NOTE:
Coral reefs
are considered
to be threatened
ecosystems.
I've heard about
"coral reefs dying"
since the 1960s.
No one blamed
global warming
back then,
because there was
no global warming
from 1940 to 1975.
Today, however
scientists often
attribute the
coral bleaching,
and coral death
to warming water,
due to climate change.
SUMMARY:
A study published in the
journal Marine Biology,
explains 30 years of data
from Looe Key Reef,
The study's co-authors are
Rachel A. Brewton and
Laura W. Herren of
FAU's Harbor Branch;
James W. Porter, Ph.D.,
emeritus professor of ecology
at the University of Georgia;
and Chuanmin Hu, Ph.D.,
of the College of Marine Science
at the University of South Florida.
"Our results provide
compelling evidence
that nitrogen loading
from the Florida Keys
and greater Everglades
ecosystem caused by
humans, rather than
warming temperatures,
is the primary driver
of coral reef degradation
at Looe Key Sanctuary
Preservation Area
during our long-term study,"
said Brian Lapointe, Ph.D.,
senior author and
a research professor
at FAU's Harbor Branch.
"Citing climate change
as the exclusive cause
of coral reef demise worldwide
misses the critical point
that water quality
plays a role, too,"
said Professor Porter.
"While there is little that
communities living near
coral reefs can do to stop
global warming, there is
a lot they can do to
reduce nitrogen runoff.
Our study shows that the
fight to preserve coral reefs
requires local, not just global,
action."
"The good news
is that we can
do something about
the nitrogen problem
such as better
sewage treatment,
reducing fertilizer inputs,
and increasing storage
and treatment of storm water
on the Florida mainland."
DETAILS:
Researchers from Florida
Atlantic University's
Harbor Branch
Oceanographic Institute
and collaborators say
coral bleaching is not
just due to a warming plane.
Improperly treated sewage,
fertilizers and top soil
are elevating nitrogen levels,
which are causing
phosphorus starvation
in the corals, reducing
their temperature threshold
for "bleaching."
These coral reefs were
dying off long before
they were impacted by
rising water temperatures.
A key finding from the study
is that land-based
nutrient runoff
has increased the
nitrogen:phosphorus ratio (N:P)
in reef algae, which indicates
an increasing degree
of phosphorus limitation
known to cause metabolic
stress and eventually
starvation in corals.
Researchers gathered data
from 1984 to 2014 and
collected seawater samples
during wet and dry seasons.
Lapointe and collaborators
from the University of Georgia
and the University of South Florida
also monitored the living coral
and collected abundant species
of seaweed (macroalgae)
for tissue nutrient analysis.
They monitored seawater salinity,
temperature and nutrient gradients
between the Everglades and Looe Key.
Data revealed that
living coral cover at Looe Key
Sanctuary Preservation Area
declined from nearly 33 percent
in 1984 to less than 6 percent
in 2008.
The annual rate of coral loss
increased from 1985 to 1987
and 1996 to 1999, following
periods of heavy rainfall and
increased water deliveries
from the Everglades.
Between 1991 to 1995,
significant increases in
Everglades runoff and
heavy rainfall resulted
in increases of
reactive nitrogen
and phytoplankton levels
at Looe Key,
above levels
known to stress
and cause die-off
of coral reefs.
Despite reduced
Everglades flows,
the water quality
has not yet recovered
to the levels of the 1980s.