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WonderOcean migration fact

Every night, vast numbers of sea animals rise from the depths towards the surface to feed, then sink back before dawn. This daily journey, called diel vertical migration, carries carbon down into the deep ocean.

Diel vertical migration

OceanBiologyClimateScience

The story behind the card

The migration was first noticed by accident. In 1942 the scientists C. F. Eyring, R. J. Christensen and R. W. Raitt, working with sonar aboard the USS Jasper, found a false seafloor 300 to 500 metres down by day that sat shallower at night. The echo came from millions of animals, above all small fish of the dim middle depths whose gas-filled swim bladders reflect sound. The layer is now called the deep scattering layer. The animals rise under cover of darkness to feed on plankton and descend at dawn to hide from predators that hunt by sight. By mass it is often described as the largest migration on Earth, and it moves carbon downwards as the animals breathe, excrete and are eaten at depth.

Türkçe oku
Her gece sayısız deniz canlısı beslenmek için derinlerden yüzeye doğru yükselir, şafaktan önce yeniden derine iner. Günlük dikey göç denen bu yolculuk, karbonu okyanusun derinliklerine taşır.

Bu göç tesadüfen fark edildi. 1942'de C. F. Eyring, R. J. Christensen ve R. W. Raitt, USS Jasper gemisinde sonarla çalışırken gündüz 300-500 metre derinlikte görünen, geceleri ise daha yukarıda duran sahte bir deniz tabanıyla karşılaştı. Yankı milyonlarca canlıdan geliyordu; bunların başında, okyanusun loş orta derinliklerinde yaşayan ve gazla dolu yüzme keseleri sesi yansıtan küçük balıklar vardı. Bu tabakaya bugün derin saçılma tabakası deniyor. Hayvanlar karanlığın örtüsü altında plankton yemek için yükselir, şafakta görerek avlanan yırtıcılardan saklanmak için derine iner. Kütle bakımından sık sık yeryüzünün en büyük göçü olarak anılır. Derinde soluk alıp verdikçe, dışkı bıraktıkça ve başka canlılara yem oldukça karbonu da aşağı taşırlar.

Sources and further reading

Background reading: Diel vertical migration
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