Anchovies Having Sex the Key to Why the Earth’s Oceans Move, Study Finds


A new study reveals that anchovies’ frantic behaviour when they spawn causes the Earth’s oceans to move.

Researchers from the University of Southampton found that when anchovies are spawning, the waters in coastal regions mix, which helps circulate nutrients and oxygen in the area.

According to the new study, the process is essential to keeping the ocean’s precious ecosystems balanced and running. The mixing of the oceans is crucial to ensure that heat, oxygen, nutrients, and pollutants are moved between the different layers.

Previous studies have shown that wide and tides drive the majority of the ocean’s mixing, but little has been known about how aquatic animals contribute to the cycle.

The researchers monitored water turbulence in Ria de Pontevedra, a bay in the northwest coastal region of the Iberian Peninsula. They did this for a total of 15 days using an instrument called a microstructure profiler. This allowed the team to monitor tiny variations in current temperature and speed.

Their conclusion revealed that the turbulence within the water increased every night as fish gathered, despite the weather staying calm throughout those 15 days. Samples collected using fishing nets also discovered the large numbers of spawned effs of European anchovy.

With this data, the team determined that the anchovies’ movements during spawning are responsible for the increased water turbulence.

Dr. Bieito Fernández Castro said: “We believe that biological mixing was intense in our observations because the bay is highly stratified – the temperature and other properties vary significantly at different depths.

“Previous studies have suggested that biological turbulence causes minimal mixing because the circular motions of water that the fish generate while swimming are too small.

“This is certainly true in the open ocean, where temperature changes occur over tens of metres.

“However, we have shown that closer to land, where the layers change over a much shorter distance, the anchovies are able to mix them together.”

The researchers believe that biological mixing isn’t necessarily important in the open ocean, it still remains a key component in keeping ecosystems thriving in coastal areas.

Castro, the leader of the study added: “The observation of how our anchovies drove mixing was totally fortuitous.

“We were set to study how turbulence affects marine life and we end up showing, for the first time, that marine life can influence ocean turbulence, which in turn influences marine life!”


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