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ERDC and Japanese experts work jointly on introduced seagrass species

Published Feb. 7, 2012
ERDC Scientist Dr. Deborah Shafer (left) with Dr. Norio Tanaka.

ERDC Scientist Dr. Deborah Shafer (left) with Dr. Norio Tanaka.

Feb. 7, 2012

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TSUKUBA, Japan — ERDC Environmental Laboratory's (EL) Dr. Deborah Shafer was recently invited to visit Dr. Norio Tanaka, curator of the Tsukuba Botanical Garden at the National Museum of Nature and Science in Tsukuba, Japan.

Tanaka is an expert on the genetics of the sea grass Zostera japonica, and Shafer is internationally recognized as an expert on the physiology of this species. The two scientists met to discuss collaborative research on the sea grass in North America. Sea grasses are widely viewed as one of the most valuable coastal habitat types, and are globally imperiled due to increased coastal development, habitat destruction and declining water quality. Z. japonica is native to Southeast Asia, but is thought to have been introduced on the Pacific coast of North America early in the 20th century as packing material for oyster seed stock imported from Japan.

"With the current threats to sea grass species, it is imperative that we understand the factors affecting their survival," said Shafer. "I understand that sometimes there are conflicts between competing industries and interests, but these plants are critical coastal habitats for a variety of species and it is very important that we find a management balance acceptable to all."

Management of this species in the U.S. varies widely, depending on location. In Washington and Oregon, regulatory policies currently make no distinction between two sea grass species in the genus Zostera,the native Z. marina and the introduced Z. japonica. In a recent port expansion project in Newport, Ore., mitigation was required to compensate for the removal of Z.japonica. However, there have been recent proposals to list Z. japonica as a noxious weed in Washington, due to conflicts with shellfish growers. In northern California, state officials are attempting to eradicate multiple populations recently discovered in the vicinity of Humboldt Bay. This varied management approach contradicts efforts to conserve and protect sea grass in other regions of the United States and around the world.

Shafer's previous research identified differences in photosynthesis and growth rates between northern and southern Pacific populations of Z. japonica. In recent collaborative studies with Environmental Protection Agency scientist Dr. Jim Kaldy of the Western Ecology Division, Pacific Coastal Ecology Branch, experiments were conducted to evaluate sea grass tolerance to stress and help understand the responses of native and introduced Pacific Coast sea grass species to sea level rise and global climate change. Based on these experiments, they discovered that Z. japonica is very adaptable and tolerant of a wide range of environmental conditions, suggesting that populations will continue to expand. Furthermore, changing climate conditions are likely favorable for the introduced Z. japonica, but unfavorable for the native Z. marina.

The collaborative research with Tanaka is aimed at identifying the source of the introduced populations and developing a set of habitat suitability parameters to predict future range expansions of this species in North America.


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