Temperature effects on the heterotrophic bacteria, heterotrophic ...

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Aquat Microb Ecol 67: 107–121, 2012
Margalef Index (D)
7
6
5
4
3
2
1
A
In situ
Ambient
Warmer
Shannon Index (H')
2.5
2
1.5
1
0.5
B
0
J F M A M J J A S O N D
Month
0
J F M A M J J A S O N D
Month
2
C
4
3.5
D
Modified Hill's number (F)
1.5
1
0.5
Warmer conditions
3
2.5
2
1.5
1
0.5
0
J F M A M J J A S O N D
Month
0
0 0.5 1 1.5 2 2.5 3 3.5 4
Ambient temperature
Fig. 5. Diversity of microbial top predators. (A) Margalef index of diversity, (B) Shannon index of diversity, and (C) evenness
(modified Hill’s numbers) in situ and after incubation in the ambient and warmer conditions. (D) Estimates of microplankton
top predator diversity (Shannon [d] or Margalef [s] indices) and evenness (modified Hill’s numbers [d]) measured at the
ambient temperature and under the warmer conditions. The dashed line is the 1:1 relationship. Error bars in all panels correspond
to 1 SE
In the present study, the increment of temperature
(near 2.7°C) was accomplished after few hours of incubation
(1°C within day-night periods
are common (Ruíz-González et al. 2012), and a warming
of 4°C has been observed during short periods of
time in the vicinity of the thermal effluents of power
stations in coastal ecosystems (Choi et al. 2002). Thus,
the warming produced in our incubations could be
found under certain natural conditions.
Richness, diversity, and evenness of the microbial
top predators are underestimated compared to the
values measurable with molecular tools (Caron et al.
2012), but the combination of the acidic Lugol fixation
and the Utermöhl technique is an accepted protocol
to study changes in morphospecies within
microplankton assemblages (i.e. Aberle et al. 2007).
Thus, rather than the absolute magnitude of change,
the present study is focused on the influence of the
warming conditions on the relative changes of the
growth and consumption rates of microorganisms
and on the community composition of microbial top
predators.
Function and seasonality of heterotrophic
microplankton
In the Bay of Blanes, experimental warming produced
an increase in biomass and gross production
rates of heterotrophic bacteria. The increases in
gross production rates (~25%) were close to those
measured in the same samples through 3 H-leucine