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For many years, the ratio of large fish to small organisms in the world’s oceans has remained unchanged. But in 2021, researchers found that due to human activity, the balance was thrown off. Where it leads?
Plankton calculation
In November 1969, the research vessel Hudson entered the waters of Nova Scotia, Canada. A ship with many biologists on board went on an expedition around both Americas – North and South. During the trip, data was discovered that helped the young scientist Ray Sheldon discover one of the fundamental laws of the ocean.
During the 1969 expedition, the ship stopped frequently so scientists could collect samples and make calculations. One of them, Ray Sheldon, was especially interested in plankton: microorganisms that can be found in almost every corner of the world’s oceans. To study them, Sheldon and his colleagues used a special apparatus. The researchers caught plankton with it and roughly calculated the size of the creatures.
Sheldon spectrum
Scientists found that almost all living creatures in the ocean followed a simple rule: the number of organisms was related to the size of their bodies. The smaller the creatures, the more there are. Krill crustaceans, for example, are a billion times smaller than tuna, but there are a billion times more of them in salt water. This rule applied to all organisms, from millimetric bacteria to giant whales. Sheldon and his colleagues figured this out by weighing buckets of seawater and measuring the amount of living creatures in it. In honor of the scientist, the universal law was named the “Sheldon spectrum”.
Violation of the law
In November 2021, a team of scientists from the University of Montreal found that Sheldon’s spectrum was broken. They collected plankton data from satellite photographs and seawater samples, and studied models that predict fish populations and estimated numbers of marine mammals. They then compared these figures with approximate data from the period before 1850. It turned out that until the middle of the 10th century, the Sheldon spectrum worked with all kinds of life in the oceans. However, this is not the case now. The total biomass of fish weighing more than 2 g and all marine mammals has decreased by XNUMX billion tons due to human actions.
Destruction of big fish
The fundamental law of the ocean, in the first place, destroyed industrial fishing. From 1890 to 2001, the whale population dropped from 2,5 million to 880. Many fish species are endangered. One of the problems is the extermination of individuals, which scientists call BOFFFF (an abbreviation that can be translated from English as “big old fat prolific mother fish”). Their large bodies are a success for trawlers, but they are extremely important for the production of offspring.
Not all is lost yet
Of course, industrial fishing is not the only problem. Global warming also plays a role here. The worst case scenario, in which the average temperature rises 5°C above pre-industrial levels, would be fatal for half of the fish species, but even an additional 1,5°C could be extremely dangerous for 10%. Fortunately, unlike many types of land animals, marine animals are extremely viable. With sound fisheries and climate policies, a balance can be found between meeting the needs of people and the health of the world’s oceans. Then the ecosystems will begin to recover and, perhaps, over time they will be able to return to the balance that nature has in the Sheldon spectrum.