Maui battling seaweed invasion
By Rebecca Carroll
KIHEI, Maui Seaweed is a common hidden ingredient in ice cream, toothpaste and luncheon meat. Some people even look for it in vitamin supplements and fancy face creams. But for an increasing number of shoreside neighborhoods and ecosystems, alien seaweeds are unwanted invaders.
David Mackwell, a member of the beach community, examines non-native and native seaweeds, tangled together on Waipu'ilani Beach.
At Waipu'ilani, conditions are nearly perfect for seaweed: Trade winds drive it toward the shore, where shallow water, ancient fishponds and a natural coral formation prevent it from drifting away.
Native seaweeds have washed ashore here for much of the past century, at least, but the addition in recent decades of the non-native Hypnea musciformis variety has significantly amplified the problem.
The variety more commonly called Hypnea probably got into Hawaiian waters in the 1970s after a failed attempt to cultivate it for kappa carrageenan, a gelling agent used in chocolate milk, puddings, toothpastes and other products.
Now the variety is among several invasive seaweeds that plague the Islands' beaches.
A modified potato-digging machine is being used to clear out seaweed at Waipu'ilani Beach in Kihei, Maui.
Caulerpa taxifolia has been vexing underwater ecosystems in the Mediterranean for about a decade. The robust and fast-growing seaweed has spread to Adriatic coasts, Australia and even California and Florida, annihilating sea grasses and other marine life along the way.
French navy divers have tried pulling it up by hand, and researchers have tried everything from killing it with salt to blocking its sunlight with giant plastic and aluminum tarps.
Waipu'ilani residents researched various seaweed-removal techniques and finally decided on the modified potato-digging machine to pick up the unwanted beach cover which, left alone, rots into a foul-smelling slime.
The county bought the machine, called a "beach master," last year.
"It's not a perfect solution, but it seems to be working pretty good compared to the bulldozer," said community member David Mackwell, referring to a souped-up Ford 2120 tractor that used to move seaweed (and sand) to one end of the beach.
Now the county plans to use the bulk of Kihei's EPA money for a truck to haul the seaweed to a composting site, as needed. In the past, some of the seaweed has been used for fertilizer and much has ended up in the county landfill.
It makes economic sense to remove the seaweed from the beach, according to a study last year, which said Waipu'ilani's seaweed costs the area millions of dollars a year because nearby property values are lower than in areas without an algae problem, and because the beach gets less recreational use than others nearby.
But to Smith, whose research focuses on nutrient levels in Kihei's water, simply removing the seaweed doesn't get to the heart of the matter. Increased seaweed is feeding off something in the water, and Smith is trying to find what that nutrient is and why it's there.
"We have to cure the problem," she said. "All that we're doing with trucking stuff away is treating the symptoms."