Scientists aboard R/V Sally Ride conducted a seafloor survey of the dumpsite in 2021.

UC San Diego’s Scripps Institution of Oceanography Awarded $5.6 Million for Southern California DDT Ocean Dumpsite Research

NOAA funding will aim to further characterize, monitor, and research dumpsite

Decades ago, the San Pedro Basin off the coast of Los Angeles was a dumpsite used by various industries. Recent research and reporting has found the dumping of waste from byproducts of the pesticide dichlorodiphenyltrichloroethane (DDT) and other industrial wastes may be larger than previously thought. New congressionally-directed funding awarding $5.6 million to Scripps Institution of Oceanography at the University of California San Diego will aim to improve characterization of the extent of the dumpsite, and support additional monitoring and research. 

Earlier this month, NOAA awarded $5.6 million in spending directed by Senators Dianne Feinstein and Alex Padilla to Scripps Institution of Oceanography. Working with collaborators from UC Santa Barbara and San Diego State University, this new research will aim to fully characterize the extent of the dumpsite, identify the toxin “fingerprint” contained in the sediments, survey the effects of toxins on microbial communities and animals on the seafloor near the site, and assess toxin pathways to the upper ocean, including the potential for exposure to toxins via fish and fisheries. The project will also explore potential remediation strategies, including the capacity for microbes to neutralize the toxins on the seafloor.

“It’s deeply concerning that we don’t yet know the full extent of the DDT and potentially other toxic materials dumped off California’s shores and the threat they pose to the environment,” said Senator Feinstein. “Until we understand the scope of the problem, we can’t develop solutions to solve it. That’s why we secured funding to map the region’s seafloor and test the barrels, sediment and water column. I’m pleased NOAA and Scripps are moving forward with the next phase of this critically needed work and eagerly await their findings as we plan for the next steps.”

Map showing the known dumpsite and the survey area

In 2011 and 2013, UC Santa Barbara professor David Valentine discovered concentrated accumulations of DDT in the sediments in the region, and visually confirmed 60 barrels on the seafloor. Scientists are also finding high levels of DDT in marine mammals including dolphins and sea lions, with exposure to industrial products or chemicals known as PCBs and DDT linked to the development of cancer in sea lions. An expedition led by Scripps Oceanography at UC San Diego in March 2021 mapped a portion of one of two known dumpsites and identified a vast debris field associated with industrial dumping. The dumping took place over a span of decades and occurred over a much larger area than previously believed. Seafloor samples of animals, microbes and sediments were subsequently collected around DDT waste barrels in August 2021 on another Scripps expedition aboard the Schmidt Ocean Institute’s Research Vessel Falkor

“DDT is a threat to California’s economy, environment, and public health which is why I worked closely with Senator Feinstein to secure this funding,” Senator Alex Padilla said. “The research led by Scripps will help us to better understand the health of the waters off the coast of Los Angeles and create a road map for mitigating pollution caused by DDT. This information is critical for maintaining confidence in California’s seafood industry and helping coastal ecosystems and communities thrive.”

DDT exposure has been linked to increased risks of cancer, premature births, developmental abnormalities, and neurological diseases in humans and animals. And since the core DDT chemical structure is extremely stable, DDT and its major breakdown products accumulate in the environment. Upon exposure, DDT and related compounds can magnify as they pass through the food web, with the health impacts of exposure appearing to persist through multiple generations. Exposure can take place in the marine environment when suspended or sedimented particles absorb DDT, and its breakdown products are ingested by organisms including fish. Once it enters the marine food web, DDT and its breakdown products can be transferred to apex predators such as birds and marine mammals, and potentially to humans. 

“This interdisciplinary team of scientists will be able to help us better understand the ecological implications of this dumpsite because of their expertise across biology, chemistry, and physics, particularly in deeper ocean environments,” said Lihini Aluwihare, chemical oceanographer at Scripps Oceanography. “The broader science team is grateful that the state, NOAA, and the Environmental Protection Agency have put their trust in this research effort.”

Specific research that will be enabled by the new NOAA funding includes:

Site characterization plan: “Find the barrels”

Led by Eric Terrill and Sophia Merrifield, Scripps Institution of Oceanography

Effective management, remediation, and scientific actions will require basin-scale mapping of the location and conditions of dumped materials within the region. A recently completed survey mapped Dumpsite Two with sidescan sonar, identifying tens of thousands of debris field targets and areas of sediment piles that may have resulted from bulk dumping. The debris field was dense and extended beyond Dumpsite Two, requiring further efforts to map the full extent of the dumpsite. In particular, additional at-sea surveys will seek to characterize the spatial extent of the dumpsites, classify debris types, and characterize the condition of containerized waste. 

Using robotic vehicles, researchers will continue the seabed mapping survey efforts at Dumpsite Two to further characterize the spatial extent, quantity, and state of the dumped materials, verifying the types and condition of the containment devices used. 

Terrill and Merrifield also intend to characterize the ocean physics in the region to understand the regional oceanography within the San Pedro Basin. A particular focus will be on bottom boundary layer currents. These data will aid in the study of transport patterns in the San Pedro Basin.


“Fingerprint” DDT Chemistry: Identifying the chemical fingerprint of DDT sludge from Dumpsite 2

 Led by Lihini Aluwihare and Anela Choy, Scripps Institution of Oceanography; David Valentine, UC Santa Barbara; Eunha Hoh, San Diego State University 

Historical data exists for the Palos Verdes Shelf sediments, which was long believed to be the primary source of DDT and its breakdown products to the marine food web in the Southern California Bight. Scientists will thoroughly characterize the relevant contaminant profiles at Dumpsite Two. They will use both a targeted approach to quantify the major DDT-related compounds, PCBs, and petroleum-related products, while utilizing a broader approach to fingerprint the less well studied breakdown products of DDT in both locations. With these combined approaches, the team hopes to identify a chemical signature unique to Dumpsite Two, that can be traced into marine life in the region. In addition to characterizing sediments at Dumpsite Two, this project will trace contaminants into the local, deep food web near and around the dumpsite. 

In 2021, as part of the National Science Foundation-funded California Current Ecosystem-Long Term Ecological Research program, chemical oceanographer Lihini Aluwhihare was able to opportunistically collect a suite of chemical and biological samples to examine the DDT and  PCB body burden of and pathways of uptake by marine organisms that inhabit deeper waters at Dumpsite Two. These data will be compared to similar samples collected outside of Dumpsite Two on another NSF-funded expedition led by biological oceanographer Anela Choy. 

This group will also assess the physical-chemical behavior of DDT-family compounds specific to the deep-sea environment of California’s offshore basins to determine whether DDT released into the environment may have been dissolved into the surrounding ocean or primarily transported directly to the deep basin sediments. The results of this effort will inform the transport and patterns of sediment accumulation, providing testable hypotheses to guide future sediment sampling campaigns.

DDT uptake, accumulation, redistribution by seafloor animals

Led by Lisa Levin, Greg Rouse, Carlos Neira, Scripps Institution of Oceanography

The sediments at Dumpsite Two are inhabited by a host of invertebrates and have been shown to contain high concentrations of DDT and related compounds. In the San Pedro Basin, the seafloor animals range from microscopic to large, and some are capable of mixing DDT compounds downward into the sediment via bioturbation and upward into the overlying water via resuspension. This alters microbial communities that degrade these elements, ingesting and accumulating DDT and its derivatives, and transports DDT compounds away from contaminated areas and into the food webs containing fish and mammals. 

Levin, Rouse, and Neira hope to obtain an understanding of benthic animal roles in this redistribution, transfer, and fates that can contribute to further environmental monitoring and remediation planning. Scientists will characterize the benthic fauna attached to, beneath, and surrounding barrels located at Dumpsite Two, their vertical distribution in sediments and horizontal distribution relative to the barrels. To the extent possible, they will assess the concentration of DDT in the organisms and examine consequences for the health of the seafloor community. This work will involve the analysis of pushcores, suction sampling of barrel surfaces, scoop samples, and video collected in August of 2021 using the ROV SuBastian aboard the R/V Falkor

Resulting data will be subjected to statistical analyses of density, community structure, and diversity related to barrel, zones, and DDT compound concentrations. The data will provide the first quantitative analysis of the possible impact of containerized, and bulk disposed DDT-related waste on macrofaunal benthic communities for the San Pedro Basin dumpsite. Understanding the interactive effects of “legacy” chemical pollution on benthic faunal community structure and distribution can help guide remediation efforts, and ultimately aid the management and conservation of nearshore coastal environments. 


Maintaining confidence in California's healthy seafood products

Led by Brice Semmens, Scripps Institution of Oceanography

To assess the fate of toxins in the marine food web across space and time, Semmens will measure toxin levels in preserved marine animals in the Scripps Institution of Oceanography and NOAA Southwest Fisheries Science Center oceanographic collections. These unparalleled collections represent specimens of marine organisms collected over the last 75-plus years, spanning the entire length of time between dumping activities and present, throughout the California Current Ecosystem. Using these samples, scientists will describe the progression, in time and space, of barrel toxins in the marine ecosystem. Marine biologist Brice Semmens will also work with coastal recreational fisheries communities to collect and analyze samples from import coastal fisheries species. Using the resulting data, researchers will generate models of toxin fate and transport in the coastal ecosystem, including species that support economically-important recreational fisheries in the region. The goal is to scientifically demonstrate the safety of California seafood products, and provide guidance to fishing communities regarding best practices for minimizing the harvest of unsafe seafood, should evidence of such seafood exist.

This effort represents a continuation of this research, which Semmens began earlier in 2022 thanks to a two-year grant from the Gordon and Betty Moore Foundation.


Microbiological effects and remediation strategies         

Led by Jack Gilbert and Paul Jensen, Scripps Institution of Oceanography; David Valentine, UC Santa Barbara

Microbes are major contributors to DDT degradation in ocean sediments but are also responsible for non-beneficial transformations between different DDT-like compounds. Capitalizing on previously collected samples, the spatial distribution of microbial communities will be assessed and compared to DDT compound concentrations in the sediments and comparable sites distant from the dump zones. Metagenomic analyses will be used to assess the potential for DDT degradation and determine which species are associated with these activities. Incubation studies will be performed in the lab to determine the rates at which transformations could and do occur. These studies will provide a method to assess sediment microbial communities for a return to “normalcy,” opportunities to identify microbes that may be useful for bioremediation, and determine the rate at which key DDT-like compounds are and can be transformed.

About Scripps Oceanography

Scripps Institution of Oceanography at the University of California San Diego is one of the world’s most important centers for global earth science research and education. In its second century of discovery, Scripps scientists work to understand and protect the planet, and investigate our oceans, Earth, and atmosphere to find solutions to our greatest environmental challenges. Scripps offers unparalleled education and training for the next generation of scientific and environmental leaders through its undergraduate, master’s and doctoral programs. The institution also operates a fleet of four oceanographic research vessels, and is home to Birch Aquarium at Scripps, the public exploration center that welcomes 500,000 visitors each year.

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