Mystic — More than 150 protesters against genetically modified organisms in the nation’s food chain gathered Saturday across from Mystic Aquarium and then marched to the DeKalb Genetics plant owned by Monsanto, where protesters allege corn-seed testing is taking place.

The March Against Monsanto, organized locally by Activate CT, ConnFact and GMO Free CT, was part of a worldwide protest against the chemical company that in recent years has become a leader in the genetic modification of seeds.

Protesters, holding up signs such as “Give Bees a Chance” and “Monsanto Cures Hunger with Cancer,” hung out quietly on Coogan Boulevard for more than an hour, getting boisterous only when drivers along the busy street beeped their horns in support. They then walked up Maritime Drive, where police and security personnel were on the watch outside the manicured grounds of DeKalb Genetics, but no incidents occurred.

“Monsanto is taking over the food supply — not just of this country, but of the world,” said protest organizer Debra Cohen. “They’re using a chemical base to contaminate food.”

Cohen said some of Monsanto’s genetically modified seeds are combined with glyphosate — the key ingredient in the herbicide Roundup — and this poisonous chemical is in turn showing up in the food supply, the bloodstream and even breast milk.

A Monsanto spokeswoman, however, downplayed food-supply concerns.

“(Genetically modified) seeds have been tested more than any other seeds in the history of agriculture — with no evidence of harm to humans or animals,” the spokeswoman, Charla Marie Lord, said in an email Saturday. “People who work at Monsanto care about the quality and safety of the food we eat, and we’re committed to developing products that contribute to safe and nutritious food choices.”

But Patrick Moore, a naturopathic doctor from New Haven who attended the protest, said Monsanto has not published research on genetically modified foods that was conducted over a period longer than nine weeks. Others alleged that Monsanto had pulled the plug on long-term academic research for fear of the results.

“We would feel more confident if there was some legitimate science published and researched by independent scientists,” Moore said. “We have a brainwashed country, I believe.”

Protester Patrick Kelley said the Connecticut legislature last year passed a measure that would allow for the labeling of genetically modified foods, but a provision requires that at least four other states must pass similar laws before it goes into effect. In January, Maine became the second state in the nation to pass a GMO labeling bill, but it similarly includes a provision that other states do the same — apparently, according to news reports, to avoid a possible Monsanto lawsuit.

Rebecca Burton, a leader with Activate CT, pointed to increased problems with gluten allergies and an uptick in celiac disease as among her concerns about the effect of genetically modified foods.

“We’re in this for the long haul,” she said. “We’re talking truth to power. It’s about these people finding their own power.”

l.howard@theday.com