Jacotot, A.,
Marchand, C., and
Allenbach, M.
2019
Increase in growth and alteration
of C:N ratios of Avicennia marina
and Rhizophora stylosa
subject to elevated CO2
concentrations and longer
tidal flooding duration.
Frontiers in Ecology and Evolution 7: 98,
doi: 10.3389/fevo.2019.00098
NOTE:
Forested mangrove ecosystems
typically develop along tropical
and subtropical coastlines
and are mainly composed
of salt-tolerant trees.
SUMMARY:
Jacotot et al. report that the
doubling of atmospheric CO2
from 400 to 800 ppm resulted in
an increase of total plant biomass
of +95.5% and +88.5% for A. marina
and +47.5% and +56.3% for R. stylosa
under normal and extended
tidal flooding cycles, respectively.
The increase in total plant biomass
was the product of photosynthesis
enhancement by elevated CO2,
which increased the biomass
both above and below ground.
The authors say
elevated CO2 should
"lead to soil vertical accretion,
thus helping mangroves to face
sea-level rise."
and is likely to
"favor seedling establishment
and mangrove colonization
of new available spaces
resulting from sea-level rise."
"Future increases in surface
temperature will further stimulate
trees development, as seasons
affected seedlings productivity
with higher relative growth rates
during the warmer period."
The authors note that
carbon/nitrogen ratios
of seedling tissues
"were increased
under elevated CO2,
which may lower organic
matter degradation
in mangrove soils
[thereby] increasing
carbon sequestration."
Jacotot et al. conclude that
"future climate changes
may enhance the productivity
of mangrove seedlings
by increasing their growth,
which may in turn
increase the carbon storage
potential of mangroves."
DETAILS:
Jacotot et al. (2019) grew seedlings
of two tree species, grey mangrove
(Avicennia marina) and stilted mangrove
(Rhizophora stylosa), under two
CO2 concentrations (400 or 800 ppm)
over a period of one year.
In addition, half of the trees
in each CO2 treatment
were subjected to a normal
tidal flooding cycle and half
to a tidal cycle that was
1.75 hours longer than normal.
The extended tidal cycle
allowed for a longer duration
of tidal flooding, which
circumstance is hypothesized
to occur in the future
in response to projections
of sea level rise.
