Oysters are more vulnerable to surface waters with low oxygen

Oysters living in shallow waters around the world where nutrient pollution is high, are much more likely to be affected by the deadly disease Dermo, he found a group of scientists from the Smithsonian Environmental Research Center (SERC).

The loss of oxygen in shallow water is a global phenomenon, but is not as well known as dead zones of the deep.

“We usually think habitats shallow as refuges high productivity over dead deepwater areas”Says Denise Breitburg, Marine Ecologist SERC and lead author of the study.

“But if low oxygen levels, these shallow waters are inhospitable to fish and seafood, and the whole system may suffer.”

In a field experiment, Breitburg and colleagues suspended hundreds of oysters (Crassostrea virginica) in cages under water at 14 sites around the Chesapeake Bay.

In various places prevalence of infection varied from at least half of up to 100%. Oysters from areas with low oxygen levels were much harsher more likely to contract the disease.

The disease also advanced to more intense levels in oysters placed on both sites had little oxygen and a salinity less than 12 parts per thousand. In these waters of higher salinity is where Dermo disease causes high mortality in wild oyster populations.

The researchers then performed a controlled laboratory experiment to define the exact role of low oxygen concentrations. In a laboratory called informally “Room DOOM” (Dissolved Oxygen Oyster Mortality), oysters were exposed to cycles under similar to oxygen bay.

Young uninfected oysters were the most vulnerable in the laboratory. Those who were exposed to low oxygen levels were almost three times more likely to be infected with the parasite in the first year of the experiment, for their counterparts with high oxygen level, consistently healthy. Unlike what was observed in field experiments, a low level of oxygen does not appear to affect the intensity of the disease.

Breitburg suspect this means that there is another factor that plays a role in the field. In the Bay and other estuaries, acidity, temperature, salinity and food also vary from place to place.

But as to the ability of oysters to clean and filter the water, the researchers discovered something amazing. The powers filtration of oysters declined during periods of low oxygen, but during periods of recovery, ability recovered and sometimes reached even higher than those of oysters that had never experienced low oxygen levels.

“Our results suggest that we have to think about the effects even short-term exposure to low levels of oxygen to choose sites for restoration of oysters”, Breitburg explains.

“But despite the problems we have encountered, these shallow waters may be candidates for high priority. ”

SOURCE: Fis.com