64
3 The Use of Scleractinian Corals for Heavy Metal Studies
Shah (2008) have reported about the loss of zooxanthellae in response to metal
exposure. These studies give an indication that heavy metals are regulated especially
in corals through zooxanthallae loss.
3.7 Summary
Scleractinian corals remain the architects of coral reefs, and consequently a good
representative of environmental changes of the ocean. Being sessile, their skeletons
integrate records of the presence and the past water chemistry in terms of pollution with respect to concentrations of certain heavy metals, sedimentation rates, sea
surface temperature and salinity and ocean acidification. Conducive environmental
conditions induce scleractinian corals to incorporate the heavy metals in their living
tissue and the skeleton through substitution of dissolved metal species via calcium
substitution. Many studies have revealed that tissues and the zooxanthallae tend to
record higher concentrations of heavy metals than skeleton.
High metal loads lead to the expulsion of zooxanthallae, causing a pale coloration
of the corals, referred to as bleaching of corals. Once incorporated into the coral
skeleton; the metals will remain embedded forever since the new growth covers the
old carbonate surface and the metals can result in acute or chronic toxicity causing
lethal effects or long-term impacts to key biological processes of corals. Ecotoxicological data show the effects of trace metals on various life stages of corals including
gamete fertilization; and hence can be used reliably to predict the effects of pollution
and thus manage discharges in the marine ecosystems.
Studies also reveal that regulation of heavy metals in the marine invertebrates
occurs through processes like excretion, impaired uptake, detoxification, storage,
sequestration of metals, metal-binding to proteins such as glutathione (GSH),
metallothioneins (MT) and release of metals via increased production of mucus,
nematocyst discharge or zooxanthallae loss.
References
Alibert C, Kinsley L, Fallon SJ, McCulloch MT, Berkelmans R, McAllister F (2003) Source of trace
element variability in Great Barrier Reef corals affected by the Burdekin flood plumes. Geochim
Cosmochim Acta 67(2):231–246. https://doi.org/10.1016/S0016-7037(02)01055-4
Al-Rousan SA, Al-Shloul RN, Al-Horani FA, Abu-Hilal A (2007) Heavy metal contents in growth
bands of Porites corals: record of anthropogenic and human developments from the Jordanian
Gulf of Aqaba. Mar Pollut Bull 54:1912–1922
Babcock RC, Heyward AJ (1986) Larval development of certain gamete-spawning scleractinian
corals. Coral Reefs 5:111–116
Baird AH, Cumbo VR, Gudge S, Keith SA, Maynard JA, Tan CH, Woolsey ES (2015) Coral
reproduction on world’s southernmost reef at Lord Howe Island, Australia. Aquat Biol 23:275–
284
3 The Use of Scleractinian Corals for Heavy Metal Studies
Shah (2008) have reported about the loss of zooxanthellae in response to metal
exposure. These studies give an indication that heavy metals are regulated especially
in corals through zooxanthallae loss.
3.7 Summary
Scleractinian corals remain the architects of coral reefs, and consequently a good
representative of environmental changes of the ocean. Being sessile, their skeletons
integrate records of the presence and the past water chemistry in terms of pollution with respect to concentrations of certain heavy metals, sedimentation rates, sea
surface temperature and salinity and ocean acidification. Conducive environmental
conditions induce scleractinian corals to incorporate the heavy metals in their living
tissue and the skeleton through substitution of dissolved metal species via calcium
substitution. Many studies have revealed that tissues and the zooxanthallae tend to
record higher concentrations of heavy metals than skeleton.
High metal loads lead to the expulsion of zooxanthallae, causing a pale coloration
of the corals, referred to as bleaching of corals. Once incorporated into the coral
skeleton; the metals will remain embedded forever since the new growth covers the
old carbonate surface and the metals can result in acute or chronic toxicity causing
lethal effects or long-term impacts to key biological processes of corals. Ecotoxicological data show the effects of trace metals on various life stages of corals including
gamete fertilization; and hence can be used reliably to predict the effects of pollution
and thus manage discharges in the marine ecosystems.
Studies also reveal that regulation of heavy metals in the marine invertebrates
occurs through processes like excretion, impaired uptake, detoxification, storage,
sequestration of metals, metal-binding to proteins such as glutathione (GSH),
metallothioneins (MT) and release of metals via increased production of mucus,
nematocyst discharge or zooxanthallae loss.
References
Alibert C, Kinsley L, Fallon SJ, McCulloch MT, Berkelmans R, McAllister F (2003) Source of trace
element variability in Great Barrier Reef corals affected by the Burdekin flood plumes. Geochim
Cosmochim Acta 67(2):231–246. https://doi.org/10.1016/S0016-7037(02)01055-4
Al-Rousan SA, Al-Shloul RN, Al-Horani FA, Abu-Hilal A (2007) Heavy metal contents in growth
bands of Porites corals: record of anthropogenic and human developments from the Jordanian
Gulf of Aqaba. Mar Pollut Bull 54:1912–1922
Babcock RC, Heyward AJ (1986) Larval development of certain gamete-spawning scleractinian
corals. Coral Reefs 5:111–116
Baird AH, Cumbo VR, Gudge S, Keith SA, Maynard JA, Tan CH, Woolsey ES (2015) Coral
reproduction on world’s southernmost reef at Lord Howe Island, Australia. Aquat Biol 23:275–
284