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Hypoxia and cyanobacteria blooms - are they really natural features of the late Holocene history of the Baltic Sea?

Zillén, Lovisa LU and Conley, Daniel LU (2010) In Biogeosciences 7(8). p.2567-2580
Abstract
During the last century (1900s) industrialized forms of agriculture and human activities have caused eutrophication of Baltic Sea waters. As a consequence, the hypoxic zone in the Baltic Sea has increased, especially during the last 50 years, and has caused severe ecosystem disturbance. Climate forcing has been proposed to be responsible for the reported trends in hypoxia (< 2 mg/l O-2) both during the last c. 100 years (since c. 1900 AD) and the Medieval Period. By contrast, investigations of the degree of anthropogenic forcing on the ecosystem on long time-scales (millennial and greater) have not been thoroughly addressed. This paper examines evidence for anthropogenic disturbance of the marine environment beyond the last century... (More)
During the last century (1900s) industrialized forms of agriculture and human activities have caused eutrophication of Baltic Sea waters. As a consequence, the hypoxic zone in the Baltic Sea has increased, especially during the last 50 years, and has caused severe ecosystem disturbance. Climate forcing has been proposed to be responsible for the reported trends in hypoxia (< 2 mg/l O-2) both during the last c. 100 years (since c. 1900 AD) and the Medieval Period. By contrast, investigations of the degree of anthropogenic forcing on the ecosystem on long time-scales (millennial and greater) have not been thoroughly addressed. This paper examines evidence for anthropogenic disturbance of the marine environment beyond the last century through the analysis of the human population growth, technological development and land-use changes in the drainage area. Natural environmental changes, i.e. changes in the morphology and depths of the Baltic basin and the sills, were probably the main driver for large-scale hypoxia during the early Holocene (8000-4000 cal yr BP). We show that hypoxia during the last two millennia has followed the general expansion and contraction trends in Europe and that human perturbation has been an important driver for hypoxia during that time. Hypoxia occurring during the Medieval Period coincides with a doubling of the population (from c. 4.6 to 9.5 million) in the Baltic Sea watershed, a massive reclamation of land in both established and marginal cultivated areas and significant increases in soil nutrient release. The role of climate forcing on hypoxia in the Baltic Sea has yet to be demonstrated convincingly, although it could have helped to sustain hypoxia through enhanced salt water inflows or through changes in hydrological inputs. In addition, cyanobacteria blooms are not natural features of the Baltic Sea as previously deduced, but are a consequence of enhanced phosphorus release from the seabed that occurs during hypoxia. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Biogeosciences
volume
7
issue
8
pages
2567 - 2580
publisher
Copernicus Publications
external identifiers
  • wos:000281431800019
  • scopus:77956291786
ISSN
1726-4189
DOI
10.5194/bg-7-2567-2010
project
BECC
language
English
LU publication?
yes
id
c339be2b-12a2-454d-8a47-ba945e463014 (old id 1672480)
date added to LUP
2010-09-23 14:07:06
date last changed
2018-05-29 10:49:58
@article{c339be2b-12a2-454d-8a47-ba945e463014,
  abstract     = {During the last century (1900s) industrialized forms of agriculture and human activities have caused eutrophication of Baltic Sea waters. As a consequence, the hypoxic zone in the Baltic Sea has increased, especially during the last 50 years, and has caused severe ecosystem disturbance. Climate forcing has been proposed to be responsible for the reported trends in hypoxia (&lt; 2 mg/l O-2) both during the last c. 100 years (since c. 1900 AD) and the Medieval Period. By contrast, investigations of the degree of anthropogenic forcing on the ecosystem on long time-scales (millennial and greater) have not been thoroughly addressed. This paper examines evidence for anthropogenic disturbance of the marine environment beyond the last century through the analysis of the human population growth, technological development and land-use changes in the drainage area. Natural environmental changes, i.e. changes in the morphology and depths of the Baltic basin and the sills, were probably the main driver for large-scale hypoxia during the early Holocene (8000-4000 cal yr BP). We show that hypoxia during the last two millennia has followed the general expansion and contraction trends in Europe and that human perturbation has been an important driver for hypoxia during that time. Hypoxia occurring during the Medieval Period coincides with a doubling of the population (from c. 4.6 to 9.5 million) in the Baltic Sea watershed, a massive reclamation of land in both established and marginal cultivated areas and significant increases in soil nutrient release. The role of climate forcing on hypoxia in the Baltic Sea has yet to be demonstrated convincingly, although it could have helped to sustain hypoxia through enhanced salt water inflows or through changes in hydrological inputs. In addition, cyanobacteria blooms are not natural features of the Baltic Sea as previously deduced, but are a consequence of enhanced phosphorus release from the seabed that occurs during hypoxia.},
  author       = {Zillén, Lovisa and Conley, Daniel},
  issn         = {1726-4189},
  language     = {eng},
  number       = {8},
  pages        = {2567--2580},
  publisher    = {Copernicus Publications},
  series       = {Biogeosciences},
  title        = {Hypoxia and cyanobacteria blooms - are they really natural features of the late Holocene history of the Baltic Sea?},
  url          = {http://dx.doi.org/10.5194/bg-7-2567-2010},
  volume       = {7},
  year         = {2010},
}