SEMINAR: MBF602 STUDENT SEMINAR: FRIDAY, 4/19 AT 1PM----RIVAH WINTER, PHILIP KUSHLAN

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

MBF Student Seminar Series

 

 

Rivah N. Winter

Advisor: Dr. Andrew Baker

 

“How does the biotic and abiotic environment influence Symbiodinium community reassembly in corals recovering from bleaching? ”

Corals’ response to climate change stressors may be influenced by the community dynamics of their algal symbionts (genus Symbiodinium) following bleaching events.  Post-bleaching recovery of these communities occurs through proliferation of existing remnant symbionts and/or the (perhaps temporary) acquisition of exogenous symbionts.  Symbiodinium vary in their physiological optima, and certain types (including some members of clade D) can increase thermal tolerance if they become sufficiently abundant within a colony.  To understand how biotic and abiotic factors influence symbiont community composition in recovering corals, we ran a study using replicate cores from three colonies of Montastraea cavernosa.  Experimental cores were bleached through exposure to heat stress (32°C) and then allowed to recover in filtered seawater (1 mm) at 22°C or 29°C.  During this recovery phase, bleached corals were exposed to (1) healthy replicate fragments; (2) previously bleached replicate fragments that had been allowed to recover at elevated temperatures with thermally tolerant symbionts in clade D; (3) both cultured and freshly isolated Symbiodinium in clades A, B, C, and D; or (4) no exogenous sources of symbionts (exposure control).  Using sensitive quantitative PCR assays, we tested the hypotheses that exposure to environmental pools of diverse symbionts influences Symbiodinium community reassembly in recovering corals, and that this process is further influenced by recovery temperature.

 

 

Philip F. Kushlan

Advisor: Dr. Andrew Baker

 

“Genomic insights into isotopic depletion in the pea aphid-Buchnera symbiosis”

Aphids and other fluid-feeding insects have unusual isotopic signatures whereby they are isotopically depleted in nitrogen with respect to their diets. It has been suggested that one reason for this depletion is the metabolism of the endosymbionts that occur in these insects.  The mutualism between the pea aphid and its bacterial endosymbiont Buchnera aphidicola is an ideal model in which to test this hypothesis because nitrogen metabolism in this system is relatively well understood and the genomes of both organisms are available. I used these genomic resources to elucidate the particular fractionating reactions and pathways involved in nitrogen metabolism in this mutualism. I first demonstrated that aphids treated to remove their symbionts are less isotopically depleted than untreated aphids. I then used artificial diets with balanced or unbalanced amino acid profiles, as well as artificial diets with ¹³C labeled sugars, to demonstrate that nitrogen depletion occurs during the metabolic steps that upgrade non-essential amino acids to essential amino acids. This is the first study to demonstrate that endosymbiont metabolism influences consumer discrimination factors and represents an example of how genomic data can advance the utilization of stable isotope data in food-web and ecosystem-level studies.  

 

 

FRIDAY, APRIL 19, 2013

1:00pm

RSMAS campus, S/A 103

 

--
Pamela Harris
Marine Biology and Fisheries
Rosenstiel School of Marine and 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/