Saturday, March 5, 2016

Sperm Whale Fall Ecosystems



When we think of whales we typically think of these giant, majestic creatures swimming through the oceans.  These animals play a major role ecologically while alive, but they also play a significant role ecologically when they die.  As their carcass reaches the ocean floor, it provides many species with a unique habitat that allows them to flourish.
An example of a whale fall carcass (from Google images).
One study researched this idea of “whale fall ecosystems.”  A team of researchers looked at the role that sperm whale carcasses play in creating these ecosystems.  Sperm whales were used because they have an oil-rich structure known as the spermaceti organ that the researchers thought would allow for a unique habitat.  In 2002, a stranding of 12 sperm whale carcasses was discovered.  These 12 sperm whales were sunk by local government authorities using barges in the waters of Cape Nomamisaki at depths of 200-300m.  The whales had decomposed internally but maintained most of their external morphology.  Each whale was wrapped in a nylon net.
Only 5 of the whales were studied using a remotely operated vehicle (ROV) with a total of 27 dives made between the years 2003-2005.  Certain bones were collected to identify the species living on them.  Epifaunal species were collected using a suction sampler and infaunal organisms were collected using a scoop sampler.  The paper presents three tables that identify the presence of different species of mollusks, polychaetes and crustaceans on the whale carcasses. 
A. pacifica. (from Google images)
The most abundant species of mollusk found on the whale carcasses was a bivalve known as Adipicola pacifica.  According to the researchers, this species coated the exposed bone while another species of mollusk, Adipicola crypta, preferred the bone that was buried beneath the sediment.  The most abundant gastropod was Dillwynella vitrea.  Polychaetes found in small pores of the whale bone were typically in the Nereididae, Capitellidae and Dorvilleidae families.  Some cirripeds (crustaceans) known as Heteralepas were found on the nets that wrapped the carcasses but not on neighboring rocks, indicating that they preferred the whale carcass.

The shell sizes of the two most abundant mollusks, A. pacifica and A. crypta, were compared.  The shell size of A. pacifica was the largest on the 1.5 year old whale carcasses and gradually decreased through the years.  The shell size of A. crypta was the smallest on the 1.5 year old carcasses and gradually increased.  This should have been an indicator of a “reef stage” of the carcasses according to the researchers, but it seems this was not really observed.
This study proved that a sperm whale carcass can sustain a working ecosystem for more than three years.  Similar studies have been reported on baleen whales, which indicated roughly the same amount of time as these sperm whales.  The organisms found on the sperm whales were similar to those found on the baleen whales at the family level, but not at the species level.
Whales are my favorite animal, and while I prefer the live ones, this study proves their importance even in their afterlife and further strengthens my passion for this animal.

Source: http://proxy.ashland.edu:2315/ehost/pdfviewer/pdfviewer?sid=ce5eb36f-7e78-4ec4-a481-4e989bb07ca4%40sessionmgr120&vid=4&hid=107
Entitled: "Three-year investigations into sperm whale-fall ecosystems in Japan"

2 comments:

  1. This sounds like a very interesting study. Can you clarify one issue? What do you mean by the 1.5 year old carcass, and the decrease in size through the years? Where the whale carcasses deposited over multiple years? Or were the research dives done over multiple years? Why did one species get larger over the years and the other smaller.

    Can you also provide a url link to the actual paper, and not the Ashland Library site? The library site will only work on campus or for people with AU accounts. Can you also provide a hyperlink to your source?

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  2. Are you referring to the size of the mollusk shells on the 1.5 year old whale carcass? These were compared to the 3.5 year old carcass I believe. Yes, the dives were made over multiple years. As for why the shells demonstrated this pattern, the paper does not mention why. The only thing I could think of would be if one species relied on a nutrient that was decreasing as the whale decomposed while the other species was thriving on an ever growing nutrient. I will be sure to look into this for my presentation. Also, try this URL for the paper: http://onlinelibrary.wiley.com/doi/10.1111/j.1439-0485.2007.00150.x/full

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