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| Titel |
Impact of change in climate and policy from 1988 to 2007 on environmental and microbial variables at the time series station Boknis Eck, Baltic Sea |
| VerfasserIn |
H.-G. Hoppe, H. C. Giesenhagen, R. Koppe, H.-P. Hansen, K. Gocke |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 7 ; Nr. 10, no. 7 (2013-07-04), S.4529-4546 |
| Datensatznummer |
250018328
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| Publikation (Nr.) |
 copernicus.org/bg-10-4529-2013.pdf |
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| Zusammenfassung |
| Phytoplankton and bacteria are sensitive indicators of environmental
change. The temporal development of these key organisms was
monitored from 1988 to the end of 2007 at the time series station
Boknis Eck in the western Baltic Sea. This period was characterized
by the adaption of the Baltic Sea ecosystem to changes in the
environmental conditions caused by the conversion of
the political system in the southern and eastern border states,
accompanied by the general effects of global climate
change. Measured variables were chlorophyll, primary production,
bacteria number, -biomass and -production, glucose turnover rate,
macro-nutrients, pH, temperature and salinity. Negative trends with
time were recorded for chlorophyll, bacteria number, bacterial
biomass and bacterial production, nitrate, ammonia, phosphate, silicate, oxygen and
salinity while temperature, pH, and the ratio between bacteria
numbers and chlorophyll increased. Strongest reductions with
time occurred for the annual maximum values, e.g. for chlorophyll
during the spring bloom or for nitrate during winter, while the
annual minimum values remained more stable. In deep water above sediment
the negative trends of oxygen, nitrate, phosphate and bacterial
variables as well as the positive trend of temperature were similar
to those in the surface while the trends of salinity, ammonia and
silicate were opposite to those in the surface. Decreasing oxygen,
even in the surface layer, was of particular interest because it
suggested enhanced recycling of nutrients from the deep hypoxic
zones to the surface by vertical mixing. The long-term seasonal
patterns of all variables correlated positively with temperature, except chlorophyll
and salinity. Salinity correlated negatively with all bacterial
variables (as well as precipitation) and positively with
chlorophyll. Surprisingly, bacterial variables did not correlate
with chlorophyll, which may be inherent with the time lag between the
peaks of phytoplankton and bacteria during spring. Compared to the
20-yr averages of the environmental and microbial variables, the
strongest negative deviations of corresponding annual averages were
measured about ten years after political change for nitrate and bacterial
secondary production (~ −60%),
followed by chlorophyll (−50%) and bacterial
biomass (−40%). Considering the circulation of surface
currents in the Baltic Sea we interpret the observed patterns of the microbial variables at
the Boknis Eck time series station as a consequence of the improved management
of water resources after 1989 and – to a minor extent – the
trends of the climate variables salinity and temperature. |
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