The 28°C cadmium-exposed group spent more time in respiratory activity, trying to take in oxygen. Their shells were open significantly longer than any of the other groups, a measure of the amount of time they spend "breathing." (When oysters open their shells, they are taking in oxygen. Oxygen flow stops when they close the shell.)
The researchers also examined the effect of cadmium and temperature on the mitochondria of the oyster's cells. The mitochondria are the cell's power plant, producing energy for the oyster, including for ventilation and circulation.
"We found that mitochondria are very sensitive to cadmium at high temperatures," Lannig noted, suggesting that the higher temperature and cadmium exposure negatively affect the mitochondria's ability to produce energy.
Blood oxygen falls
In a second experiment, the researchers acclimated two groups of oysters to 20°C water. One group was exposed to cadmium. Both groups were then subjected to an acute temperature increase of 4°C overnight (to 24°C).
"Here we saw that the cadmium-exposed oysters showed a decrease in blood oxygen content with the higher temperature, but not the control group that was not exposed to cadmium," Lannig said. Once again, this shows that the combination of temperature and pollution combine to intensify the stress placed on the oyster's physiological system.
In future experiments, the researchers will try to determine whether the combination of temperature and pollution is preventing oysters from obtaining enough oxygen or whether it is interfering with the animal's ability to use the oxygen it obtains, Lannig said. These experi
Source:American Physiological Society