Geoscience Reference
In-Depth Information
A
•
Consistent
No change
0
Opposite
50
OJ
"0
.a
0
ii
...J
o
Longitude
-150
-100
-50
50
100
150
Figure 5.2
Locations where marine climate change impacts have been observed
Source: Poloczanska et al., 2013
Note
a Derived from 208 studies of 857 species of assemblages containing 1,735 individual
observations. Pie charts used in regions bounded by dotted lines.
see Report Cards of Marine Climate Change in Australia,
www.oceanclimate
change.org.au
). For example, temperate macroalgae (seaweed) are retreating
from warmer waters on both the east and west coastlines (Wernberg et al., 2011)
and increases of warm-water fish species in south-east waters indicate the distri-
bution of these organisms is shifting (Last et al., 2010). Extreme temperatures are
driving die-backs of coastal marine plants and animals as extremely warm days
affect intertidal and shallow water organisms and communities (Poloczanska et
al., 2007). Similarly, anomalously warm sea temperatures driven by high levels
of insolation during still conditions can have a big impact on organisms such as
coral reefs (Hoegh-Guldberg, 1999). For example, small increases in sea temper-
ature (1-3°C) above the long-term summer maxima for even a few weeks can
cause mass coral bleaching. Coral bleaching is the breakdown of the symbiosis
between corals and dinoflagellates (
Symbiodinium
), the latter of which are criti-
cally important for trapping solar energy and providing energy and nutrients to
the coral host.
Mass coral bleaching across hundreds and sometimes thousands of km
2
has
been seen regularly on the Great Barrier Reef since the early 1980s, with no
reports of mass coral bleaching appearing in the scientific literature (or elsewhere
globally) prior to this time. The two most widespread events (triggered by seas
being 1-3°C above the long-term maxima for over a month) affected 50 per cent
of reefs within the Great Barrier Reef in 1998 and 2002 Berkelmans et al. 2004).
The relationship between mass coral bleaching and elevated sea temperature has
been extensively verified in laboratory and field studies, and is so reliable that
