Environmental Engineering Reference
In-Depth Information
dynamics in both DCM and SCM. The actual effect can be different in different types
of water. Waters with low contents of DOM (apparently <100 mM C) can yield low
contents of photo- and microbial products (H
2
O
2
, CO
2
, DIC) in the euphotic zone,
with limited enhancement of productivity. This effect is often found in the oligo-
trophic regions of the ocean where the nutrient-poor upper layer is made even poorer
as a result of enhanced stratification. The phenomenon has a negative impact on net
primary production and can produce oceanic 'oligotrophication' as a direct effect of
global warming (Sarmento et al.
2010
; Falkowski and Oliver
2007
; Falkowski and
Wilson
1992
; Karl et al.
2001
; Polovina et al.
2008
; Behrenfeld et al.
2006
).
A regional decrease in wind velocity in Lake Tanganyika, East Africa has con-
tributed to reduced mixing, decreasing the deep-water nutrient upwelling and
entrainment into surface waters (O'Reilly et al.
2003
).
Increased stability of the water column may enhance the photoinduced degra-
dation of DOM by combination of high temperature and longer summer season.
In waters with high contents of DOM this would lead to the production of high
contents of photo- and microbial products (such as H
2
O
2
, CO
2
and DIC). This
process enhances photosynthesis and can result into in high primary production.
Phytoplankton or algae productivity in DOM-rich waters would also enhance the
production of autochthonous DOM and nutrients (Mostofa et al.
2009b
; Stedmon
et al.
2007a
,
b
; Malkin et al.
2008
; Fu et al.
2010
; Li et al.
2008
; Zhang et al.
2009
; Carrillo et al.
2002
; Kopáˇek et al.
2000
,
2004
). High production of fur-
ther DOM and nutrients would severely worsten the quality of waters with high
contents of DOM, particularly in lakes, reservoirs, estuaries, coastal waters and
in the Arctic and Antarctic regions. Such effects of climate warming may simulta-
neously promote harmful algal blooms or toxic phytoplankton populations (Davis
et al.
2009
; Mudie et al.
2002
; Richardson and Jorgensen
1996
; Hallegraeff
1993
;
Harvell et al.
1999
; Braun and Pfeiffer
2002
). The occurrence of cyanobacterial
blooms in freshwater has increased over the last few decades all over the world
(Xu et al.
2000
; Chen et al.
2003
; McCarthy et al.
2007
).
An increase in dissolved primary production is one of the consequences of the
temperature rise in the Southern Ocean (Morán et al.
2006
). Similar processes in
subarctic lakes are likely to result in higher DOC concentration, bacterial production
and respiration, and into emission of CO
2
to the atmosphere (Jansson et al.
2008
).
The penetration to significant depths of solar UV radiation can affect arthro-
pods, cyanobacteria, phytoplankton, macroalgae and aquatic plants in both fresh-
water and marine environments, including Antarctic and Arctic waters (Ballaré
et al.
2011
; Huisman et al.
2006
; Häder et al.
2003
,
2007
,
2011
; Karl et al.
2001
;
Sinha et al.
2001
; Day and Neale
2002
; Frenot et al.
2005
; Rastogi et al.
2010
).
Changes in the timing of primary producers, possibly forced by UV-B radiation
and temperature increase, would change connectivity in the food web among phy-
toplankton, zooplankton, crustaceans, amphibians, fish, corals and birds (Kitaysky
and Golubova
2000
; Morrison et al.
2002
; Johannessen and Macdonald
2009
;
Häder et al.
2007
,
2011
; Pomeroy and Wiebe
2001
).
The primary producers (e.g. phytoplankton cells) tend to be smaller in a warmer
ocean (Falkowski and Oliver
2007
; Daufresne et al.
2009
; Morán et al.
2010
). It has
