Bertarelli Summer2024 FINAL - Flipbook - Page 40
But what about the coral themselves? By tagging young colonies, following their growth every year for six years, and measuring their isotopes,
Graham and his colleagues discovered that guano enriched ¹⁵N was not
only detectable in corals, but it also significantly improved growth rates.
That data allowed Graham to build a mathematical model of the growth
of a particularly important branching coral called Acropora in the wake of
a major bleaching event. Recovery occurred after just eight months when
seabirds were present compared to 18 months when they were absent.
“So that’s really quite promising because obviously bleaching events are
becoming more frequent so the rate at which reefs bounce back is going to
be critical,” Graham says.
Graham’s work also led to a key insight about coral survival in a more
polluted world. “A lot of nutrients that we put into the environment
through agriculture and through sewage,” Graham says, “are very rich in
nitrogen and very limited in phosphorus. You get a very imbalanced input.
And that impairs coral physiology.” Seabird guano, it turns out, delivers
nitrogen and phosphorus in the proper ratios to enhance coral health. They
withstand higher temperatures without bleaching, and they grow faster.
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D UD ENH O F E R / O CE AN I MAGE BA NK
KEY TO SUCCESS Healthy
coral reefs are vital to a healthy
ecosystem, both underwater and
on land.
