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Our oceans are quickly losing their ability to support fish populations

Recent research has unveiled a concerning trend: climate change is stealthily undermining the ocean’s capacity to sustain plankton, resulting in the rapid decline of fish populations.

This revelation is crucial as even minor reductions in plankton, the ocean’s primary food source, lead to significant decreases in fish stocks.

Oceans and fish rely on phytoplankton

Leading this investigation are Dr. Angus Atkinson from the Plymouth Marine Laboratory and Dr. Axel Rossberg of Queen Mary University of London.

Their study illuminates a previously unnoticed amplifying effect within the ocean’s food chain. They found that a 16-26% decrease in plankton, as predicted in areas like the North Atlantic, could result in a staggering 38-55% drop in the ocean’s capacity to support fish.

This phenomenon is largely attributed to the decline in phytoplankton in various latitudes, a result of warmer waters and nutrient insulation from deeper layers.

Interestingly, while the North Atlantic has seen a decline in plankton over the past 50 years, the impact on fish populations remains uncertain, with models showing varied projections.

What the research team learned

Departing from traditional global-scale computer models, the team adopted a unique, data-driven approach.

By examining the size structure of plankton and compiling a comprehensive global database, they could better understand how energy is transferred from microscopic phytoplankton to larger fish species.

Contrary to common beliefs, the study reveals that temperature plays a secondary role in disrupting food webs.

The primary factor is the abundance of phytoplankton, which dictates energy transfer efficiency.

“Our global analysis sheds light on a hidden vulnerability,” says Dr Atkinson. “We were surprised to find temperature didn’t directly affect food web efficiency. Instead, we see ecosystems adapting to warming by changing plankton size.”

Warmer oceans reduce the nutrient supply from deeper waters, leading to smaller phytoplankton and less efficient energy flow.

Atkinson continued, “This suggests the main threat comes from reduced nutrient supply, leading to smaller plankton, longer food chains, and inefficient foraging.” 

Implications for ocean fish stocks

While this finding may seem counterintuitive, Dr. Rossberg explains the broader context, saying, “Close to shore or in lakes, excess nutrients from land can cause imbalances like harmful algal blooms.”

“But at the vast scales relevant to climate change, it’s the lack of nutrients from deeper waters that becomes the major bottleneck,” Dr. Rossberg expounded.

This research underscores the need to integrate climate change considerations into fisheries management.

Dr. Atkinson points out that global averages can obscure significant declines in fish populations, especially in heavily fished areas.

Urgent action needed

The study underlines the urgency of factoring climate change into fisheries management.

“Global averages can mask the true picture,” explains Dr Atkinson. “Some of the most significant projected declines are in areas with concentrated fishing activities.” 

Recognizing the urgency, Dr. Rossberg emphasizes a multi-faceted approach for sustainable fisheries in the era of climate change.

“A combination of data on plankton size structure and advanced computer models is essential for developing effective, climate-smart ocean protection strategies,” he asserts.

Safeguarding our oceans, plankton, and fish stocks

The study highlights a hidden aspect of climate change, calling for a deeper understanding of the ocean’s food webs, namely the importance of phytoplankton.

By recognizing these hidden amplifiers, we can better protect our oceans and the critical resources they provide, ensuring a sustainable future for marine life.

“We need a combination of data on plankton size structure and sophisticated computer simulation models to design truly ‘climate-smart’ ocean protection strategies,” concludes Dr Rossberg.

“By understanding the hidden amplifiers within the food web, we can better safeguard the future of our oceans and the vital resources they provide.” 

In summary, this eye-opening research by Drs. Atkinson and Rossberg offers a new perspective on the ocean’s vulnerability to climate change.

It paves the way for innovative strategies in marine conservation, emphasizing the importance of understanding the intricate dynamics of oceanic ecosystems in the face of global warming.

The full study was published in the journal Nature Communications.


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