DDT found in frogs in Hamilton wetland
Scientists planning major study of sediments in Cootes Paradise to determine chemical’s spread
Traces of the banned pesticide DDT have been found in frogs in Hamilton’s Cootes Paradise, leading researchers to fear the chemical is causing untold ecological damage in the bay.
Faced with the discovery, scientists from Environment Canada and Climate Change, the Royal Botanical Gardens (RBG) and other agencies, are drafting plans for a major study of sediments to find out how widespread the chemical is.
DDT — which is the short form for dichlorodiphenyltrichloroethane — has been banned in Canada and the U.S. since 1972 because of its negative effects on birds and wildlife.
“It was a bit of a jaw dropper to discover it in the frogs,” said Tys Theijsmeijer, head of natural lands for the RBG.
DDT is known to persist in the environment for a long time. But the finding of the chemical in two leopard frogs in Cootes Paradise could be a sign the bay may have hot spots for the pesticide. “It just sort of popped out of left field that they had some detectable DDT in them … It was quite a shocker, so we are trying to launch a project to see if we have a DDT problem in Cootes Paradise.”
The frogs were gathered by federal researchers five years ago and, over a period of time, tested for a wide range of contaminants when someone decided to check for DDT.
A spokesperson for the federal department could not be reached for comment.
Theijsmeijer said DDT was used for insect control in Cootes Paradise before it was banned.
“We don’t know a lot about the history, but we do know that in the early 1950s there was a fair bit of DDT put on Cootes to kill mosquitoes.”
After finding evidence of DDT all these years after it was used, Theijsmeijer said, “Step one now is to look at the sediments, figure out what is actually there and quantify it.
“If it is a big number, then we start working on the implications for wildlife.”
Meanwhile, a team of researchers from several universities — including McMaster University — has found more disturbing news about lingering effects of DDT in the environment.
The team looked at sediments from remote lakes in New Brunswick and found “concerning levels” of the pesticide “affecting key aquatic species and potentially entire lake food webs.”
McMaster University professor and study co-author Karen Kidd said, “The lesson from our study is that pesticide use can result in persistent and permanent changes in aquatic ecosystems.”
The researchers took core samples of sediments that gave tthem a kind of blow-by-blow time line of changing DDT levels and the evolving effect on plankton that had been fossilized. “When the DDT levels wwere really high in the 1950s a and ’60s, the plankton commu- nity also changed. It shifted from a large-bodied plankton to more of a small-bodied plankton. That shift persisted into the more recent years of the sediment core.”
Lead author Josh Kurek, assistant professor in Geography aand Environment at Mount Al- lison University in New Brunswwick said, “What was consid- ered yesterday’s environmental crisis in the 1950s through 1970s remains today’s problem.”
Asked about the findings in Hamilton, Kidd said, “There is DDT in the Great Lakes sediments and fish, but the levels are going down over time and bird populations are recovering from this exposure.
“It will be interesting to learn about the work in the Hamilton Harbour and how high the DDT levels are.”
The issue for many bird species — especially raptors such as bald eagles — is that DDT decreased their reproductive rate by causing a thinning of eggshells and embryo deaths.
Through time, after the ban, reproduction became more successful.
As evidence of that in Cootes Paradise, a nesting pair of bald eagles aret again the proud parents of a couple of eaglets this spring. As well, a pair of other young bald eagles have recently moved into the area.