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
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
Amount of oil found on shoreline*
low
moderate
high
* Data from U.S. Fish and Wildlife Service; National Oceanic and Atmospheric Administration; National Park Service; state and local officials; NY Times
BarratariaBasin
Gulf of Mexico
ChandeleurIslands
Estimated that between 0.8 to 3.4 mi2 of Gulf Coast was oiled
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 ifrhizomes survive
Rhizomes
Oiled Marsh in LA
Oil soaking into sediment
Oiled grasses may die-back but survive if rhizomes survive
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 ResponsesDo (Almost) Nothing 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
• Put out booms
• Skim off oil that can be reached by boat
• Depend upon rhizomes to produce new shoots
Direct Clean-Up ResponsesBurning 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
• Removes almost all oil
• Maximum results during time of senescence
• Amount of water on marsh has impact on rhizome survival
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 – Marine Science
The Richard Stockton College of New Jersey
P.O. Box 195
Pomona, NJ 08240
Phone: 609-652-4249
Email: [email protected]
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