Natural Stress Relief: Oysters, Both Wild and Farmed, Clean Polluted Marine Waters
By ROB SMITH/ecoRI
News staff
Eating oysters is good
for the environment, according to a pair of Narragansett Bay-centric experts.
Scientists Robinson Fulweiler of Boston University and Christopher Kincaid from
the University of Rhode Island’s Graduate School of Oceanography shared their
latest findings during a recent webinar.
Fulweiler studies the
impact wild and aquaculture oysters have on their surrounding waters. A single
oyster can filter up to 50 gallons of water daily. Their most important
service, and the one Fulweiler studies most, is removing nitrogen from marine
waters that could trigger algal blooms.
“Aquaculture, as well as
restored oyster reefs, have high rates of nitrogen removal,” Fulweiler said.
Excessive nitrogen in
waters such as Narragansett Bay is dangerous for aquatic habitats and marine
life, as it can feed toxic blooms. These events are also linked to low levels
of oxygen in the water, which can lead to fish kills like the one in Greenwich Bay in 2003
that killed tens of thousands of fish.
Oysters, including those
in aquaculture operations, help out by removing nitrogen and other pollutants
from stressed waters. Instead of being biologically available to feed algae
growth, the chemical used in fertilizers is released into the atmosphere as
nitrous oxide. Aquaculture and restored reefs have a strong impact on
denitrification, according to Fulweiler.
“Oyster aquaculture and oyster reefs are behaving similarly in terms of the nitrogen removal process,” she said.
The two biggest
greenhouse gases oysters emit are nitrous oxide and carbon dioxide, and while
they are powerful climate emissions, the amounts oysters release as part of
denitrification are negligible. In fact, Fulweiler sees moving toward protein
sources from aquaculture as key to reducing emissions generated by land-based
farming.
“The take-home message
is if you eat a whole bunch of oysters, the amount of nitrous oxide released
into the environment is negligible compared to [if you ate] chicken, pigs,
sheep or cows,” Fulweiler said.
Kincaid has spent the past 20 years tracking
the movements of water and nitrogen in Narragansett Bay. A self-described
“coastal plumber,” he is building a predictive computer model to use in the
state’s coastal waters. Kincaid cited the 2003 fish kill as a prime reason to examine
water quality, nutrient dynamics, and algal blooms.
Low oxygenated areas in
the coves, harbors, and estuarine waters of Narragansett Bay have “amazingly
stable” gyres, or vortexes, that move currents slowly in a clockwise direction.
Kincaid and his team use Regional Ocean Modeling Systems
to track these currents after accounting for tidal flows.
“We could use [this
data] around aquaculture farms and predict how water flows in and out,” he
said.
Nitrogen enters
Narragansett Bay from the north and south. In the north, it comes from
wastewater treatment plants. In the south, it comes in through massive water
intrusions from Rhode Island Sound, traveling through the East Passage — the
channel of water between Jamestown and Aquidneck Island.
“The amount of water
coming in on these intrusions is on average twice the same amount that goes
over Niagara Falls every day,” Kincaid said.
The professor of
oceanography said he and his research team aren’t entirely sure what else is in
some of these East Passage water intrusions besides high levels of nitrogen,
but has a future study planned to investigate.
The Nov. 23 seminar was
sponsored by the Coastal Resources Management Council, URI’s Coastal Resources
Center, and Rhode Island Sea Grant.
