Premium
CHARACTERIZATION OF NITROGEN UPTAKE BY NATURAL POPULATIONS OF AUREOCOCCUS ANOPHAGEFFERENS (CHRYSOPHYCEAE) AS A FUNCTION OF INCUBATION DURATION, SUBSTRATE CONCENTRATION, LIGHT, AND TEMPERATURE 1
Author(s) -
Lomas Michael W.,
Gilbert Patricia M.,
Berg Gry M.,
Burford Michele
Publication year - 1996
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.0022-3646.1996.00907.x
Subject(s) - urea , nitrogen , zoology , biology , incubation , bloom , botany , biochemistry , ecology , chemistry , organic chemistry
Nitrogen uptake studies were conducted during an aestival “brown tide” bloom in Shinnecock Bay, Long Island, New York. The same station was sampled in late July and mid‐August 1995 when Aureococcus anophagefferens composed >90% and 30–40% of the total cell density, respectively. Experiments were designed to examine the effect of incubation duration on the uptake kinetics, and the effect of light and temperature dependencies of NH 4 + , urea, and NO 3 − uptake. Maximum specific uptake rates (V' max ) decreased in the order NH 4 + , urea, NO 3 − and were nonlinear with time for NH 4 + and urea, both of which exhibited an exponential decline between 1 and 10 min and then did nut significantly change for 60 min. Nitrogen uptake kinetic experiments exhibited a typical hyperbolic response for urea and NO 3 − . Half‐saturation constants. (K s ) were calculated to he 0.03 and 0.12 μmol · L −1 for urea and NO 3 − ; respectively, but could not be calculated for NH 4 + under these experimental conditions. Nutrient uptake rate versus, irradiance (NI) experiments showed that maximum uptake rates occurred at ≤% of incident irradiance on both sampling dates and that values of V′ max‐cell (NH 4 + ) were on average 30% greater than V′ max‐cell (urea). A7°–9°C temperature decrease in incubation temperature between the two NI experiments in August resulted in a 30% decrease in V′ max‐cell (NH 4 + ), no change in V′ max‐cell (urea), and a 3–4‐fold decrease in calculated K lt values for both NH 4 + and urea. The results from these experiments demonstrate that A. anophagefferens has a higher affinity for NH 4 + and urea than for NO 3 − and that this particular species is adapted to use these substrates at low irradiances and concentrations. The data presented in this study are also consistent with the hypothesis that A. anophagefferens may be an oceanic clone that was displaced by an anomalous oceanographic event.