Developing a Thermal Shock Method to Control Disease and Biofouling on Oyster Farms

View the project final report

Commodities

• Animals: shellfish

Practices

• Animal Production: aquaculture, parasite control, therapeutics

Dermo disease, caused by the parasite Perkinsus marinus, is a prevalent problem in northeastern oyster stocks. We hope to exploit known temperature vulnerabilities via thermal shock treatments (a novel approach) to reduce disease loss. Oysters living intertidally in the Southeast are regularly exposed to temperatures exceeding the thermal tolerance of P. marinus—but not that of the oysters—which should limit the proliferation of the parasite within oysters.  If this hypothesis is correct, subjecting Northeastern oysters to similar conditions may help mitigate dermo disease, potentially providing a non-chemical therapeutic treatment for commercial stocks. Temperature can be readily elevated during low tide by temporarily covering oysters with clear plastic. Because oysters have a higher thermal tolerance, such exposures may reduce parasite loads without harming the oysters. Reducing biofouling may be a secondary benefit of this treatment. However, elevated temperatures could also disrupt the microbiome, potentially creating human health risks if pathogenic bacteria increase. Understanding how such temperature modulation impacts P. marinus and alters the oyster microbiome is critical to exploring if this could be a safe and effective treatment for aquaculture in the Northeast. Laboratory and field trials will be used to identify effective treatment regimens to reduce P. marinus loads and biofouling, while monitoring bacterial safety. If successful, this preliminary study will be used to design treatments for beta-tests on local oyster farms.

1. Determine how environmental conditions (e.g., sun, clouds, wind) impact heat treatments.
2. Model the changes in the marinus and bacterial populations in vitro when exposed to single or repeated acute heat shocks peaking at 45, 50 and 55 °C for periods of 2, 3 and 4 hrs.
3. Confirm the tolerance and in vivo response of Northeastern oysters to temperatures of 45, 50 and 55 °C for periods of 2, 3 and 4 hrs as identified in objective 2.
4. Assess the effect of heat treatment frequency and seasonality in a farm-like context on:
   1. Dermo infection intensity
   2. Biofouling
   3. The bacterial microbiome, including pathogens of human concern
   4. Oyster growth, condition, and mortality

Objectives 1, 2 and 3 will inform objective 4 and provide baseline data for further improvements should this technology prove fruitful in reducing dermo disease, minimizing biofouling, or impacting bacterial dynamics.  Testing both the frequency and seasonality of treatment will reveal if either factor has a particularly strong impact on Dermo infection intensity since P. marinus abundance changes seasonally, increasing exponentially from Spring to Fall as temperatures warm. Similarly, biofouling changes seasonally, as does the microbiome, which is defined in part by the bacterial community in the surrounding waters. If results indicated that heat treatments can provide an effective means of pest management on oyster farms, then we will pursue farm trials.