Natural Resource Damage Assessment Research Articles

Marine Mammals and Respiration: Evidence of Poor Pulmonary Health in Bottlenose Dolphins Following the Deepwater Horizon Oil Spill

ABSTRACT The Deepwater Horizon (DWH) disaster resulted in large-scale contamination of bays, sounds, and estuaries in the northern Gulf of Mexico (GoM), home to multiple stocks of bottlenose dolphins. Inhalation, direct aspiration, ingestion with subsequent aspiration, and dermal absorption of oil and its toxic components were all considered possible routes of exposure for dolphins living within the oil spill footprint. To determine if dolphins were adversely impacted, capture-release health assessments were performed in heavily-oiled Barataria Bay (BB), Louisiana, and in Sarasota Bay (SB), Florida, a comparison site with no DWH oil contamination. Initial studies were conducted as part of a Natural Resource Damage Assessment (2011–2014), with follow-on studies supported by the Gulf of Mexico Research Initiative (2016–2018). To specifically evaluate pulmonary health, transthoracic ultrasound techniques previously developed for managed dolphins were applied to wild dolphins. Results showed that BB dolphins were ~5 times more likely to have moderate to severe lung disease than SB dolphins in 2011, the year following the spill. Concurrent pathology investigations of dead dolphins in the northern GoM reported similar pulmonary findings. In 2013 and 2014, moderate to severe lung disease persisted among BB dolphins, and remained elevated relative to the prevalence at the SB comparison site. More recent live animal health assessments (2016–2018) showed long-term persistence and potential worsening of moderate to severe lung disease in BB dolphins, specifically in animals alive during the oil spill (prevalence of 0.20, 0.35, and 0.55 in 2016, 2017, and 2018, respectively). Long-term monitoring of dolphin populations is critical to fully understand the potential for and timeline of individual and population recovery from the impacts of a large-scale oil spill event, as well as the cost-benefit trade-offs for restoration activities. In particular, BB dolphins provide valuable insight into the long-lasting effects of oil and oil-related contaminants on animal, human, and ecosystem health.

The SONS Money Tale: From Exxon Valdez to Deepwater Horizon to ??

Synopsis SONS (Spill of National Significance) have been extensively studied from multiple perspectives. In the realm of the Incident Command Structure (ICS) there have been numerous Operations, Planning, and Logistics examinations, reviews, and recommendations. The fourth ICS node – Finance – has seen little such scrutiny or review. This paper, written by two individuals at the heart of each respective response, will address that gap and identify the problems that arose, were solved, or remain problematic for the next SONS that occurs in the United States. Each spill posed different problems, driven by statute, prior experience, fiscal systems, and the expectations of outside stakeholders. The paper will examine the following dimensions. 1) The available fund balance at the start of the response, and how the fund could be replenished under existing statute.2) The financial role taken by the spillers/responsible parties.3) The mechanisms to provide response funding to the FOSC during the incident.4) Funding National Contingency Plan participants (Federal, State, Local) supporting the FOSC response.5) Funding Trustee led natural resource damage assessments and damage restoration plans during and after the response concluded.6) Payment of claims to injured third parties.7) Billing the spillers/responsible parties for the incident costs and the disposition of the resulting payments. The paper will conclude with an examination of the financial issues that remain and will probably arise for the next SONS. It will summarize possible solutions, reflecting when appropriate a number of legislative changes that have been proposed by various parties.

Biogeochemical Processes Affecting the Fate of Discharged Deepwater Horizon Gas and Oil: New Insights and Remaining Gaps in Our Understanding

Research funded under the Gulf of Mexico Research Initiative provided new insights into the biogeochemical processes influencing the fate of petroleum chemicals entering the Gulf of Mexico from the Deepwater Horizon (DWH) accident. This overview of that work is based on detailed recent reviews of aspects of the biogeochemistry as well as on activities supported by the US Natural Resource Damage Assessment. The main topics presented here are distribution of hydrocarbons in the water column; the role of photo-oxidation of petroleum compounds at the air-sea interface; the role of particulates in the fate of the DWH hydrocarbons, especially marine oil snow (MOS) and marine oil snow sedimentation and flocculent accumulation (MOSSFA); oil deposition and accumulation in sediments; and fate of oil on beaches and in marshes. A brief discussion of bioaccumulation is also included. Microbial degradation is addressed in a separate paper in this special issue of Oceanography. Important future research recommendations include: conduct a more robust assessment of the mass balance of various chemical groupings and even individual chemicals during specific time intervals; seek a better understanding of the roles of photo-oxidation products, MOS, and MOSSFA and their relationships to microbial degradation; and determine the fates of the insoluble highly degraded and viscous oil residues in the environment.

Assessment of the efficacy of six field cleaning protocols for hydrocarbon quantification.

The defensibility of field sampling data collected in support of natural resource damage assessments and other environmental investigations depends on rigorous quality assurance and control both in the field and laboratory. One important step in field procedures is the cleaning of sampling equipment between samples to minimize the carryover of contaminants. Large-scale sampling efforts during the Deepwater Horizon oil spill event have highlighted the importance of understanding how multiple equipment cleaning protocols affect interstation cross-contamination and the resulting chemical data quality. In this study, six field cleaning techniques were tested on metal sampling equipment using two different sediment types spiked with crude oil in order to understand their relative and absolute effectiveness in reducing chemical carryover. The complexity of the cleaning protocols ranged from a simple water and scrub brush application to protocols that included soap and/or solvent. In this study, percent residual hydrocarbon transfer, relative to total loading in sediments, never exceeded 0.032%. The least labor-intensive protocol, water and scrub brush application, had the highest potential for hydrocarbon transfer (0.011-0.032%). Statistical differences were observed among treatments, and it was found that protocols containing a solvent step were more effective than protocols without solvents. Depending on the data quality objectives, the differences may not be meaningful, and choosing a cleaning technique should be governed by health, safety, and environmental factors. The residual hydrocarbons measured after equipment cleanings for all techniques in this study were negligible when compared with other variables that occur during routine sampling and laboratory activities.

Integrating marine oil snow and MOSSFA into oil spill response and damage assessment

Marine snow formation and vertical transport are naturally occurring processes that carry organic matter from the surface to deeper waters, providing food and sequestering carbon. During the Deepwater Horizon well blowout, oil was incorporated with marine snow aggregates, triggering a Marine Oil Snow (MOS) Sedimentation and Flocculent Accumulation (MOSSFA) event, that transferred a significant percentage of the total released oil to the seafloor. An improved understanding of processes controlling MOS formation and MOSSFA events is necessary for evaluating their impacts on the fate of spilled oil. Numerical models and predictive tools capable of providing scientific support for oil spill planning, response, and Natural Resource Damage Assessment are being developed to provide information for weighing the ecological trade-offs of response options. Here we offer considerations for oil spill response and recovery when assessing the potential for a MOSSFA event and provide tools to enhance decision-making.

A Physiologically Based Oiling Model (PBOM) to Predict Thermoregulatory Response in Birds

When birds are exposed to oil, their ability to thermoregulate is impaired as a result of damage to the insulative properties of their feathers. If an oiled bird is unable to maintain thermal homeostasis, hypothermia and death can follow rapidly. Physiological responses to oiling depend on several variables including environmental conditions (e.g., ambient air and water temperatures), life history of bird species (e.g., body size and habitat selection), and foraging strategies (e.g., divers, surface feeders, shorebirds). The most widely used approach to assess the effect of spilled oil on birds is the US Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Type A Natural Resource Damage Assessment (NRDA) Model for Coastal and Marine Environments. This approach addresses body size and time spent in a hypothetical slick but lacks the flexibility to assess other variables related to physiological response. We developed a dynamic physiologically based oiling model (PBOM) for birds to address this need. The PBOM has been validated against empirical data from a dose-response study in which common eiders were exposed to Statfjord A crude oil. The PBOM can be used to predict time to hypothermia for birds of differing body size and habitat preferences, in environments ranging from Arctic to subtropical. The model presently includes 5 representative bird species: common eider, spotted sandpiper, great blue heron, dovekie, and American white pelican, but could be adapted to represent almost any bird. Environ Toxicol Chem 2021;40:251-260. © 2020 SETAC.

Seasonal movements of Gulf of Mexico sperm whales following the Deepwater Horizon oil spill and the limitations of impact assessments

As part of the Deepwater Horizon Oil Spill Natural Resource Damage Assessment in the Gulf of Mexico, we conducted a large passive acoustic survey across the eastern Gulf continental shelf edge to assess impacts to sperm whale population. In the months immediately after the spill, sperm whale occurrence was significantly higher in areas closest to the spill. Over the following seasons in 2010–2011, we documented cyclical patterns of decreased and increased occurrence suggesting that this population exhibits a seasonal occurrence pattern in the region, with seasonal movements to other regions, and not likely directly influenced by the oil spill. Unfortunately, a lack of adequately scaled, pre-spill data on sperm whales, along with limitations on the survey duration constrain our ability to infer spill-related changes in sperm whale occurrence. However, our study establishes post-disaster baseline data for continued monitoring, and an expanded study design could provide a model for continued monitoring.

Beyond Thresholds: A Holistic Approach to Impact Assessment Is Needed to Enable Accurate Predictions of Environmental Risk from Oil Spills.

The risk assessment for the environmental impact of oil spills in Australia is often conducted in part using a combination of spill mapping and toxicological thresholds derived from laboratory studies. While this process is useful in planning operational responses, such as where to position equipment stockpiles and whether to disperse oil, and can be used to identify areas near the spill site where impacts are likely to occur, it cannot accurately predict the environmental consequences of an oil spill or the ecosystem recovery times. Evidence of this disconnect between model predictions and observed impacts is the lack of a profound effect of the Deepwater Horizon wellhead blowout on recruitment to fisheries in the northern Gulf of Mexico, contrary to the predictions made in the Natural Resources Damage Assessment and despite the occurrence of impacts of the spill on marine mammals, marshes, and deep water ecosystems. The incongruity between predictions made with the current approach using threshold monitoring and impacts measured in the field results from some of the assumptions included in the oil spill models. The incorrect assumptions include that toxicity is acute, results from dissolved phase exposure, and would be readily reversible. The toxicity tests from which threshold models are derived use members of the ecosystem that are easily studied in the lab but may not represent the ecosystem as a whole. The test species are typically highly abundant plankton or planktonic life stages, and they have life histories that account for rapid changes in environmental conditions. As a consequence, these organisms recover quickly from an oil spill. The interdependence of ecosystem components, including the reliance of organisms on their microbiomes, is often overlooked. Additional research to assess these data gaps conducted using economically and ecologically relevant species, especially in Australia and other understudied areas of the world, and the use of population dynamic models, will improve the accuracy of environmental risk assessment for oil spills. Integr Environ Assess Manag 2020;16:813-830. © 2020 SETAC.

Restoring barrier habitat in Louisiana to compensate for natural resource injuries: Shell Island and Chenier Ronquille Barrier Restoration Projects

Coastal Louisiana received significant funds tied to BP penalties as a result of the Deepwater Horizon incident. As it is widely considered that the State of Louisiana sustained most of the damage due to this incident, there has been a firm push to waste no time in implementing habitat restoration projects. Sustaining the land on the coast of Louisiana is vital to our nation’s economy, as several of the nation’s largest ports are located on the Gulf coast in Louisiana. In addition, the ecosystems making up the Louisiana coast are important to sustain some of the largest and most valuable fisheries in the nation. Funded by BP Phase 3 Early Restoration, the goals of the Natural Resource Damage Assessment (NRDA) Outer Coast Restoration Project are to restore beach, dune, and marsh habitats to help compensate spill-related injuries to habitats and species, specifically brown pelicans, terns, skimmers, and gulls. Four island components in Louisiana were funded under this project; Shell Island Barrier Restoration, Chenier Ronquille Barrier Island Restoration, Caillou Lake Headlands Barrier Island Restoration, and North Breton Island Restoration (https://www. gulfspillrestoration.noaa.gov/louisiana-outer-coast-restoration, NOAA 2018). Shell Island and Chenier Ronquille are critical pieces of barrier shoreline within the Barataria Basin in Plaquemines Parish, Louisiana. These large-scale restoration projects were completed in the years following the Deepwater Horizon incident, creating new habitat and reinforcing Louisiana’s Gulf of Mexico shoreline. The Louisiana Coastal Protection and Restoration Authority (CPRA) finished construction of the Shell Island NRDA Restoration Project in 2017, which restored two barrier islands in Plaquemines Parish utilizing sand hydraulically dredged from the Mississippi River and pumped via pipeline over 20 miles over levees and through towns, marinas, and marshes to the coastline. The National Marine Fisheries Service (NMFS) also completed the Plaquemines Parish barrier island restoration at Chenier Ronquille in 2017 utilizing nearshore Gulf of Mexico sediment, restoring wetland, coastal, and nearshore habitat in the Barataria Basin. A design and construction overview is provided herein.

Turning a tragedy into large-scale barrier island restoration in Louisiana: A three-project case study

Louisiana has successfully utilized the proceeds from the fines imposed for the Deepwater Horizon incident to significantly jump start barrier island restoration as identified in the Coastal Protection and Restoration Authority (CPRA) of Louisiana Coastal Master Plan (CPRA 2017). The Riverine Sand Mining/ Scofield Island Restoration (BA-40) project was the first to be implemented through a commitment of remaining funds in the initial emergency protective berms’ construction budget formulated into the Berms to Barrier Islands plan. The berm/ restoration conversion at Scofield Island was the first to utilize this funding mechanism. The Caminada Headland Beach and Dune Restoration–Increment II (BA-143) project was funded through the National Fish and Wildlife (NFWF) Gulf Environmental Benefit Fund and capitalized on a prior project constructed to the west completing the beach and dune restoration of the entire headland. Lastly, the Caillou Lake Headlands Restoration (TE-100) project was funded through the Natural Resource Damage Assessment (NRDA). The TE-100 project restored the entire degraded beach and dune system backed by a created marsh habitat to complement a prior restoration effort. Scofield Island is located west of the active Mississippi River bird’s foot delta in Plaquemines Parish, Louisiana. A primary objective of this project was the excavation and delivery of Mississippi riverine sand for beach and dune restoration; a first in our nation’s history. Multiple design and construction challenges arose requiring the CPRA, consulting team, and construction contractor to adapt. Construction of the beach and dune component of this project required approximately 22 miles (mi) of pipeline and four booster pumps along a sediment pipeline corridor that crossed two hurricane protection levees, went underneath two highways and a navigation channel, traversed the Empire Waterway, crossed Pelican Island, entered the Gulf of Mexico, and extended to Scofield Island. The restoration footprint length was approximately 2.4 mi, total volume placed was approximately 3.5 million cubic yards (MCY), and the benefit equaled 510 restored acres (CEC 2014). The pipeline corridor has subsequently been utilized for two other restoration projects, Shell Island East Berm Barrier Island Restoration (BA-110) and Shell Island West NRDA Restoration (BA-111). As a first in Louisiana’s restoration history, the Caminada Headland Beach and Dune Restoration–Increments I and II (BA-45 and BA-143) utilized sand dredged from Ship Shoal, an Outer Continental Shelf (OCS) sand resource located approximately 26-38 mi from the restoration areas. The 13.3 mi long headland was restored with approximately 3.7 MCY for BA-45 and 5.5 MCY for BA-143 from the borrow area (CEC 2015 and CEC 2017). A combination of cutterhead dredge/scow barges and hopper dredges were used to construct the project. A key goal of this project was restoring and protecting the fragile ecosystem which provides critical habitat for nesting shorebirds. The headland is of critical importance in serving as a defense of our national energy infrastructure. The western portion of the headland directly protects Port Fourchon, one of the nation’s most important energy ports. Caillou Lake Headlands (TE-100), known locally as Whiskey Island, is centrally located in the Isle Dernieres chain and it is a remnant of the single, larger Isle Dernieres (Last Island), which was segmented into multiple smaller islands by a major hurricane in 1856. The project included restoring the beach and dune along approximately 4.5 mi while simultaneously creating a marsh platform along approximately 5,500 feet (ft) utilizing 10.4 MCY of sand from the borrow area (CEC 2018). The borrow area lies within Ship Shoal OCS Lease Block 88 located over 10 mi along the conveyance corridor offshore of Whiskey Island. This project represents the largest barrier island restoration project to date in terms of volume per linear foot of shoreline with an average density of over 441 cubic yards per linear foot (CEC 2018).

Coastal monitoring and data management for restoration in Louisiana

The Coastal Protection and Restoration Authority (CPRA) of Louisiana was created after the devastating hurricanes of 2005 (Katrina and Rita) and is responsible for planning and implementing projects that will either reduce storm-induced losses (protection) or restore coastal ecosystems that have been lost or are in danger of being lost (restoration). The first task of the CPRA board was to develop Louisiana’s first Coastal Master Plan (CPRA 2007), which formally integrates and guides the protection and restoration of Louisiana’s coast. The System-Wide Assessment and Monitoring Program (SWAMP) was subsequently developed as a long-term monitoring program to ensure that a comprehensive network of coastal data collection activities is in place to support the planning, development, implementation, and adaptive management of the protection and restoration program and projects within coastal Louisiana. SWAMP includes both natural-system and human-system components and also incorporates the previously-developed Coastwide Reference Monitoring System (CRMS), the Barrier Island Comprehensive Monitoring (BICM) program, and fisheries data collected by the Louisiana Department of Wildlife and Fisheries (LDWF) in addition to other aspects of system dynamics, including offshore and inland water-body boundary conditions, water quality, risk status, and protection performance, which have historically not been the subject of CPRA-coordinated monitoring. This program further facilitates the integration of project-specific data needs into a larger, system-level design framework. Monitoring and operation of restoration and protection projects will be nested within a larger hydrologic basin-wide and coast-wide SWAMP framework and will allow informed decisions to be made with an understanding of system conditions and dynamics at multiple scales. This paper also provides an update on the implementation of various components of SWAMP in Coastal Louisiana, which began as a Barataria Basin pilot implementation program in 2015. During 2017, the second phase of SWAMP was initiated in the areas east of the Mississippi River. In 2019, development of SWAMP design was completed for the remaining basins in coastal Louisiana west of Bayou Lafourche (Figure 1). Data collection is important to inform decisions, however if the data are not properly managed or are not discoverable, they are of limited use. CPRA is committed to ensuring that information is organized and publicly available to help all coastal stakeholders make informed, science-based decisions. As a part of this effort, CPRA has re-engineered its data management system to include spatial viewers, tabular download web pages, and a library/document retrieval system along with a suite of public-facing web services providing programmatic access. This system is collectively called the Coastal Information Management System (CIMS). CPRA and U.S. Geological Survey (USGS) are also developing a proposal to create an interface for CIMS data to be exported to a neutral template that could then be ingested into NOAA’s Data Integration Visualization, Exploration and Reporting (DIVER) repository, and vice versa. DIVER is the repository that the Natural Resource Damage Assessment (NRDA) program is using to manage NRDA-funded project data throughout the Gulf of Mexico. Linking CIMS and DIVER will make it easier to aggregate data across Gulf states and look at larger, ecosystem-level changes.

Effect of Louisiana sweet crude oil on a Pacific coral, Pocillopora damicornis

Recent oil spill responses such as the Deepwater Horizon event have underscored the need for crude oil ecotoxicological threshold data for shallow water corals to assist in natural resource damage assessments. We determined the toxicity of a mechanically agitated oil-seawater mixture (high-energy water-accommodated fraction, HEWAF) of a sweet crude oil on a branched stony coral, Pocillopora damicornis. We report the results of two experiments: a 96 h static renewal exposure experiment and a “pulse-chase” experiment of three short-term exposure durations followed by a recovery period in artificial seawater. Five endpoints were used to determine ecotoxicological values: 1) algal symbiont chlorophyll fluorescence, 2) a tissue regeneration assay and a visual health metric with three endpoints: 3) tissue integrity, 4) tissue color, and 5) polyp behavior. The sum of 50 entrained polycyclic aromatic hydrocarbons (tPAH50) was used as a proxy for oil exposure. For the 96 h exposure dose response experiment, dark-adapted maximum quantum yield (Fv/Fm) of the dinoflagellate symbionts was least affected by crude oil (EC50 = 913 μg/L tPAH50); light-adapted effective quantum yield (EQY) was more sensitive (EC50 = 428 μg/L tPAH50). In the health assessment, polyp behavior (EC50 = 27 μg/L tPAH50) was more sensitive than tissue integrity (EC50 = 806 μg/L tPAH50) or tissue color (EC50 = 926 μg/L tPAH50). Tissue regeneration proved to be a particularly sensitive measurement for toxicity effects (EC50 = 10 μg/L tPAH50). Short duration (6−24 h) exposures using 503 μg/L tPAH50 (average concentration) resulted in negative impacts to P. damicornis and its symbionts. Recovery of chlorophyll a fluorescence levels for 6−24 h oil exposures was observed in a few hours (Fv/Fm) to several days (EQY) following recovery in fresh seawater. The coral health assessments for tissue integrity and tissue color were not affected following short-term oil exposure durations, but the 96 h treatment duration resulted in significant decreases for both. A reduction in polyp behavior (extension) was observed for all treatment durations, with recovery observed for the short-term (6−24 h) exposures within 1–2 days following placement in fresh seawater. Wounded and intact fragments exposed to oil treatments were particularly sensitive, with significant delays observed in tissue regeneration. Estimating ecotoxicological values for P. damicornis exposed to crude oil HEWAFs provides a basis for natural resource damage assessments for oil spills in reef ecosystems. These data, when combined with ecotoxicological values for other coral reef species, will contribute to the development of species sensitivity models.

Evaluating Population Recovery Characteristics and Potential Recovery Actions for a Long‐Lived Protected Species: A Case History of Gulf Sturgeon in the Apalachicola River

AbstractIn the U.S. Gulf of Mexico, Gulf Sturgeon Acipenser oxyrinchus desotoi supported an intense and short‐lived commercial fishery in the early twentieth century. Thereafter, it persisted at very low levels until the fishery was closed by individual U.S. states in the Gulf of Mexico region in the mid‐1980s. Despite the closure of the fishery, the stock has not recovered and there have been threats to population recovery including the potential effects of the Deepwater Horizon oil spill, storm events, and harmful algal blooms. We developed an age‐structured population model for Gulf Sturgeon to examine their population recovery characteristics. We paired this model with simple population reference points to assess the factors that influence the population recovery rate and strategies that resource managers could adopt to promote the recovery of the species. We used the Gulf Sturgeon population in the Apalachicola River as a case history and the date of 2023 that has been identified in Gulf Sturgeon Recovery Plan (GSRP) as the point at which to evaluate recovery, and under current management we predict that (1) age‐4+ Gulf Sturgeon (fish 4 years of age and older) will be approaching 50% of current estimated carrying capacity; (2) the dynamic spawning potential ratio is likely >0.3, suggesting a low chance of recruitment overfishing; (3) the population age structure is likely slowly recovering; (4) the recovery of the Gulf Sturgeon population is sensitive to increases in total mortality; and (5) the estimated values for exploitation rate (UMSY) and biomass at maximum sustainable yield (BMSY) are about 0.058 and 1,859 kg (or <200 age‐4+ fish per year [age‐4 and older fish]), respectively. Our results demonstrate the relative efficacy and influence of various recovery efforts and threats, respectively, and demonstrate that “recovery” is much different when it is based on historic versus currently available habitat. These model results provide reference points for comparing field assessments as part of the planned restoration efforts and upcoming population status reviews for Gulf Sturgeon that are funded as part of the Natural Resource Damage Assessment following the Deepwater Horizon oil spill.

Restoration Scaling Approaches to Addressing Ecological Injury: The Habitat-Based Resource Equivalency Method

Natural resource trustee agencies must determine how much, and what type of environmental restoration will compensate for injuries to natural resources that result from releases of hazardous substances or oil spills. To fulfill this need, trustees, and other natural resource damage assessment (NRDA) practitioners have relied on a variety of approaches, including habitat equivalency analysis (HEA) and resource equivalency analysis (REA). The purpose of this paper is to introduce the Habitat-Based Resource Equivalency Method (HaBREM), which integrates REA’s reproducible injury metrics and population modeling with HEA’s comprehensive habitat approach to restoration. HaBREM is intended to evaluate injury and restoration using organisms that use the habitat to represent ecological habitat functions. This paper seeks to expand and refine the use of organism-based metrics (biomass-based REA), providing an opportunity to integrate sublethal injuries to multiple species, as well as the potential to include error rates for injury and restoration parameters. Applied by NRDA practitioners in the appropriate context, this methodology can establish the relationship between benefits of compensatory restoration projects and injuries to plant or animal species within an affected habitat. HaBREM may be most effective where there are appropriate data supporting the linkage between habitat and species gains (particularly regionally specific habitat information), as well as species-specific monitoring data and predictions on the growth, density, productivity (i.e., rate of generation of biomass or individuals), and age distributions of indicator species.

Oiling of American white pelicans, common loons, and northern gannets in the winter following the Deepwater Horizon (MC252) oil spill

The Natural Resource Damage Assessment and Restoration Trustees for the Deepwater Horizon oil spill assessed the external oiling of migratory bird species dependent on open water in the Gulf of Mexico following the aforementioned spill. The assessment was designed to evaluate birds that use open water during the winter within 40 km of the Gulf shoreline. We focused on the American white pelican (Pelecanus erythrorhynchos), common loon (Gavia immer), and northern gannet (Morus bassanus). Point counts (pelican, loon) or strip transects (gannet) were used and each target species was assessed for oiling (unoiled, trace, light, moderate, or heavy amounts) and photographed. Due to distance at sighting and/or poor visibility, not all visible birds were assessed. The percentage of birds oiled varied by species, with the common loon being the highest (23.6%), followed by American white pelican (16.9%), and northern gannet (6.9%). Most of the American white pelicans and common loons had trace (83% and 72%, respectively) or light levels (11% and 24%, respectively) of oiling. The northern gannet had just trace levels of oiling. Some pelicans (6%) and loons (4%) had moderate amounts of oiling. Based on expert derived-mortality estimates and our estimates of oil exposure, we used Monte Carlo simulations to predict expected decreases of 2.5%, 4%, and 11% in the observed population for the northern gannet, American white pelican, and common loon, respectively. While these values are underestimates of the true values given the long time lag (10–12 months) between the oil spill and the assessment, these data represent some of the few estimates of exposure for these species and describe minimum risk estimates to these species.

Pelagic seabird density and vulnerability in the Gulf of Mexico to oiling from the Deepwater Horizon/MC-252 spill

Using ship-based surveys, the Natural Resource Damage Assessment (NRDA) Trustees assessed the external oiling of offshore and pelagic marine birds inhabiting the northern Gulf of Mexico (Gulf) in the year following the Deepwater Horizon oil spill (DWH spill). Study objectives were to (1) collect data on pelagic seabirds that were visibly oiled, (2) collect data to estimate abundance of seabirds in offshore and pelagic waters, and 3) document the location and condition of any bird carcasses encountered. Methods employed included strip line transects and station point counts. Surveys were conducted within a study area bound by the Texas-Mexico border and the Dry Tortugas of Florida to the south, and the nearshore coastal waters of the northern Gulf of Mexico. A total of 5665 strip line transects and 386 station point-counts of variable duration were collected during the study. More than 23,000 individual seabirds comprising 45 estuarine, coastal, offshore, and pelagic species were tallied. Average daily abundance of seabirds detected varied from a low of approximately 7 birds/day in November 2010 along regions of the mid- and outer continental shelf to a high of more than 580 birds/day in June 2011 within the near-shore, coastal waters of the northern Gulf.

Persistence of avian carcasses on sandy beaches and marsh edges in the northern Gulf of Mexico

As part of the natural resource damage assessment for the Deepwater Horizon oil spill, a mathematical model was used to estimate the total number of bird carcasses deposited on shorelines based on the number of carcasses collected and adjustment factors such as detection probability and carcass persistence. Studies of carcass persistence occurred along sandy beaches and marsh edges in the northern Gulf of Mexico to obtain site-specific inputs for the model. We estimated persistence rates for these habitat types and evaluated the influence on persistence of carcass size, location of the carcass on the beach, dominant vegetation type in the marsh, carcass distance into marsh vegetation, and length of time a carcass was stranded on a shoreline. The length of time stranded had the greatest influence on persistence in both habitat types, with persistence initially relatively low and increasing logarithmically. Carcass size and position were weakly influential on sandy beaches. Carcass size had stronger influences along marsh edges, and marsh habitat type also affected persistence. We found evidence of a positive relationship between distance into the marsh and persistence during the first 24 h after carcass deployment.

NORTH BRETON ISLAND RESTORATION, DESIGNING TO INCREASE A BARRIER ISLAND’S HABITAT AND LONGEVITY

The product and purpose of a well-planned program of investigation and design will be realized later this year when restoration construction begins on North Breton Island. North Breton Island is the southern-most of a chain of barrier islands forming the Chandeleur Islands. The barrier island formation lies within the Mississippi River delta plain system approximately 62 miles southeast from the metropolitan city of New Orleans, LA. Under the authority of the Natural Resource Damage Assessment (NRDA) process, NRDA Trustees selected enhancement of North Breton Island as part of the 2014 Deepwater Horizon NRDA Phase III Early Restoration Plan to help restore injuries to natural resources (Trustees, 2014). The U.S. Fish and Wildlife Service (USFWS) is the lead implementing agency for this Project. The Project includes restoring the barrier shoreline along the entire length of North Breton Island through beach, dune, and marsh fill placement utilizing an offshore sand source in the Borrow Area located approximately 3.3 nautical miles (NM) east of the Restoration Area in the Gulf of Mexico.

Recovery of Salt Marsh Invertebrates Following Habitat Restoration: Implications for Marsh Restoration in the Northern Gulf of Mexico

Recovery following salt marsh restoration in the northern Gulf of Mexico is investigated using meta-analysis for two salt marsh indicator invertebrates, the periwinkle snail (Littoraria irrorata) and amphipod crustaceans (Amphipoda). These invertebrates serve key marsh ecosystem functions including facilitating nutrient cycling and serving as prey for larger ecologically and economically important species. Recovery of periwinkles in restored marshes compared to reference sites is quantified by progression in population density and, because the species is long-lived (~ 10 years), in terms of biomass added per unit area each year following restoration. Amphipods are shorter-lived with high annual turnover; thus, recovery through time is estimated by the density of individuals rather than by biomass. The results of the analyses indicate progressive periwinkle recovery to equivalence with reference systems by year 4 in terms of density and year 6 with respect to annual biomass addition, while amphipod densities do not fully recover in the first 20 years following restoration. Although periwinkle recovery in terms of annual biomass addition reaches equivalence by year 6, the development of an age class structure characteristic of reference marshes would likely take longer because of the relatively long lifespan for this species. In addition to providing insight into the benefits of salt marsh restoration in the northern Gulf of Mexico, the approach described can be applied more generally to restoration scaling in a natural resource damage assessment context.

Contingent Valuation of Environmental Goods: A Comprehensive Critique, edited by DanielMcFadden and KennethTrain. Published by Edward Elgar Publishing, Cheltenham, United Kingdom, 2017, pp. 319, ISBN: 978‐1‐78643‐468‐5, AU$210.

Contingent Valuation of Environmental Goods: A Comprehensive Critique, edited by DanielMcFadden and KennethTrain. Published by Edward Elgar Publishing, Cheltenham, United Kingdom, 2017, pp. 319, ISBN: 978‐1‐78643‐468‐5, AU$210.