Environmental Engineering Reference
In-Depth Information
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 cyano-
bacterial (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 phytoplank-
ton 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 exper-
imental observations (Zhang et al.
2009
; Kasprzak et al.
2008
; Desortová
1981
;
Shlgren
1983
; Wojciechowska
1989
; Watson et al.
1992
; Talling
1993
; Chow-
Fraser 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 bio-
mass 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
con-
centrations 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 environ-
mental factors, but Chl
a
is the only parameter that allows precise and rapid deter-
mination of phytoplankton biomass or primary production in natural waters.
