Most reefs are not oasis in nutrient-scarce waters, says Renato Morais

The image of coral reefs as oases in a “marine desert” is misleading, states a new paper by Branco Weiss Fellow Renato Morais and published in Current Biology. Coral reefs are frequently described as “oases in marine deserts” for thriving in nutrient-depleted oceans. This contrast implies high productivity despite nutrient-poor waters as a hallmark of reefs worldwide and is often termed “Darwin’s paradox” – a misnomer, because, as the paper reveals, the fundamental knowledge required to formulate this idea did not exist at the time of Charles Darwin’s 1842 coral reef treatise.

For the paper, Dr. Morais and his colleagues compared reef productivity across ecosystems and assessed how globally widespread oligotrophic, low-nutrient reef conditions are. Their findings support earlier work placing coral reefs among the most productive ecosystems on Earth. However, relatively few coral reefs exist in oligotrophic waters; 80 % of them occur in more productive mesotrophic and eutrophic conditions. Reefs range across the tropical ocean spectrum of phosphate, nitrate, iron, and silicate concentrations but are disproportionally common in moderate levels of these vital nutrients.

Thus, coral reefs as oases in marine deserts are not the norm: their existence in nutrient-deprived oceans is the exception rather than the rule. Dr. Morais’s research highlights the need to recognize environmental variability and both intrinsic and extrinsic pathways sustaining reef productivity.

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Read the article in Current Biology