Campbell, J.E. and
Fourqurean, J.W.
2018
Does nutrient
availability regulate
seagrass response
to elevated CO2 ?
Ecosystems 21: 1269-1282.
NOTE:
The study says:
"Many seagrasses
may benefit from
forecasted increases
in CO2 concentrations
because photosynthesis
is limited by CO2
availability at the
pH of modern
seawater".
This was an
Investigation
of the long-term
response
of a seagrass
community,
dominated by
Thalassia
testudinum,
to elevated CO2
and nutrient supply.
SUMMARY:
Campbell and
Fourquerean
2018 write that
"elevated CO2
modestly increased
seagrass standing crop,
providing evidence
that carbon enrichment
will likely prove beneficial
to submerged plants
beyond enhancements
in photosynthetic output."
They note
that because
positive responses
"were not influenced
by NP addition",
it suggests that
these CO2-induced
benefits will occur
"even in relatively
nutrient-poor
systems."
Elevated CO2
had a positive impact
on seagrass growth,
increasing the
standing crop
by +35% and +42%,
and the below
ground biomass
by +27% and +46%
under ambient
and enriched
nutrient
application,
respectively.
DETAILS:
Conducted in situ at a
shallow seagrass bed
( 1 meter depth )
located in the
Florida Keys, USA.
Clear, open-top
acrylic chambers
were placed inside
the seagrass bed
and
CO2 was injected
into half of the
chambers
to maintain
an approximate
0.3-unit reduction
in seawater pH.
The other half
of the chambers
were maintained
at normal
seawater pH.
Half the chambers
in each pH treatment
received no fertilizer,
and half received
a dose of nitrogen (N)
and phosphorus (P)
on a monthly basis.
CO2 and
nutrient
treatments
were
maintained
for a period
of one year.
Growth parameters
tended to respond
positively to nutrient
application, but in a
less-significant
manner to that
of CO2.
There were
no additive
effects of CO2
and nutrient supply.
The authors say
because nutrient
availability
"did not alter
CO2 effects
at our site,
[the data suggest]
that even relatively
nutrient-poor
plant communities
may positively
respond to
elevated CO2
over sufficient
timescales."
There was
"no long-term effect
of elevated CO2
on seagrass
nutrient content."
Figure 1.
Standing crop and
( left panel )
below ground
( right panel )
biomass response
of a Florida
seagrass
community,
to CO2(aq)
and nutrient
enrichment:
