Just as Lowell City Council was preparing to vote for the state’s first data center moratorium, a bat flew into the chamber, sending the packed crowd ducking for cover and prompting a brief recess.

The bit of comic relief that sent the dozens of attendees spilling into the hallway quickly surrendered to the tensions that dominated the night.

During the recess, councilmembers sparred with representatives for Markley, the company that owns a data center in a densely-populated Lowell neighborhood that was the subject of debate. Arguments broke out about Markley’s role in the community and the economic and environmental tradeoffs associated with a pause on data centers. IBEW union workers donning T-shirts reading “Stand with Markley” congratulated one another on their earlier testimony about how the data center propelled their careers. Within each camp, there were many heads shaking in exasperation at the opposing side.

But when the meeting resumed and the final 10-0 vote came down from council to back a one-year moratorium on new data center construction, people on all sides of the issue understood that that judgment would reverberate far beyond the confines of Lowell.

“It’s part of a national wave,” Charlie Desourdy, Markley’s chief information officer, told CommonWealth Beacon after the vote.

The vote pitted two core Democratic constituencies against each other: union members, who lavished praise on Markley, which employs about 100 workers at the Lowell site and is expected to pay the city about $12 million in net taxes over a 20-year period, against environmentalists and neighbors along the property fenceline. They worry about the facility’s unfettered growth, diesel fuel stored on site for backup power, noise pollution, and increased water and energy consumption, the latter of which prompted National Grid to increase the electrical load to the data center by upgrading 199 utility poles.

Markley, which also operates Massachusetts’s largest data center in Boston, opened its 350,000-square foot Lowell site in 2015 in what is now a state-designated environmental justice zone on a previously blighted property with the help of a $77 million tax break. The moratorium came about in reaction to Markley’s efforts to expand, including the company’s recent purchase of additional properties in the neighborhood. Markley had also asked the city permission to store another roughly 100,000 gallons of diesel for emergency backup power at the site but withdrew that request. Lowell’s moratorium will allow the city to consider zoning changes and a possible community benefit agreement requirement.

Desourdy said the expansion proposals that have occurred throughout the past decade are a sign that business is booming and that the moratorium may slow new hirings. But the council, ultimately, decided the need for guardrails was greater.

“Since Markley has taken over the property, it’s magnificent. I’m not going to deny that,” Rita Mercier, a council member, said before voting to support the moratorium. “I also know neighbors there, and I know of their concerns. I’m faced with a dilemma: Which one of my children do I like the best? Do I like the neighbors or do I like the union? I’m torn,” she added. “My heart is broken.”