52 SMITHSONIAN | April 2020
Proponents of in-stream tidal—that is, with turbines lo-
cated in the water column, not embedded in dams—claim
marine mammals and fi n fi sh can easily avoid the blades be-
cause nothing impedes the animals’ passage. During a 2017
pilot study that introduced striped bass to a spinning turbine
in a circular tank at Dalhousie University in Nova Scotia, fi sh
appeared to avoid the blades, even with the current moving
at 3.9 knots. These results “will inform real-world scenarios,”
says Sue Molloy, who conducted the study, “and some tests
that are done with wild-caught fi sh will translate very well.”
A study of SeaGen, the world’s fi rst large-scale tidal-stream
generator, which operated commercially between 2008 and
2016 in Northern Ireland’s Strangford Lough, suggested that
seals avoid moving rotors. In a multiyear pilot study of three
riverbed-mounted tidal turbines in New York City’s East Riv-
er—a demonstration project run by Verdant Power—research-
ers found no evidence of harm to fi sh.
Environmental monitoring in Grand
Passage, Hayman says, has yielded no
evidence that marine animals, save jel-
lyfi sh, touched Plat’s turbines. Still, as
one so often hears when discussing po-
tential environmental impacts, absence
of evidence isn’t evidence of absence.
Monitoring the environment around
turbines is diffi cult and expensive. “It’s
a highly dynamic environment with lots
of turbulence and sediment in the water
that hinders visibility,” Anna Redden, a
marine ecologist at Acadia University’s
Tidal Energy Institute , told me when we
met in her offi ce. Air bubbles interfere
with acoustic signal detection, as do the
engines of seafaring vessels and the whir
and blip of other monitoring equipment.
Because lights could attract or repel ma-
rine life, cameras can record only in day-
light hours. Tidal platforms are designed
to work in strong currents, but sensors are
not. “We’re using off -the-shelf technology
that isn’t designed for washing machines.”
I asked Redden what science did
know about marine life and turbines.
“Nothing for sure,” she said. “And we
won’t know if these turbines kill fi sh
until the device is in the water” for a
signifi cant amount of time. She paused,
then said with a note of tristesse, “There
is never zero impact. But what level of
impact will we fi nd acceptable?”THERE ARE TIDES in tidal power devel-
opment. Flows correspond with spikes
in the price of oil, investor interest and
government subsidies that help tidal
power compete with wind and solar,
which are cheaper. The recent burst of
activity in Nova Scotia was sparked by
the global climate emergency and Cana-
da’s commitment to reduce greenhouse
gas emissions 30 percent by 2030, com-
pared with 2005 levels. (Nova Scotia has
already reduced emissions 31 percent, thanks in part to its
own wind turbines and to renewable energy imported from
Newfoundland, New Brunswick and Quebec.)
But interest in tidal power also ebbs, such as when herald-
ed projects fail. In 2009, Nova Scotia Power partnered with the
Dublin-based company OpenHydro to lower a six-story-high,
400-ton circular turbine into Minas Passage. Within days, the
current ripped the device apart. In glass-half-full mode, engi-
neers acknowledged they’d underestimated the tide’s force.
The company tried again seven years later, with an 1,100-ton
model. It generated two megawatts until the company ex-
tracted the device for repair andBYLINESElizabeth Royte is the author of Garbage Land: On the Secret
Trail of Trash. She lives in Brooklyn.
Greta Rybus, co-creator of Handcrafted Maine, photographs
the impacts of climate change on communities.The village of
Westpor t, on
Brier Island,
Nova Scotia, has
a population of
fewer than 200
residents. It is
reached by boat
or the ferry from
Long Island.CONTINUED ON PAGE 57