SEMINAR: MBF602 Chen and Bignami at NOON MCS343

["Sean Bignami" <sbignami@rsmas.miami.edu>]

Please NOTE:
Time of Friday seminars tomorrow: 12 noon
Place of seminars tomorrow only: MSC343

There is no faculty speaker, therefore the 12-1
time slot will be filled by students Bignami and
Chen. Cookies and coffee will be available.



Acute copper toxicity mechanisms in blue crab, Callinectes sapidus at
different salinities


Abstract


The interactions between salinity and acute toxicity of copper in
euryhaline teleost are determined by Na+ gradients across the gill.
However, there is limited information regarding acute copper toxicity in
euryhaline invertebrates such as crustaceans at different salinities. Blue
crabs are strongly euryhaline, of sufficient size for physiological
measurements and as such well suited for the study of copper toxicity at
different salinities. Blue crabs were acclimated to different salinities
for one week after which water and hemolymph samples were collected to
determine Na+ gradients and thus the Na+ equilibrium potential (Ep). In
addition, the gill transepithelial potential (TEP) was measured. The
electrochemical (ECp) Na+ gradients of blue crabs across a range of
salinities were obtained from the calculated Ep and measured TEP. Results
showed that the hemolymph osmolarity and ion concentrations increased with
increasing salinity and that TEP decreased. From these observations, the
magnitude of the gill ECp of blue crabs increase with decreasing salinity
illustrating a greater need for active Na+ transport at lower salinities
compared to SW. Based on this analysis higher sensitivity to acute copper
toxicity is expected at lower salinities, an expectation which is
currently being tested.

Cheryl Chan


B.S. Zoology, Universiti Sains Malaysia (2002)

M.Sc Aquatic, Universiti Sains Malaysia (2006)

Entered Ph.D. program in fall of 2008


Advisor: Martin Grosell




Ocean acidification and larval fish: preliminary investigations of the
impact on growth and flexion

Anthropogenic carbon dioxide is increasing at an unprecedented rate,
diffusing into the oceans and causing measurable decline in the pH of
surface waters. This process of ocean acidification has been shown to
negatively impact many organisms, although most research has focused on
calcifying invertebrates, with a limited number of studies involving
fishes. My research is designed to determine whether future predicted
levels of ocean acidification could impact the growth, development, and
behavior of larval fishes. Established aquaculture techniques and methods
of seawater chemistry alteration have been adapted to produce an
experimental setup that allows for replicated application of ocean
acidification treatments to larval fishes under a semi-intensive
aquaculture scenario. During initial trials using Rachycentron canadum
(Rachycentridae), or cobia, there was difficulty attaining proper levels
of acidification, often resulting in lower pH than desired. However,
results from these ?extreme? treatments show a significant decrease in
size-at-age and a delay in flexion during the early development of larval
cobia. In a subsequent trial, protocols were modified to attain more
accurate treatment conditions, but no significant results were detected.
This second trial was greatly affected by a loss of larval food supply at
an early date, resulting in high, likely size-selective, mortality.
Preliminary behavioral studies were also performed, although data have not
yet been analyzed. Future trials will incorporate improved treatment
application and include additional tests of the effects of ocean
acidification on larval growth, development, and behavior.

Sean Bignami

Marine Biology and Fisheries
Entered PhD Program: 2008
Advisors: Su Sponaugle & Robert Cowen






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