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You are here: /main/research/NOWRAMP 2002/features/halimeda algae


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Creature Feature - Halimeda algae

Halimeda algae
Halimeda opuntia ()

Halimeda opuntia.  Photo by Larry Basch, NPS.
Halimeda opuntia, photo by Larry Basch, NPS.

This green seaweed, Halimeda, was the first we saw underwater at Mokumanamana, scattered across the surge swept limestone platform in between sand patches and little bushy Laurencia tufts, a red seaweed.

Halimeda is calcified, meaning that all around its cell walls is a deposit of calcium carbonate. Halimeda is prevalent in most tropical ocean waters. It is famous for being the source of "oatmeal sand". As you can see in the picture, as segments of the plant die the calcified parts remain intact. These break off to form white flakes that pile up to make significant amounts of sea floor sediment on reefs and in lagoons. The specimen pictured was found off of Mokumanamana (Necker Island).

Some fish eat Halimeda and there are even small sea slugs that suck the cell sap!

From: Karla McDermid, Expedition Scientist

Talk About It!

What are the benefits of Halimeda?

Asked by Alief on Feb 22, 2003.
What are the benefits of Halimeda for humans possible uses)? How deep did you go?

Answered by Karla of the NOW-RAMP Crew on Feb 23, 2003.
Halimeda is an important contributor to marine sediments on reefs and in tropical lagoons. In a recent literature search conducted by my students, I don't recall any human uses for Halimeda. Our deepest dive on NOWRAMP was about 85 feet.

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