Whale Fall- the strange ecosystem in the ocean
- Author: Linda Chivell
- Sunday, 12 June 2016
The prolific afterlife of a whale
Whales play a pivotal role in the ocean’s ecosystem. But just as important is a whale’s funeral. Some whales have a fairly short funerals. Either washing up on beaches, or floating around in shallows where they are quickly eaten by predators and scavengers.
However more than 50 percent of whales can have funerals lasting more than 50 years. This is known as whale fall.
When the whale dies the carcass falls into the Bathyal or Abyssal zone of the ocean floor They are found at depths of 2,000 m or 6,600 ft, they can create complex localized ecosystems that supply sustenance to deep-sea organisms for decades.
The first whale fall was accidentally discovered by a team of scientists in 1987. The bacteria that the team found on the whale bone were similar to those found in places like hydro thermal vents.
WHALE FALL COMMUNITY
A dead whale can affects the ecosystem by introducing nutrients to the seafloor. The skeleton of a 90-ton whale contains 5 tons of oil The animals body provides more nutrients to the tens of thousands of organisms that visit it. More than 400 animal species maybe more depend on one whale fall
It all starts with STAGE ONE
Just after the whale dies and its body reaches the ocean floor.
The first scavengers to show up are creatures like sleeper sharks, hag fish and tiny shrimplike crustaceans called anthropoids that strip the flesh down to the bone.
Combined these animals can eat 40 to 60 kilograms of tissue per day. But even at that rate it can take them years to finish off something the size of a whale. Once they have polished off most of it ,
..it is time for Stage Two
A swarm of invertebrates moves in, bringing crustaceans, molluscs, and bristly polycheate worms -- a type of worm that’s good at surviving in extreme environments, like the coldest parts of the ocean. They feed on anything that’s left over, plus the sediment surrounding the whale, which is now packed with bits of decomposing tissue. Some of these animals have never been spotted anywhere else, like a species of snail found on that first 1987 whale fall that led to the discovery of a whole new family of aquatic snails.
In the case of the Antarctic Minke whale, 41 species, most of them unknown to science, were found grazing on and around its bones.
After about two years, mats of bacteria colonize the whale bones,
kickstarting Stage Three
These bacteria feed on lipids -- the fats and oils -- from the whale bones, turning them into hydrogen sulfide gas, which would be very toxic to most forms of life. But in this case, it’s a key part of the whole ecosystem.
All that hydrogen sulfide creates a sulphophilic, or sulfur-loving, community made up of the bacteria, the organisms that feed on them, and other scavengers that show up late to the party. An average of 185 different sulfur-loving species end up in each whale..
This stage can last for decades -- 50 to 100 years -- and it’s a lot like some of the other strange things you’ll find on the ocean floor like hydrothermal vents and cold seeps. These vents are cracks in the ocean floor that spew hot, mineral-rich stuff into the ocean, and the seeps are briny pools of liquids and gases that include lots of sulfide and methane, also on the ocean floor.
Since all these places provide so much potential food on the seafloor -- which is otherwise pretty barren -- life tends to take over. And it’s not totally clear how the organisms that colonize a whale fall get from place to place, or how they find the carcass at all.
Biologists are also trying to figure out how whaling, which would have lowered the number of whale falls, might have changed life on the seafloor,.
The life forms that colonize these places have had to evolve all kinds of adaptations to survive without oxygen or sunlight, surrounded by chemicals that would be toxic to anything else.
“A whale fall is not just a carcass but a carcass that holds a community of specialist organisms,” says Sumida, a marine biologist studying whale fall. “It’s a whole ecosystem.”