737
Chlorophylls and their Degradation in Nature
concentrations reflect the occurrence and features of microorganisms present in natural
waters. Therefore, Chl a can be used to estimate the primary production or the cyanobacterial (algal) bloom in a variety of waters (Fielding and Seiderer 1991; Ondrusek et
al. 1991; Williams and Claustre 1991; Millie et al. 1993; Jeffrey et al. 1999; Bianchi et
al. 1993, 2002; Kasprzak et al. 2008). Chl a concentration is a predictor of phytoplankton biomass across a broad trophic gradient of lakes, ranging from oligotrophic to
highly eutrophic. It is also the most generally used indicator of eutrophication (Blanco
et al. 2008; Kasprzak et al. 2008). Concentrations of Chl a depend on the fractional
contributions of three phytoplankton size classes (micro-, nano- and picoplankton),
whereas small cells dominate at low Chl a concentrations and large cells at high
Chl a concentrations (Sathyendranath et al. 2001; Brewin et al. 2010).
The specific Chl a content per unit of phytoplankton biomass typically
decreases with an increase of phytoplankton standing stocks in filed and experimental observations (Zhang et al. 2009; Kasprzak et al. 2008; Desortová 1981;
Shlgren 1983; Wojciechowska 1989; Watson et al. 1992; Talling 1993; ChowFraser et al. 1994; Schmid et al. 1998; Felip and Catalan 2000; Sandu et al. 2003;
Kiss et al. 2006). The decreases in Chl a content per unit of phytoplankton biomass presumably involves two facts: First, Chl a bound to microorganisms is the
individual component that can be rapidly degraded by either photoinduced or
microbial processes (Zhang et al. 2009; Takamiya et al. 2000; Hörtensteiner 2006;
Kräutler and Hörtensteiner 2006; Moser et al. 2009; Hörtensteiner and Kräutler
2011). Second, the release of autochthonous DOM from phytoplankton biomass,
by either photoinduced or microbial assimilation/respiration (see also chapter
“Dissolved Organic Matter in Natural Waters”) (Parlanti et al. 2000; Mostofa et
al. 2009; Mostofa et al. 2009; Zhang et al. 2009) may affect the decrease in the
total content of Chl a in phytoplankton standing stocks. In addition, Chl a concentrations are substantially affected by the occurrence of phytoplankton species
or of size-fractionated phytoplankton, which undergoes seasonal variations in
different waters (Bianchi et al. 2002; Satoh et al. 2001; Goedheer 1970; Prezelin
1981; Aguirre-Gomez et al. 2001; Pérez et al. 2007; Hoepffner and Sathyendranath
1991; Parab et al. 2006; Huang et al. 2004, 2005; Buchanan et al. 2005; Qiu et
al. 2010). Micro- and nano-Chl a are both higher than pico-Chl a, but pico-Chl a
can reach 40 % of total Chl a in Wanshan islands in summer (Huang et al. 2005).
Micro- and nano-Chl a in Pearl River Estuary (South China Sea) generally account
for 60 % of total Chl a, and pico-Chl a account for 20 % of total Chl a in most
samples (Qiu et al. 2010). In September, picophytoplankton is dominant except
for the estuary head, where nano-phytoplankton is predominant. Pico-Chl a in
far offshore samples accounts for 69 and 75 % of total Chl a (Qiu et al. 2010).
Picophytoplankton typically accounts for less than 10 % of the total phytoplankton
biomass during winter and early spring in Chesapeake Bay. However, it can often
contribute to more than 50 % of total phytoplankton biomass in summer and early
autumn, particularly in mesohaline and polyhaline waters (Buchanan et al. 2005).
Variations in Chl a concentrations among phytoplankton species and changes in
Chl a concentrations per unit of phytoplankton biomass are caused by environmental factors, but Chl a is the only parameter that allows precise and rapid determination of phytoplankton biomass or primary production in natural waters.
Chlorophylls and their Degradation in Nature
concentrations reflect the occurrence and features of microorganisms present in natural
waters. Therefore, Chl a can be used to estimate the primary production or the cyanobacterial (algal) bloom in a variety of waters (Fielding and Seiderer 1991; Ondrusek et
al. 1991; Williams and Claustre 1991; Millie et al. 1993; Jeffrey et al. 1999; Bianchi et
al. 1993, 2002; Kasprzak et al. 2008). Chl a concentration is a predictor of phytoplankton biomass across a broad trophic gradient of lakes, ranging from oligotrophic to
highly eutrophic. It is also the most generally used indicator of eutrophication (Blanco
et al. 2008; Kasprzak et al. 2008). Concentrations of Chl a depend on the fractional
contributions of three phytoplankton size classes (micro-, nano- and picoplankton),
whereas small cells dominate at low Chl a concentrations and large cells at high
Chl a concentrations (Sathyendranath et al. 2001; Brewin et al. 2010).
The specific Chl a content per unit of phytoplankton biomass typically
decreases with an increase of phytoplankton standing stocks in filed and experimental observations (Zhang et al. 2009; Kasprzak et al. 2008; Desortová 1981;
Shlgren 1983; Wojciechowska 1989; Watson et al. 1992; Talling 1993; ChowFraser et al. 1994; Schmid et al. 1998; Felip and Catalan 2000; Sandu et al. 2003;
Kiss et al. 2006). The decreases in Chl a content per unit of phytoplankton biomass presumably involves two facts: First, Chl a bound to microorganisms is the
individual component that can be rapidly degraded by either photoinduced or
microbial processes (Zhang et al. 2009; Takamiya et al. 2000; Hörtensteiner 2006;
Kräutler and Hörtensteiner 2006; Moser et al. 2009; Hörtensteiner and Kräutler
2011). Second, the release of autochthonous DOM from phytoplankton biomass,
by either photoinduced or microbial assimilation/respiration (see also chapter
“Dissolved Organic Matter in Natural Waters”) (Parlanti et al. 2000; Mostofa et
al. 2009; Mostofa et al. 2009; Zhang et al. 2009) may affect the decrease in the
total content of Chl a in phytoplankton standing stocks. In addition, Chl a concentrations are substantially affected by the occurrence of phytoplankton species
or of size-fractionated phytoplankton, which undergoes seasonal variations in
different waters (Bianchi et al. 2002; Satoh et al. 2001; Goedheer 1970; Prezelin
1981; Aguirre-Gomez et al. 2001; Pérez et al. 2007; Hoepffner and Sathyendranath
1991; Parab et al. 2006; Huang et al. 2004, 2005; Buchanan et al. 2005; Qiu et
al. 2010). Micro- and nano-Chl a are both higher than pico-Chl a, but pico-Chl a
can reach 40 % of total Chl a in Wanshan islands in summer (Huang et al. 2005).
Micro- and nano-Chl a in Pearl River Estuary (South China Sea) generally account
for 60 % of total Chl a, and pico-Chl a account for 20 % of total Chl a in most
samples (Qiu et al. 2010). In September, picophytoplankton is dominant except
for the estuary head, where nano-phytoplankton is predominant. Pico-Chl a in
far offshore samples accounts for 69 and 75 % of total Chl a (Qiu et al. 2010).
Picophytoplankton typically accounts for less than 10 % of the total phytoplankton
biomass during winter and early spring in Chesapeake Bay. However, it can often
contribute to more than 50 % of total phytoplankton biomass in summer and early
autumn, particularly in mesohaline and polyhaline waters (Buchanan et al. 2005).
Variations in Chl a concentrations among phytoplankton species and changes in
Chl a concentrations per unit of phytoplankton biomass are caused by environmental factors, but Chl a is the only parameter that allows precise and rapid determination of phytoplankton biomass or primary production in natural waters.