Media Release

**Embargoed Until June 12, 2019, 8:00am EST**


Budworm City. “Budworm City” was established in the early 1950s near Upsalquitch Lake and used as a base for DDT spray operations in northern New Brunswick. Photo credit: D.C. Anderson.


New study shows legacy of DDT to lake ecosystems

New findings of a multi-university research team show the pesticide DDT persists in remote lakes at concerning levels half a century after it was banned, affecting key aquatic species and potentially entire lake food webs.

"What was considered yesterday’s environmental crisis in the 1950s through 1970s remains today’s problem," says lead author Josh Kurek, Assistant Professor at Mount Allison University. "Decades of intense insecticide applications to our conifer forests have left a lasting mark on these lakes—and likely many others in eastern North America."

Between roughly 1950 and 1970 prior to legal restrictions, DDT insecticides were widely applied to eastern North American forests to manage naturally occurring insect outbreaks, such as spruce budworm. Although often applied to forests by airplane, chemicals like DDT are highly persistent and can eventually wash into lakes from their surrounding landscape. This study looked at dated sediments from the bottom of five remote lakes located within different watersheds in north-central New Brunswick, Canada. Lake sediments provide a well-recognized and powerful archive of environmental conditions, which allows us to assess chemical and biological conditions in lakes before, during, and after pesticide use.  

Historical trends in the lake sediments mirrored the known use of this pesticide in the province, with high levels of DDT in sediment layers from the 60s and 70s. Levels of DDT in lake sediments were among the highest found in previously-sprayed areas of Canada and the U.S., suggesting very intensive past use of pesticides for spruce budworm control. Surprisingly, DDT and its toxic breakdown products are still very high in modern sediments—above levels where harmful biological effects tend to occur.

Additionally, an important invertebrate within lake food webs, the small water flea Daphnia sp., has declined substantially, often coincident with increased DDT. Loss of Daphnia sp. often negatively impacts lake food webs. These impacts may lead to greater algae production and fewer prey for fish.

"Our results suggest that these lakes are now radically different compared to years before use of DDT," says Kurek.

"We have learned a lot of tough lessons from the heavy use of DDT in agriculture and forestry. The biggest one is that this pesticide was concentrated through food webs to levels that caused widespread raptor declines in North America," notes McMaster University professor Karen Kidd, Jarislowsky Chair in Environment and Health. "The lesson from our study is that pesticide use can result in persistent and permanent changes in aquatic ecosystems."

This study, published in the peer-reviewed journal Environmental Science & Technology of the American Chemical Society, the world’s largest scientific society, highlights the chemical legacy of one of North America’s largest aerial spray programs of insecticides ever coordinated by forest stakeholders.

"You would think that 50 years after you have banned an insecticide infamous for its environmental and health effects, you would be done with it," says Kurek. "But DDT persists and continues to remind us of our past actions."

Funding for the research was provided by Natural Sciences and Engineering Research Council of Canada (NSERC) and Mount Allison University.

PLEASE NOTE: An electronic copy of the study can be obtained from Environmental Science & Technology, or by contacting Dr. Josh Kurek at

View published manuscript:

Ecological legacy of DDT archived in lake sediments from eastern Canada published in Environmental Science & Technology, DOI: 10.1021/acs.est.9b01396

Study lakes. Five remote lakes from north-central New Brunswick, Canada were studied. Study lakes have no major inflowing streams and are located within conifer-dominated forests. Access to each lake was possible with a 4-wheel drive vehicle on rough gravel roads. California, Goodwin, and Middle Peaked Mountain lakes are managed for their Brook Trout fishery by the Government of New Brunswick’s Energy and Resource Development.

Researchers in the field. Study lakes were visited by our multi-university research team in early June 2016. Sediment cores were collected from each lake’s deep, central basin using a standard approach. In a laboratory, sediments can be dated to provide age estimates (e.g. 1960 AD ± 5 years) and establish a detailed timeline of environmental changes, including the deposition and levels of contaminants such as DDT. Undergraduate students from Mount Allison and University of New Brunswick (Saint John) pictured here at Upsalquitch Lake were active contributors to this project, including both field and laboratory work.

Daphnia. An image of the aquatic organism Daphnia, commonly known as a water flea. They are often numerous in lakes and important grazers of algae, and are eaten by small fish, waterfowl, and large invertebrates. Daphnia are sensitive to their aquatic environment, including DDT levels and other contaminants. Daphniids are used worldwide in toxicology and ecology studies, and are often considered a keystone aquatic species. The postabdominal claw (indicated by the arrow) of Daphnia are preserved in lake sediments and useful to their identification. Photo credit: Kim Lemmen (Queen's University).

Sediments from Sinclair Lake. Sediments accumulate in an orderly fashion in lakes, making them valuable archives of past environmental conditions. They are composed of materials carried into the lake by water or wind (e.g. DDT, pollen, soil), as well as materials produced within the lake (e.g. aquatic organisms). At our study lakes, we studied the uppermost ~15 to 22 cm of sediment, about half of the core length that was collected. These uppermost sediments represent about 100 years of environmental history at each study lake and capture the time periods before, during, and after use of DDT in the mid-20th century.

Sedimentary remains of Daphnia. Postabdominal claws of Daphnia are well-preserved in lake sediments. Daphnia are key members of a lake’s zooplankton community. In several of our study lakes, Daphnia have decreased substantially in relative abundance since the mid-20th century, coincident with the widespread use of DDT in north-central New Brunswick, Canada. Studies demonstrate that loss of daphniids in some lake ecosystems result in greater algae populations and/or less food available to predators that consume Daphnia, such as small fish.

Sectioning a sediment core. Once a lake sediment core is collected it is brought to shore. Each core is photographed, measured, and sectioned at 0.5-cm throughout. Each 0.5-cm sediment interval is carefully handled to minimize contamination and placed in labelled storage bags for transport to and storage in the laboratory. Each interval represents a distinct time period captured within each sediment archive. Typically, intervals near the top of the core (younger material) capture fewer months or years than intervals near the base of the core (older material). Pictured here is a researcher sectioning a core from California Lake. .

Sedimentary remains of Bosmina. Remains of the small-bodied aquatic organism Bosmina are very common in lake sediments and one of the most frequent zooplankton remains found. Bosmina live in the open-water area of lakes where they consume algae. Studies indicate Bosmina populations often increase relative to other zooplankton when lakes experience stressors, such as pollution, or other environmental changes such as the indirect effects of climate change. Pictured here is a headshield (right) and carapace (left) of Bosmina magnified at 400x.

All images courtesy of Josh Kurek (Mount Allison University)
unless otherwise indicated.

Contact information for authors (*media contacts)

Joshua Kurek*, Mount Allison University
Environmental Change & Aquatic Biomonitoring (ECAB) Lab
Sackville, NB Canada
Office: 506-364-2390

Paul MacKeigan, Mount Allison University
Sackville, NB Canada

Sarah Veinot, University of New Brunswick 
Saint John, NB Canada

Angella Mercer, University of New Brunswick 
Saint John, NB Canada

Karen A Kidd*, McMaster University
Dept of Biology
Hamilton, ON Canada
Cell: 506-650-0973 (texts only)