Environment: whale poop helps maintain vital parts of the ecosystem – study

Could the decline in whale numbers throughout the 1900s have had a major impact on the ocean ecosystem? That appears to be exactly the case, according to new research.
The study itself, published in the academic journal Nature And the result of a collaboration between Stanford University, NOAA’s Division of Environmental Research, and the University of California, Santa Cruz, among others, had posed a question: How much food do whales eat?

The answer: much more than previously thought.

Discovering this was, in itself, incredibly difficult. Cetaceans are some of the most fascinating animals on the planet, due to their immense size, wide distribution range, cultural value, and their intelligence and potential vocal abilities. However, they are also some of the most difficult animals to study.

Due to their incredibly large size, in fact, they are the largest living things on the planet throughout the entire history of the planet, in addition to being underwater, it is incredibly difficult to keep them in captivity. In fact, for the largest whales, it is absolutely impossible.

A blue whale rises to the surface to breathe in an undated image from the U.S. National Oceanic and Atmospheric Administration (Credit: NOAA / REUTERS BOOKLET)

But studying them is possible, though incredibly difficult.

Because of these limitations, the best thing researchers could do when trying to study the feeding habits of whales would be to study dead whales.

This time, however, they had used high-tech tags to monitor the whales. The whales specifically studied here were all baleen whales, meaning that instead of biting their prey with teeth, they instead use small baleen plates in their mouths to filter and swallow massive amounts of smaller prey.

Despite eating such small prey, these whales are some of the largest whales of all; in fact, the largest of them, the blue whale, is the largest life form that ever existed.

The tags were able to record the whales’ movements, sounds and videos, light permitting, and drones were used to measure individual whales. The study also employed an echo finder, which was used to detect how much prey was around.

Being so large, it was thought that baleen whales like blue whales and humpback whales had to eat a lot of krill, which are incredibly small, in order to support themselves. And according to this study, that number is much higher than previously believed, and whales eat 2-3 times more krill than expected.

Krill is seen on a finger (illustrative).  (credit: Wikimedia Commons)Krill is seen on a finger (illustrative). (credit: Wikimedia Commons)

“As large baleen whales grow older, the anatomical machinery that allows them to eat also becomes relatively larger,” he explained. Jeremy goldbogen, co-director of the Hopkins Marine Station and associate professor of biology in the College of Humanities and Sciences, who is the lead author of the paper. “They have developed these systems that allow them to be eating machines. That disproportionately larger drink allows them to take advantage of hearty foods, like krill. “

However, these findings raise some serious questions regarding this ecosystem as a whole.

Earth’s diverse ecosystems are often incredibly delicate, and slight changes can often have major consequences.

Before 1910, the whale population in the Southern Ocean, near Antarctica, was much larger. These numbers began to decline massively from 1910 to 1970, when whaling operations began in the region. Although whaling has stopped since then, the whale population is still a fraction of what it was before.

A map indicating the location of the Southern Ocean.  (credit: Wikimedia Commons)A map indicating the location of the Southern Ocean. (credit: Wikimedia Commons)

But if whales eat that much krill, then prior to 1910, the krill population must logically have been able to accommodate it. According to the researchers, this means that the current krill population is five times smaller than it should have been before whaling began in 1910.

And this has serious implications beyond krill numbers.

The circle of life

The fact that a decrease in the number of whales means a decrease in the number of krill may seem paradoxical, as one might think that the population of the prey would increase if its predator were no longer present. However, this is not the case, and it can be explained by understanding how the ecosystem itself works.

Krill, along with other small fish and crustaceans, is consumed by other animals as part of the food chain. And at the top of this food chain, and also eating these krill, are the whales.

However, krill is not at the end of the food chain. They, and small fish and crustaceans, survive by eating phytoplankton, a type of microscopic algae essential for the function of the global ecosystem.

A collection of phytoplankton.  (credit: Wikimedia Commons)A collection of phytoplankton. (credit: Wikimedia Commons)

These plankton have chlorophyll and therefore photosynthesize. This means that they need to be close to sunlight and are therefore generally on top of the water. They are found in bodies of water throughout the world; in fact, their distribution is so wide that they vastly outshine plant life.

They are so essential to the function of the planet that many scientists estimate that between 50% and 80% of all oxygen production on Earth is derived specifically from ocean life such as plankton. In fact, only one species of this plankton, the smallest type known as Prochlorococcus, produces more oxygen than all rainforests combined.

They also have another important role: helping to move through the carbon cycle, the means by which heat and carbon dioxide expelled into the atmosphere are essentially reabsorbed by the planet. This in itself is an essential means of stopping climate change, as the amount of carbon dioxide currently being expelled into the atmosphere due to the use of fossil fuels far outshines what the carbon cycle can support.

Due to its small size, this plankton generally cannot be seen with the naked eye, but when the concentration is large enough in a certain area, patches of color can be seen in the water.

Phytoplankton are seen flourishing across the Barents Sea near northern Europe.  The high concentration allows these microscopic organisms to show through the coloration of their collective chlorophyll.  (credit: Wikimedia Commons)Phytoplankton are seen flourishing across the Barents Sea near northern Europe. The high concentration allows these microscopic organisms to show through the coloration of their collective chlorophyll. (credit: Wikimedia Commons)

Phytoplankton are everywhere, but there is an especially great abundance in the Southern Ocean. Here, they are also a vital part of the food chain.

But despite being at opposite ends of the food chain, it is the whales that are essential in helping to maintain the ocean’s phytoplankton population.

And this was done through the poop.

Although they photosynthesize, phytoplankton also need iron to survive. They were able to get this through the iron released when baleen whales defecate after eating krill, thus releasing the iron from the krill back into the water. It is through this circle of life that phytoplankton were able to thrive. It is a very important process, and when the whale population was larger, it was even more effective.

“Think of these large whales as mobile krill processing plants,” explained Matthew Savoca, a postdoctoral fellow in the Goldbogen lab at Stanford’s Hopkins Marine Station and lead author on the paper. “Each fin whale is the size of a commercial airplane. So in the first half of the 20th century, before whaling, there were an additional million of these 737-size krill processing plants that moved around the Southern Ocean eating, defecating and fertilizing. “

These findings have more ramifications than this, as they further show how important whales are to the environment and how humans and whales impact ocean ecosystems, making them essentially less productive. It also sheds more light on the complexity of ecosystems as a whole, and how there is still so much that humanity has yet to understand.


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