SEMINAR: Seminar:MBF 602 Nancy Muehllehner, Friday April 15, 1pm, RSMAS Seminar Room

["Nancy Muehllehner" <nancymuehllehner@gmail.com>]

Volcanic Vents & Seagrass Beds:
Effects of decades-long exposure to ?ocean acidification? in the seagrass
ecosystem

While short term experiments provide indications of the effects of ocean
acidification, long term data taking advantage of natural CO2 seeps have
the unique ability to develop community level changes in seagrass
ecosystems.  The CO2 seeps studied here are unique in that they occur in
the tropics and represent the first community assessment of tropical
seagrass beds exposed to decades-long high CO2 (190ppm higher than control
sites).  The community was assessed by randomly distributed quadrates to
quantify species diversity (lower), shoot density (up 2x), epibiont
density (down 5x), above (unchanged) and below ground biomass (up 3x). 
Preliminary data was also collected on community respiration and
photosynthesis through oxygen evolution using submersible incubation
chambers.  As expected, high CO2 conditions resulted in significantly
higher oxygen evolution producing net production at midday, almost
doubling in the high CO2 site.  Unexpectedly, respiration was not equally
enhanced in the high CO2 site, indicting perhaps additional oxygen
transport toward the rhizomes.  The overall picture that emerges from this
initial data set is an ecosystem shifted towards increased net
productivity with denser & thicker seagrass beds, but also exhibiting the
tradeoffs of reduced seagrass diversity and the lack of an epibiont
community.  Sites such as these that expose a portion of seagrass bed
ecosystem to decades of low pH & high CO2 water provide us a unique way to
estimate the effects of ocean acidification on our oceans.

Nancy Muehllehner
B.S. University of Delaware
M.A. University of California, Berkeley 2000
M.S. California State University 2008
Entered Ph.D. Program, Fall 2008

Advised by:  Dr Chris Langdon



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