Well, it actually kind of is impressive. A documentary was broadcast on British Channel 4 (don’t ask me, I have no idea) about a science experiment conducted on an elephant carcass to examine what happens after death. While I can’t access the full video (I’ve tried, but you can too here), I was able to get a trailer off Youtube:
It seems pretty impressive, and I am bummed I haven’t been able to watch the full show. Hopefully sometime soon it will become available.
But reading the article got me to thinking about whale falls. I mean if you think what happens to this dead elephant is impressive, just imagine what the ultimate fate is for dead whales, some of which are 10 times the size of elephants. These are called whale falls, as the whales carcass sinks to the bottom of the deep sea. The process isn’t nearly as rapid as the above video, and whale falls undergo a series of successional communities, supporting life for years after the whale has died. (That’s not to say the elephant carcass doesn’t support some sort of community for longer time periods, I am guessing there is all sorts of microbial activity that is affected by the nutrient pulse long after the elephant’s bones have been picked clean, it just doesn’t make for good television).
Whale falls are rather impressive deep sea features. But to imagine how impressive these things are, we first need to consider the deep sea floor. We are talking about life at the bottom of the ocean here – there is no light (with the exception of any biogenic light). There is also little food on the bottom. One reason, of course, is that with no light, there are no producers. Most of the organisms that inhabit the deep sea floor have adapted to life with a small drizzle of organic particles from the surface waters. This rain of detritus (wouldn’t that be an awesome band name?) is known as the biological pump, and is one of the mechanisms of carbon sequestration in the deep sea. This is great in shallow waters, where this productivity reaches the bottom. However, due to simple sinking, horizontal transport, and use, only about 1% of the surface organic matter reaches a depth of 1000 meters, and much of the stuff that reaches the bottom are refractory particles – essentially particles that are barely usable.
But species have adapted to this environment. In fact, there is a surprising amount of diversity found on the deep sea floor. There are a some theories as to why this might be the case such as the stability time hypothesis which states that organisms, given enough time, will become specially adapted to very narrow niches (although this theory is less supported now). Another hypothesis is that of intermediate disturbance – disturbances reset the clock, so to speak, allowing more species to compete and prevents preventative exclusion. At some intermediate level of disturbance there is expected to be the maximum amount of species. Some of this is also likely attributed to the wide array of habitats, including the muddy abyssal plains, hyrdothermal vents, seeps, seamounts, and canyons. Regardless, there is a lot of diversity on the deep sea floor. (In fact, you can learn about many of these things over on Deep Sea News, if you aren’t already following them, you should!)
So now, picture you are out on this deep sea floor, where there is a high diversity of organisms, but low abundances. There is limited food. Then this giant whale carcass comes crashing down. I am sure you can imagine what happens, but first, a little more about whales, and their importance to the benthos. Their mere actions in the water column might be vital to the global carbon pump. Whale waste contains high concentrations of nitrogen and iron. These recycled nutrients enhance phytoplankton activity, known as the “whale pump,” which, in turn, stimulates the biological pump. Granted, there are complex interactions going on, but simply, whale excrement facilitates alga growth, which in turn, facilitates flux to the bottom. So whales are already good. But what happens when that whale dies? Well, we know they (mostly) sink to the seafloor, and deliver all that carbon sequestered in their tissues to the bottom.
Now the whale is on the bottom. The impact on the sea floor is immense. One whale carcass is close to the equivalent of 1000 years worth of marine snow falling at once. Now, there is tens to a hundred tons of organic matter and nutrients, a veritable all-you-can-eat buffet of sorts. Which reminds me of an expression I was told the other day – How do you eat a whale? Give up? One spoon at a time! Ok, ok I digress. It becomes a site teeming with life, and a biodiversity hot spot. Professor Craig Smith at the University of Hawaii has made a career of investigating these deep sea features. Some of the organisms found at whale falls are also found at hydrothermal vent systems, leading some researchers to believe that these communities act as stepping stones, allowing dispersal of organisms between vents. There is also a succession of animals which colonize and utilize whale falls, so if you visit a whale fall over a period of time you might find entirely different communities. There are even worms that eat whale bones! This is a truly amazing progression of carbon and nutrient transfer from one giant organisms to thousands of deep sea floor animals.
So, that is impressive. Granted, I’ll give you the entire elephant being devoured in days. But whale falls can support entire different communities of organisms for years. And while I am sure I have gotten some of the information a little wrong, there are definitely sites you should check out to learn more, such as MBARI, Dr Craig Smith’s site, and Deep Sea News. There is also a really nice write-up about whale falls at the Audubon Magazine.