Environmental Engineering Reference
In-Depth Information
affect the physiology of water breathing animals, causing physiological
stress, decreased reproductive potential, slower growth and increased
susceptibility to diseases (Pörtner et al
.
2004). Those organisms will continue
to be affected by ocean acidifi cation is well established, but less attention
has been paid to the impact of the ecosystem at a higher trophic-level:
organisms that depend on these calcifi ers for shelter, nutrition, and other
core functions (Fabry et al. 2008, Guinotte and Fabry 2008).
Effects of Climate Change on Coral Reefs
Coral reefs are one of the most productive and diverse ecosystems on Earth,
providing critical habitats that support approximately 25% of marine species
(Connell 1978). In addition to human reliance on coral reefs for food supply,
livelihoods and tourism (Salvat 1992, Wilkinson and Souter 2008, Pandolfi et
al. 2011), they also provide important ecosystem services such as coastline
protection from storm damage, erosion and fl ooding, by reducing the
action of waves along the shore. The protection afforded by coral reefs also
enables the formation of associated ecosystems such as sea-grass beds and
mangroves (Moberg and Folke 1999). Coral reefs are also areas of spawning,
nursery, breeding and feeding for a multitude of organisms; they export
fi sh and invertebrate larvae to adjacent ecosystems (mangroves, sea-grass
beds) and support pelagic food webs (Hoegh-Guldberg 1999, Moberg and
Folke 1999).
There has been a dramatic decline in tropical coral reefs over the
centuries, the pace of coral mortality and reef degradation accelerating
in particular over the past 20-50 years (Pandolfi et al
.
2003). Coral reefs
around the world have suffered both gradual and chronic stress as a result
of anthropogenic activities in the form of over- and destructive fi shing,
pollution, coral diseases, mining of coral rock and sand and coastal
developments that have modifi ed the reefs; however, the main threat now
lies in global climate change (Hoegh-Guldberg 1999, Pandolfi et al. 2003).
Coral bleaching occurs when coral colonies under physiological stress
expel their symbiotic algae (zooxanthellae), which provide much of the
energy for coral and coral reef growth. Among the different kinds of stress
leading to bleaching, by far the most signifi cant cause over the past two
decades has been related with the increase in sea surface temperature
(Wilkinson and Souter 2008). Corals may partially or fully recover from
bleaching events, but may also die (Lough 2000). Even in cases of apparent
recovery, thermal stress can have long-term effects in terms of reduced
reproduction, reduced growth rates and increased susceptibility to other
disturbances, such as coral diseases (Lough 2008). The increased frequency
of bleaching reduces the capacity of coral reefs to recover and repeated
mass coral bleaching events since 1970 have caused a decline in coral
