SEMINAR: MGG Student Seminar, Tues. 2/2/10: Quinn Devlin

["Kelly L. Jackson" <kjackson@rsmas.miami.edu>]

MGG STUDENT SEMINAR 

Does elevated DIN directly affect zooxanthellate corals?
Quinn B. Devlin

and

TBA

CIMAS CONFERENCE ROOM

12:00 - 1:00 PM

Devlin Abstract: 

Eutrophication is repeatedly cited as a leading cause of coral reef

decline; however, the mechanisms in which elevated nutrient levels degrade
reefs remain poorly understood. Studies suggest a “phase shift” scenario
to macroalgal dominated communities under high levels of dissolved
inorganic nitrogen (DIN) and low grazing pressure, but the direct effect
of elevated DIN levels on scleractinian corals is unclear. While some
studies suggest that DIN elevation leads to decreased skeletal growth
related to uncontrolled algal symbiont populations, others have found that
DIN is recycled within the coral-algal symbiotic system. This recycling
would suggest that an increase in DIN would stimulate both the growth of
the symbiotic zooxanthellae and coral host. Several experimental
incubations have been proposed to understand N budgets and the fate of DIN
within the coral-algal symbiosis and to investigate the behavior of the
symbiosis under prolonged exposure to elevated DIN levels.  Pocillopora
damicornis is growing in culture under conditions of 10, 20, and 50 µM
treatments of  NO3- and NH4+ with control treatments for 4 and 8 weeks.
Daily DIN uptake rates are measured during experimental incubations, as
well as coral growth rates. Algal and host tissue lipid content and C/N
ratios will be analyzed, and zooxanthellae density determined after 4 and
8 weeks. Isotopic labeling will be employed to investigate the extent to
which labeled N is recycled within the symbiotic system prior to exposure
to elevated DIN, after 4 and 8 weeks of treatment.