Menu
Article Ecology
Dengue-resistance Spreads in Mosquitoes
Satellites Spy on Fish Farms
Fukushima Birds Affected
Boozing for Better Health
Climate Conflict of Interest?
One Year On
Antarctic Invasion
Lions Up Close
More Maternal Effort Means More Robust Offspring
Pesticide Problems for Bees
Ants Share Pathogens for Immunity
Poisonous Shrooms Battle Cancer
Colony Collapse from Pesticides?
Insect Battles, Big and Small
Spotted: Emperor Penguins
Melting Ice Releases Ancient Microbes
Pigeon GPS Identified
It’s Raining Mice
Ocean Plastic Aid Insects
Can Fish Eco-Labeling be Trusted?
How Prawns Lure Prey
Food's Afterlife
A Greener Arctic
The Ecology of Fear
  Mixed Report for Oiled Salt Marshes
Two years after the Louisiana coastline was coated by crude oil released from the broken Deepwater Horizon oil rig, much of the 75 kilometres of affected salt marshes has recovered, but some areas that were already degraded by human activities have been irrevocably lost. The report, published today in the Proceedings of the National Academy of Sciences, is thus cause for both optimism and concern.

“It would be premature to conclude that the oil-impacted marshes are out of the proverbial woods yet,” said Christopher D'Elia, dean of the School of the Coast and Environment at Louisiana State University.

Salt marshes protect the land and sea from each other. They shelter the shoreline from eroding waves, while their plants absorb nutrients from inland run-offs that might otherwise cause harmful algal blooms. They also provide nurseries for fish and shellfish. “Louisiana coastal waters usually boil with fish and shrimp with the help of [the marshes],” said ecologist Brian Silliman from the University of Florida, who led the study.

Unfortunately, the marshes are under threat. Even before the BP oilrig sprung a leak in the spring of 2010, pollution and other man-made disturbances were destroying a football field’s worth of wetlands every hour.

In October 2010, 5 months after the oil reached Louisiana, Silliman surveyed three affected sites at Barataria Bay, one of the most heavily contaminated areas. Tall grasses prevented the spill from reaching beyond 15 metres of the shoreline but at the edge of the marsh, up to 82 percent of the local vegetation was smothered by oil. “It looked like a thick, black belt alone the shoreline,” said Silliman.

The oiled zone contained dead and flattened grass, piles of snail corpses, and empty mussel shells. Below ground, around 95 percent of plant roots were dead.

When Silliman’s team revisited the same sites in April 2011, the marshes had started to bounce back. Plant cover in the barren areas had increased by around 20 percent. The grasses from the unaffected areas had sent roots into the dead zones, and had started to repopulate them.

Silliman expected the quick recovery. “Salt marsh theory holds that marsh grasses are resilient to oil coverage and will bounce back in a few years from being covered with oil,” he said. By January 2012, much of the marshland had completely recovered.

But not all areas were so lucky. In places where the marsh was already receding, the oil more than doubled the pace of erosion, with the shoreline retreating by 3 meters per year, compared to the usual average rate of 1.4 metres per year.

“The data confirm what other researchers have reported: oiled marshes are subject to enhanced rates of erosion,” said D'Elia.

By killing the local plants, the oil also destroyed the network of roots that binds the soil together. And with no new roots to fill in, the looser sediment was more quickly washed away by incoming wave. “This erosion permanently transforms the marsh into subtidal mudflats and grasses cannot regrow there,” said Silliman.

Silliman said that the study emphasises the need to stop the salt marshes from eroding away under normal conditions. “Most importantly, that includes increasing the supply of silt to these sediment-starved marshes,” he said. In Louisiana, the construction of channels along the Mississippi has robbed the salt marshes of valuable sediment, which they need to prevent erosion.

Whether this report holds true for all of Louisiana’s marshes affected by the oil spill remains to be seen, however. Silliman’s team only studied a small number of sites, D’Elia said, and the damaged zone may extend far deeper into the marshes at other locations.
Microbial Awakening
Little Fish in a Big Pond
No Sex Required
Old New Species
Beetles Warm BC Forests
Coughing Seashells
Marlboro Chicks
Fighting Microbes with Microbes
Fly Guts Reveal Animal Inventory
Cities Affect Global Weather Currents
Modeling All Life?
Killer Kittens
Opinion: Paradoxical Amphibians
Oil Additive Harming Seabirds
Diversity Defeats Disease
Icy Algae in a Changing Arctic
Native Frogs Beat Invasive Toads
Bridges for UK Water Voles
Mysterious Sea Lion Stranding Continues
Can CO2 Help Grow Rainforests?
Arctic Foxes Suffer from Seafood Diet
Plants Communicate with Help of Fungi
Ladybird Bioterrorists
Arctic Bacteria Thrives at Mars Temps
Mary O’Connor: Warming Up
Bird Bullies
An Ocean of Viruses
Science on Lockdown
 
West Coast Marine Threat
The Gigapixel Camera
Mixed Report for Oiled Salt Marshes
EPA to Regulate Greenhouse Emissions
Genetic Shift in Salmon
A Scientist Emerges
Life (Re)Cycle
How Green Are Your Fish?
School Teachers Release Invasives
Zoo Virus Swap
Mothers-In-Law and Menopause
Stalking Sharks
From Plants and Fungi to Clouds
Good Vibrations
Down and Dirty
Dogs Improve Beach Sanitation
A Funding Reboot
Agriculture-Ecology Initiative Announced
Evolving Dependence
Beard Beer
Opinion: Controlling Invasion
Natural-Born Doctors
Opinion: Fishy Deaths
A Celebrated Symposium