SEMINAR: MBF STUDENT SEMINAR *** FRI 11/16 @ 1PM*** William Harford & Nancy Muehllehner

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

 

MBF Student Seminar Series

 

William Harford

Advisor: Dr. Elizabeth Babcock

 

“Spatial variation in habitat use by Juvenile Grouper in

the Florida Keys coral reef ecosystem”

A common approach for quantifying species occurrence patterns is through the use of resource selection functions (RSFs), although applications to marine ecosystems remain relatively scarce. Two objectives aimed at fostering an improved understanding of spatial patterns in habitat use by juvenile red grouper and juvenile black grouper in the Florida Keys coral reef tract were carried out. First, a general paucity of information about juvenile grouper habitat use led to the development of RSFs using a long-term fishery-independent diver visual survey with a cross-shelf stratification design. RSFs accounting for spatial variation in habitat use among cross-shelf strata were developed using a generalized linear mixed-modeling framework. Second, RSFs were used to evaluate whether grouper-habitat correlations differed systematically among cross-shelf habitat strata. The red grouper RSF consisted of a negative response in occurrence probability to vertical relief and a trend of decreasing odds of occurrence from near-shore to off-shore strata. The black grouper RSF consisted of a negative response in occurrence probability to latitude, a positive response to vertical relief, and responses to depth that varied among habitat strata. Describing variation in grouper-habitat correlations was viewed as a requisite to improved understanding of habitat selection processes.

 

 

Nancy Muehllehner

Advisor: Dr. Chris Langdon

“Are the Florida Keys close to a tipping point?

Seasonal dissolution on the reef in contrast to net coral calcification in the lab

Benthic metabolism from large photosynthesizing and calcifying communities can exert a strong control on coastal water chemistry.  During summer months on the Florida Reef Tract (FRT), strong benthic metabolism results in an average net community production (NCP) of 40 ± 37 mmol m-2 d-1 and a drawdown of pCO2, subsequently elevating aragonite saturation state (Ωa) and leading to net community calcification (12 ± 14 mmol m-2 d-1).  Conversely, wintertime rates of NCP were negative (-45 ± 39 mmol m-2) and led to increased pCO2, depressed Ωa and seasonal dissolution of -11 ± 22 mmol CaCO3 m-2 d-1.  The cross-over point between positive and negative net ecosystem calcification occurred at an aragonite saturation state of 3.63 ± 0.16 (standard error).  Thus the seasonal flip-flopping between positive and negative calcification indicates that the FRT is approaching a tipping point which we can predict will occur when the annually averaged Ωa falls below 3.63.  While Ωa>3.6 may be critical for long-term survival of the reef structure, corals such as Acropora cervicornis grown in the lab for 2 months and exposed to under-saturated conditions (Ω=0.5) still exhibited net calcification indicating that corals have very different tipping points, and may continue to calcify while the reef structure as a whole is endangered.

 

FRIDAY, NOVEMBER 16, 2012

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/

 

On 11/14/2012 3:59 PM, Pam Harris wrote:

MBF Student Seminar Series

 

William Harford

Advisor: Dr. Elizabeth Babcock

“Spatial variation in habitat use by Juvenile Grouper in

the Florida Keys coral reef ecosystem”

 

 

Nancy Muehllehner

Advisor: Dr. Chris Langdon

“Are the Florida Keys close to a tipping point?

Seasonal dissolution on the reef in contrast to net coral calcification in the lab

 

FRIDAY, NOVEMBER 16, 2012

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/