Abstract
This report describes shoreline surveys conducted in the marshes of Louisiana in areas impacted by oil spilled from the Deepwater Horizon offshore oil drilling platform in the Gulf of Mexico. Three field expeditions were conducted on July 7-10, August 12-14, and August 24-26, 2010, in central Barataria Bay and the Bird's Foot area at the terminus of the Mississippi River delta. This preliminary report includes locations of survey points, a photographic record of each site, field observations of vegetation cover and descriptions of oil coverage in the water and on plants, including measurements of the distance of oil penetration from the shoreline. Oiling in Barataria Bay marshes ranged from lightly oiled sections of stems of the predominant species Spartina alterniflora and Juncus roemerianus to wide zones of oil-damaged canopies and broken stems penetrating as far as 19 m into the marsh. For the 34 survey points in Barataria Bay where dimensions of oil damaged zones were measured, the depth of the oil-damaged zone extended, on average, 6.7 m into the marsh, with a standard deviation of 4.5 m. The median depth of penetration was 5.5 m. The extent to which the oil-damaged zone stretched along the shore varied with location but often extended more than 100 m parallel to the shoreline. Oil was observed on the marsh sediment at some sites in Barataria Bay. This oiled sediment was observed both above and a few centimeters below the water surface depending on the level of the tide. Phragmites australis was the dominant vegetation in oil-impacted zones in the Bird's Foot area of the Mississippi River delta. Oiling of the leaves and portions of the thick stems of P. australis was observed during field surveys. In contrast to the marshes of Barataria Bay, fewer areas of oil-damaged canopy were documented in the Bird's Foot area. In both areas, oil was observed to be persistent on the marsh plants from the earliest (July 7) to the latest (August 24) surveys. At sites repeatedly visited in Barataria Bay over this time period, oiled plant stems and leaves, laid over by the weight of the oil, broke and were removed from the vegetation canopy, likely due to tidal action. In these areas, a zone of 2-5 cm high plant stubble remained at the edge of the marsh. Signs of both further degradation and recovery were observed and varied with site. Oil damage to the marsh at some sites resulted in complete reduction of live vegetation cover and erosion of exposed sediments, while other damaged zones had signs of regrowth of vegetation in up to 10 percent of the areal coverage.
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Claims 12
Claim · model-written summary
Oiling ranged from lightly oiled Spartina and Juncus stems to damaged canopies up to 19 m inland.
- Taxon
- Spartina alterniflora and Juncus roemerianus
Sporobolus alterniflorusJuncus roemerianuse0 - Outcome
- oil-damaged canopies and broken stemse0
- Value
- 19 me0
- Setting
- Barataria Bay marshese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Oiling in Barataria Bay marshes ranged from lightly oiled sections of stems of the predominant species Spartina alterniflora and Juncus roemerianus to wide zones of oil-damaged canopies and broken stems penetrating as far as 19 m into the marsh.”
Claim · model-written summary
The oil-damaged zone averaged 6.7 m deep at 34 Barataria Bay survey points.
Verbatim
e0“For the 34 survey points in Barataria Bay where dimensions of oil damaged zones were measured, the depth of the oil-damaged zone extended, on average, 6.7 m into the marsh, with a standard deviation of 4.5 m.”
t0“marsh”
Claim · model-written summary
The median oil penetration depth was 5.5 m.
Verbatim
e0“The median depth of penetration was 5.5 m.”
t0“marsh”
Claim · model-written summary
Oil-damaged zones often stretched more than 100 m along the shore.
Verbatim
e0“The extent to which the oil-damaged zone stretched along the shore varied with location but often extended more than 100 m parallel to the shoreline.”
t0“marsh”
Claim · model-written summary
Phragmites australis dominated oil-impacted zones in the Bird’s Foot area.
- Taxon
- Phragmites australis
Phragmites australise0 - Outcome
- dominant vegetatione0
- Setting
- Bird's Foot area of the Mississippi River deltae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Phragmites australis was the dominant vegetation in oil-impacted zones in the Bird's Foot area of the Mississippi River delta.”
Claim · model-written summary
Oil covered leaves and thick stems of Phragmites australis.
- Taxon
- Phragmites australisPhragmites australise1
- Organ / stage
- leaves and portions of the thick stemse0
- Outcome
- Oiling of the leaves and portions of the thick stemse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Oiling of the leaves and portions of the thick stems of P. australis was observed during field surveys.”
e1“Phragmites australis was the dominant vegetation”
Claim · model-written summary
Fewer oil-damaged canopies were documented in the Bird’s Foot area than in Barataria Bay.
Verbatim
e0“In contrast to the marshes of Barataria Bay, fewer areas of oil-damaged canopy were documented in the Bird's Foot area.”
t0“marsh”
Claim · model-written summary
Oil persisted on marsh plants from July 7 through August 24 in both areas.
Verbatim
e0“In both areas, oil was observed to be persistent on the marsh plants from the earliest (July 7) to the latest (August 24) surveys.”
Claim · model-written summary
Oiled stems and leaves broke and left the canopy at revisited Barataria Bay sites.
Verbatim
e0“At sites repeatedly visited in Barataria Bay over this time period, oiled plant stems and leaves, laid over by the weight of the oil, broke and were removed from the vegetation canopy, likely due to tidal action.”
Claim · model-written summary
A 2–5 cm tall stubble zone remained at the marsh edge.
Verbatim
e0“In these areas, a zone of 2-5 cm high plant stubble remained at the edge of the marsh.”
Claim · model-written summary
Some sites lost all live vegetation cover and experienced sediment erosion.
Verbatim
e0“Oil damage to the marsh at some sites resulted in complete reduction of live vegetation cover and erosion of exposed sediments”
Claim · model-written summary
Some damaged zones showed vegetation regrowth covering up to 10 percent of the area.
Verbatim
e0“other damaged zones had signs of regrowth of vegetation in up to 10 percent of the areal coverage.”
t0“marsh”