725
Chlorophylls and their Degradation in Nature
caused by accumulation of algal species in the ice bed. Interestingly, observation of
a series of ice age classes indicated that older ice has higher concentrations of particulate organic carbon, Chl and algal cells (Gleitz and Thomas 1993). Substantial
increases have been observed for the abundance of Chaetoceros neogracile, F. cylindrus, and Nitzschia lecointei, implying growth of these algae (Gleitz and Thomas
1993). The abundance of other species (F. kerguelensis, Dactyliosolen) decreased
with the age of the sea ice, implying that they can possibly accumulate in ice but are
selected against over time (Gleitz and Thomas 1993). Correspondingly, algal pigment
signatures in sea ice also suggest that older ice is more diatom-dominated (Lizotte et
al. 1998). Lower concentrations of Chl a, which have been observed in a light perturbation experiment (3.54 ± 1.00 to 14.2 ± 12.4 μg L −1 ) compared to the control
experiment (5.21 ± 2.33 to 111 ± 30 μg L −1 ) in Antarctica ice seawater (Palmisano
et al. 1985) can also support the above phenomena. The occurrence of more elevated
concentrations of dissolved O 2 in Arctic and Antarctic Oceans compared to tropical
and subtropical waters (Codispoti and Christensen 1985; Falkner et al. 2005; Garcia et
al. 2005; Schmittner et al. 2007; Araoye 2009; Abowei 2010; Keeling et al. 2010) are
also responsible for the rapid formation of H 2 O 2 under low irradiance. These phenomena can support high photosynthesis in seawater ice. (ii) The occurrence of the ozone
hole, and a corresponding increase in UV-B exposure, can cause unequivocal increase
of direct or indirect oxidative damage, either directly or indirectly through formation
of ROS. It has been shown that the latter can alter biomolecules (lipids, DNA, amino
acids, proteins, Chls) and can affect photosynthetic efficiency, reproduction and development in Antarctic marine organisms (see also chapter “Photosynthesis in Nature:
A New Look”) (Bidigare 1989; Smith et al. 1992; Arrigo 1994; Lesser et al. 2001,
2004; Lesser and Barry 2003; Karentz et al. 2004; Leu et al. 2007; Lister et al. 2010;
Cullen and Neale 1997). The effects of the ozone hole and of the corresponding UV-B
exposure is largely mitigated by sea ice coverage, in the case of aquatic organisms
that live beneath the ice cover (Moreno 2012; Karentz et al. 2004; Lister et al. 2010;
Tremblay et al. 2006; Perovich 1993; Trodahl and Buckley 1989). (iii) Intracellular
and extracellular production of H 2 O 2 from algae (or phytoplankton species) can
take place under light conditions in the ice layer (see also chapter “Photosynthesis
in Nature: A New Look”) (Hong et al. 1987; Bazanov et al. 1999; Premkumar and
Ramaraj 1999; Lobanov et al. 2008; Palenik et al. 1987; Palenik and Morel 1988;
Komissarov 2003), and could enhance photosynthesis. A further enhancement effect
could be caused by relatively high amounts of DIC, H 2 O 2 and nutrients produced
from DOM and POM, either by microbial or photoinduced processes in Arctic and
Antarctic Oceans.
Photosynthesis could rapidly occur under low irradiance conditions in the presence of large amounts of algae (or phytoplankton), and if H 2 O 2 , DIC and nutrients
are available. It has been shown that nutrient concentrations (e.g. nitrate) are considerably high (2–12 μM) in the Arctic Ocean (Tremblay et al. 2006). In the Antarctic
Ocean, Chl a concentrations in coastal surface seawater ice are high (0.45–4.03 μg
L −1 ), and at the same time there are low contents of NH 4
+ (0.05–2.21 μM), NO 3
−
(7.82–23.1 μM), and PO 4
3− (0.60–3.0 μM) compared to those of oceanic offshore waters (Table 1) (Verlencar et al. 1990). In contrast, Chl a concentrations are
Chlorophylls and their Degradation in Nature
caused by accumulation of algal species in the ice bed. Interestingly, observation of
a series of ice age classes indicated that older ice has higher concentrations of particulate organic carbon, Chl and algal cells (Gleitz and Thomas 1993). Substantial
increases have been observed for the abundance of Chaetoceros neogracile, F. cylindrus, and Nitzschia lecointei, implying growth of these algae (Gleitz and Thomas
1993). The abundance of other species (F. kerguelensis, Dactyliosolen) decreased
with the age of the sea ice, implying that they can possibly accumulate in ice but are
selected against over time (Gleitz and Thomas 1993). Correspondingly, algal pigment
signatures in sea ice also suggest that older ice is more diatom-dominated (Lizotte et
al. 1998). Lower concentrations of Chl a, which have been observed in a light perturbation experiment (3.54 ± 1.00 to 14.2 ± 12.4 μg L −1 ) compared to the control
experiment (5.21 ± 2.33 to 111 ± 30 μg L −1 ) in Antarctica ice seawater (Palmisano
et al. 1985) can also support the above phenomena. The occurrence of more elevated
concentrations of dissolved O 2 in Arctic and Antarctic Oceans compared to tropical
and subtropical waters (Codispoti and Christensen 1985; Falkner et al. 2005; Garcia et
al. 2005; Schmittner et al. 2007; Araoye 2009; Abowei 2010; Keeling et al. 2010) are
also responsible for the rapid formation of H 2 O 2 under low irradiance. These phenomena can support high photosynthesis in seawater ice. (ii) The occurrence of the ozone
hole, and a corresponding increase in UV-B exposure, can cause unequivocal increase
of direct or indirect oxidative damage, either directly or indirectly through formation
of ROS. It has been shown that the latter can alter biomolecules (lipids, DNA, amino
acids, proteins, Chls) and can affect photosynthetic efficiency, reproduction and development in Antarctic marine organisms (see also chapter “Photosynthesis in Nature:
A New Look”) (Bidigare 1989; Smith et al. 1992; Arrigo 1994; Lesser et al. 2001,
2004; Lesser and Barry 2003; Karentz et al. 2004; Leu et al. 2007; Lister et al. 2010;
Cullen and Neale 1997). The effects of the ozone hole and of the corresponding UV-B
exposure is largely mitigated by sea ice coverage, in the case of aquatic organisms
that live beneath the ice cover (Moreno 2012; Karentz et al. 2004; Lister et al. 2010;
Tremblay et al. 2006; Perovich 1993; Trodahl and Buckley 1989). (iii) Intracellular
and extracellular production of H 2 O 2 from algae (or phytoplankton species) can
take place under light conditions in the ice layer (see also chapter “Photosynthesis
in Nature: A New Look”) (Hong et al. 1987; Bazanov et al. 1999; Premkumar and
Ramaraj 1999; Lobanov et al. 2008; Palenik et al. 1987; Palenik and Morel 1988;
Komissarov 2003), and could enhance photosynthesis. A further enhancement effect
could be caused by relatively high amounts of DIC, H 2 O 2 and nutrients produced
from DOM and POM, either by microbial or photoinduced processes in Arctic and
Antarctic Oceans.
Photosynthesis could rapidly occur under low irradiance conditions in the presence of large amounts of algae (or phytoplankton), and if H 2 O 2 , DIC and nutrients
are available. It has been shown that nutrient concentrations (e.g. nitrate) are considerably high (2–12 μM) in the Arctic Ocean (Tremblay et al. 2006). In the Antarctic
Ocean, Chl a concentrations in coastal surface seawater ice are high (0.45–4.03 μg
L −1 ), and at the same time there are low contents of NH 4
+ (0.05–2.21 μM), NO 3
−
(7.82–23.1 μM), and PO 4
3− (0.60–3.0 μM) compared to those of oceanic offshore waters (Table 1) (Verlencar et al. 1990). In contrast, Chl a concentrations are