Abstract
In a 3-year study of Castle Lake, California, potential nutrient (N,P) limitation of phytoplankton growth occurred rapidly (within 1-4 d of ice-out). Both N and P acted as potential limiting factors to phytoplankton growth in short-term (4-5 d) bioassays. Phytoplankton responded strongly to single additions of N or P in 1990 and 1992 but weakly so in 1991. This difference was associated with low inorganic N concentrations during spring 1991. In 1998 and 1991, variation of the primary limiting element correlated with the N:P ratio of the zooplankton community; phytoplankton tended to be N limited when the zooplankton was dominated by species with high N:P ratios (Diaptomus novamexicanus and Diacyclops thomasi: N:P ratios, by mass = 10.6-12.5) but limited by P when low N:P taxa (Daphrziar rosea, N:P = 4.7) dominated. However, N vs. P limitation and zooplankton elemental data for 1992 did not fit the 1990-1991 pattern and there was no correlation for the 3-year data set. A field experiment demonstrated that the inorganic N:P ratio (NH4/SRP) increased dramatically with elevated Daphrzia grazing but declined significantly with increased Diaptomus; this supported the 1990-1991 correlation between phytoplankton N/P limitation status and zooplankton community elemental ratio.
Original language | English |
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Pages (from-to) | 93-104 |
Number of pages | 12 |
Journal | Canadian Journal of Fisheries and Aquatic Sciences |
Volume | 52 |
Issue number | 1 |
DOIs | |
State | Published - Jan 1995 |