Deep Horizon Oil Spill: Impacts on Costal Plant Communities Dr. Jessie C. Jarvis Marine Science Program The Richard Stockton College of New Jersey
Gulf Coast Aquatic Plant Communities • Louisiana contains ~7,200 mi2 of wetlands – 12% of the nation's coastal wetlands
• Emergent habitats: – Salt marsh/black mangrove
• Submerged habitats: – Seagrass
• Ecological functions: – – – –
Habitat/nursery grounds Food source Storm protection Increase water quality
Emergent Wetland Species Spartina alterniflora Smooth Cordgrass
Avicennia germinans Black Mangrove
Seagrass Species Thalassia testudinum Turtle grass
Syringodium filiforme Manatee grass
Threats Prior to BP Spill • Under severe stress before Deep Horizon oil spill • Since 1956 ~ 1 million acres of coastal marsh has been lost in LA – Average loss of 16,000 acres yr-1
• 1990 - 2001, wetland loss in LA was equivalent of one football field lost every hour • Seagrass loss due to: – Boat propeller scars – Boat groundings – Sediment burial (storms)
Coastal Areas Affected by Direct Oiling Events Combined oil spill slick area May 8 – Aug 7
Barrataria Basin Chandeleur Islands
Gulf of Mexico
Amount of oil found on shoreline* low moderate high
Estimated that between 0.8 to 3.4 mi2 of Gulf Coast was oiled * Data from U.S. Fish and Wildlife Service; National Oceanic and Atmospheric Administration; National Park Service; state and local officials; NY Times
NOAA
Effects of Oil on Aquatic Plants • Impact can vary depending upon: – – – – – –
Affected species Amount of oil Characteristics of oil Extent of weathering Number of oil events Soil penetration*
• Complicated by other stressors – Subsidence – Sea level rise
Effects of Oil on Emergent Wetlands • Soil penetration is key factor • Rely on belowground rhizomes (underground stems) for new shoot production every year • Leaves /shoots can die and plant survive if rhizomes survive Rhizomes
Oiled Marsh in LA
Oiled grasses may die-back but survive if rhizomes survive
Oil soaking into sediment
Effects of Oil on Wetlands • If oil penetrates sediment then rhizomes may die • If rhizomes die: – Soil compacts and collapses – Soil elevation too low for plant recolonization – Open water area created – Erosion increases in surrounding marsh – More rhizomes die
USGS
Effects of Oil on Seagrass • The water soluble fraction of oil negatively affects seagrass – Dispersants increase bioavailability (Thorhaug et al., 1986) – Break down waxy cuticle = greater exposure to hydrocarbons – Sub-lethal effects make plants more susceptible to other stressors
• Other oil spills show limited short term (<1 yr) negative effects – Long term effects unknown (Kenworthy et al., 1993)
Direct Clean-Up Responses Do (Almost) Nothing • Put out booms • Skim off oil that can be reached by boat • Depend upon rhizomes to produce new shoots
Low-Pressure Wash • Skim oil from surface with skimmer • Manually wash shoots with low-pressure hose • Potential impacts from: – Walking through wetland – Vehicles with hoses
Direct Clean-Up Responses Burning • Removes almost all oil • Maximum results during time of senescence • Amount of water on marsh has impact on rhizome survival
Natural Additives • Soak up between 3-15 times their weight • May sink and be difficult to collect • Examples: peat moss, straw, sawdust, feathers, ground corncobs
Current Status • Immediate short term impacts comparable to other smaller events – Next spring real test
• Some loss of area but not the catastrophic decline predicted • Small areas of recovery already observed • Need for long term monitoring
Thank you Contact Information: Jessie Jarvis, PhD NAMS â&#x20AC;&#x201C; Marine Science The Richard Stockton College of New Jersey P.O. Box 195 Pomona, NJ 08240 Phone: 609-652-4249 Email: jessie.jarvis@stockton.edu
Conclusions • Greater impact on intertidal than subtidal aquatic plant communities – Next spring earliest to begin to understand how oil spill impacted wetlands
• Based on the characteristics of this oil spill may be best to take the “Do (Almost)Nothing” approach • Need for immediate action can lead to greater problems • Restoration need already great in LA marshes • Future monitoring of affected areas is essential