The bottom of the ocean is one of the most mysterious and fascinating places on earth. Creatures from down there seem like they’re from another planet, not just from the deep ocean. I mean, look at this deep sea member of the anglerfish family… And these fish don’t actually live as deep down as some other organisms. Scary.
Due to the lack of light that far down in the ocean, some organisms have found other ways of producing their own food as photosynthesis is not an option. Hydrothermal vents provide a source of nutrients deep in the ocean, as they spew out geothermally heated water from under the earth’s surface. Some bacteria use the chemicals thrown up from these vents (mainly sulfur compounds) to make their own food. Other organisms are attracted to these bacteria to feed, leading to the formation of food webs and many predator-prey relationships.
It was an expedition to learn more about this kind of ecosystem that led to a marine biologist and her team from the Natural History Museum and the University of Southampton to come across a natural ‘whale-fall’. A whale-fall is the carcass of a dead whale that has fallen to the deep ocean floor and provides a habitat for deep-sea dwelling creatures. A whale-fall is a particularly large example of ‘marine snow’ – floating debris from higher up in the ocean that finds its way down into the deeper waters and provides food for deep-sea creatures. Not quite the food source that the researchers were out to investigate.
What makes this so interesting?
Well, only 6 natural whale falls have ever been recorded and there has never been one found in the Southern Ocean before. When the vastness of the open water of the world is taken into consideration, and the relatively few deep-sea humans out there, it’s hardly surprising. In order to study the effect a whale’s dead body can have on deep sea biodiversity, scientists experimentally sink whale carcasses to the ocean floor and study the consequences. These types of studies can provide real insight into what happens to a whale after it dies.
A discovery of this kind is nothing short of extraordinary, and the whale-fall teeming with life – the scientists discovered 9 new species living on the carcass. Using their Remotely Operated Vehicle (ROV), the researchers were able to investigate the composition of the community of organisms living off the whale-fall via videos. The new species included 4 new species of worms, 2 new crustaceans and 3 new gastropods.
The team used DNA barcoding to identify the species of whale the bones belonged to – an Antarctic Minke Whale. The skeleton’s layout and size was that of an adult, possibly a female. The types and amount of species differed depending on which bone of the skeleton the researchers looked at, which linked to something called the ‘oil-gradient hypothesis’. It’s thought that differing oil levels in different bones of whale skeletons might lead to differences in rates of decay and the amount of bacteria able to grow on the bones. Therefore organisms varying in their lifestyle and diet thrived at different points of this skeleton. The oil in the skeleton is one of reasons why a whale-fall can support so much life.
Deep sea exploration is important for discoveries like this. If 9 new species were found on this whale-fall alone, who knows what else is out there?
Diva Amon and her team have published their findings in Deep-Sea Research II: Topical Studies in Oceanography. To read more at the Natural History Museum website click here.