Sara A. Lombardi & Kennedy T. Paynter
Marine Estuarine Environmental Science
University of Maryland
College Park, MD USA

Population decline
of Crassostrea virginica


1% of historic population (Newell 1988)
Ecosystem service decline
 Before 1870: 6 day Bay filtration
 Now: approximately 325 days (Newell 1988)

Introduction of C. ariakensis as a solution?

Increased comparisons
between the species
 Growth
 Perkinsis marinus infection (Dermo)
“C. ariakensis began gaping during the
sparging process ….. The native oyster
remained closed until 1-2 days before its death”
Harlan 2007

Risk: Greater exposure to predators


Probably a physiological underpinning
Is gaping a response to release CO2?
 Acidic metabolic byproducts accumulating in the
hemolymph
CO2 + H2O  H2CO3  HCO3- + H+

Compare the physiological responses of
Crassostrea ariakensis and Crassostrea virginica to
low oxygen
Assess gaping response after hypoxic exposure




Frequency of gape
Extent of gape
Analyze correlations between gaping and external
water pH
Inhibit gaping and assess hemolymph pH


Effect of time
Effect of species





Oysters from Horn Point Lab,
Cambridge, MD
Starved for 1 week in 15ppt 25° C
water
Respiration chambers filled and
sparged until oxygen concentration
below 0.5mgL-1
Individual oysters were placed into
a chamber which was then sealed
At periodic intervals, oyster gaping
response was assessed


8-72 hours after hypoxic immersion the pH of
the water surround each oyster was analyzed.
Repeated Measure Analysis of
Variance
12 hrs
10 days
C. ariakensis gapes more often than C. virginica (p<0.0006)
C. ariakensis gapes to a greater degree than C. virginica
during early (0-72 hours) hypoxic exposure (p=0.0057)
Gaping is correlated with acidic external
environments (p=0.034)






Clamped using 2” binder clips and
placed on lab bench at ~25° C air
temperature
Sacrificed at hr 0 (control), 2, 4, 6, 8,
10, 12, & 24
Dorsal and ventral side drilled
Hemolymph sampled with 5ml
glass syringe
pH analyzed with bench top meter
and micro pH probe
Performed Perkinsis marinus analysis


Excluded those with P. marinus score
greater than 1 from analysis
Two-way ANOVA
Species: p<0.0001
Time: p<0.0001
Interaction: p=0.2934
*
*
Species: p= 0.0214
Time: p<0.0001
Interaction: p=0.2934



C. ariakensis gapes more often than C. virginica
(p<0.0006)
C. ariakensis gapes to a greater extent than C. virginica
(p=0.0057)
Gaping is correlated with acidic external
environments (p=0.034)
When gaping is prevented…

C. ariakensis hemolymph pH is more acidic than C.
virginica (p<0.0001)


C. ariakensis may respond differently to low
oxygen and different acid-base homeostatic
abilities
Gaping may be a mechanism to prevent or
limit metabolic acidosis in C. ariakensis


Assess pH over time simultaneously with
calcium and carbon dioxide concentration
Assess hemolymph pH of gaping and ungaped
oysters when exposed to low oxygen


Effect of gaping on hemolymph pH
Assess the effect of acidosis on adductor
muscle function
References
Acknowledgements





Dwyer J. J & Burnett L.E 1996. Acid-base status of the
oyster Crassostrea virginica in response to air exposure
and to infections by Perkinsus marinus. Biol. Bull. 190
:13-137


Newell R. I. E 1998. Ecological changes in Chesapeake
Bay: Are they the result of overharvesting the
American oyster, Crassostrea virginica? Understanding
the estuary: Advances in Chesapeake bay research.
Proceedings of a conference 29-31. Chesapeake
Research consortium publication 129.
Harlan N.P. 2007 A comparison of the physiology and
biochemistry of the eastern oyster, Crassostrea
virginica, C. ariakensis. Masters of Science.
Funding


Stickle W.B., Kapper M.A, Liu L., Gnaiger E., & Wang
S.Y. 1989. Metabolic adaptations of several species of
crustaceans and Molluscs to Hypoxia: Tolerance and
Microcalorimetric studies. Biological Bulletin 177:303312
University of Maryland’s
Horn Point Lab Oyster
Hatchery




Oyster Recovery Partnership
National Oceanographic and
Atmospheric Administration –
Chesapeake Bay Office
Army Corp of Engineers –
Baltimore district
Dr. Donald Merrit
Stephanie Tobash Alexander
University of Maryland
Paynter lab staff and students