December 2011, Vol. 23, No.12

Waterline

Floating islands launched to protect Louisiana marshes

Volunteers from the American Wetland Foundation (New Orleans) have helped launch 187 floating islands off the coast of Houma, La., as a demonstration project for a new technology to protect coastal areas from erosion, according to an American Wetland Foundation news release.

The islands, measuring 1.5 m (5 ft) × 2.4 m (8 ft), are designed to mimic wetlands and to both protect land from wave erosion and build new land in shallow open waters in areas that have seen large land loss, the news release says.

The islands are constructed from recycled plastic bottles and marine foam to provide buoyancy and are held together by a frame of polyvinyl chloride pipe. Each island is planted with 40 to 60 plant species.

For this project, the islands were anchored together to span 457 m (1500 ft) near the Isle de Jean Charles, located south of Houma. This area has experienced extreme erosion, the news release says. The plants extend their roots down into the water, reaching the bottom and forming traps for land-building sediments. Several islands will be stacked away from the shore to test their ability to build land in open water, the release says.

Martin Ecosystems (Baton Rouge, La.) installed the islands with help from volunteers from several local organizations. Local Native American tribes will monitor the islands’ effectiveness during the next year. America’s WETLAND Foundation (New Orleans), the Coastal Conservation Association (Houston), Shell (The Hague, Netherlands), Entergy (New Orleans), and Terrebonne Parish Consolidated Government (Houma) teamed up to sponsor the demonstration project.

 

 

Arctic Ocean survey reveals disruption in water temperatures

A group of scientists and explorers investigated the effects of climate change by measuring temperature and salinity in the water column beneath surface ice on the Prince Gustav Adolf Sea in the Arctic Ocean. The results from the Catlin Arctic Survey investigation commissioned in 2011 by the Catlin Group (Hamilton, Bermuda) could increase understandings of the ways shifting ocean currents affect the climate in northern Europe, according to a YSI Hydrodata Ltd. (Letchworth, England) news release.

The researchers used hand-held castable instruments to obtain conductivity, temperature, and depth measurements down to 100 m, according to the news release. Researchers deployed the instruments into bore holes created in the Arctic ice and let them free-fall 100 m, where sensors gathered data.

This survey studied freshwater currents beneath the ice surface to help understand their effect on bottom-up ice melting, which disrupts global ocean circulation. One key measurement parameter taken was colored dissolved organic matter (CDOM). High levels of CDOM can result in higher light absorption, which, in turn, leads to increased melting that can disrupt the flow of the Gulf Stream, explained oceanographer Victoria Hill in the release.

Researchers anticipated that the Arctic Ocean would be highly transparent, because the rivers contributing CDOM were frozen, but their findings contradicted their assumptions. The researchers found that 70% to 80% of solar radiation was being absorbed by CDOM. They also found that at a depth below 200 m, the temperature was 1°C colder than expected, which is a significant change in normally stable, deep water. This temperature change suggests that surface meltwater was sinking, driving warmer water up into contact with the surface ice, the release says.

©2011 Water Environment Federation. All rights reserved.