Invasive brown kelp proves hard to kill

It sounds like something out of a horror movie. It’s brown, slimy, can attach to just about anything, and shoots spores into the water that grow into more of alien stuff in just two months.

This invader is a species of brown kelp — Undaria pinnatifida — common to Japan and popular in miso soup. Since 2009, the stubborn kelp has moved into San Francisco Bay and is staying put.

It multiplies quickly and has already severely altered ecosystems in Argentina, New Zealand and parts of Europe.

Since it was discovered in the Bay in 2009 around harbors and docks, researchers and biologists have been on the alert, urging that an effort be made to destroy the species.

The kelp likely hitched a ride here on boats from Japan. With boats coming in and out of the harbor regularly, it’s difficult to curb its growth rate.

As for the spores released by the kelp, biologist Chela Zabin told the Chron they make wiping out the species nearly impossible:

“We pull out the large sprouts, but any time we find one that has released spores it sets the clock back for two years. … even if we were getting rid of every single individual we’d still have that two-year lag time, and that’s assuming another boat doesn’t come in and reinfect the area.”

The seaweed can be killed by removing it and dumping it in fresh water or exposing it to heat.

Zabin said that if it’s not dealt with, the species could compete or muscle aside native Bay plant life such as giant kelp. Fish and other animals depend on native species for food and shelter.

This new species cannot replace other kelp as a food source for native species, and therefore could endanger the livelihood of other creatures.