40
barrier, and, from an ecological point of view, these findings help to explain the ability of certain species to flourish in copper- enriched environments.
Another adaptive mechanism involves the participation of ATP-binding cassette
(ABC) transporter proteins in translocating a wide variety of compounds across cell
membranes, including lipids, xenobiotics, drugs, and heavy metals (Ehrmann et al.
1998; Gaillard et al. 2008; Ritter et al. 2014), and the overexpression of ABC transporter
proteins in tolerant seaweed species modulates copper homeostasis and oxidative stress
(Contreras et al. 2010) (Fig. 3.1). Dictyota kunthii (Phaeophyceae) and Ectocarpus
siliculosus (Phaeophyceae) counteract copper excess through various mechanisms
including metal accumulation and the activation of antioxidant enzymes, oxygenated
polyunsaturated fatty acids (oxylipins), and heavy metal- binding compounds (Fig. 3.1).
For example, the copper-binding capacity of exudates in D. kunthii (determined by
anodic stripping voltammetry (ASV)) revealed an increased ligand capacity of the
medium when the plants were exposed to copper excess (Sordet et al. 2014).
3.3 Influence of Abiotic Factors on Metal Toxicity: The Case
of the Ocean Acidification
Due to human activities, atmospheric CO 2 content has increased by 100 ppm since
the industrial revolution and today stands at 380–400 ppm (Gattuso and Hansson
2011; IPCC 2014; NOAA 2016). It is expected that this concentration will continue
to rise. The oceanic uptake of CO 2 reduces both pH and the availability of carbonate
ions ( CO 3
2− ), thereby increasing the concentration of bicarbonate [ HCO 3
− ] (WolfGladrow et al. 1999; Orr et al. 2005) through a process called ocean acidification
(Feely et al. 2004; Solomon et al. 2007), where the concentration of protons [H
+
] is
proportional to the ratio of [ HCO 3
− ]/[ CO 3
2− ].
On a global scale, ocean surface pH is nearly 0.1 unit lower now than the values
registered in the preindustrial era (Orr et al. 2005). There is a predicted decrease of
0.4 unit by the end of the century and nearly 0.8 unit within the next 300 years.
Meanwhile, carbonate concentration ( CO 3
2− ) could drop by ~50% by the end of the
century, concomitant with a 192% increase in CO 2 and a 14% increase in HCO 3
− .
Metal speciation, or the form of the metal in terms of chemical species, influences its bioaccessibility, bioavailability fate, and toxic effects. Metal bioavailability and associated toxicity vary widely according to the physical, chemical, and
biological conditions to which an organism is exposed; and sensitivity to metals
varies with age, sex, nutritional status, and genetic polymorphisms. Due to this, the
toxic action of metals on one particular organism conceptually depends on a wide
array of abiotic and biotic factors (Fig. 3.2). In this context and because pH variation
is probably one of the most important environmental factors influencing metal speciation and behavior (Byrne 1988), ocean acidification is expected to modify metal
speciation, thereby altering the effects that these nondegradable contaminants have
on marine organisms, including seaweeds.
L. Contreras-Porcia et al.
barrier, and, from an ecological point of view, these findings help to explain the ability of certain species to flourish in copper- enriched environments.
Another adaptive mechanism involves the participation of ATP-binding cassette
(ABC) transporter proteins in translocating a wide variety of compounds across cell
membranes, including lipids, xenobiotics, drugs, and heavy metals (Ehrmann et al.
1998; Gaillard et al. 2008; Ritter et al. 2014), and the overexpression of ABC transporter
proteins in tolerant seaweed species modulates copper homeostasis and oxidative stress
(Contreras et al. 2010) (Fig. 3.1). Dictyota kunthii (Phaeophyceae) and Ectocarpus
siliculosus (Phaeophyceae) counteract copper excess through various mechanisms
including metal accumulation and the activation of antioxidant enzymes, oxygenated
polyunsaturated fatty acids (oxylipins), and heavy metal- binding compounds (Fig. 3.1).
For example, the copper-binding capacity of exudates in D. kunthii (determined by
anodic stripping voltammetry (ASV)) revealed an increased ligand capacity of the
medium when the plants were exposed to copper excess (Sordet et al. 2014).
3.3 Influence of Abiotic Factors on Metal Toxicity: The Case
of the Ocean Acidification
Due to human activities, atmospheric CO 2 content has increased by 100 ppm since
the industrial revolution and today stands at 380–400 ppm (Gattuso and Hansson
2011; IPCC 2014; NOAA 2016). It is expected that this concentration will continue
to rise. The oceanic uptake of CO 2 reduces both pH and the availability of carbonate
ions ( CO 3
2− ), thereby increasing the concentration of bicarbonate [ HCO 3
− ] (WolfGladrow et al. 1999; Orr et al. 2005) through a process called ocean acidification
(Feely et al. 2004; Solomon et al. 2007), where the concentration of protons [H
+
] is
proportional to the ratio of [ HCO 3
− ]/[ CO 3
2− ].
On a global scale, ocean surface pH is nearly 0.1 unit lower now than the values
registered in the preindustrial era (Orr et al. 2005). There is a predicted decrease of
0.4 unit by the end of the century and nearly 0.8 unit within the next 300 years.
Meanwhile, carbonate concentration ( CO 3
2− ) could drop by ~50% by the end of the
century, concomitant with a 192% increase in CO 2 and a 14% increase in HCO 3
− .
Metal speciation, or the form of the metal in terms of chemical species, influences its bioaccessibility, bioavailability fate, and toxic effects. Metal bioavailability and associated toxicity vary widely according to the physical, chemical, and
biological conditions to which an organism is exposed; and sensitivity to metals
varies with age, sex, nutritional status, and genetic polymorphisms. Due to this, the
toxic action of metals on one particular organism conceptually depends on a wide
array of abiotic and biotic factors (Fig. 3.2). In this context and because pH variation
is probably one of the most important environmental factors influencing metal speciation and behavior (Byrne 1988), ocean acidification is expected to modify metal
speciation, thereby altering the effects that these nondegradable contaminants have
on marine organisms, including seaweeds.
L. Contreras-Porcia et al.