Thursday, August 13, 2015

Nutrient oasis is just a nice way of saying rotting corpse

A whale fall is a pleasant little ecosystem that springs up whenever a whale dies and sinks to the bottom of deeper parts of the ocean. Sunlight doesn't penetrate to such depths, so there aren't any plants or algae churning out bits of easily digestible organic matter for other organisms to eat. Thus, it's feast or famine for any creatures living in the deep sea, and a whale carcass is a five star buffet. Whale fall communities are mostly made up of invertebrates, including worms capable of drilling their way into bones to access the delicious fatty marrow contained within. The vibrant and highly localized community that sets up shop on a sunken dead whale (or any other large chunk of organic matter, including fish, trees, and piles of kelp) stands in stark contrast to the desolate surrounding seafloor. For this reason, a whale fall is sometimes referred to as a nutrient oasis, akin to the small areas of lush vegetation growing wherever water flows out of an underground reservoir and reaches the surface in an otherwise barren desert.

Various critters munching on wood that fell to the deep sea floor (Source)

Another such nutrient oasis can be found in regions of Antarctica with rocky terrain and not much life. Occasionally a seal or penguin will wander inland and die from exposure or starvation. Their decomposition at the hands of microorganisms results in the release of nutrients into the surrounding gravel. These nutrients can support the growth of lichens and mosses that form fuzzy green skeleton markers. [Edit: A more recent paper on this]

A third type of nutrient oasis is found in the Arctic tundra. Plant growth in this setting is typically limited by the availability of nitrogen. Thus plants will grow vigorously around the corpse of a dead animal, having gained access to a concentrated store of nitrogen and other nutrients that are released as it decays. It's kinda like how grass grows greener on a lawn over where the septic tank is buried. In the mostly treeless tundra, well-fertilized patches of grass marking the final resting place of a muskox can often be spotted far in the distance.


References

Danell K, Berteaux D, Bråthen KA. 2002. Effect of muskox carcasses on nitrogen concentration in tundra vegetation. Arctic 55(4):389-392. [First page]

Glover AG, Källström B, Smith CR, Dahlgren TG. 2005. World-wide whale worms? A new species of Osedax from the shallow north Atlantic. Proceedings of the Royal Society B: Biological Sciences 272(1581):2587-2592. [Full text]

Higgs ND, Gates AR, Jones DO. 2014. Fish food in the deep sea: Revisiting the role of large food-falls. PLoS One 9(5):e96016. [Full text]

Kiel S, Goedert JL. 2006. Deep-sea food bonanzas: Early Cenozoic whale-fall communities resemble wood-fall rather than seep communities. Proceedings of the Royal Society B: Biological Sciences 273(1601):2625-2631. [Full text]

http://www.photo.antarctica.ac.uk/external/guest/detail/cart/10001295/1/3


http://www.photo.antarctica.ac.uk/external/guest/detail/cart/10004613/1/8

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