Climate change is impacting life in the sea more quickly than scientists are realizing. Heat from rising temperatures is currently affecting life on the surface of the water, this could make ocean food chains less productive and could reduce the number of fish in the sea.

It would take centuries for the warm water to work its way down to the ocean depths.

Only A Few Fish In The Sea

A team of U.S. based scientists released a study in the journal Science which examines the consequences of climate warming for the next couple of centuries ending in the year 2300 on food supply and aquatic biome. The study focused on how the warming climate would affect the number of essential nutrients that support plankton which then go on to support fish.

Researchers found that current trends in rising temperatures would affect a large number of factors that make up the marine ecosystem. It would alter the winds, water temperatures, sea ice cover, and ocean circulation. All of these changes would shift nutrients from upper levels of the ocean to the lower depths. This would reduce the plankton growth at the surface.

By 2300 this reduction of plankton would leave the surface nutrient-starved, and reduce the global fish catch by 20 percent. It would have a great impact in the northern part of the Atlantic reducing the fish catch by nearly 60 percent.

Biological Pump

Scientists analyzed how these changes could affect the biological pump. The process which transfers nutrients from the surface water to the deep ocean and vice versa. At the bottom of the food chain are phytoplankton are consumed by zooplankton, which is then consumed by smaller fish, up to the top that includes animals such as whales and sharks.

Dead organisms sink down to the deep ocean. This releases carbon, nitrogen, phosphorus, and other nutrients into the depths of the ocean. It provides the nutrients for the phytoplankton at the bottom of the chain which then continues the cycle.

In the study, they found that this process would be disrupted. It would leave areas of the ocean north of the Antarctic zone without much nitrogen and phosphorous. Using current trends, they found that temperatures on the surface would rise by 17.2º F (9.6º C).

If the warming continues, the poles wouldn't be able to freeze over even during the winter.

In the researchers model, nutrients would build up in the deep ocean. It would leave surface waters with a continuously decreasing nitrogen and phosphorous but would see an increase in the deep ocean.

This would cause phytoplankton growth to decrease which would have an impact on the food chain. The global fish catch would be reduced by 2300. Their simulations showed that after over a 1,000 years enough carbon dioxide would be absorbed that the climate would begin to cool down. It would take centuries for the biological pump to be restarted again.

The biological pump not only works to transfer nutrients all over the Earth's oceans but it also serves a role in removing carbon dioxide from the atmosphere. 

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