Fish Tales – How African Fossils Feed the Amazon

Recent research has found that the world’s greatest reservoir of biodiversity is built on the bones of a long extinct ecosystem.

Over 5,500,000 square kilometres of the Amazon Basin is covered in tropical rainforest and it has been estimated that this amounts to 390 billion individual trees. However, the soil of the Amazon is actually rather nutrient poor having been drained dry by generations of plant growth. Instead it looks to the skies for fresh inputs of nutrients. It has long been recognised that windblown dust from the Sahara desert is essential to maintaining this fantastically rich ecosystem but it is only now that we know where the phosphorous found in that dust comes from.

Phosphorous is essential for life. It forms the chemical backbone for DNA and allows cells to maintain their shape, but in vertebrates most of it is found in our bones and our teeth. For plants it is equally essential for growth and is one of the major components of fertilisers. You might be surprised however, at where the world’s largest rainforest is getting its phosphorous.

The Bodélé Depression in the Sahara couldn’t be any greater contrast to the Amazon Basin. It is a 350,000 square kilometre depression in the desert which was once a vast lake. Around 600,000 years ago this lake dried out, leaving only the modern Lake Chad at its furthest southern end. What remains of the lake is now the world’s largest single source of windblown dust, responsible for feeding a constant stream of nutrients across the Atlantic to the Amazon. Earlier this week (25th September) a team of UK researchers published a paper which revealed that most of the phosphorous found in the Bodélé dust actually comes from the bones and scales of fossilised fish which are slowly eroding out of the rocks. The main fish responsible is Nile Perch, but the team found that fossil turtles and lungfish also contributed their remains. This type of phosphorous is ideal as a fertiliser because it is highly soluble and in fact fish scales are used by gardeners today to feed their plants.

Phot Source: Wikimedia Commons

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Emma Gregg

I have an MSci in Palaeontology and Evolution and a passion for all things extinct! I've always loved writing about the science that interests me and I have a particular fascination for palaeopathology.

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