Environmental Engineering Reference
In-Depth Information
may prolong the photochemical processes, with high production of photoproducts,
pH alteration, and microbial food web stimulation (Baulch et al.
2005
; Morris and
Hargreaves
1997
; Cooke et al.
2006
; Malkin et al.
2008
). These issues can result
into high photosynthesis, thereby enhancing phytoplankton productivity in lakes and
oceans. These phenomena will particularly affect the Arctic and Antarctic regions.
Climate models predict that global warming will increase the stability of the verti-
cal stratification in large parts of lakes and oceans (Huisman et al.
2006
; Sarmiento
et al.
1998
,
2004
; Bopp et al.
2001
,
2005
; Schmittner
2005
). This will subsequently
reduce vertical mixing and suppress the upward flux of nutrients, leading to a
decrease in primary production. However, increased stability of the water column
might also increase the photochemical degradation of DOM, and cause high pho-
tosynthesis via high temperature and longer summer season. Reduced vertical mix-
ing can generate oscillations and chaos in phytoplankton biomass, size and species
composition of DCM (Huisman et al.
2006
; Barbiero and Tuchman
2004
; Winder et
al.
2009
). These perturbations are generated by the difference in timescale between
the sinking flux of phytoplankton and the upward flux of nutrients. Increasing back-
ground light attenuation can increase light limitation, shifting phytoplankton towards
the surface and generally decreasing DCM depth and total biomass, particularly in
the mixed layer (Mellard et al.
2011
). Climate warming may promote the growth of
toxic, rather than non-toxic, phytoplankton populations (Davis et al.
2009
). Therefore,
changes induced by global warming can significantly impact the SCM, DCM, species
composition, nutrients dynamics, and carbon cycle. This issue is also extensively dis-
cussed in other chapters (see chapters
“
Photosynthesis in Nature: A New Look
” and
5 Degradation of Chl
It has been shown that terrestrial plants adapt their annual life cycles of growth,
reproduction and senescence to the annual climate cycle with period of one year.
In contrast, phytoplankton biomass can turn over around 100 times each year as a
result of fast growth and equally fast consumption by grazers (Calbet and Landry
2004
; Behrenfeld et al.
2006
; Winder and Cloern
2010
). Therefore, the signifi-
cance of the degradation of Chl
a
bound to higher plants and aquatic microorgan-
isms shows characteristic differences.
5.1 Degradation of Chl
a
in Aquatic Microorganisms
Chl
a
bound to phytoplankton or cyanobacteria can be degraded by both pho-
toinduced and microbial degradation processes and can produce chlorophyl-
lide
a
, pheophorbide
a
, pheophytin
a
, and pyropheophytin
a
in aqueous media
