Honolulu Star-Advertiser © Susan Scott
February 22, 2002
Last summer, I wrote about seaweeds growing like mad in Hawaii’s waters. Carpets of the stuff are smothering coral heads in Kaneohe Bay, stinky masses of it occasionally foul some of Maui’s beaches, and other unknown species are out there doing who-knows-what-all. At the time, scientific information about these problems was so scarce, it was downright depressing.
Now there’s good news. Due to a grant from the Hawaii Coral Reef Initiative Research Program, managed by the state’s Division of Aquatic Resources and the University of Hawaii, researchers are getting a handle on Hawaii seaweeds, both native and alien.
During this study, algae specialists, called phycologists or algologists, collected 1,200 specimens of algae from 33 sites throughout the Islands. Of these, more than 500 species of algae were identified and catalogued. Fifteen, the workers discovered, are new here.
This research may not sound exciting, but before anyone can begin to solve seaweed growth problems, scientists must know what’s here, what isn’t and where they all grow.
Besides providing clues to troubleshooting, algae studies will also help managers learn how to maintain the health of our coral reefs. Algae are the basis of the marine food web.
There are 10 times more algae species than coral species on our reefs. Sea urchins, snails, fish and countless other creatures graze on reef algae. Since algae grow faster than corals, the grazing process keeps plant life from overgrowing and smothering the reefs. If the algae go, so do the animals, including corals.
This formal, extensive collection of seaweeds is a first for Hawaii and was greatly needed. Not only are algae critical to our reefs’ health, but no other Pacific Islanders have incorporated seaweed, or limu, into their diet like the Hawaiians.
One reason limu was so popular here is that before the missionaries arrived, and before Queen Ka’ahumanu’s intervention in 1819, women were not allowed to eat the same foods as men. Forbidden to women were coconuts, all but three types of bananas, sea turtles and several kinds of fish. Seaweed, therefore, became a valuable alternative food source for women.
Because much ancient knowledge of limu has been lost over the years, no one knows how many seaweed species the Hawaiians ate. One rough estimate is around 60; however, different regional names for the same species, many even on the same island, makes this hard to sort out.
Hawaiians did not name inedible seaweeds and sometimes referred to them as opala, meaning rubbish. But to coral reefs, Hawaii’s inedible seaweeds are anything but rubbish.
One group, called coralline algae, is the glue that holds our reefs together. These plants take in calcium carbonate from sea water and then turn stony. Some form crusts, and others grow in cracks and crevices, cementing together coral and rubble.
These calcium carbonate-depositing plants are vitally important in the formation and maintenance of Hawaii’s fringing reefs. You can see them on reef flats at low tide where they look like lumpy, pink cement.
Another type of seaweed containing large amounts of calcium carbonate is Halimeda, with greenish, calcified blades (seaweeds don’t have leaves). A significant amount of sand on some of Hawaii’s beaches comes from dead, decomposing Halimeda.
Hawaii’s seaweed problems aren’t solved yet, but this study is a giant step forward. Our marine plants are finally getting the attention they deserve.