HARPSWELL — For those paying attention to Maine’s shellfish industry, new predators who pose a threat to the shell-sporting species are hogging headlines.

But another risk to the state’s coastal industries is perched on the horizon, with ominous, lesser-known outcomes that could potentially affect lobster, too.

The waters are warming, and they’re also getting more acidic, Aaron Strong, a University of Maine scientist studying the gulf’s changing oceans, told the Harpswell Heritage Land Trust Oct. 17.

Strong spoke about the looming threat of ocean acidification, a climate-change-induced plunging of ocean pH that is experiencing an especially rapid rate of occurrence along Maine’s coastline. His talk was part of the land trust’s series on Maine’s changing oceans.

In his analogy, the damage by invasive green crabs and milky ribbon worms is something akin to an infection in Casco Bay’s clam flats – an acute problem with tangible consequences.

Ocean acidification, on the other hand, is more like the sea’s rising blood pressure: a foreboding, chronic ailment with a hazier set of outcomes.

Although one can guess.

Strong’s provocatively titled talk –”Ocean Acidification: Will lobsters and clams disappear?” – hinted at the worst-case scenario: a more acidic ocean will prevent shelled creatures from forming their shells.

He explained that acidification affects the amount of calcium carbonate in the water, which is needed to create a shell.

The thought of Maine without lobsters – let alone clams and oysters – not only threatens the state’s tourism industry, but a $700 million industry that supports an entire coastline of fishing communities.

Globally, scientists estimate economic damages in the hundreds of billions by 2100.

Strong assured his audience that clam and lobster shells are not dissolving in Maine’s waters just yet.

But he said he knows of oyster farmers – a key group in Maine’s emerging aquaculture industry – that have already felt the effects of changing carbonate levels on larval populations. At least one farmer left the state for Hawaii, he said.

There is less known about how acidification will affect lobster shells, as opposed to clam and oyster shells.

In more acidic environments, “we see craziness in the metabolism of juvenile lobsters,” Strong said. But he predicted around another two years of research is needed until scientists have a clearer picture of how lobsters could be affected.

Rising water temperatures, which could affect larval populations, might pose a bigger threat, he added.

But compared to the rest of the globe, he said, “the Gulf of Maine is uniquely vulnerable.”

Increased carbon emissions are causing pH – the scale used in chemistry to measure acids and bases – to drop “really, really fast,” he explained.

Other, more localized factors cause fluctuations, as well – such as nutrient pollution from septic and wastewater, and extreme weather.

These escalated, environmental changes are hitting a state with a lot to lose in the absence of a productive ocean.

Work is ongoing to combat the issue, Strong said, mostly as a grassroots effort by scientists, academics, and nonprofit organizations.

Notably without state funding, they have formed councils to learn more about what local communities can do to help shield coastal industries, remediate waters, and slow the rate of change.

If local drivers are accelerating acidification, Strong said communities like Harpswell might be able to play a direct role in those efforts.

For example, the town can protect water quality through septic and wastewater management.

To an extent, that is already on the town’s radar; selectmen and staff met with a Department of Marine Resource to discuss water quality during an August workshop.

Setting up a more robust water quality monitoring network is a good place to start, Strong said.

Right now, there are a few sensors in the bay that track pH levels and some chemical readings, including one near Chebeague Island.

But Strong called for the expansion of those programs, which civilians are able to participate in as volunteers.

With more data, scientists might be able to create “real-time ecological forecasts” to identify “hot spots” for shellfish harvesters – analogous to a weather report, he said.

As far as remediation, there’s the promise of kelp farms.

Through underwater photosynthesis, the seaweed has the potential to reverse the effects of greenhouse emissions, creating “a halo effect.”

“Will a bunch of kelp farms change the system?” Strong asked.

Like so many things, he reiterated, the answer is still unknown.

Callie Ferguson can be reached at 781-3661, ext. 100, or cferguson@theforecaster.net. Follow Callie on Twitter: @calliecferguson.

Aaron Strong, a scientist at the University of Maine, discusses ocean acidification an its impact on Maine’s shellfish industry at the Harpswell Heritage Land Trust Oct. 17.