Massive Fall of Deep-sea Dead Red Crabs ... What Does it Mean?

Scientists from the National Oceanography Center (NOC) have made a surprise discovery of thousands of dead swimming crabs, 4000 metres deep in the abyssal Pacific. NOC scientists, working in partnership the GEOMAR Helmholtz Center for Ocean Research Kiel and the Scottish Association for Marine Science (SAMS) made the discovery while exploring the area using NOC ocean robot Autosub6000 for the first time.

The crabs were found 1500km away from their spawning areas off the NW American coast, raising questions for ecologists and oceanographers about how such a large swarm ended up in the depths of the Pacific Ocean. This unexpected discovery will change the way scientists view how carbon is transferred from the atmosphere to the deep-ocean floor.

A critical part of the Earth’s carbon cycle occurs in the ocean, where carbon recycling occurs through the marine food web. This discovery suggests that these mass crab falls supply a very large quantity of food to the area - an amount of carbon far greater than was expected for the whole year. Before the study, there was no knowledge that these crabs could fall to such depths and provide food to the region, as well as playing a role in carbon transfer.

Although relatively little is known about the deep sea, the most characteristic feature of abyssal ecosystems of depths from 3000-6000m, is the extremely low availability of food. Deep-sea animals are thought to have adapted to very low food supplies, meaning this feast of surface ocean swimming crabs must represent an extraordinary bonus food input for these abyssal communities.