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Ocean acidification reduces the hatching success of a keystone fish species

Oceans serve as a carbon sink by absorbing emissions from the atmosphere. A potential ripple effect in atmospheric emissions could lead to severe impacts throughout the ocean ecosystem. For example, absorbing carbon causes ocean water to become more acidic, and leads to a process called ocean acidification.

A new, experimental study has found that an important forage fish called sand lance is very sensitive to ocean acidification and this could lead to widespread ecosystem impacts by 2100. 

Sand lance spawn in offshore environments that tend to have stable, low levels of CO2 during the winter, explains lead author Hannes Baumann.

The study took an interdisciplinary approach by combining model forecasts and frequent experimentation. This approach found that sand lance embryos are very sensitive to increased CO2 levels and fewer embryos hatched under future oceanic CO2 conditions. As a result, the research team agrees that the sand lace are one of the most CO2-sensitive fish species.

“Because our findings are backed up by repeated independent evidence, they are more robust than many published ocean acidification studies to date.” Bauman says. 

A second negative response was discovered – higher CO2 levels appear to make it harder for sand lace embryos to hatch. This is because lowered pH in the ocean water reduces enzymes that are needed for successful hatching, leaving the embryos unable to break through their eggshell to hatch.

The results show that by 2100, ocean acidification will reduce sand lace hatching success to 71 percent of today’s levels. These fish are a critical component of the food web; a reduced number of sand lace would have profound impacts throughout the ecosystem.

“Sand lances are surely one of the most important forage fish here on the Northwest Atlantic shelf,” said Baumann. “Their range spans from the Mid Atlantic Bight all the way to Greenland.” 

“Where we studied them, on Stellwagen Bank, they are called the backbone of the ecosystem. The humpback whales, sharks, tuna, cod, shearwaters, terns – you name it – they are all relying on sand lance, and if sand lance productivity goes down, we will see ripple effects to all these higher trophic animals. Even though we humans don’t fish for sand lance, we need to take care of the species because it has such a huge effect on everything else.”

As a result of ocean acidification, sand lace and food webs will likely be impacted very soon, and the researchers stress that we must act now.

“We need strategic thinking about what species we are testing next, because we cannot test every marine fish species, that’s an impossible task,” said Baumann.

“We should concentrate on fish species that are likely the most vulnerable, and therefore the ones that are probably being affected first and this research makes a compelling argument that those are the fish species at higher latitudes and in more offshore than nearshore environments.”

The team’s findings are published in the journal Marine Ecology Progress Series.

By Katherine Bucko, Staff Writer

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