Ocean acidification may reduce sea scallop fisheries

Washington: Turns out, each year, fishermen harvest more than USD 500 million worth of Atlantic sea scallops from the waters off the east coast which might be affected by ocean acidification.
A new model created by scientists at the Woods Hole Oceanographic Institution (WHOI), however, predicted that those fisheries may potentially be in danger.

As levels of carbon dioxide increase in the Earth’s atmosphere, the upper oceans become increasingly acidic–a condition that could reduce the sea scallop population by more than 50 per cent in the next 30 to 80 years, under a worst-case scenario. Strong fisheries management and efforts to reduce CO2 emissions, however, might slow or even stop that trend.

The model combined the existing data and models of four major factors: future climate change scenarios, ocean acidification impacts, fisheries management policies, and fuel costs for fishermen.

“What’s novel about our work is that it brings together models of changing ocean environments as well as human responses,” said Jennie Rheuban, the lead author of the study. “It combines socioeconomic decision making, ocean chemistry, atmospheric carbon dioxide, economic development, and fisheries management. We tried to create a holistic view of how environmental changes might play out across different aspects of the sea scallop fishery,” she noted.

Since the oceans can absorb more than a quarter of all excess carbon dioxide in the atmosphere, fossil fuel carbon emissions can cause a dip in ocean pH as well. That acidity can corrode the calcium carbonate shells that are made by shellfish like clams, oysters, and scallops, and even prevent their larvae from forming shells in the first place.

To estimate its impact on the model, researchers incorporated a range of effects based on studies of related shellfish species. Combined with estimates of changing water chemistry, this new model lets scientists explore how plausible impacts of ocean acidification may change the future of the scallop population.

They tested four different levels of impact in each of the four different factors influencing the model, ultimately creating 256 different scenario combinations.

One group of scenarios looked at possible pathways of how ocean acidification may impact scallop biology. Another examined different levels of atmospheric CO2, including one future where emissions continue to skyrocket, and one where they fall due to an aggressive climate change policy. A third set included a range of future fuel costs, which themselves are related to climate change policies. Higher fuel costs can lead to fewer active fishing days, reducing stress on the fishery itself, but also reducing profitability and revenues of the industry. The fourth and final set involved different federal fisheries management techniques.

In all of the model’s possible scenarios, high levels of CO2 in the atmosphere consistently led to increased ocean acidification and fewer sea scallops, despite introducing stricter management rules or even closing certain parts of the fishery entirely.

“The model highlighted the potential risks to sea scallops and likely other commercial shellfish fisheries of unabated carbon emissions to the atmosphere” added the researchers.
The findings appeared in the Journal of PLOS ONE.