Marine mammals are apex consumers on every trophic level in the marine environment. Marine Mammals and especially whales not only consume in large quantities but they also can grow to vast sizes making them the largest mammals on the planet. Whale poop (excrement) has an important trophodynamic function as it induces primary productivity, and it can be also regarded as a climate geo-engineering tool.
Phytoplankton, which are tiny microscopic organisms that live on the surface of the ocean, require sunlight, carbon-dioxide from the atmosphere and nutrients in order to carry out photosynthesis. However, seawater itself is not uniformly rich in these substances (phosphorus, nitrogen and iron), which is why planktons are clustered into patches. The average lifespan of Planktonic clusters can be up to several weeks, and if they don’t get eaten, at the end of their life they then sink to the bottom where they bury large amount of organic carbon. This is known as the carbon or biological pump.
Deep diving marine mammals, such as whales, have high amount of iron in their blood and since their metabolism is reduced at depth and regularly come up to breathe, they defecate at the surface. Their faeces is rich in both nitrogen and iron, which stimulates primary productivity, especially at areas with limited amount of nutrients. To put this into perspective, it is estimated that 50 tonnes of whale poop, via primary productivity, can remove 40000 car’s carbon emission.
One of the major contributors to the decline in whale populations has been industrial whaling, which has resulted in population estimations to be around 10 times lower in the oceans. And even though the International Whaling Commission introduced a whaling moratorium in 1986, species such as the grey whales, sperm whales, right whales, humpback whales and blue whales are still listed as species of concern or as endangered on the IUCN list.
So if these ‘ocean gardeners’ have such an important function, what impact has whaling had on the ocean ecosystem? The removal of whales can not only upset the balance of the food web, but since they have such an important role in the global carbon cycle, whaling might have deprived us of an important partner in our fight against climate change.
By Wanda Bodnar