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Diseases in the ocean, caused by viruses, bacteria or parasites, can have far-reaching consequences for marine ecosystems. For this reason research has primarily focused on their ecological significance. However, the socioeconomic impacts on coastal communities have received little attention so far.

In a recent study in the journal Ocean and Coastal Management, researchers from Kiel University (CAU), together with international partners, present an expanded risk assessment framework that highlights marine diseases as an underestimated threat to coastal regions and society. When applying this approach to oyster farming as a case study, the extent of the health risks posed by the ocean becomes significantly clear.

"The ocean and society are deeply intertwined. When marine diseases disrupt ecosystems, it always has consequences for humans, through impacts on health, the economy, and cultural identity. We need to be prepared for these risks with not only diagnostics, but also with political instruments," says lead author Dr. Lotta Clara Kluger from Kiel University.

Study is based on a proven risk assessment framework

Building on the United Nations widely recognized Disaster Risk Reduction (UNDRR) framework, the researchers have adapted the model to account for disease outbreaks in marine environments. A key feature of their approach is the inclusion of a second level of analysis, that considers how a disease outbreak, such as the mass mortality of oysters, impacts the local community or economy. This is known as the spillover effect. These analysis levels reflect risk, which, according to the definition of the Intergovernmental Panel on Climate Change (IPCC), is the product of hazard, exposure and vulnerability.

"Until now, existing regulations have been rather fragmented—often limited to known pathogens and not including broader social dynamics. However, the complex dynamics of marine disease outbreaks require new forms of management that consider ecological, economic and social factors equally," says Kluger, head of the marine food security working group at Kiel University's Center for Ocean and Society (CeOS), which is part of the priority research area Kiel Marine Science (KMS).

From oyster populations to societal impacts

In their paper, the researchers use oyster populations as a case study. Oysters, the most extensively studied species of shellfish in terms of infectious diseases, are of great commercial and cultural importance to humans, extending far beyond their use as food. They are considered ecosystem engineers, filtering the water and not requiring additional feeding.

The effects of marine diseases among oysters are felt in various areas of society. In aquaculture, for instance, oyster die-offs can result in lost profits or higher treatment costs. Diseased oysters negatively impact the overall health of a reef because oysters serve as water filters, promote nutrient cycling and control algal blooms. Disease also limits their ability to function as wave breakers and protect against coastal erosion.

They also provide shelter, habitat and food resources for other animals, thus influencing fisheries and their value chain. Water quality also affects the tourism sector and recreational activities. In certain places, oysters also have high cultural value and are considered part of the local heritage, traditions and history.

Risk minimization can be addressed at two levels

Specific strategies to minimize risk can be implemented at the ecological and social levels to address exposure and vulnerability factors. For oyster populations, farmers can select favorable conditions. This includes site selection, artificial water filtration and transfer restrictions.

Exposure can be reduced by selecting species that are less susceptible to disease. At the second level, risk minimization is financially important: Seeking insurances, diversifying sources of income, and expanding product diversity are possible ways to counteract the damage caused by disease outbreaks.

"Instead of only reacting to events, risks should be recognized and minimized in advance. Our goal is to provide concrete tools that can be used to reduce risks for aquaculture farms, communities, and policymakers. That way we strengthen ocean health, food security, and societal resilience," said Kluger.

The new study was conducted as part of the international, interdisciplinary and transdisciplinary project Beyond One Ocean Health (B1OH). The project is led by Prof. Dr. Marie-Catherine Riekhof, Director of the CeOS at Kiel University's priority research area Kiel Marine Science. The third United Nations Ocean Conference () is taking place in Nice, France until June 13.