Hypothesized Model

1
Hypothesized Model
AbstractDue to the increased concentrations of
organic and inorganic nitrogen from anthropogenic
eutrophication, much effort has gone into
studying possible effects on phytoplankton. This
study intends to test whether the growth of
Pseudo-nitzschia multiseries is enhanced by the
addition of dissolved organic nitrogen (DON)
under various light conditions. Previous studies
have shown that some phytoplankton species can
use DON, and that P. multiseries might be
included among this list (Palenik et al., 1990,
Hillebrand Sommer, 1996, Seitzinger et al.,
1997 2002, Mengelt Prézelin, submitted).
Examining the heterotrophic abilities that this
species has in the dark will further the
knowledge on the link between eutrophication/runof
f and bloom initiation via the extended survival
of a seed population in the dark. This is
especially important since P. multiseries is a
marine planktonic diatom that produces the
neurotoxin domoic acid. This neurotoxin is
potentially deadly to humans and other marine
mammals when consumed via contaminated shellfish
and fish, such as anchovies (Mos, 2001).
Consequently, P. multiseries can cause large
economical, and environmental damage. Therefore,
this study presents results from organic and
inorganic nitrogen addition experiments under
various light/dark conditions. Our experimental
results show enhanced light-growth with the
addition of glutamate, one form of DON,
confirming a heterotrophic ability of P.
multiseries.
IntroductionResearch Question Can
Pseudo-nitzschia multiseries grow in the dark and
under various light levels on organic nutrients
?Significance - Pseudo-nitzschia blooms
cause high mortality among higher trophic levels.
- Blooms result in significant economic loss
for fisheries and potentially tourism.-
Eutrophication has been implicated in other
harmful algal blooms events.
Definition Eutrophication
Non - point sources Agricultural urban runoff
Euphotic Zone
Photo- autotrophic
Algal nutrient enrichment
Aphotic Zone
heterotrophic
Conceptual Working Model Pseudo-nitzschia
blooms are associated with moderate upwelling
events (Trainer et al., 2000) and/or runoff
(Smith et al, 1990). Upwelling of a seed
population from depth was suggested as a bloom
initiation mechanism. If this is correct than why
or how do P. multiseries survive in the dark. The
question now becomes whether there is a resting
stage (seed like) or whether it has heterotrophic
abilities.
Previous research
Results and Discussion

• Antibiotics affects the growth rates minimally
• Glutamate increases growth rates significantly
• Glutamate increases the maximum cell density
• This confirms Pseudo-nitzschia multiseries
  ability to utilize glutamate as a growth
  supplement.

Experimental Set-up
Track growth
While in log-phase
Grown in the light

• Daily Measurements
• Growth (cell counts chl a)
• Absorption Spectra

REFERENCE Hillebrand, H., Sommer, U., 1996
Nitrogenous nutrition of the potentially toxic
diatom Pseudo-nitzschia punges f. multiseries
Hasle, Journal of Plankton Research Vol. 18(2)
295-301Mengelt, C., and Prézelin, B. B.,
submitted. Dark Survival and Subsequent Light
Recovery for Pseudo-nitzschia multiseries. 10th
HAB Conference Proceedings, St. Petersburg,
Florida.Mos, L., 2001 Domoic acid a fascinating
marine toxin. Environmental Toxicology and
Pharmacology, 9, 79-85Palenik, B., Morel, F. M.
M., 1990 Amino acid utilization by marine
phytoplankton A novel mechanism, Limnology and
Oceanography. 35(2), 260-269Seitzinger, S. P.,
Sanders, R. W., 1997 Contribution of dissolved
organic nitrogen from rivers to estuarine
eutrophication, Marine Ecology Progress Series.
Vol. 159 1-12Seitzinger, Sybil P., Sanders R.
W., Styles Renee, 2002 Bioavailability of DON
from natural and anthropogenic sources to
estuarine plankton. Limnology and Oceanography.
47(2), 353-366.Smith, J.C., and others, 1990.
Toxic blooms of the domoic acid containing diatom
Nitzschia pungens in the Cardigan River, Prince
Edward Island. In Toxic marine Phytoplankton .
E. Graneli, B. Sundstrom, L. Edler and D. M.
Anderson (eds.), Elsevier, p.227-232.Trainer,
V.L., Adams, N.G., et al., 2000. Domoic acid
production near California coastal upwelling
zones, June 1998. Limnology and Oceanography
45(8), 1818-1833.
ACKNOWLEDGMENTUCSB, National Science
Foundation, HRD-9624189, UC Marine Council, 02T
CEQI 080094Barbara B. Prézelin, Claudia Mengelt,
Joseph GorgaSteve Mckagan, Toni Mizerek
Experimental Set-up - Medium was prepared in
advance. The medium was left acclimating at
incubator temperature 2 days before experiment.
On the 1st day of the experiment, media was
inoculated with 75mL of culture. Glutamate was
added to two treatments (one of which contained
antibiotics) to yield a final concentration of
0.2 mM. The initial measurement was taken at this
point. Then, vials of each medium treatment was
placed in the light incubator.