WILLIAM BRANGHAM: We turn now to the second of two stories about the growth of offshore wind farms and the questions surrounding their impact.

Science correspondent Miles O'Brien takes us to New Bedford, Massachusetts, where local officials are trying to find a balance between greener renewable energy and the potential impact on the critical fishing industry in that region.

MILES O'BRIEN: In the early 19th century, New Bedford, Massachusetts was one of the wealthiest cities in the country because of a grim industry.

It was the whaling capital of the world.

The oil produced from the carcasses lit the Eastern Seaboard before the transition to fossil fuels.

This city, ironically, is on the cusp of being a center of energy once again.

This time, the resource is blowing in the wind.

The tall pylons at the Marine Commerce Terminal are the most conspicuous features in an evolving harbor, an economic transition spurred by the energy transition.

There are cranes everywhere.

You're really remaking this port, aren't you?

JON MITCHELL, Mayor of New Bedford, Massachusetts: Yes, we really are.

Yes.

MILES O'BRIEN: And it's pretty significant.

Mayor Jon Mitchell took me on a cruise around the harbor.

You have got construction all up and down this harbor.

JON MITCHELL: Yes.

MILES O'BRIEN: So what's the total dollar amount right now?

JON MITCHELL: It's about $1.1 billion.

MILES O'BRIEN: Would that have happened without wind?

JON MITCHELL: A lot of it wouldn't.

In fact, most of it would not.

What we're doing is playing to our advantages.

That's what you see here.

MILES O'BRIEN: The mayor is on a political tightrope.

The wind industry that he's been courting for a dozen years is caught in a net of opposition from the economic engine that has propelled New Bedford for the last century.

CASSIE CANASTRA, BASE Seafood Auction: We don't know, are my scallops that I harvest now going to be there in 20 years in the same spot that they have always been?

MILES O'BRIEN: Cassie Canastra and her family run the largest fish auction the U.S. East Coast.

About 70 percent of all the scallops that land on your plate first land here.

The largest scallops can fetch about $20 a pound.

And there are eager buyers for every last morsel.

CASSIE CANASTRA: Scallops are just such a high-value product.

That's like the biggest resource we have coming in through the harbor.

So I think that just is what made us such a lucrative port.

MILES O'BRIEN: New Bedford is the most lucrative fishing port in the U.S.

But scalloper Eric Hansen is very wary of what may lie ahead.

In raising your concern now, you're trying to get out ahead of this.

Is that the idea?

ERIC HANSEN, Owner, Hansen Scalloping Inc.: Get out ahead is an interesting way to say it.

I envision that we have a bunch of steamrollers coming to steamroll our fishery, and we're just trying to steer them.

I don't think we can stop them.

MILES O'BRIEN: He's asking the wind industry to slow down to allow some time for scientists to do some solid research to try and uncover the unintended consequences of wind farms in the ocean.

ARAN MOONEY, Woods Hole Oceanographic Institution: So it's obviously super loud here.

MILES O'BRIEN: That's what this racket is all about.

ARAN MOONEY: What we're doing is basically measuring how animals are responding to the sound.

MILES O'BRIEN: Aran Mooney is a marine biologist at the Woods Hole Oceanographic Institution, which is where I met him as he was pile-driving for data.

Beneath the surface, flounder, lobsters and scallops, bottom dwellers, are getting blasted with a lot of noise to see how they respond.

ARAN MOONEY: We have actually cameras and sensors on animals under this water, as we measure sort of their behavior and their physiological sort of responses to this.

MILES O'BRIEN: The sensors they attach to the fish record their movement during the jarring noises.

In the lab, he showed me how they work.

They contain small accelerometers and magnetometers to capture the motion.

What is the hardware all about?

ARAN MOONEY: Yes, so we have basically this custom-built tag that we have for them.

So this is kind of like a little scallop Fitbit.

On the back here is just...

MILES O'BRIEN: Scallop Fitbit?

ARAN MOONEY: Yes, a scallop Fitbit.

So it allows us to get the movement patterns and energetics of the scallop.

MILES O'BRIEN: They have been conducting tests like these for three years.

They started with squid and black sea bass.

Can we say for certain that it causes stress in these animals?

ARAN MOONEY: So it really depends on which species and the context that they're in.

MILES O'BRIEN: And what they're doing.

ARAN MOONEY: So, resting squid were very sensitive to the sound.

Mating squid couldn't care less.

MILES O'BRIEN: Scallops close tight each time a pile driver strikes.

ARAN MOONEY: Those responses repeated again over hours and days could be really stressful for the animals.

So I think that may tire them out and make them more susceptible to predation.

MILES O'BRIEN: The pedestals that wind turbines sit on are 30 feet in diameter.

And each requires about two hours of pile-driving to be firmly planted in the seafloor.

The Biden administration's goal of 30 gigawatts of offshore wind equates to about 2,500 turbines.

Mooney is hopeful his work will lead to a more informed construction strategy, things like limiting pile-driving to when squid are mating, avoiding scallop beds, and ramping up the sound gradually.

ARAN MOONEY: At the beginning of the day, start with a low-amplitude sound and then just increase that over a course of a few minutes.

And so you kind of give those animals a warning that that's coming.

MILES O'BRIEN: There are a lot of missing pieces to this puzzle; 27 miles off the coast of Virginia Beach, Brendan Runde is angling for answers.

He's a fisheries biologist with The Nature Conservancy.

This is the site of the Coastal Virginia Offshore Wind Farm.

When complete, it will be the largest in the U.S.

He and his team are catching sea bass and attaching acoustic tags to them.

BRENDAN RUNDE, The Nature Conservancy: This is the part that might be a little uncomfortable for some viewers.

MILES O'BRIEN: The pinging signals they emit are captured by a few dozen acoustic receivers on the seafloor amid the turbines.

BRENDAN RUNDE, Nature Conservancy: And those receivers are constantly listening for the very specific frequency that our tags are pinging.

MILES O'BRIEN: The system allows him to track the fish.

In addition, he has installed hydrophones to measure the underwater sound.

WOMAN: Awesome.

Away she goes.

MILES O'BRIEN: Comparing the spikes and decibels to the movement of the fish may fill in some blanks.

BRENDAN RUNDE: Maybe they will hunker down near the seafloor, and if that does happen, how long does it last?

Another possible response is that black sea bass and the other fish we're tagging might simply leave the area when pile-driving happens.

MILES O'BRIEN: But it's very likely they will come back.

Runde says these fish are actually attracted to the turbines, which become artificial reefs.

BRENDAN RUNDE: The structure that's created by these offshore wind turbines is great habitat for a lot of different species.

As a recreational fisherman, I, for one, am looking forward to having all of these structures.

MILES O'BRIEN: While scientists try to get some real data, many opponents of offshore wind are peddling alternative facts.

Donald Trump is leading the chorus, vowing to try and stop offshore windmill construction.

This is why, in New Bedford, Mayor Mitchell has carefully tailored his pro-wind argument around economic development, jobs, not the climate emergency.

He thinks this has created a firmer foundation of support now that the political winds have shifted in Washington.

Are you worried at all that offshore wind is still, if you will excuse the expression, not on firm ground politically and otherwise?

JON MITCHELL: Yes, I think so.

I guess the question about offshore wind fundamentally is how rapidly it will deploy.

It is here in the United States.

It's here to stay.

There's just too much that's been sunk in the way of major investment by major players here in the U.S. and in Europe for it to stop entirely.

The horse is out of the barn in offshore wind.

And it's a question of how rapidly that horse is going to run at this point.

MILES O'BRIEN: For now, it is a one-horse race.

Electric vehicles and artificial intelligence are fueling a dramatic increase in demand for electricity.

In September, Microsoft announced a deal to reopen a mothballed nuclear reactor at Three Mile Island, Pennsylvania, to power data centers.

Besides that, here in the Northeast, there are no other renewable options on the horizon.

For the "PBS News Hour," I'm Miles O'Brien off the coast of Massachusetts.