In the Water: Corals

Elkhorn coral

Acropora palmata

Jumplinks:

About

In Saba’s crystalline waters, forests of branching corals — featuring structures reminiscent of the antlers on an elk — thrive. On Saba, these colonies are most frequently found at sites east of the harbor, but no matter where you encounter them, elkhorn coral play a critical role in the balance of underwater Caribbean ecosystems.

Elkhorns are essential architects of the reef, constructing vast, intricate formations inhabited by many other key marine species. Known for their rapid growth, their branches can extend by up to 5–10 cm/2–4 inches every year, and colonies typically reach their maximum size in just over a decade. Their vibrant colors come from symbiotic algae called zooxanthellae that live inside their tissue — the same algae that allows coral to photosynthesize nutrients.

Climate change and ocean acidification are heavily impacting elkhorn coral around the world, and the species is currently listed as Critically Endangered. As humans come to terms with just how critical reefs are to our survival — supporting food sources for millions of people, protecting lands from extreme weather and erosion, and harboring many thousands of other marine species — scientists and communities are in a race against time.

For one example of how this collaborative work is being done, read about the Academy’s Hope for Reefs initiative, and learn how Saba Bank National Park protects critical reef biodiversity. And as always, you can help by documenting the coral and other reef species you see, then uploading those images to iNaturalist.org.

Header image by @djscho (CC-BY).

This species is:
Native

Why that matters:
Native species are those that evolved in the region naturally, without human influence. That means they’re specifically adapted to Saba’s habitat, and play a key role in island biodiversity. When we lose native species, gaps appear in the ecosystem. That leads to cascades of additional extinctions, and to the loss of the ecosystem services (food, clean air and water, flood and coastal protections, and more) that we humans rely on.

Elkhorn corals’ massive branches provide habitat for a wide diversity of marine life. Credit: @zahnerphoto, iNaturalist (CC-BY-NC).

iNaturalist Observations

Elkhorn coral

iNaturalist user @zahnerphoto (CC-BY-NC)

iNaturalist user @neild (CC-BY-NC)

iNaturalist user @mark-groeneveld (CC-BY)

Where locals, researchers, and visitors have seen this species.

Saba Island Map and Pins: iNat Taxonomy ID 93312

This map shows geotagged observations of this species made on iNaturalist, the world’s largest community-science platform.

iNat depends on people like you. By uploading photos of species you see in the wild, you can easily learn more about them — while also contributing critical data used by scientists and conservation-managers around the globe.

See something odd?

Observations of land species in water:
Connectivity can affect how accurate location services are, and in the case of endangered species, location is often automatically obscured.
Missing observations:
Your help is needed to collect more data for this species!

Ask a Scientist

Question: Are all corals basically the same?

Answer: Coral species that look identical can be very different in terms of their ecology and physiology, from when they reproduce to what depths they prefer. This means that our current framework for classifying reef-building corals based primarily on morphology is limiting our ability to understand and protect them. At a moment when reefs around the world are experiencing rapid degradation, it’s critical to start capturing this hidden diversity — not only of species, but of how they live and function — to improve our understanding and ability to protect these fragile ecosystems.

Dr. Pim Bongaerts
Curator of Invertebrate Zoology, California Academy of Sciences