Wednesday, February 20, 2008

Alien invasion at high levels in Hawaiian waters

Wander through your backyard or other places in the urban environment, and most of the plants you find are aliens—from the grass in your lawn to the weeds infesting the lawn.

The coastal environment has many of the same issues--weeds by the dozens.

(Photos: Divers feed invasive gorilla ogo into the mouth of the Super Sucker. In photo below, the alien seaweed is inspected as it comes aboard. Kanako Uchino images courtesy The Nature Conservancy of Hawai'i.)

A new study by The Nature Conservancy, published in the journal Frontiers in Ecology and the Environment, reports that Hawaiian waters have 73 species of marine invasives, and while most are comparatively benign, a full 42 percent are harmful and are disrupting the natural environment.

The report, entitled, “Assessing the Global Threat of Invasive Species to Marine Biodiversity,” lists Hawai'i as an ecoregion with “high levels of invasion.”

At some level, if you ever get in the water with a mask on, you know the stuff that's causing the problems. It's the seaweeds like gorilla ogo that are growing like, well, weeds on the reefs. It's the schools of imported yellow taape fish.

Where do they come from? Those two examples were both brought here on purpose. But most arrive as hitchhikers on the bottoms or in the bilgewater of shipping. Before humans were here, a bit of drifting debris might carry an invader, or the larval form of an alien species might wash ashore during unusual sea conditions. But that would happen in small amounts and infrequently.

Today, big ships whose bottoms are covered with living material arrive daily from exotic ports around the world. And some of that stuff drops off to find an initial home clinging to a harbor piling, in a nearby estuary or on an adjacent reef.

The Nature Conservancy study estimates that 68 percent of invasive species in the Islands came on or in or under ships.

Nationwide, there are 800 invasive marine species.

“The scale of this problem is vast. Every day, thousands of vessels cross our oceans with invasive species hitchhiking on their hulls. Because of this, as many as ten thousand species are estimated to be in transit at any one time,” said Jennifer Molnar, lead author of the study. She is a conservation scientist with The Nature Conservancy.

The Conservancy report estimated it costs the nation $120 billion each year to deal with the invasives, which cause disease, clog pipelines, foul ships, damage the productivity of fisheries and do other sorts of damage.

And it can be impossible with current technology to reverse the damage.

“Once alien species become established in marine habitats, it can be nearly impossible to remove them. The best way to address these invaders is to prevent their arrival or introduction in the first place,” Molnar said.

In Hawai'i, one of the techniques being employed to address the problem of weeds already here is the regular vacuuming up of some of the most aggressive alien seaweeds, using a device known as the Super Sucker. It is essentially a barge fitted with a pump and a hose, and divers use the hose to suck up fast-growing unwanted limu off the reefs—presumably giving native reef creatures room to grow.

"The Super Sucker is an essential component of a comprehensive management strategy for controlling these alien algae. The research we’ve done shows that we can efficiently remove mass quantities of algae from impacted reefs. In some cases, we can restore the reef to a condition that native fishes are able to maintain in an algae-free state, which allows corals to recover,” said Eric Conklin, marine science advisor with The Nature Conservancy of Hawai'i.

The Hawai'i State Legislature is at this writing considering two bills, HB 2828 and SB 2638, which would fund the full-time use of the Super Sucker a Kāne‘ohe Bay for a year, as well as to pay for another unit that would be more portable.

For more on the marine invasives report, see

For more on the Super Sucker, see

One of the issues for the rest of the Pacific is that while Hawai'i may have the financial strength to keep some of its worst invasions at bay, small, fragile economies may not be able to fund such efforts.

“Many in Hawai‘i have seen what alien algae have done to some of our reefs. We need all the tools that can be provided for wise management of our coasts. Our next concern is that reefs in other parts of the Pacific may be similarly impacted but have no scientists there to help.” said University of Hawai'i botany professor Celia Smith.

© 2007 Jan W. TenBruggencate