SEMINAR: MBF STUDENT SEMINAR ***TOMORROW @ 1PM*** TARA BARIS & ALYSON VENTI

[Pam Harris <pharris@rsmas.miami.edu>]

 

MBF Student Seminar Series

 

Tara Baris

Advisor: Dr. Marjorie Oleksiak

“Evolution of Two Genomes:

Impact of sequence divergence on Mitochondrial Function”

We are investigating the divergence in oxidative phosphorylation (OxPhos) metabolism among populations of Fundulus heteroclitus.  The OxPhos pathway occurs in mitochondria and uses oxygen to produce the majority of ATP in a cell.  This pathway consists of 5 large enzyme complexes with 45 to 4 proteins per complex and is the only pathway in which the proteins involved are coded by both mitochondrial and nuclear genomes.  F. heteroclitus populations have sequence divergence in OxPhos genes in both mitochondrial and nuclear genomes.  These populations are distributed along a steep thermal cline on the east coast of the United States and have evolved by natural selection to adapt to this clinal variation in temperature.  Thus, F. heteroclitus serve as a model species to enhance our understanding of the impact of nucleotide divergence on physiological function.  The initial studies of OxPhos function used 24 individuals from two different populations of F. heteroclitus, and differences in mitochondrial respiration were measured using a high-resolution respirometer (Oxygraph-2k, Oroboros Instruments, Innsbruck, Austria). The fish from each population were acclimated to both 12°C and 28°C.  Hearts were isolated from each individual, permeabilized, and assayed at 3 different temperatures (12°C, 20°C, and 28°C).  Total mitochondrial respiration and individual enzyme complexes of oxidative phosphorylation were measured by addition of complex specific substrates and poisons.  Differences among populations and temperatures will provide insights into the evolution and adaptation of natural populations.

 

Alyson Venti (MAC)

Advisor: Dr. Chris Langdon

“A spatial-temporal analysis of coral calcification rates in Bermuda”

The biogeochemical processes that govern reef systems may differ from those that impact individual organisms and thus the two may be affected differently by changes induced by global climate change. To understand how coral reef ecosystems respond to pressures attributed to global climate change, specifically ocean acidification (OA), there is a need to monitor net ecosystem calcification (NEC) rates, and to quantify the contribution of scleractinian corals calcification to this reef community rate. 

Natural growth-rate fluctuations across diurnal and seasonal timescales have direct feedbacks on the surrounding water chemistry which are analogous to changes driven by elevated CO2. A temporal assessment encompassing both seasonal and diurnal analyses may therefore identify threshold environmental conditions that only support net positive calcification during the summer or daytime. This data can be applied to predict a critical tipping point between net positive calcification and dissolution for corals living in a future higher CO2 world.  

Seasonal net community calcification rates were measured at 4 sites across the Bermuda reef platform by application of a novel radiochemical approach to the alkalinity anomaly method which revealed the greatest seasonal variability at the platform edge with net community calcification rates ranging from 90 (± 20) mmolCaCO3 m-2 d-1 in November 2008 to -7.0 (0.7) mmolCaCO3 m-2 d-1 in February 2009. Calcification rates of individual coral colonies were also measured through the application of a calcein dye staining method and showed similar temporal and spatial variations. Diurnal calcification rates were achieved by in situ incubations of coral nubbins which indicates net positive calcification during the day and depressed rates or net dissolution at night.

 

FRIDAY, FEBRUARY 1, 2013

1:00pm

RSMAS campus, S/A 103

Pamela Harris

Marine Biology and Fisheries

Rosenstiel School of Marine & Atmospheric Science

University of Miami

4600 Rickenbacker Causeway/SLAB-118

Miami, FL 33149

(305) 421-4176

fax - (305) 421-4600

pharris@rsmas.miami.edu  

 

http://www.rsmas.miami.edu/academics/divisions/marine-biology-fisheries/