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Biogeochemical and environmental drivers of coastal hypoxia

Caballero-Alfonso, Angela LU ; Carstensen, Jacob and Conley, Daniel LU (2015) In Journal of Marine Systems 141. p.190-199
Abstract
Recent reports have demonstrated that hypoxia is widespread in the coastal zone of the Baltic Sea. Here we evaluate the long-term trends of dissolved oxygen in bottom waters and of the drivers of coastal hypoxia. Eleven of the 33 sites evaluated had increasing trends of bottom water dissolved oxygen, but only the Stockholm Archipelago presents a consistent positive increasing trend in time. The vast majority of sites continue to worsen, especially along the Danish and Finnish coasts, in spite of remediation efforts to reduce nutrients. Surface temperatures were relatively comparable across the entire coastal Baltic Sea, whereas bottom water temperatures varied more strongly among sites, most likely due to differences in mixing (or... (More)
Recent reports have demonstrated that hypoxia is widespread in the coastal zone of the Baltic Sea. Here we evaluate the long-term trends of dissolved oxygen in bottom waters and of the drivers of coastal hypoxia. Eleven of the 33 sites evaluated had increasing trends of bottom water dissolved oxygen, but only the Stockholm Archipelago presents a consistent positive increasing trend in time. The vast majority of sites continue to worsen, especially along the Danish and Finnish coasts, in spite of remediation efforts to reduce nutrients. Surface temperatures were relatively comparable across the entire coastal Baltic Sea, whereas bottom water temperatures varied more strongly among sites, most likely due to differences in mixing (or stratification) and water exchange with the open Baltic Sea. Nutrient concentrations varied by factors 2-3 with highest levels at sites with restricted water exchange and higher land based nutrient loading. None of the sites were permanently stratified during the summer seasonal window although most of the sites were stratified more than half of the time. The frequency of hypoxia was also quite variable with sites in Gulf of Bothnia almost never experiencing hypoxia to enclosed sites with more than 50% chance of hypoxia. There are many factors governing hypoxia and the complexity of interacting processes in the coastal zone makes it difficult to identify specific causes. Our results demonstrate that managing nutrients can create positive feedbacks for oxygen recovery to occur. In the absence of nutrient reductions, the recovery from hypoxia in coastal marine ecosystems is unlikely. (C) 2014 The Authors. Published by Elsevier B.V. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Hypoxia, Coastal zone, Baltic Sea, Nutrients
in
Journal of Marine Systems
volume
141
pages
190 - 199
publisher
Elsevier
external identifiers
  • wos:000347868800018
  • scopus:84921323711
  • scopus:85027942874
ISSN
0924-7963
DOI
10.1016/j.jmarsys.2014.04.008
language
English
LU publication?
yes
id
92c49e21-4e80-4fce-8718-7efc9f8d7d50 (old id 5070028)
date added to LUP
2015-02-25 15:44:17
date last changed
2017-11-19 03:56:15
@article{92c49e21-4e80-4fce-8718-7efc9f8d7d50,
  abstract     = {Recent reports have demonstrated that hypoxia is widespread in the coastal zone of the Baltic Sea. Here we evaluate the long-term trends of dissolved oxygen in bottom waters and of the drivers of coastal hypoxia. Eleven of the 33 sites evaluated had increasing trends of bottom water dissolved oxygen, but only the Stockholm Archipelago presents a consistent positive increasing trend in time. The vast majority of sites continue to worsen, especially along the Danish and Finnish coasts, in spite of remediation efforts to reduce nutrients. Surface temperatures were relatively comparable across the entire coastal Baltic Sea, whereas bottom water temperatures varied more strongly among sites, most likely due to differences in mixing (or stratification) and water exchange with the open Baltic Sea. Nutrient concentrations varied by factors 2-3 with highest levels at sites with restricted water exchange and higher land based nutrient loading. None of the sites were permanently stratified during the summer seasonal window although most of the sites were stratified more than half of the time. The frequency of hypoxia was also quite variable with sites in Gulf of Bothnia almost never experiencing hypoxia to enclosed sites with more than 50% chance of hypoxia. There are many factors governing hypoxia and the complexity of interacting processes in the coastal zone makes it difficult to identify specific causes. Our results demonstrate that managing nutrients can create positive feedbacks for oxygen recovery to occur. In the absence of nutrient reductions, the recovery from hypoxia in coastal marine ecosystems is unlikely. (C) 2014 The Authors. Published by Elsevier B.V.},
  author       = {Caballero-Alfonso, Angela and Carstensen, Jacob and Conley, Daniel},
  issn         = {0924-7963},
  keyword      = {Hypoxia,Coastal zone,Baltic Sea,Nutrients},
  language     = {eng},
  pages        = {190--199},
  publisher    = {Elsevier},
  series       = {Journal of Marine Systems},
  title        = {Biogeochemical and environmental drivers of coastal hypoxia},
  url          = {http://dx.doi.org/10.1016/j.jmarsys.2014.04.008},
  volume       = {141},
  year         = {2015},
}