When we think about the baleen whaleswe usually imagine giant animals that sail the seas and feed on huge schools of fish, without much relevance to us as humans. However, they have been more important than we can think, being crucial when it comes to talking about the survival of our marine ecosystems. And all thanks to their excrement.
What we knew. For years science has known that whale feces acted as a natural fertilizer top level. Now, a new study has brought to light the sophisticated chemical mechanism behind this ‘floating gold’.
To understand its great importance, we must look at the base of the marine food chain that is in the phytoplankton. These are nothing more than microscopic algae that have the function of being the lungs of the ocean and the basis of marine life. The ‘problem’ is that to thrive they need iron, since without this mineral these algae cannot grow and could spell the end of all marine life.
The feces. This is where enter the classic and revealing study led by Stephen Nicol in 2010, where something astonishing was quantified: the fecal iron measured in the whales was about ten million times higher than that of the Antarctic water that surrounded them. This was important because the whales functioned as a “biological bomb,” recycling and releasing about 50 tons of iron a year into surface waters before industrial hunting depleted their populations.
But we were seeing that adding iron to the sea was not enough, since it tends to sink or become inaccessible quickly. So we were asking ourselves a logical question: how is this whale fertilizer made so effective?
We already know it. The answer has recently come thanks to research published in Nature which shows how a team analyzed five fecal samples from baleen whales. Here they were able to discover that the secret of being such a good marine ‘fertilizer’ is not in the amount of metals they excrete, but in how they package it, since the feces contain high concentrations of what are known in chemistry as organic ligands.
Its function. We can find that it is twofold, the first being the enhancement of the bioavailability of iron. This means it acts like molecular ‘tweezers’ that trap dissolved iron, preventing it from precipitating to the sea floor and keeping it in a format that phytoplankton can easily absorb.
But in addition to this, it neutralizes the copper that is present in the ocean and that in high concentrations is lethal for this phytoplankton. In this way, the ligands present in whale feces bind to copper, drastically reducing its toxicity and creating a safe environment for algae growth.
Its importance. In addition to being a very curious fact, the reality is that this discovery has changed our understanding of the biogeochemistry of the ocean. And, although we think that whales are not only consumers at the top of the food chain, the reality is that they are gardeners of the sea, since they fertilize the surface waters and protect the phytoplankton that is essential for the rest of the animals that live in the ocean.
But these blooms not only feed the entire marine ecosystem, they also capture millions of tons of carbon dioxide from the atmosphere, helping to mitigate climate change. In this way, whale feces help their environment, but also us indirectly.
Images | Todd Cravens Annie Spratt
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