Seagrasses face extinction threat

Matt Walker BBC News 23 May 11;

Seagrasses around the world are disappearing, with some species now threatened with extinction.

The first global survey of individual seagrass species has found that 14% are at risk of going extinct.

More common species are also in decline, meaning both seagrass habitat and diversity is being lost.

Seagrasses provide food and habitat for a variety of ocean species including manatees, sea turtles and fish such as sea horses.

Seagrasses are flowering plants that grow on the ocean floor.

They form vast meadows that flower and seed underwater, having evolved from land-based plants that entered the water millions of years ago.

Seagrasses alone form important marine habitats.

They act as nurseries for young fish and shellfish, and are the primary food for large marine mammals such as manatees and dugongs, as well as reptiles such as some sea turtles.

They also contribute to the health of coral reefs and mangroves, salt marshes and oyster reefs.

It has been known for a while that seagrasses are declining in many parts of the world.

The reasons are many, seagrass expert Frederick Short told the BBC.

Professor Short, of the University of Hampshire in Durham, US is the director of SeagrassNet, an international seagrass monitoring program with 114 sites around the world.

For example, seagrasses are gone from the most developed coastlines due to pollution, said Professor Short.

Seagrasses are in decline in the developing world due to sedimentation, caused by runoff from impacted watersheds and deforestation, and being overloaded with nutrients flowing into the sea from sewage and agricultural runoff.

Seagrasses are also being directly damaged by the dredging of seafloors.

"But there has never been a review of individual species status," said Professor Short.

So he and an international team of experts convened three workshops to gather all the knowledge about individual seagrasses, and used it to evaluate how at risk each species is. The workshops were hosted by Conservation International, the Global Marine Species Assessment programme and SeagrassNet.

The results are published in the journal Biological Conservation.

"I was surprised by the level of threat to many species of seagrass and to discover that seagrass biodiversity is under greater threat than I believed," he said.

Of the 72 species, his team found that 15 seagrasses should be considered Endangered, Vulnerable or Near Threatened, under criteria laid down by the International Union for Conservation of Nature (IUCN) Red List.

Of those, ten face a significant risk of extinction.

Phyllospadix japonicus is an important habitat-forming grass along the rocky shorelines of China, North and South Korea and Japan. But it has gone from swathes of China's coastline, due to seaweed aquaculture.

Zostera chilensis is known from only two locations on the coast of Chile, and seems to have already disappeared from one.

Of the 57 remaining species, 48 are considered of Least Concern, while sufficient data doesn't exist to make a judgement on the others.

"Many widespread, common seagrass species which are not presently threatened are nonetheless in decline, so we have both an overall loss of habitat and a loss of biodiversity," said Professor Short.

"Seagrasses are both direct food for important species and as they break down within the coastal ecosystem, they are part of a vast food web that provides food to many organisms within the coastal ocean, including many commercially and recreationally important species.

"Unfortunately, being submerged in the ocean they are rarely directly seen except by swimmers or snorkelers."

New Study Provides Global Analysis of Seagrass Extinction Risk
ScienceDaily 25 May 11;

A team of 21 researchers from 11 nations, including professor Robert "JJ" Orth of the Virginia Institute of Marine Science, has completed the first-ever study of the risk of extinction for individual seagrass species around the world.

The 4-year study, requested by the International Union for the Conservation of Nature (IUCN), shows that 10 of the 72 known seagrass species (14%) are at an elevated risk of extinction, while 3 species qualify as endangered.

The authors caution that loss of seagrass species and seagrass biodiversity will seriously impact marine ecosystems and the human populations that depend on the resources and ecosystem services that seagrasses provide. A 1997 study placed the value of those services at US$34,000 per hectare per year. Seagrasses offer critical habitat for aquatic life, clear the water by reducing wave action, absorb excess nutrients, and reduce shoreline erosion.

The study, in the online issue of Biological Conservation, determines the likelihood of extinction for each of the world's 72 species of seagrass using the categories and criteria of the IUCN's Red List of Threatened Species.

The IUCN Red List is the most widely accepted method for assessing a species' probability of extinction and its conservation status on a global scale. Red List categories run from "least concern" to "near threatened," "vulnerable," "endangered," "critically endangered," "extinct in the wild," and "extinct."

Placement in a category reflects a species' abundance, reproductive rate, geographic range, and other such factors. A "data deficient" category holds species for which there is inadequate information to assess extinction risk based on distribution, population status, or both. The researchers placed 9 seagrass species (12.5%) in that category.

The researchers listed 48 species (67%) in the "Least Concern" category, including eelgrass (Zostera marina), the most common seagrass in lower Chesapeake Bay. Orth notes, however, that most of these species -- including eelgrass -- are declining in their area of coverage. (Data from VIMS' annual aerial survey shows that eelgrass is absent from one-half of its former range and continues to decline in the areas where it remains).

Orth says that eelgrass was listed as a species of least concern -- despite severe declines in Chesapeake Bay, San Francisco Bay, and other parts of its range -- because it is still widespread elsewhere and thrives in less developed and clear-water areas. He cites his team's successful efforts to replant eelgrass in the seaside bays of Virginia's Eastern Shore as evidence of the species' ability to rebound quickly given clear and cool water.

VIMS scientists have been restoring eelgrass to Virginia's seaside bays since 1997. Their efforts have resulted in the largest and most successful seagrass restoration project in the world, with 38 million eelgrass seeds broadcast onto 309 acres during the last decade. As of 2010, these restored sites have spread naturally to more than 4,200 acres.

Journal Reference:

Frederick T. Short, Beth Polidoro, Suzanne R. Livingstone, Kent E. Carpenter, Salomão Bandeira, Japar Sidik Bujang, Hilconida P. Calumpong, Tim J.B. Carruthers, Robert G. Coles, William C. Dennison, Paul L.A. Erftemeijer, Miguel D. Fortes, Aaren S. Freeman, T.G. Jagtap, Abu Hena M. Kamal, Gary A. Kendrick, W. Judson Kenworthy, Yayu A. La Nafie, Ichwan M. Nasution, Robert J. Orth, Anchana Prathep, Jonnell C. Sanciangco, Brigitta van Tussenbroek, Sheila G. Vergara, Michelle Waycott, Joseph C. Zieman. Extinction risk assessment of the world’s seagrass species. Biological Conservation, 2011; DOI: 10.1016/j.biocon.2011.04.010

New study provides global analysis of seagrass extinction risk
Virginia Institute of Marine Science EurekAlert 25 May 11;

A team of 21 researchers from 11 nations, including professor Robert "JJ" Orth of the Virginia Institute of Marine Science, has completed the first-ever study of the risk of extinction for individual seagrass species around the world.

The 4-year study, requested by the International Union for the Conservation of Nature (IUCN), shows that 10 of the 72 known seagrass species (14%) are at an elevated risk of extinction, while 3 species qualify as endangered.

The authors caution that loss of seagrass species and seagrass biodiversity will seriously impact marine ecosystems and the human populations that depend on the resources and ecosystem services that seagrasses provide. A 1997 study placed the value of those services at US$34,000 per hectare per year. Seagrasses offer critical habitat for aquatic life, clear the water by reducing wave action, absorb excess nutrients, and reduce shoreline erosion.

The study, in the online issue of Biological Conservation, determines the likelihood of extinction for each of the world's 72 species of seagrass using the categories and criteria of the IUCN's Red List of Threatened Species.

The IUCN Red List is the most widely accepted method for assessing a species' probability of extinction and its conservation status on a global scale. Red List categories run from "least concern" to "near threatened," "vulnerable," "endangered," "critically endangered," "extinct in the wild," and "extinct."

Placement in a category reflects a species' abundance, reproductive rate, geographic range, and other such factors. A "data deficient" category holds species for which there is inadequate information to assess extinction risk based on distribution, population status, or both. The researchers placed 9 seagrass species (12.5%) in that category.

The researchers listed 48 species (67%) in the "Least Concern" category, including eelgrass (Zostera marina), the most common seagrass in lower Chesapeake Bay. Orth notes, however, that most of these species—including eelgrass—are declining in their area of coverage. (Data from VIMS' annual aerial survey shows that eelgrass is absent from one-half of its former range and continues to decline in the areas where it remains).

Orth says that eelgrass was listed as a species of least concern—despite severe declines in Chesapeake Bay, San Francisco Bay, and other parts of its range—because it is still widespread elsewhere and thrives in less developed and clear-water areas. He cites his team's successful efforts to replant eelgrass in the seaside bays of Virginia's Eastern Shore as evidence of the species' ability to rebound quickly given clear and cool water.

VIMS scientists have been restoring eelgrass to Virginia's seaside bays since 1997. Their efforts have resulted in the largest and most successful seagrass restoration project in the world, with 38 million eelgrass seeds broadcast onto 309 acres during the last decade. As of 2010, these restored sites have spread naturally to more than 4,200 acres.