Communities inundated by the unprecedented rainfall that hit south- eastern Texas last week are tallying the damage and mourning those who died. Some scientists are figuring out how to rebuild devastated laboratories. Meanwhile, out of the spotlight, the
Gulf of Mexico and its bountiful offshore
ecosystems are contending with the record-setting pulse of freshwater—a volume of
water exceeding the entire Chesapeake Bay—
that surged off the land, sweeping along sediment, nutrients, and pollutants.
“This is going to be a huge test,” says
marine biologist Larry McKinney, director
of the Harte Research Institute for Gulf of
Mexico Studies at Texas A&M University in
Corpus Christi. Marine creatures that live
along the coast are used to dramatic swings
in salinity and other conditions, he notes,
and studies have found that populations
can bounce back from extreme events. But
Harvey is unlike any past test of the gulf’s
resilience, McKinney says. “Will it shift
[coastal ecosystems] to a new paradigm we
haven’t seen before?”
He and other researchers are jump-
starting studies to find out. They can build
on baseline data from existing research
projects; some have been underway for
decades. McKinney and Harte biological
oceanographer Paul Montagna, for exam-
ple, have spent more than 30 years assess-
ing the impact of freshwater flows into the
gulf’s bays, estuaries, and coastal waters.
Every few years, lesser storms trigger floods
large enough to wreak havoc on marine
life, smothering seagrass beds, oyster reefs,
and seafloor life in sediment, and pushing
shrimp and fish populations out to sea.
But ecosystems often recover within a
year or two, and the nutrients pushed into
the sea can fuel the growth of plankton that
bolster the rest of the food web. Sometimes,
the postflood plankton bonanza sparks
“this big boom in crab and shrimp populations,” says Jace Tunnell, a marine biologist
at the Mission-Aransas National Estuarine
Research Reserve in Port Aransas, Texas,
which was in the hurricane’s path. Floods
can be “almost restorative—a lot like a forest fire,” Montagna says.
But the sheer magnitude of Harvey’s outflow could have the opposite effect, creating a known threat to gulf life: low-oxygen
“dead zones.” The zones are created when
lighter freshwater spreads over denser saltwater, creating a cap that denies oxygen to
organisms below. Newly arrived nutrients
can kick phytoplankton production into
high gear. After the plankton die and sink,
their decay consumes more oxygen and creates hypoxic zones near the sea floor. Mobile
creatures often flee; others die. The gulf’s
best known dead zone appears each summer off the mouth of the Mississippi River;
this year’s was the largest ever recorded.
Now, the question is whether similar zones
will appear near smaller rivers to the west,
where Harvey hit hardest.
Pamela Plotkin, director of the Texas Sea
Grant program at Texas A&M University in
Corpus Christi, worries that researchers “will
see a big impact.” And she’s concerned that
the oil, pesticides, and other chemicals carried by floodwaters will make matters worse.
“Nobody really knows what all those toxins
are going to do to the environment,” she says.
To find out, researchers are heading into
the field. As Science went to press, Texas
research institutes had already committed
at least $800,000 to studies, according to
McKinney. Researchers were planning
cruises to collect physical and biological
data, while others prepared to deploy instrumented underwater drones called gliders.
Coastal geologists were anxious to return
to barrier islands and beaches to see how
they were resculpted by Harvey’s winds and
waves.“This is an unprecedented opportunity to collect data,” Plotkin says—and possibly help prepare for the next hurricane.
Understanding how barrier islands respond to storm surge, for example, could
help coastal engineers strengthen natural defenses. Oceanographers also hope
to “plug observations into models, and
determine how good the models are,” says
Anthony Knap, an oceanographer at Texas
A&M University in College Station. Some
of these models concern sea level rise;
others predict flood effects. The knowledge gleaned from Harvey, researchers
say, could point to ways to make the gulf’s
communities—human and natural—more
resilient in a sometimes harsh world. j
Storm runoff (brown) surges into the Gulf
of Mexico on 31 August, after Hurricane
Harvey’s torrential rains had eased.
By Elizabeth Pennisi and David Malakoff
Record storm puts gulf resilience to the test
Researchers aim to understand impact of Hurricane Harvey’s unprecedented flood