@article {474,
	title = {Nitrogenous preference of toxigenic Pseudo-nitzschia australis (Bacillariophyceae) from field and laboratory experiments},
	journal = {Harmful Algae},
	volume = {6},
	number = {2},
	year = {2007},
	note = {138WSTimes Cited:15Cited References Count:48},
	month = {Feb},
	pages = {206-217},
	abstract = {Field and laboratory experiments were designed to determine the differential growth and toxin response to inorganic and organic nitrogen additions in Pseudo-nitzschia spp. Nitrogen enrichments of 50 mu M nitrate (KNO3), 10 mu M ammonium (NH4Cl), 20 mu M urea and a control (no addition) were carried out in separate carboys with seawater collected from the mouth of the San Francisco Bay (Bolinas Bay), an area characterized by high concentrations of macronutrients and iron. All treatments showed significant increases in biomass, with chlorophyll a peaking on days 4-5 for all treatments except urea, which maintained exponential growth through the termination of the experiment. Pseudo-nitzschia australis Frenguelli abundance was 10(3) cells l(-1) at the start of the experiment and increased by an order of magnitude by day 2. Particulate domoic acid (pDA) was initially low but detectable (0.15 mu g l(-1)), and increased throughout exponential and stationary phases across all treatments. At the termination of the experiment, the urea treatment produced more than double the amount of pDA (9.39 mu g l(-1)) than that produced by the nitrate treatment (4.26 mu g l(-1)) and triple that of the control and ammonium treatments (1.36 mu g l(-1) and 2.64 mu g l(-1), respectively). The mean specific growth rates, calculated from increases in chlorophyll a and from cellular abundance of P australis, were statistically similar across all treatments.These field results confirmed laboratory experiments conducted with a P. australis strain isolated from Monterey Bay, CA (isolate AU221-a) grown in artificial seawater enriched with 50 mu M nitrate, 50 mu M ammonium or 25 mu M of urea as the sole nitrogen source. The exponential growth rate of P australis was significantly slower for cells grown on urea (ca. 0.5 day(-1)) compared to the cells grown on either nitrate or ammonium (ca. 0.9 day(-1)). However the urea-grown cells produced more particulate and dissolved domoic acid (DA) than the ammonium- or nitrate-grown cells. The field and laboratory experiments demonstrate that P australis is able to grow effectively on urea as the primary source of nitrogen and produced more pDA when grown on urea in both natural assemblages and unialgal cultures. These results suggest that the influence of urea from coastal runoff may prove to be more important in the development or maintenance of toxic blooms than previously thought, and that the source of nitrogen may be a determining factor in the relative toxicity of west coast blooms of P. australis. (c) 2006 Elsevier B.V. All rights reserved.},
	keywords = {artificial seawater medium, Batch culture, california, diatom pseudonitzschia-australis, domoic acid, domoic acid production, harmful algae, monterey bay, multiseries, nitrogen, phytoplankton, Pseudo-nitzschia australis, silicate limitation, urea, west-coast},
	isbn = {1568-9883},
	url = {<Go to ISI>://000244394600005},
	author = {Howard, M. D. A. and Cochlan, W. P. and Ladizinsky, N. and Kudela, R. M.}
}
@article {607,
	title = {Inorganic and organic nitrogen uptake by the toxigenic diatom Pseudo-nitzschia australis (Bacillariophyceae)},
	journal = {Harmful Algae},
	volume = {8},
	number = {1},
	year = {2008},
	note = {Sp. Iss. SI384RRTimes Cited:7Cited References Count:79},
	month = {Dec},
	pages = {111-118},
	abstract = {The nitrogen uptake capabilities of the toxigenic diatom Pseudo-nitzschia australis (Frenguelli), freshly isolated from Monterey Bay California, were examined in unialgal laboratory cultures at saturating photosynthetic photon flux densities (100 mu mol photons m(-2) s(-1)) and 15 degrees C. The kinetics of nitrogen (nitrate, ammonium, urea and glutamine) uptake as a function of substrate concentration were estimated from short (20.5 min) incubations using the N-15-tracer technique. Based on the estimated maximum specific uptake rates and measures of N affinity(the initial slope of the uptake versus nutrient concentration curve), nitrate is the preferred nitrogen substrate, followed by glutamine and ammonium,which are equivalent. Rates of urea uptake by P. australis did not saturate at concentrations as high as 36 mu g-at N L-1, and urea uptake as a function of concentration could not be described by Michaelis-Menten kinetics over the concentration gradient tested. Although there is a clear preference for nitrate at equivalent concentrations (compared to ammonium, urea, and glutamine), these laboratory results demonstrate the capability of this pennate diatom to utilize both inorganic and organic forms of nitrogen, supporting field observations that A australis blooms during both upwelling and non-upwelling conditions. off the west coast of North America. Substantial differences in the nitrogenous nutrition of P. australis can be expected in these environments, and anthropogenic inputs of N substrates such as ammonium and urea can support its growth, and may contribute significantly to both harmful diatom blooms and the maintenance of seed populations at non-bloom abundances, particularly during periods of reduced or absent upwelling. (C) 2008 Elsevier B.V. All rights reserved.},
	keywords = {2 marine diatoms, ammonium, Bacillariophyceae, diatom, domoic acid production, environmental-conditions, glutamine, limiting nutrient, nitrate, nitrate uptake kinetics, nitrogen uptake kinetics, prorocentrum-minimum, Pseudo-nitzschia australis, skeletonema-costatum, southern california, urea, urease activity, washington-state},
	isbn = {1568-9883},
	url = {<Go to ISI>://000261762400014},
	author = {Cochlan, W. P. and Herndon, J. and Kudela, R. M.}
}
@article {606,
	title = {The potential role of anthropogenically derived nitrogen in the growth of harmful algae in California, USA},
	journal = {Harmful Algae},
	volume = {8},
	number = {1},
	year = {2008},
	note = {Sp. Iss. SI384RRTimes Cited:7Cited References Count:54},
	month = {Dec},
	pages = {103-110},
	abstract = {Cultural eutrophication is frequently invoked as one factor in the global increase in harmful algal blooms, but is difficult to definitively. prove due to the myriad of factors influencing coastal phytoplankton bloom development. To assess whether eutrophication could be a factor in the development of harmful algal blooms in California (USA), we review the ecophysiological potential for urea uptake by Pseudo-nitzschia australis (Bacillariophyceae), Heterosigma akashiwo (Raphidophyceae), and Lingulodinium polyedrum (Dinophyceae), all of which have been found at bloom concentrations and/or exhibited noxious effects in recent years in California coastal waters. We include new measurements from a large (Chlorophyll a > 500 mg m(-3)) red tide event dominated by Akashiwo sanguinea (Dinophyceae) in Monterey Bay, CA during September 2006. All of these phytoplankton are capable of using nitrate, ammonium, and urea, although their preference for these nitrogenous substrates varies. Using published data and recent coastal time series measurements conducted in Monterey Bay and San Francisco Bay, CA, we show that urea, presumably from coastal eutrophication, was present in California waters at measurable concentrations during past harmful algal bloom events. Based on these observations, we suggest that urea uptake could potentially sustain these harmful algae, and that urea, which is seldom measured as part of coastal monitoring programs, may be associated with these harmful algal events in California. (C) 2008 Elsevier B.V. All rights reserved.},
	keywords = {ammonium, Eutrophication, heterosigma-akashiwo, laboratory cultures, marine-phytoplankton, nitrate, nitrate uptake, nitrogen uptake kinetics, phytoplankton blooms, Pseudo-nitzschia, santa-barbara channel, southern-california, uptake kinetics, urea},
	isbn = {1568-9883},
	url = {<Go to ISI>://000261762400013},
	author = {Kudela, R. M. and Lane, J. Q. and Cochlan, W. P.}
}
@article {595,
	title = {Intra- and interspecies differences in growth and toxicity of Pseudo-nitzschia while using different nitrogen sources},
	journal = {Harmful Algae},
	volume = {8},
	number = {5},
	year = {2009},
	note = {459ZWTimes Cited:0Cited References Count:102},
	month = {Jun},
	pages = {792-810},
	abstract = {Clonal cultures of plankton are widely used in laboratory experiments and have contributed greatly to knowledge of microbial systems. However, many physiological characteristics vary drastically between strains of the same species, calling into question our ability to make ecologically relevant inferences about populations based on studying one or a few strains. This study included 19 non-axenic strains of three species of the diatom Pseudo-nitzschia isolated primarily from the mid-Atlantic coastal region of the United States. Toxin (domoic acid) production and growth rates were measured in cultures using different nitrogen sources (NH4+, NO3- and urea) and growth irradiances. The strains exhibited broad differences in growth rate and toxin content even between strains isolated from the same water sample. The influence of bacteria on toxin production was not investigated. Both A multiseries clones produced toxin, yet preferentially used different nitrogen sources. Only two of nine P. calliantha and two of five P. fraudulenta isolates were toxic and domoic acid content varied by orders of magnitude. All three species had variable intraspecies growth rates on each nitrogen source, but A fraudulenta strains had the broadest range. Light-limited growth rate and maximum growth rate in P. fraudulenta and P. multiseries varied with species. These findings show the importance of defining intra- and interspecies variability in ecophysiology and toxicity. Ecologically relevant functional diversity in the form of ecotypes or cryptic species appears to be present in the genus Pseudo-nitzschia. (C) 2009 Elsevier B.V. All rights reserved.},
	keywords = {amino-acid, ammonia, australis bacillariophyceae, Batch culture, complex bacillariophyceae, diatom, domoic acid, domoic acid production, marine-phytoplankton, nitrate, nitrate uptake, Pseudo-nitzschia, pungens f-multiseries, seriata bacillariophyceae, skeletonema-costatum bacillariophyceae, urea},
	isbn = {1568-9883},
	url = {<Go to ISI>://000267153900021},
	author = {Thessen, A. E. and Bowers, H. A. and Stoecker, D. K.}
}
