56
3 The Use of Scleractinian Corals for Heavy Metal Studies
2012). Environmental parameters such as SSTs, precipitation, salinity, sedimentation
and pollution can easily be obtained from the coral records.
Peters et al. (1997) mentioned that scleractinian corals and particularly those of
the genus Acropora have been identified as sensitive to changes in water quality
and chemical contaminants; making them an appropriate representative tropical test
species for use in investigating potential risks from contamination to coral reefs.
Scleractinian corals (particularly their skeletons) are used as proxy tools to record
environmental conditions/pollution such as trace metals (Guzman and Jimenez 1992;
Bastidas and Garcia 1999; Esslemont 1999; Fallon et al. 2002; David 2003; Runnalls
and Coleman 2003; Khaled et al. 2003; Ramos et al. 2004). Their skeletons assimilate
records of the presence and concentrations of certain metals over centuries, without
being killed by the relatively high levels present in the marine environment.
Since the trace metal concentrations in the skeletons reveal the environmental
metal loads, hence scleractinian corals become an excellent environmental indicator
for pollution studies. Prouty et al. (2013) highlighted that since corals precipitate
their CaCO 3 skeleton directly from seawater, the geochemistry of coral skeletons
had been widely used to study environmental variability. At the time of accretion of
its CaCO 3 skeleton, corals obtain an unaltered record of the chemical and physical
conditions that exist in the surrounding seawater and this record becomes useful in
monitoring studies.
One of the advantages of corals being an oceanic recorder is the availability of the
enhanced time resolution (biweekly to seasonal) records obtainable from the high
growth rate and according to Prouty et al. (2013), these high-resolution proxy records
provide detailed information on environmental change by accurately recording variations in physical and chemical parameters such as SST, river input, salinity and
pollution. It is important to note that corals are a well-established indicator taxon
of metal pollution (Schyff et al. 2020); and that metal pollution studies are best
conducted on sessile or sedentary organisms to ensure some certainty about exposure rate (Reichelt-Brushett 2012). Coral reefs are gradually exposed to a variety of
anthropogenic stressors (Gissi et al. 2019) and metals may contribute to the decline
in the health of coral reef ecosystems (Mitchelmore et al. 2007). The metal contaminants originate from a range of sources including industrial effluent, agricultural
runoff and antifouling paints (van Dam et al. 2011). Rainbow (1995) highlighted that
marine pollution increases the concentration of natural metals beyond background
concentration to levels that may harm organisms.
3.2 Reproduction in Scleractinian Corals
Corals are the principal structural architects of coral reef ecosystems and therefore
coral reproduction becomes an essential process that sustains the maintenance of the
structure and functions of the coral reef ecosystems (Baird et al. 2015). Coral reproduction is controlled by several life processes such as gamete production, fertilization,
3 The Use of Scleractinian Corals for Heavy Metal Studies
2012). Environmental parameters such as SSTs, precipitation, salinity, sedimentation
and pollution can easily be obtained from the coral records.
Peters et al. (1997) mentioned that scleractinian corals and particularly those of
the genus Acropora have been identified as sensitive to changes in water quality
and chemical contaminants; making them an appropriate representative tropical test
species for use in investigating potential risks from contamination to coral reefs.
Scleractinian corals (particularly their skeletons) are used as proxy tools to record
environmental conditions/pollution such as trace metals (Guzman and Jimenez 1992;
Bastidas and Garcia 1999; Esslemont 1999; Fallon et al. 2002; David 2003; Runnalls
and Coleman 2003; Khaled et al. 2003; Ramos et al. 2004). Their skeletons assimilate
records of the presence and concentrations of certain metals over centuries, without
being killed by the relatively high levels present in the marine environment.
Since the trace metal concentrations in the skeletons reveal the environmental
metal loads, hence scleractinian corals become an excellent environmental indicator
for pollution studies. Prouty et al. (2013) highlighted that since corals precipitate
their CaCO 3 skeleton directly from seawater, the geochemistry of coral skeletons
had been widely used to study environmental variability. At the time of accretion of
its CaCO 3 skeleton, corals obtain an unaltered record of the chemical and physical
conditions that exist in the surrounding seawater and this record becomes useful in
monitoring studies.
One of the advantages of corals being an oceanic recorder is the availability of the
enhanced time resolution (biweekly to seasonal) records obtainable from the high
growth rate and according to Prouty et al. (2013), these high-resolution proxy records
provide detailed information on environmental change by accurately recording variations in physical and chemical parameters such as SST, river input, salinity and
pollution. It is important to note that corals are a well-established indicator taxon
of metal pollution (Schyff et al. 2020); and that metal pollution studies are best
conducted on sessile or sedentary organisms to ensure some certainty about exposure rate (Reichelt-Brushett 2012). Coral reefs are gradually exposed to a variety of
anthropogenic stressors (Gissi et al. 2019) and metals may contribute to the decline
in the health of coral reef ecosystems (Mitchelmore et al. 2007). The metal contaminants originate from a range of sources including industrial effluent, agricultural
runoff and antifouling paints (van Dam et al. 2011). Rainbow (1995) highlighted that
marine pollution increases the concentration of natural metals beyond background
concentration to levels that may harm organisms.
3.2 Reproduction in Scleractinian Corals
Corals are the principal structural architects of coral reef ecosystems and therefore
coral reproduction becomes an essential process that sustains the maintenance of the
structure and functions of the coral reef ecosystems (Baird et al. 2015). Coral reproduction is controlled by several life processes such as gamete production, fertilization,