Sea bottom anoxia in the Archipelago Sea, northern Baltic Sea—Implications for phosphorus remineralization at the sediment surface

Virtasalo, Joonas J.; Kohonen, Tuula; Vuorinen, Ilppo; Huttula, Timo

doi:10.1016/j.margeo.2005.07.010

Cited by 50 publications

(73 citation statements)

References 39 publications

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“…proximity (Virtasalo et al, 2005). Water exchange in the area mostly occurs through deep straits following the fault-lines of the crystalline bedrock, which are mostly aligned in a north-south direction.…”

Section: Study Locationmentioning

confidence: 99%

“…Water exchange in the area mostly occurs through deep straits following the fault-lines of the crystalline bedrock, which are mostly aligned in a north-south direction. In enclosed basins, a strong thermocline impedes mixing of dissolved oxygen to the bottom waters during summer, which together with high delivery of reactive OM to the seafloor commonly results in seasonal hypoxia (Virtasalo et al, 2005;Jokinen et al, 2015). Mixing of the water column through thermal convection takes place in spring and autumn due to the lack of a permanent halocline (Leppäranta and 5 Myrberg, 2009).…”

Section: Study Locationmentioning

confidence: 99%

“…Due to this apparent sensitivity of the basin to bottom water hypoxia, as manifested in the continuous laminations, together with the central location middle of the Archipelago Sea, we expected the site to be representative of the past environmental changes in the area. Importantly, despite the contrasting bottom water oxygenation between adjacent sub-basins in the area (Virtasalo et al, 2005), the long-term trends in environmental conditions are largely congruent over the entire Archipelago Sea, excluding areas close to prominent nutrient point sources (Suomela, 2011). 5…”

Section: Sediment Coring Subsampling and Analysis Of Grain Sizementioning

confidence: 99%

“…Yet, although long-term trends in the expansion of hypoxia in offshore areas of the Baltic Sea have been widely studied, little is known about the past evolution of hypoxia in the shallow 20 coastal areas, where episodic or seasonal oxygen deficiency is forced by thermal rather than salinity stratification (Virtasalo et al, 2005;Conley et al, 2011). Importantly, these coastal areas act as a filter for nutrients received from the catchment .…”

Section: Introductionmentioning

confidence: 99%

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A 1500-year multiproxy record of coastal hypoxia from the northern Baltic Sea indicates unprecedented deoxygenation over the 20<sup>th</sup> century

Jokinen¹,

Virtasalo²,

Jilbert³

et al. 2018

Preprint

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Abstract. The anthropogenically forced expansion of coastal hypoxia is a major environmental problem affecting coastal ecosystems and biogeochemical cycles throughout the world. The Baltic Sea is a semi-enclosed shelf sea whose central deep basins have been highly prone to deoxygenation during its Holocene history, as shown previously by numerous paleoenvironmental studies. However, long-term data on past fluctuations in the intensity of hypoxia in the coastal zone of the Baltic Sea are largely lacking, despite the significant role of these areas in retaining nutrients derived from the catchment.Here 5 we present a 1500-year multiproxy record of near-bottom water redox changes from the coastal zone of the northern Baltic Sea, encompassing the climatic phases of the Medieval Climate Anomaly (MCA), the Little Ice Age (LIA), and the Modern Warm Period (MoWP). Our reconstruction shows that although multicentennial climate variability has modulated depositional conditions and delivery of organic matter (OM) to the basin the modern aggravation of coastal hypoxia is unprecedented, and besides gradual changes in the basin configuration, it must have been forced by excess human-induced nutrient loading. The 10 progressive deoxygenation since the beginning of 1900s was originally triggered by the combined effects of gradual shoaling of the basin and warming climate, which amplified sediment focusing and increased the vulnerability to hypoxia. Importantly, the anthropogenic eutrophication of coastal waters in our study area began decades earlier than previously thought, leading to a marked aggravation of hypoxia in the 1950s through fueling primary productivity, while we find no evidence of anthropogenic forcing during the MCA. These results have implications for the assessment of reference conditions for coastal 15 water quality. Furthermore, this study highlights the need for combined use of sedimentological, ichnological, and geochemical proxies in order to robustly reconstruct subtle redox shifts especially in dynamic, non-euxinic coastal settings with strong seasonal contrasts in the bottom water quality. 25Biogeosciences Discuss., https://doi

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Section: Study Locationmentioning

confidence: 99%

Section: Study Locationmentioning

confidence: 99%

Section: Sediment Coring Subsampling and Analysis Of Grain Sizementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A 1500-year multiproxy record of coastal hypoxia from the northern Baltic Sea indicates unprecedented deoxygenation over the 20<sup>th</sup> century

Jokinen¹,

Virtasalo²,

Jilbert³

et al. 2018

Preprint

Self Cite

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“…marine sediments rich in phosphorus (P) compounds that are deposited in hypoxic/anoxic zones. The release of phosphates from sediments may intensify the primary production, especially in oligotrophic and Plimited waters, while changes in the relative proportions of the dissolved nutrients may modify the species composition of algal blooms (Koop et al 1990;Conley et al 1997;Conley et al 2002;Friedrich et al 2002;Denis, Grenz 2003;Virtasalo et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Phosphate exchange across the sediment-water interface under oxic and hypoxic/anoxic conditions in the southern Baltic Sea

Łukawska‐Matuszewska

Burska

2011

Oceanological and Hydrobiological Studies

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Benthic fluxes of phosphate and phosphorus distribution in sediments from the southern Baltic Sea were investigated in spring and autumn in 2005 and 2007-2010. Strong spatial variability of phosphate fluxes was observed across the sediment-water interface. The highest values of phosphate flux from sediment (up to 37 μmol m −2 h −1 ), resulting from the high mineralization rate of organic matter and rapid phosphorus turnover due to macrofaunal activity and hydrodynamic conditions, were observed in the shallow area at depths ranging from 50 to 69 m. The rate of phosphate exchange in the transportation and accumulation bottom area with the water depth ≥72 m was several times lower (2.12 -6.22 μmol m −2 h −1 ). In continuously hypoxic or anoxic sediments, phosphorus was preserved in the refractory organic form, and sediments were depleted of redox-dependent phosphorus forms. In shallow area with well oxygenated near-bottom water, phosphorus was present mainly in the calcium-bound form.

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Particulate organic carbon (POC) in surface sediments of the Baltic Sea

et al. 2010

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Sea bottom anoxia in the Archipelago Sea, northern Baltic Sea—Implications for phosphorus remineralization at the sediment surface

Cited by 50 publications

References 39 publications

A 1500-year multiproxy record of coastal hypoxia from the northern Baltic Sea indicates unprecedented deoxygenation over the 20<sup>th</sup> century

A 1500-year multiproxy record of coastal hypoxia from the northern Baltic Sea indicates unprecedented deoxygenation over the 20<sup>th</sup> century

Phosphate exchange across the sediment-water interface under oxic and hypoxic/anoxic conditions in the southern Baltic Sea

Particulate organic carbon (POC) in surface sediments of the Baltic Sea

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Sea bottom anoxia in the Archipelago Sea, northern Baltic Sea—Implications for phosphorus remineralization at the sediment surface

Cited by 50 publications

References 39 publications

A 1500-year multiproxy record of coastal hypoxia from the northern Baltic Sea indicates unprecedented deoxygenation over the 20&lt;sup&gt;th&lt;/sup&gt; century

A 1500-year multiproxy record of coastal hypoxia from the northern Baltic Sea indicates unprecedented deoxygenation over the 20&lt;sup&gt;th&lt;/sup&gt; century

Phosphate exchange across the sediment-water interface under oxic and hypoxic/anoxic conditions in the southern Baltic Sea

Particulate organic carbon (POC) in surface sediments of the Baltic Sea

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Product

Resources

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A 1500-year multiproxy record of coastal hypoxia from the northern Baltic Sea indicates unprecedented deoxygenation over the 20<sup>th</sup> century

A 1500-year multiproxy record of coastal hypoxia from the northern Baltic Sea indicates unprecedented deoxygenation over the 20<sup>th</sup> century