SEMINAR: MBF602 STUDENT SEMINAR FRIDAY 9/21 @ 1PM---Rachael Heuer & Jay Fisch

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

 

MBF Student Seminar Series

 

Rachael Heuer

Advisor: Dr. Martin Grossell

“Ocean acidification leads to counterproductive intestinal

base loss in the Gulf toadfish”

Ocean acidification research on marine teleosts has revealed effects on behavior, anatomy, and sensory systems, especially in younger animals. Although teleosts are known to be strong acid-base regulators, recent work has demonstrated that CO₂ exposure as low as 1000 matm induces an acidosis in adult toadfish (Opansus beta), leading to metabolic compensation by retention of blood HCO₃^- to defend blood pH. In the first portion of the present study, blood elevation of HCO₃^- and PCO₂ during acute 1900 matm CO₂ exposure was predicted to increase intestinal base secretion rates. Rectal excretions collected from toadfish exposed to 1900 matm CO₂ over 72 hours revealed higher rectal base excretion rates compared to 380 (control) exposures. These observations confirm that increased base loss occurs in the intestine during exposure to elevated CO₂ which seems counterproductive to whole-body acidosis compensation. Contrary to expectations, isolated intestinal tissue from toadfish exposed to 1900 matm CO₂ for two weeks exhibited significantly higher base secretion rates than control toadfish, suggesting that these fish do not have the capacity to reduce base loss during prolonged CO₂ exposure. Furthermore, the elevation of base secretion rates above control values suggests that chronic hypercapnia exposure likely incurs an increased intestinal tissue metabolic cost.

 

 

Jay Fisch (MBF)

Advisors: Drs. Chris Langdon and Margaret Miller (NOAA)

“Montastraea faveolata-

Early life history stages and climate change: respiration”

Montastraea faveolata was recently found to be at one of the greatest risks of extinction among 82 coral species petitioned to be listed under the Endangered Species Act.  In order to better understand how this species may fare under increased temperature and carbon dioxide (CO2) levels in the coming century, gamete bundles were collected near Key Largo, FL for exposure experiments.  Two days post-spawn, larvae were subject to two temperatures (29 and 31C) and two targeted CO2 levels (400 and 900 ppm).  Respiration was measured using an incubation method involving Winkler titrations.  Respiration was significantly elevated under both increased temperature and increased CO2 relative to the control conditions (0.57 and 0.49 respectively vs. 0.35 nmol O2larvae-1min-1, p=0.00 and 0.02).  This increase was not observed when both of these factors were combined (0.38 nmol O2larvae-1min-1).  Elevated metabolic rates at increased temperatures may account for higher respiration rates at 31C.  Studies of adult invertebrates have yielded reduced metabolism at increased CO2, but aposymbiotic coral larvae may exhibit a different response as seen in this study.  The combined stress of the high temperature/high CO2 treatment may depress cellular response and explain the measured values.  Further studies are needed as respiration rates can affect larval dispersal and ultimately the repopulation of Caribbean reefs.

 

FRIDAY, SEPTEMBER 21, 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/