and the relative concentrations of nitrogen and phosphorus can determine phytoplankton biomass and species compo-161 sition of lakes (Smith, 1982(Smith, , 1983McQueen & Lean, 1987 ;Suttle & Harrison, 1988 ;Lathrop, 1988).…”

Eutrophication of lakes cannot be controlled by reducing nitrogen input: Results of a 37-year whole-ecosystem experiment

“…In another case study, N addition was futile because it was rapidly denitrified. Water quality improved, but this was attributed to a fish kill and subsequent expansion of macrophyte cover (28). Unless N concentrations are of concern for human health, funds for eutrophication control are better spent on more complete removal of P sources.…”