Animals & Wildlife Magazine

Whale Fall

By Frontiergap @FrontierGap

The blue whale (Balaenoptera musculus) is the largest known animal to have ever existed, this being very understandable with an average 30 meters in length and 180 tonnes (or more) in weight. These majestic animals pose several questions about their behavior and biology, but they also raise questions about what happens to their bodies when they die.

Whale Fall

Image courtesy of sprklg

Whales generally die in shallow waters, thereby allowing other scavengers to consume and recycle the organic matter in the carcass. There are several documented scavenging frenzies of whale carcasses by sharks and sea birds, as well as by land scavengers such as polar bears when the body washes up a beach. However, blue whales are known to live in deeper oceans of up to 2 km, where few scavengers exist. When a whale dies in these circumstances, the body eventually sinks to the bottom of the ocean floor where it becomes a whale fall.  The final resting place of this body provides an ideal habitat for numerous deep ocean bottom dwelling species.

The mystery of deep see whale carcasses has puzzled researchers for a long time, especially since these bodies become large ‘oasis’ of organic matter on an otherwise organic poor seabed. Given the virtual inaccessibility of the deep ocean floor, the first documented discovery of a whale fall occurred in 1987, when submersible technologies became more advanced. Since then, whale falls have increasingly become well documented, with several new species being identified living on the carcass. It has been stipulated that the whale fall is consistently inhabited by organism’s over three stages. In the first stage of decomposition, flesh feeding scavengers such as hagfish and sleeper sharks consume the soft tissue in a process that may last up to two years. In the second stage, opportunistic scavengers such as shrimps, squat lobsters, bristleworms, tube worms, bone eating worms (Osedax) and sea cucumbers colonize the bones and surrounding sediment, feeding on the scraps left by stage one scavengers. This phase also lasts up to two years. In the final stage, called the sulfophilic stage, anaerobic bacteria live on lipids present in the bones, releasing hydrogen sulphide as a by-product. This process provides the basis for a food chain that supports several species of clams, mussels and limpets, and can last from 50 to 100 years!

Whale falls provide a macabre yet beautiful example of abundant life after death.

By Antoine Borg Micallef

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