Geoscience Reference
In-Depth Information
Increased
atmospheric
CO
2
levels
Increased
air temperatures
Increased
storm frequency
and intensity
Increased photosythesis
and leaf production
promoting mangrove
growth
Increased
sea-level
Increased coral
and mangrove damage
(+ structural changes)
Increased
sea-surface
temperatures
Renewed reef
growth
Coral bleaching
Reduced CO
3
2
−
concentrations
and reduced
coral calcification
Increased tidal
inundation
Sediment warming
leading to increased
organic matter degradation,
CH
4
+ H
2
S release
and root turnover
New coral growth in
high latitude areas?
Degradation and destabilization
of reef structures and changing rates
and patterns of carbonate production?
Mangrove expansion of
low-lying areas?
or
Substrate destabilization
and mangrove mortality?
Changes in sediment chemistry?
Promote mangrove
growth/expansion?
or
Mangrove mortality and
substrate destabilization?
Fig. 9.22
Simplified schematic diagram illustrating some of the key processes associated with climate change (boxed) and both
positive (bold italics) and negative (italics) responses within coral reef and mangrove environments. Note that many of the potential
responses have questions marks, highlighting either the uncertainties that exist, or the likely site-specific nature of the responses.
such increases were evident most recently on a
regional scale following the strong El Niño of
1997-98, which resulted in widespread coral
mortality across the Indo-Pacific. Such bleaching-
related mortality has major consequences for
reef carbonate production, as has been quanti-
fied in Panama (Eakin 1996; see section 9.3.3).
Temperature-related bleaching events have also
been documented in higher latitude settings,
where corals are adapted to lower average
temperatures (Celliers & Schleyer 2002) and
hence the effects of such bleaching events are
likely to be globally significant. The rate at
which coral communities will recover from
these widespread bleaching episodes remains
unclear, but may depend upon the ability of
corals to adapt to increasing mean sea-surface
temperatures.
Shifts towards net erosional regimes on many
shallow reefs are thus a potential consequence of
increased bleaching. This may lead to destabil-
ization of reef frameworks and reduced structural
integrity, although the response of framework
accumulation processes (such as bioerosion
and encrustation) to such disturbances remains
poorly documented. Any suppression of car-
bonate production will, however, inhibit the
potential for reefs to respond positively to sea-
level increases (see section 9.6.2) and increase
the frequency of storm-wave overtopping. This,
in turn, may result in changes in nearshore
sediment dynamics and changes in shoreline
morphology (Fig. 9.22). Climate change may
also modify storm patterns and intensities, and
shift the position (or latitudinal range) of the
cyclone/hurricane belt, and thus influence reef
and mangrove structure (Smith et al. 1994). In
addition to any increase in physical disturbance,
more frequent/intense storms may also have an
impact on mangroves by increasing rainfall and
sediment runoff.
9.6.2 Impacts of sea-level change on coral reef and
mangrove sedimentary systems
A major consequence of global climatic change
with implications for coral reef and mangrove
environments is sea-level change. Future trends
