Scott Zengel

Extent and Degree of Shoreline Oiling: Deepwater Horizon Oil Spill, Gulf of Mexico, USA

The oil from the 2010 Deepwater Horizon spill in the Gulf of Mexico was documented by shoreline assessment teams as stranding on 1,773 km of shoreline. Beaches comprised 50.8%, marshes 44.9%, and other shoreline types 4.3% of the oiled shoreline. Shoreline cleanup activities were authorized on 660 km, or 73.3% of oiled beaches and up to 71 km, or 8.9% of oiled marshes and associated habitats. One year after the spill began, oil remained on 847 km; two years later, oil remained on 687 km, though at much lesser degrees of oiling. For example, shorelines characterized as heavily oiled went from a maximum of 360 km, to 22.4 km one year later, and to 6.4 km two years later. Shoreline cleanup has been conducted to meet habitat-specific cleanup endpoints and will continue until all oiled shoreline segments meet endpoints. The entire shoreline cleanup program has been managed under the Shoreline Cleanup Assessment Technique (SCAT) Program, which is a systematic, objective, and inclusive process to collect data on shoreline oiling conditions and support decision making on appropriate cleanup methods and endpoints. It was a particularly valuable and effective process during such a complex spill.

Shoreline oiling from the Deepwater Horizon oil spill

We build on previous work to construct a comprehensive database of shoreline oiling exposure from the Deepwater Horizon (DWH) spill by compiling field and remotely-sensed datasets to support oil exposure and injury quantification. We compiled a spatial database of shoreline segments with attributes summarizing habitat, oiling category and timeline. We present new simplified oil exposure classes for both beaches and coastal wetland habitats derived from this database integrating both intensity and persistence of oiling on the shoreline over time. We document oiling along 2113km out of 9545km of surveyed shoreline, an increase of 19% from previously published estimates and representing the largest marine oil spill in history by length of shoreline oiled. These data may be used to generate maps and calculate summary statistics to assist in quantifying and understanding the scope, extent, and spatial distribution of shoreline oil exposure as a result of the DWH incident.

Heavily Oiled Salt Marsh following the Deepwater Horizon Oil Spill, Ecological Comparisons of Shoreline Cleanup Treatments and Recovery

The Deepwater Horizon oil spill affected hundreds of kilometers of coastal wetland shorelines, including salt marshes with persistent heavy oiling that required intensive shoreline “cleanup” treatment. Oiled marsh treatment involves a delicate balance among: removing oil, speeding the degradation of remaining oil, protecting wildlife, fostering habitat recovery, and not causing further ecological damage with treatment. To examine the effectiveness and ecological effects of treatment during the emergency response, oiling characteristics and ecological parameters were compared over two years among heavily oiled test plots subject to: manual treatment, mechanical treatment, natural recovery (no treatment, oiled control), as well as adjacent reference conditions. An additional experiment compared areas with and without vegetation planting following treatment. Negative effects of persistent heavy oiling on marsh vegetation, intertidal invertebrates, and shoreline erosion were observed. In areas without treatment, oiling conditions and negative effects for most marsh parameters did not considerably improve over two years. Both manual and mechanical treatment were effective at improving oiling conditions and vegetation characteristics, beginning the recovery process, though recovery was not complete by two years. Mechanical treatment had additional negative effects of mixing oil into the marsh soils and further accelerating erosion. Manual treatment appeared to strike the right balance between improving oiling and habitat conditions while not causing additional detrimental effects. However, even with these improvements, marsh periwinkle snails showed minimal signs of recovery through two years, suggesting that some ecosystem components may lag vegetation recovery. Planting following treatment quickened vegetation recovery and reduced shoreline erosion. Faced with comparable marsh oiling in the future, we would recommend manual treatment followed by planting. We caution against the use of intensive treatment methods with lesser marsh oiling. Oiled controls (no treatment “set-asides”) are essential for judging marsh treatment effectiveness and ecological effects; we recommend their use when applying intensive treatment methods.

Impacts of the Deepwater Horizon Oil Spill on Salt Marsh Periwinkles (Littoraria irrorata).

Deepwater Horizon was the largest marine oil spill in U.S. waters, oiling large expanses of coastal wetland shorelines. We compared marsh periwinkle (Littoraria irrorata) density and shell length at salt marsh sites with heavy oiling to reference conditions ∼16 months after oiling. We also compared periwinkle density and size among oiled sites with and without shoreline cleanup treatments. Densities of periwinkles were reduced by 80-90% at the oiled marsh edge and by 50% in the oiled marsh interior (∼9 m inland) compared to reference, with greatest numerical losses of periwinkles in the marsh interior, where densities were naturally higher. Shoreline cleanup further reduced adult snail density as well as snail size. Based on the size of adult periwinkles observed coupled with age and growth information, population recovery is projected to take several years once oiling and habitat conditions in affected areas are suitable to support normal periwinkle life-history functions. Where heavily oiled marshes have experienced accelerated erosion as a result of the spill, these habitat impacts would represent additional losses of periwinkles. Losses of marsh periwinkles would likely affect other ecosystem processes and attributes, including organic matter and nutrient cycling, marsh-estuarine food chains, and multiple species that prey on periwinkles.

Monitoring of oysters and sediments in Acajutla, El Salvador

Oysters (Ostrea irridescens) and fine-grained sediments from Acajutla, El Salvador were analysed for petroleum hydrocarbons, chlorinated organic compounds, pesticides and trace elements. Most oysters contained only background levels of PAHs, with the exception of those collected very close to an industrial discharge canal which were up to 100 times background levels. Only black mud accumulating in the main harbour contained PAHs at levels of environmental concern. Pesticides in oysters and fine-grained sediments were below the detection levels in most samples. PCBs were also low. Trace elements in sediments and oysters varied widely, reflecting differences in loadings and degree of bioavailability. Zinc and copper in oysters were elevated to levels normally considered representative of moderately polluted sites, whereas arsenic, cadmium, chromium, lead and nickel were not elevated at most sites. These results were generally associated with potential sources of contamination identified through a questionnaire on product storage, handling and waste disposal from facilities operating in the area.

Salt Marsh Remediation and the Deepwater Horizon Oil Spill, the Role of Planting in Vegetation and Macroinvertebrate Recovery

ABSTRACT The Deepwater Horizon oil spill resulted in persistent heavy oiling in salt marshes, particularly in northern Barataria Bay, Louisiana. Oiling conditions and several ecological variables w...

Vegetation cutting as a clean-up method for salt and brackish marshes impacted by oil spills: a review and case history of the effects on plant recovery

Abstract Manual cutting of marsh vegetation contaminated by oil spills is often debated as a clean-up technique. Cutting oiled marsh vegetation may be proposed to prevent the oiling of sensitive wildlife associated with marshes. Less frequently, oiled marshes may be cut to aid vegetation recovery. This paper reviews several studies of oiled marsh cutting, and presents a case history of the Grand Eagle oil spill, where marsh cutting was used as a clean-up technique. The paper focuses on the effects of cutting on oiled vegetation survival and structural recovery. We conclude that cutting is often detrimental. Marshes should not be cut when impacted by light oils, where high flushing rates are present, or where re-oiling would be likely. Cutting should only be considered for areas where oil may persist, significant impacts to wildlife are likely, and less destructive clean-up techniques have proven insufficient. Seasonality should be considered prior to cutting, since vegetation impacts may be less likely during fall and winter. Concurrent stresses, such as unusual or extreme salinity or hydrological conditions, should also be considered prior to cutting, to avoid stressing oiled vegetation beyond recovery. Finally, if vegetation cutting is used in marsh environments, substrate disturbance should be avoided.

Environmental Effects of In Situ Burning of Oil Spills in Inland and Upland Habitats

Abstract In situ burning of inland and upland habitats is an alternative oil spill cleanup technique that, when used appropriately, may be more environmentally acceptable than intrusive manual, mechanical, and chemical treatments. There have been few published reports documenting the environmental effects of in situ burning in inland and upland habitats. Thus, this study, sponsored by the American Petroleum Institute, used two approaches to increase the knowledge base and improve the appropriate use of in situ burning: (1) detailed review of published and unpublished in situ burn case histories for inland and upland spills; and (2) summaries of fire effects and other information from the literature on fire ecology and prescribed burning. Thirty-one case histories were summarized to identify the state of the practice concerning the reasons for burning, favorable conditions for burning, and evaluations of burn effects. The fire ecology and effects summaries included information from the extensive knowledge base surrounding wildfire and prescribed burning (without oil) as a natural resource management tool, as well as fire tolerance and burning considerations for dominant vegetation types of the United States. Results from these two approaches should improve the application of in situ burning for inland and upland spills.

INTEGRATED PLANNING FROM THE MOUNTAINS TO THE SEA: ENVIRONMENTAL SENSITIVITY MAPPING IN THE CARIBBEAN

ABSTRACT Sensitivity mapping recently completed for Puerto Rico, the U.S. Virgin Islands, and the British Virgin Islands combines information on natural resources for both coastal and inland areas, covering both U.S. Coast Guard and U.S. Environmental Protection Agency jurisdictions. This planning and response tool includes detailed Environmental Sensitivity Index (ESI) maps for the coastal zones of Puerto Rico, the U.S. Virgin Islands, and the British Virgin Islands. Reach Sensitivity Index (RSI) maps for small rivers and streams in Puerto Rico have been developed, and sensitive biological and human-use resources have been mapped throughout inland and upland habitats for the entire project area.

Best Practices for Shoreline Cleanup and Assessment Technique (SCAT) from Recent Incidents

ABSTRACT The Shoreline Cleanup and Assessment Technique (SCAT) process, from initial reconnaissance, to generation of Shoreline Treatment Recommendations (STRs) and signoff, is an integral part of oil spill response operations. It is and should remain flexible and scalable based on spill conditions. Several challenging spill responses have contributed to the continuing evolution of the SCAT program. This review examines best practices and unique applications for the SCAT process, coordination within the Incident Command System (ICS), field implementation and tools, and data management. While the basic SCAT process remains the same, the detailed steps can vary greatly from spill to spill. STRs and incident specific forms may be required, additional review procedures for documents and shorelines may occur, endpoints and signoff can become extremely complex, intermediate plans may be generated to manage complexity, and various regulatory consultations may be necessary. Within the ICS, the SCAT program is typ...