54 Scientific American, May 2022requires a lot of power, as does heating the water in win-
ter and cooling it in summer—all of which can contrib-
ute to the climate crisis. “We really don’t have data on
the energy use in these systems compared to other
approaches, but it’s clearly very high,” Lewis says. A
review sponsored by Maine’s Department of Environ-
mental Protection concluded that the plant will release
as much as 759,000 metric tons of carbon dioxide equiv-
alents into the atmosphere every year, roughly equal to
the annual CO 2 contributions of 47,000 Americans.
There are also fundamental objections to raising free-
ranging creatures such as salmon in crowded captivity.
The animals we lump together and call “fish” represent
a staggeringly diverse array of species, some of which
have incredibly complex social structures and navigation
abilities, says Becca Franks of New York University, a psy-
chologist who researches animal behavior and welfare.
Atlantic salmon are a case in point: they migrate 2,000
nautical miles to and from their spawning grounds
guided only by Earth’s magnetic fields and an acute sense
of smell. “Farming salmon is the moral equivalent to
farming hawks,” Franks says. “We need to think about
the stress and suffering of these animals ... about how
they live their natural lives.”
N
ot all sea aNimals are the aquatic
equivalent of a hawk, however, and some take
well to domestication. Sandra Shumway, a
marine scientist at the University of Connecticut, is an
internationally recognized expert on the cultivation of
sea life. “I do think it’s very important that we grow
more micronutrients and protein for human consump-
tion,” she says. “But let’s think about bivalves.”
Bivalves require little space, and some—such as mus-
sels and oysters—barely demonstrate an inclination to
move. “They’re more like potatoes or avocados than
salmon,” Franks says. Even better, unlike potatoes and
avocados, bivalves can be grown without human-sup-
plied fertilizer, water or food. Farmed oysters typically
start as larvae, which quickly mature into tiny “seed” oys-
ters that attach to a hard surface such as shell or lime-
stone and are then transferred into estuarine bodies of
brackish water to feed on whatever nutrients naturally
float their way. These “filter feeders” siphon water
through their gills to extract phytoplankton, of which
Maine harbors at least 300 species. Waterways inhabited
by bivalves are often so clear that sunlight penetrates far
below the surface, further promoting the growth of phy-
toplankton. Some scientists and farmers are hoping to
build on this “virtuous cycle” by deliberately planting
kelp and other seaweed in close proximity to bivalves.
Under this arrangement, the animal waste would pro-
vide nutrients for the plants, and the plants would
remove CO 2 and generate oxygen for the animals.
Maine’s coastline, crenellated with deep estuaries
and bays fed by rivers mixing with cold ocean water that
pumps nutrients up from below, may seem like a bivalve
paradise. But frigid water is a double-edged sword.
Oceans store up to 30 percent of the world’s output ofCO 2 , and cold water, in which the gas is most soluble,
absorbs far more than its share, making it more acidic.
The rising acidity of Maine’s rivers and estuaries threat-
ens to erode the shells of soft-bodied invertebrates such
as bivalves left to their own devices.
Bill Mook has had painful experience with this prob-
lem. Founding owner of Mook Sea Farm and Hatchery
on Maine’s Damariscotta River, one of the two largest
oyster producers in the state, he grows both mature and
seed oysters. A few years ago he noticed that his oyster
larvae were not developing normally, a problem he
traced to increased acidity of the river water flowing
through his hatchery. The water also softened the shells
of mature oysters, especially during hard rains, when
the river ran highest. Mook found a way to buffer sea-
water to protect the oysters growing in the indoor
hatchery, a remarkable innovation that—though highly
labor-intensive—may well catch on with other Maine
bivalve farmers if acid levels continue to rise.
Housed in a pair of Quonset huts, Mook’s oyster-
growing facility looks more like a laboratory than a
farm. In the spring of 2021 Meredith White, director of