Assessing the Environmental Impact of the Deepwater Horizon Oil Spill

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New Research Articles from Abt Associates Offer Novel Methods for Describing and Estimating Effects of the Oil Spill on Sea Turtles and Marine Mammals

The Deepwater Horizon disaster contaminated habitats across the northern Gulf of Mexico, including deep water corals, shallow bays and estuaries, coastal marshes and beaches, and affected wildlife such as birds, dolphins and sea turtles. New research articles from Abt Associates, the U.S. National Oceanic and Atmospheric Administration and other organizations describe and quantify the impacts of the oil spill on these mammals and other species. The studies were published in a special issue of the international scientific journal, Endangered Species Research.

The northern Gulf of Mexico is home to five species of sea turtles and many marine mammal species, including dolphins and whales. The compiled research studies presented in the special issue offer the clearest depiction of unprecedented impacts, including death and injuries, to marine life. Sea turtles and marine mammals suffered significant losses due to Deepwater Horizon across the Gulf. The articles in the special issue are based on more than five years’ of research, and findings helped to inform the Natural Resources Damage Assessment for up to $8.8 billion to restore the Gulf. Research data indicate it could take decades for these protected species to recover to their pre-spill numbers.

Advancing Environmental Scientific Research

In “Estimating sea turtle exposures to Deepwater Horizon Oil,” Abt authors Bryan Wallace, Matthew Rissing, Dave Cacela and James Holmes, and their co-authors, explain how the team combined direct observations of oiled turtles rescued by boat-based researchers with daily satellite images of the oil footprint to describe how sea turtles were affected. Scientists used these relationships to estimate oil exposure for sea turtles that were sighted during plane-based surveys, but not examined directly. This approach allowed researchers to expand their direct observations from part of the spill area to assess total impacts to sea turtles across the entire spill area.

“Researchers have used satellites or direct observations to support conservation and environmental response work before, but not necessarily together to estimate the total impacts of an oil spill on protected species like sea turtles,” said Wallace, lead author of the article. Wallace also served as theme coordinator for the issue. “This research was important because it bridged gaps between various types of data to expand and quantify the full nature and extent of the injuries.”

Assessing Oil Exposure and Injuries to Marine Mammals

The sheer scale of the spill and its effects on marine mammals required interdisciplinary research to quantify how many dolphins were affected. In the article, “The Deepwater Horizon oil spill marine mammal injury assessment," Abt’s Ryan Takeshita, Ph.D., and colleagues describe the variety of studies used to estimate the damage from the oil spill on marine mammals in the northern Gulf of Mexico, using the bottlenose dolphin injury assessment as an example.

Like sea turtles, dolphins are particularly susceptible to negative effects of oil spills because they must surface to breathe, even in places where oil coats the water’s surface. The authors discuss the harmful cumulative effects dolphins experienced as they inhaled, aspirated, ingested and/or absorbed oil over repeated exposures. The article describes how the Deepwater Horizon oil spill increased mortality, reproductive failure and poor health effects that last years beyond the duration of the spill.

With the wealth of data from these studies and a more complete understanding of exposure and injury pathways to marine life, researchers were able to overcome the significant challenges of assessing the comprehensive impact of the spill to protected species. The overall findings are reported in the final Deepwater Horizon natural resources damage assessment and restoration plan.

Commented Takeshita, “These articles describe advances in how environmental assessments integrate cutting edge scientific research. Our ability to describe and quantify the injuries to sea turtles and marine mammals is a testament to the multidisciplinary teams that responded in the days just after the spill and still continue to collect and analyze data about the oil spill’s impacts.”

This latest research builds on Abt’s prior contributions to all aspects of the Deepwater Horizon natural resources damage assessments and restoration plans.

To read the full articles, visit:

About Abt Associates
Abt Associates is a mission-driven, global leader in research, evaluation and program implementation in the fields of health, social and environmental policy, and international development. Known for its rigorous approach to solving complex challenges, Abt Associates is regularly ranked as one of the top 20 global research firms and one of the top 40 international development innovators. The company has multiple offices in the U.S. and program offices in more than 40 countries.

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