Rhodolith beds likely to fuel protection debate
September 17, 2004
The discovery in June of a single bed of rhodoliths, colorful marine algae that resemble coral, was made near Knight Island in Prince William Sound by scientists at the University of Alaska Fairbanks (UAF) School of Fisheries and Ocean Sciences (SFOS). Rhodolith beds have been found throughout the world's oceans, including in the Arctic near Greenland and in waters off British Columbia, Canada. But they have never been documented in Alaska waters.
"This is exciting because it represents a new type of habitat scientists had not identified before in Alaska," said Brenda Konar, associate professor of marine biology at SFOS and staff scientist with the West Coast and Polar Regions Undersea Research Center at UAF.
Rhodoliths belong to a group known as coralline red algae that deposit calcium carbonate within their cell walls to form hard structures that closely resemble beds of coral. But unlike coral, rhodoliths do not attach themselves to the rocky seabed. Rather, they drift like tumbleweeds along the seafloor until they grow heavy enough to settle and form brightly colored beds. And while corals are animals that filter plankton and other organisms from the water for food, rhodoliths produce energy through photosynthesis.
Globally, rhodoliths fill an important niche in the marine ecosystem, serving as a transition habitat between rocky areas and barren, sandy areas. Rhodoliths provide habitat for a wide variety of species, from commercial species such as clams and scallops to true corals. The discovery of rhodoliths in Alaska is likely to fuel the debate over the protection of seafloor habitats.
"Now that we found them, we want to find more of these beds and learn precisely what their role in the Alaska marine ecosystem is."
Mike Foster, professor emeritus at Moss Landing Marine Laboratory in California, has studied the global distribution of rhodoliths, and is the author of numerous scientific papers on the subject. He says the discovery of rhodoliths in Alaska marks an important milestone in scientists' understanding of coralline algae.
"If these beds are anything like those elsewhere in the world, they are likely critical habitat for associated species, and there are probably more new species in them than just the rhodoliths," said Foster. "Such discoveries also send an important message about how little we know about the sea."
The discovery came after Konar and Katrin Iken, assistant professor of marine biology with the university's Institute of Marine Science, accidentally dropped a small strainer, or sieve, overboard. The scientists had been conducting nearshore surveys of marine life as part of an international study sponsored by the Census of Marine Life NaGISA program and funded by the Gulf Ecosystem Monitoring program.
"A sieve is worth about $75, so we wanted to get it back," said Konar. "We descended into about 60 feet of water and found the sieve right away. But then I noticed these little pink tumbleweeds everywhere. I thought I was looking at a rhodolith bed, but rhodolith beds had never been described in Alaska. We were shocked to see how many there were down there."
Konar said she knew right away the find was significant. She'd seen rhodoliths in places like Baja California, Mexico. But in her more than 15 years of diving Alaska waters, she had never come across them.
"The biggest ones may have been about the size of a ping-pong ball, but many were smaller. They have lots of branches that come out of a centerpiece. They look like toy jacks, except they are pink. It was a very large bed, at least 60 meters (197 feet) long. It was very exciting."
Konar and Iken collected several rhodolith specimens and sent them to Rafael Riosmena-Rodriguez, an internationally recognized marine taxonomist who specializes in identifying rhodoliths. During the past several months, Riosmena-Rodriguez conducted a number of tests aimed at identifying the rhodoliths at his laboratory at the Marine Botany Program at Autonomous University of Baja California Sur in La Paz, Mexico. Some of the tests involved slicing the specimens into thin sections and comparing their structure and reproductive parts to a global database of known rhodolith species.
"I believe we have at least two rhodolith species in the samples I received," said Riosmena-Rodriguez. "One species is Phymatolithon calcareum. This species is widely distributed in the North Atlantic Ocean."
While scientists agree that ocean currents are key to distributing rhodoliths around the world, debate centers on where P. calcareum originated. Riosmena-Rodriguez says the species may have actually originated in Alaska waters. More research on the species' evolutionary history is needed to be sure.
The other rhodolith specimen collected by Konar and Iken is potentially a species new to science.
"It does not seem to match anything we have seen," said Riosmena-Rodriguez.
Riosmena-Rodriguez said the as-yet unidentified species is similar to a type of rhodolith found in eastern Canada, called Lithothamnion glaciale. But in important ways the Alaska rhodolith is different.
"It has very large conceptacles, the reproductive structures," explained Riosmena-Rodriguez. "And the thallus is very thin. This is something unique that you don't find in very many species."
Riosmena-Rodriguez said additional samples and further testing are needed to confirm whether the second species is indeed new.
Scientists believe rhodoliths have been present in the world's oceans since at least the Eocene epoch, some 55 million years ago. Because rhodoliths probably grow very slowly in Alaska's cold waters, Riosmena-Rodriguez said they probably have been in Alaska a very long time, perhaps long enough to have evolved into an entirely new species.
While they search for funding to look for and identify additional rhodolith beds, Konar, Iken, and Riosmena-Rodriguez will submit a scientific paper on their discovery to a marine journal. And if one of their rhodoliths turns out to be a new species, they'll have the honor of naming it.
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