62
3 The Use of Scleractinian Corals for Heavy Metal Studies
about induced bleaching due to higher concentrations of Cd and Cu; Gissi et al. (2017)
stated that Cu inhibits coral fertilisation, larval metamorphosis, and survival between
15 and 150 µg Cu/L; Reichelt-Brushett and Harrison (2005), Reichelt-Brushett and
Hudspith (2016) and Gissi et al. (2017) found that Ni inhibits fertilisation success
at very high concentrations (>1000 µg Ni/L); Goh (1991) stated that 9000 µg Ni/L
inhibited larval survival and settlement; Gissi et al. (2019) reported that the toxicity
of dissolved Ni on adult corals and their microbiome occurred at 470 µg Ni/L after
an exposure of 96 h; Heyward (1988) and Reichelt-Brushett and Harrison (2005)
mentioned that high concentrations of Zn had deleterious effects on the fertilization
of coral gametes; and Negri et al. (2002) stated that excess Zn concentrations affected
the settlement, metamorphosis and survival rate of coral larvae.
Furthermore, Zn can also have deleterious effects on the fertilization of corals
gametes (Heyward 1988; Reichelt-Brushett and Harrison 2005) as well as on the
settlement, metamorphosis and survival rate of coral larvae (Negri et al. 2002) when
present in excess concentrations. In addition to this, Gilbert and Guzman (2001)
highlighted that increased Cu exposure in marine environments impair coral physiology through carbonic anhydrase activity. Increased Cu exposure can also lead to
declines in photosynthetic efficiency of algal symbionts (Bielmyer et al. 2010). In
their study, Reichelt-Brushett and Hudspith (2016) reported that Platygyra daedalea
gametes validated an acute sensitivity to Cu, having an estimated EC 50 of 33 µg/L.
Studies concerning the effect of Cu on coral gamete fertilization success include
Reichelt-Brushett and Harrison (1999); Negri and Heyward (2001); Heyward (1988).
The fertilization success of the gametes was dependent on the Cu concentration. For
example: Negri and Heyward (2001) showed that in Acropora. millepora < 30%
fertilization success occurred at about 70 µg/L Cu; whilst Reichelt-Brushett and
Harrison (2005) observed that Goniastera.aspera gametes showed 1% fertilization
success at 96.8 µg/L Cu.
It is also important to note that seasonal and interannual deviation in Mn concentrations in corals can serve as an indicator of El-Nino Southern Oscillation events
and sediment input into coastal waters from rivers (Shen and Sanford 1990; Fallon
et al. 2002; Alibert et al.2003; Lewis et al. 2007).
3.6 Heavy Metal Pathways in Corals and Understanding
the Role of Zooxanthallae
Heavy metal regulation in marine invertebrates can be acquired through 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 or nematocyst discharge. GSH functions in metal
detoxification via oxidative stress from redox active metals by oxidation of GSH to
GSSG (glutathione disulphide); and metals also bind to GSH and be removed from
the organism via GSH-conjugation reactions (Mitchelmore et al. 2007).
3 The Use of Scleractinian Corals for Heavy Metal Studies
about induced bleaching due to higher concentrations of Cd and Cu; Gissi et al. (2017)
stated that Cu inhibits coral fertilisation, larval metamorphosis, and survival between
15 and 150 µg Cu/L; Reichelt-Brushett and Harrison (2005), Reichelt-Brushett and
Hudspith (2016) and Gissi et al. (2017) found that Ni inhibits fertilisation success
at very high concentrations (>1000 µg Ni/L); Goh (1991) stated that 9000 µg Ni/L
inhibited larval survival and settlement; Gissi et al. (2019) reported that the toxicity
of dissolved Ni on adult corals and their microbiome occurred at 470 µg Ni/L after
an exposure of 96 h; Heyward (1988) and Reichelt-Brushett and Harrison (2005)
mentioned that high concentrations of Zn had deleterious effects on the fertilization
of coral gametes; and Negri et al. (2002) stated that excess Zn concentrations affected
the settlement, metamorphosis and survival rate of coral larvae.
Furthermore, Zn can also have deleterious effects on the fertilization of corals
gametes (Heyward 1988; Reichelt-Brushett and Harrison 2005) as well as on the
settlement, metamorphosis and survival rate of coral larvae (Negri et al. 2002) when
present in excess concentrations. In addition to this, Gilbert and Guzman (2001)
highlighted that increased Cu exposure in marine environments impair coral physiology through carbonic anhydrase activity. Increased Cu exposure can also lead to
declines in photosynthetic efficiency of algal symbionts (Bielmyer et al. 2010). In
their study, Reichelt-Brushett and Hudspith (2016) reported that Platygyra daedalea
gametes validated an acute sensitivity to Cu, having an estimated EC 50 of 33 µg/L.
Studies concerning the effect of Cu on coral gamete fertilization success include
Reichelt-Brushett and Harrison (1999); Negri and Heyward (2001); Heyward (1988).
The fertilization success of the gametes was dependent on the Cu concentration. For
example: Negri and Heyward (2001) showed that in Acropora. millepora < 30%
fertilization success occurred at about 70 µg/L Cu; whilst Reichelt-Brushett and
Harrison (2005) observed that Goniastera.aspera gametes showed 1% fertilization
success at 96.8 µg/L Cu.
It is also important to note that seasonal and interannual deviation in Mn concentrations in corals can serve as an indicator of El-Nino Southern Oscillation events
and sediment input into coastal waters from rivers (Shen and Sanford 1990; Fallon
et al. 2002; Alibert et al.2003; Lewis et al. 2007).
3.6 Heavy Metal Pathways in Corals and Understanding
the Role of Zooxanthallae
Heavy metal regulation in marine invertebrates can be acquired through 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 or nematocyst discharge. GSH functions in metal
detoxification via oxidative stress from redox active metals by oxidation of GSH to
GSSG (glutathione disulphide); and metals also bind to GSH and be removed from
the organism via GSH-conjugation reactions (Mitchelmore et al. 2007).