Environmental Engineering Reference
In-Depth Information
at higher temperatures (Vaqué et al.
2009
). Polar oceans at temperatures of
−
1 to
2
−
3 ºC have microbial communities, both bacterial and algal, which are physi-
ologically stressed. In fact, the environmental temperature is well below the opti-
mum temperature for growth of many inhabitants (Nedwell
1999
). As average
Arctic temperatures have increased at almost twice the global average rate in the
past 100 years (IPCC
2007a
), the microbial activity in the Arctic and Antarctic
regions is expected to undergo a significant enhancement due to the effect of
global warming.
Winter warming typically results in both stimulation (abundance and biomass)
of the biofilm ciliate communities and in significant shifts in the community struc-
ture. Summer warming induces a significant decline in the ciliate biomass but does
not affect the relative community composition (Norf and Weitere
2010
). Gradual
freeze-thaw incubation decreases the microbial activity in the frozen state to
0.25 % of the initial levels at 4 °C, but activity resumes rapidly reaching >60 % of
the initial activity in the thawed state (Sawicka et al.
2010
).
Uptake of nitrate by bacteria and algae is strongly dependent on tempera-
ture and consistently decreases at temperatures below the optimum. In contrast,
ammonium uptake is increased at low temperatures (Reay et al.
1999
). Increasing
temperature can significantly accelerate the colonization speed and reduce the
carrying capacity in particular seasons, e.g. during winter. At the same time, the
strongest response to the temperature increase occurs during the highest DOC
loadings (Norf et al.
2007
). Overall, the response of microbial communities to
local temperature increases strongly depends on the seasonal setting, the resource
availability and the stage of succession (Norf et al.
2007
).
Bacterioplankton production depends on ambient temperature, availability of
nutrients and other labile substrates, and on the total DOM contents in natural
waters (Ochs et al.
1995
; Felip et al.
1996
; Vrede
1996
,
2005
; Morris and Lewis
1992
; Wang et al.
1992
; Coveney and Wetzel
1995
; Elser et al.
1995
; Cotner
et al.
1997
; Simon and Wünsch
1998
; Caron et al.
2000
; Pomeroy and Wiebe
2001
; Vrede et al.
1999
). Bacteria in temperate lakes are temperature-dependent
up to a certain threshold value, above which other factors regulate their growth
(Ochs et al.
1995
; Felip et al.
1996
). In the mesotrophic Lake Constance it has
been found that during most of the year the bacterial community is well adapted to
in situ temperatures (ranging from 4 to 23 ºC) in the upper water column, whilst in
the deeper strata the bacterial growth is limited by temperature (ranging between 4
and 10 ºC) (Simon and Wünsch
1998
). The growth of bacteria that live at low tem-
peratures is stimulated both by increases in temperature and by addition of organic
substrates (Pomeroy et al.
1991
). Bacterioplankton growth can be limited by inor-
ganic nutrients, by phosphorus (P) and by organic carbon (C), and the limitation
effect is observed either for each constituent alone or for variable constituent com-
binations in both freshwater and marine systems (Vrede
1996
,
2005
; Morris and
Lewis
1992
; Wang et al.
1992
; Elser et al.
1995
; Cotner et al.
1997
; Caron et al.
2000
; Vrede et al.
1999
). Substrate concentrations and temperature intergo very
close interactions, and the interactive effects can vary with the temperature regime
(Pomeroy and Wiebe
2001
). It has been shown that increased temperature can
