"Studies have shown that there are more than 300 species reliant on oyster reefs, including at least 12 species important for their commercial or recreational value, such as blue crabs, sheepshead, croaker and stone crab," Sokolova said. "Some of these species, such as blue crabs, use oyster beds and reefs as nursery areas and as feeding grounds." The oyster beds are also important to a variety of marine life that serves as food for larger fish. It was within this context that the North Carolina team did their study.
Warm water increases energy demand
The researchers divided oysters into three groups. One group was acclimated to water that was 20° C (68°F), one to 24°C (75°F) and a final group to 28°C (82°F). All three temperatures are within the range that oysters are exposed to in their natural environment, Lannig said. In fact, this summer, which was unusually hot, water temperatures reached 32°C, she said. Each temperature group was subdivided into two subgroups, oysters that were exposed to cadmium and those that were not.
The 20-day study found that oysters, as expected, consumed more oxygen as the water temperature rose. Warmer temperatures raise the oyster's metabolic rate, which raises its oxygen and energy requirements, Lannig explained.
In addition, oysters exposed to cadmium at 20°C and 24°C needed more oxygen than the oysters in their groups not exposed to cadmium. That makes sense, because the pollutant places stress on the oyster, which increases metabolism and oxygen demand.
Temperature plus cadmium = power disruption
However, there was no difference in oxygen consumption between the two groups acclimated to 28°C. The researchers concluded that the cadmium-exposed oysters in this group needed more oxyge
Source:American Physiological Society