Phytoplankton nutrient limitation in Colorado mountain lakes

Abstract

SUMMARY. 1. Limiting nutrients for phytoplankton were studied experimentally in eight mountain lakes of central Colorado between May and November of 1984. 2. Five categories of phytoplankton limitation were identified: no limitation, N limitation, P limitation, concurrent limitation (stimulation only by simultaneous additions of N and P), and reciprocal limitation (stimulation by addition of either N or P). The phytoplankton communities of three lakes were primarily N‐limited, one was primarily phosphorus‐limited, and four showed primarily combined limitation (concurrent or reciprocal). Switching between categories of limitation was also observed within lakes. Nitrogen was the most frequently limiting nutrient; N, either alone or in combination with P, accounted for 79% of all observed instances of limitation. 3. Nine indices were tested for effectiveness in predicting phytoplankton limitation by N and P. The best indices for discriminating all limitations were ratios of dissolved inorganic N: total P (84% accuracy) and dissolved inorganic N:total dissolved P (80% accuracy). The effectiveness of these indices may be explained by the degree to which they represent N and P fractions actually available to the phytoplankton.

Nutrient limitation of bacterioplankton growth in Lake Dillon, Colorado

“…2). Similar primary production trends have been noted previously for the lake (Lewis et al 1984;Morris and Lewis 1988) and can be explained by the relief of nutrient limitation that develops during summer stratification. Pheophytin a, which is an index of decomposition or of zooplankton grazing (Carpenter and Bergquist 198 5), showed only slight seasonal variation; maximum values occurred in fall and under the ice (Fig.…”

“…NO3 concentrations in the epilimnion were between 15 and30 pg N liter-' in 1987 and~2 pg N liter-l in 1988. NO3 concentrations in the 1988 epilimnion indicate severe N limitation of phytoplankton (Morris and Lewis 1988).…”

“…Nomenclature and categories of nutrient limitation defined for phytoplankton nutrient limitation by Morris and Lewis ( 1988) are applicable to bacterioplankton communities and are used here. Four distinct Tdr incorporation responses to nutrient additions are possible: no significant difference in mean Tdr incorporation rates between nutrient addition treatments (no limitation); significantly greater means in treatments that include C (C limitation), N (N limitation), or P (P limitation); significantly greater means only with simultaneous additions of two or more nutrients (concurrent limitation, symbolized N+P, N+C, C+P, or N + P+ C); and significantly greater means with separate applications of two or more nutrients and with addition of these nutrients in combination (reciprocal limitation, symbolized N/P, N/C, C/P, or N/P/C).…”

“…During 1987 and 1988, we studied bacterioplankton growth and nutrient limitation in Lake Dillon, a mesotrophic Colorado mountain reservoir (elevation, 2,750 m; surface area, 1,330 ha; Morris and Lewis 1988;Lewis et al 1984). Our purpose was to quantify the role of bacterioplankton in the C cycle of the lake and to determine the relative importance of C, P, and N in regulating the growth of bacteria.…”

Melting Alpine Glaciers Enrich High-Elevation Lakes with Reactive Nitrogen

“…Although algal growth is often N-limited in alpine lakes (15,16), algal biomass was lower in the N-rich GSF lakes than in the N-poor SF lakes (p ) 0.06; Figure 4a). The ratio of dissolved inorganic N: total phosphorus (DIN:TP (32)) suggests that SF lakes are N-limited, while GSF lakes are P-limited (Figure 4a).…”