Phyto- and Bacterioplankton During Early Spring Conditions in the Baltic Sea and Response to Short-Term Experimental Warming
Laen...
Kuupäev
2018
Kättesaadav alates
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Frontiers
Abstrakt
Predicted increases in sea surface temperatures are expected to shift the balance
between autotrophic production and the heterotrophic degradation of organic matter
toward a more heterotrophic system. For early phytoplankton spring blooms at low water
temperature the impact of rising temperatures has been mainly investigated in mesocosm
experiments, while field observations are scarce. During a Baltic Sea research cruise we
examined early spring bloom conditions, characterized by low temperatures (0–3◦C),
and performed on-board warming experiments to compare the responses of phyto- and
bacterioplankton production to an increase in temperature. In the northern Baltic Sea,
the low phytoplankton biomass indicated pre-bloom conditions. In the southern Baltic
Sea, a diatom-dominated phytoplankton bloom with increased primary production (PP)
occurred. Associated with this bloom were increases in bacterial production (BP) and
bacterial abundance as well as shifts in bacterial community composition toward an
increased proportion of Gammaproteobacteria and Bacteroidetes. However, the low
BP/PP ratios (average: 1.2 ± 0.14%) indicated weak coupling between the bacterial and
phytoplankton communities. Short-term warming (6 h, 1+6◦C) significantly enhanced
PP (mean Q10 1.4) and especially BP (mean Q10 2.3). Hence, the higher water
temperature increased both carbon flow into the bacterial community and bacterial
processing of organic matter, thereby confirming previous experimental studies. By
contrast, BP/PP ratios remained relatively low after warming (average: 1.7 ± 0.5%),
unlike in previous mesocosm experiments performed at comparable temperatures and
with similar plankton communities. Overall, these results imply that bacterial activities are
suppressed during early phytoplankton blooms at low temperatures in the Baltic Sea and
are not substantially altered by short-term warming events.
This work was funded by the German Science Foundation (DFG), grants JU367/7-3 (priority program AQUASHIFT) and JU 367/15-1 to KJ. DH was supported by the grant MOBTT24 (Estonian Research Council, and European Union).
This work was funded by the German Science Foundation (DFG), grants JU367/7-3 (priority program AQUASHIFT) and JU 367/15-1 to KJ. DH was supported by the grant MOBTT24 (Estonian Research Council, and European Union).
Kirjeldus
Märksõnad
phytoplankton spring bloom, bacteria, primary production, bacterial production, temperature, global warming, Baltic Sea, bacterial community composition, articles