In June SRA dove on one of our sanctuary reefs and brought up oysters to send for disease testing. We just received the report back from Maryland Department of Natural Resources. This assessment looked at both overall oyster health as well as testing for multiple diseases. For reference, an oyster at optimal health has a certain amount of fatty tissues, and we found that our oysters were just slightly below this ideal amount, so on average our oysters are pretty healthy!
In terms of disease we tested for Dermo, MSX, and SSO, which are each caused by a different parasite. Dermo disease was only found at low intensity, and only in 30% of the oysters sampled, so it is unlikely to be killing any of the oysters. MSX and SSO diseases can spread rapidly and kill lots of oysters, but fortunately were not detected at all.
Low salinity gave oysters the time to strengthen their shell interiors, preventing sponges from burrowing and weakening the shells. If salinity increases this fall, then the prevalence and intensity of the parasites and boring sponges could increase, which in turn might negatively impact the Severn River’s oyster population. On the other hand, oysters grow faster in saltier water, so there is a trade-off. Fortunately, no other potentially lethal conditions were observed in our oysters and none of the diseases observed are harmful to humans. You can read the full report here.