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An analysis of long-term, water quality monitoring data
reveals that climate change is already having an impact on ecosystems
in the coastal waters of Buzzards Bay, Mass. The impacts relate
to how nitrogen pollution affects coastal ecosystems.
(Tom Kleindinst, Woods Hole Oceanographic Institution)
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An analysis of long-term, water quality monitoring
data reveals that climate change is already having an impact on ecosystems in
the coastal waters of Buzzards Bay, Mass. The impacts relate to how nitrogen
pollution affects coastal ecosystems.
Utilizing 22 years of data collected by a network of citizen
scientists, researchers from the Woods Hole Oceanographic Institution (WHOI)
and their colleagues at the Buzzards Bay National Estuary Program, the Buzzards
Bay Coalition, and the Marine Biological Laboratory found that average
summertime temperatures in embayments throughout Buzzards Bay warmed by almost
2 degrees Celsius—roughly 4 degrees Fahrenheit.
In addition, Rheuban added, the warmer water temperatures are
fueling an increase in algae growth.
While algae and other microscopic plants,
which form the base of the marine food chain, are vital to a healthy ecosystem,
too much can cause murky water, reduce sunlight and oxygen levels, and
ultimately cause harm to marine life.
This means added challenges for improving water quality in some
Cape Cod and southeastern Mass. watersheds that are already suffering from too
much nitrogen, which is most commonly caused by releases from septic systems
and wastewater treatment plants, atmospheric pollution, and fertilizer runoff.
Excess nitrogen also boosts algae growth.
"What we're seeing in the long-term data is that the same
levels of nitrogen in the system results in much more algae growth than it did
two decades ago," Rheuban said.
This increase in algae growth and chlorophyll means that water
quality is worse for the same amount of nitrogen, which has big implications
for water quality targets and clean up plans.
Identifying and understanding how different ecosystems respond to
climate change will aid in future monitoring and clean up efforts as coastal
communities prepare to adapt.
This research is part of multi-pronged
project funded in 2014 by the John D. and Catherine T. MacArthur Foundation
aimed at partnering with local organizations to develop science-based climate
change solutions for coastal communities.
Summer Snapshots Over Time
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| Warmer water temperatures are fueling an increase in algae growth, said Jennie Rheuban, a research associate at WHOI and lead author of the paper published in the journal Biogeosciences. (Kirsten Karplus, West Falmouth Oyster Reef Demonstration Project Volunteer) |
Every summer since 1992, volunteers working with the Buzzards Bay
Coalition have headed out to their local beaches and docks to help monitor the
health of the bay.
At sampling sites from Westport to the Elizabeth Islands,
trained citizen scientists gather samples and test temperature, salinity, water
clarity, and dissolved oxygen at the same locations, every five days from late
May through September.
In July and August, volunteers also collect water
samples that are taken to the Marine Biological Laboratory where they are
analyzed for nitrogen, phosphorus, and chlorophyll.
The Baywatchers program has amassed more than two decades of data
that has been a valuable resource over the years not only to the Coalition's
education and outreach efforts, but also to agencies that monitor water quality
and draft clean up plans.
"The data has been used by every level of government to make
decisions about the management of waterways from deciding which waters are
impaired to determining how much nitrogen a specific estuary can handle,"
said Rachel Jakuba, PhD, science director for the Buzzards Bay Coalition and a
coauthor of the paper.
This is the first time that over 20 years of the monitoring data
has been analyzed for long-term trends and patterns, in particular with a focus
on climate change. First, researchers looked at which locations and sites
had the most consistent data over the 22-year period (from 1992 to 2012), and
then divided those into 17 distinct embayments (see accompanying map for
sites).
"We analyzed the data on an embayment by embayment
scale," Rheuban said. "The degree of pollution in each embayment is very
different and that has to do with a number of different factors —levels of
development, whether there's agriculture or urbanization nearby."
For example, expanded sewering of larger towns on the west side of
the bay has helped reduce excess nitrogen from reaching nearby waterways more
than sites along the Cape Cod side of Buzzards Bay that do not have such
infrastructure already in place.
"We don't see nitrogen increases across the board,"
Rheuban said. "But what we do see in the analysis of the data is an
increase in temperatures and chlorophyll concentration across the bay and a
changing relationship between nitrogen and chlorophyll—an indicator of algae
growth and water quality—as those waters warm."
"This is potentially important because it suggests that in a
future world with higher temperatures, towns around Buzzards Bay will have to
remove more nitrogen from coastal watersheds to maintain the same water
quality," added Christopher Neill, director of the Marine Biological
Laboratory's Ecosystems Center and one of the study’s co-authors.
These types of ecosystem responses to higher temperatures,
researchers said, are crucial to include in updated management and clean up
plans.
"Nutrient pollution plagues coastal waters up and down the
east coast," said Scott Doney, a marine chemist at WHOI and a coauthor of
the paper. "We hope the lessons learned from Buzzards Bay can help
improve management efforts in many other locations."
Joe Costa, Executive Director of the Buzzards Bay National Estuary
Program, who helped establish the Buzzards Bay monitoring program and a
co-author of the paper, praised the WHOI team that initiated the study.
"This is a great example of the value citizen science data,
and we appreciate the focus on the changing conditions in Buzzards Bay,"
he said. "The findings have clear implications on how we need to
accommodate climate change in our strategies to reduce nitrogen
pollution."
Additional coauthors of the paper are Tony Williams of the
Buzzards Bay Coalition, and Shanna Williamson, David Glover, and Dan McCorkle
of WHOI.
