Coastal hypoxia and sediment biogeochemistry

Middelburg, Jack J.; Levin, Lisa A.

doi:10.5194/bg-6-1273-2009

Cited by 564 publications

(373 citation statements)

References 205 publications

(272 reference statements)

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“…The optimization minimized the influence of bioturbation, likely a reflection of the negative impact of hypoxia on sediment biota (Diaz and Rosenberg, 1995;Middelburg and Levin, 2009). This result is also consistent with the dominance of bacteria over invertebrates in the sediment community as observed by .…”

Section: Discussionmentioning

confidence: 99%

Parameterization of biogeochemical sediment–water fluxes using in situ measurements and a diagenetic model

et al. 2016

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Abstract. Diagenetic processes are important drivers of water column biogeochemistry in coastal areas. For example, sediment oxygen consumption can be a significant contributor to oxygen depletion in hypoxic systems, and sedimentwater nutrient fluxes support primary productivity in the overlying water column. Moreover, nonlinearities develop between bottom water conditions and sediment-water fluxes due to loss of oxygen-dependent processes in the sediment as oxygen becomes depleted in bottom waters. Yet, sedimentwater fluxes of chemical species are often parameterized crudely in coupled physical-biogeochemical models, using simple linear parameterizations that are only poorly constrained by observations. Diagenetic models that represent sediment biogeochemistry are available, but rarely are coupled to water column biogeochemical models because they are computationally expensive. Here, we apply a method that efficiently parameterizes sediment-water fluxes of oxygen, nitrate and ammonium by combining in situ measurements, a diagenetic model and a parameter optimization method. As a proof of concept, we apply this method to the Louisiana Shelf where high primary production, stimulated by excessive nutrient loads from the Mississippi-Atchafalaya River system, promotes the development of hypoxic bottom waters in summer. The parameterized sediment-water fluxes represent nonlinear feedbacks between water column and sediment processes at low bottom water oxygen concentrations, which may persist for long periods (weeks to months) in hypoxic systems such as the Louisiana Shelf. This method can be applied to other systems and is particularly relevant for shallow coastal and estuarine waters where the interaction between sediment and water column is strong and hypoxia is prone to occur due to land-based nutrient loads.

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Section: Discussionmentioning

confidence: 99%

Parameterization of biogeochemical sediment–water fluxes using in situ measurements and a diagenetic model

et al. 2016

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“…These fjords differ significantly in their physical characteristics (Table 1) and bottom water oxygen conditions. Hypoxic bottom water conditions are recognised as an important factor in C burial and preservation within depositional coastal environments (Middelburg and Levin, 2009;Woulds et al, 2007). However, of these 111 fjords, only Loch Etive's upper basin is known to be permanently hypoxic (Friedrich et al, 2014).…”

Section: Scotland's Fjordsmentioning

confidence: 99%

Scotland's forgotten carbon: a national assessment of mid-latitude fjord sedimentary carbon stocks

et al. 2017

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Abstract. Fjords are recognised as hotspots for the burial and long-term storage of carbon (C) and potentially provide a significant climate regulation service over multiple timescales. Understanding the magnitude of marine sedimentary C stores and the processes which govern their development is fundamental to understanding the role of the coastal ocean in the global C cycle. In this study, we use the mid-latitude fjords of Scotland as a natural laboratory to further develop methods to quantify these marine sedimentary C stores on both the individual fjord and national scale. Targeted geophysical and geochemical analysis has allowed the quantification of sedimentary C stocks for a number of mid-latitude fjords and, coupled with upscaling techniques based on fjord classification, has generated the first full national sedimentary C inventory for a fjordic system. The sediments within these mid-latitude fjords hold 640.7 ± 46 Mt of C split between 295.6±52 and 345.1 ± 39 Mt of organic and inorganic C, respectively. When compared, these marine mid-latitude sedimentary C stores are of similar magnitude to their terrestrial equivalents, with the exception of the Scottish peatlands, which hold significantly more C. However, when areanormalised comparisons are made, these mid-latitude fjords are significantly more effective as C stores than their terrestrial counterparts, including Scottish peatlands. The C held within Scotland's coastal marine sediments has been largely overlooked as a significant component of the nation's natural capital; such coastal C stores are likely to be key to understanding and constraining improved global C budgets. Highlights-Scottish fjords are a more effective store of C than the terrestrial environment.-A total of 640.7 ± 46 Mt of C is stored in the sediment of Scotland's 111 fjords.-An estimated 31 139-40 615 t yr −1 of C is buried in the sediment of Scotland's fjords.-Fjord sediments are potentially the most effective store of C globally.

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“…Upon bottom water deoxygenation, phosphorus (P) is released efficiently to the water column from surface sediments, fueling further primary productivity and dinitrogen (N2) fixation by diazotrophic cyanobacteria, thus triggering a self-sustaining positive feedback mechanism commonly associated with eutrophication (Vahtera et al, 2007). In addition, the ability of benthic ecosystems to remove 10 nitrogen via denitrification and anaerobic ammonium oxidation may be reduced upon repeated or prolonged exposure to bottom water hypoxia (Conley et al, 2009a;Middelburg and Levin, 2009;Carstensen et al, 2014b). Due to these internal feedback mechanisms, recovery from hypoxia is often slow, hampering management of the problem through reductions in external nutrient loading (Vahtera et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

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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Coastal hypoxia and sediment biogeochemistry

Cited by 564 publications

References 205 publications

Parameterization of biogeochemical sediment–water fluxes using in situ measurements and a diagenetic model

Parameterization of biogeochemical sediment–water fluxes using in situ measurements and a diagenetic model

Scotland's forgotten carbon: a national assessment of mid-latitude fjord sedimentary carbon stocks

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

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Coastal hypoxia and sediment biogeochemistry

Cited by 564 publications

References 205 publications

Parameterization of biogeochemical sediment–water fluxes using in situ measurements and a diagenetic model

Parameterization of biogeochemical sediment–water fluxes using in situ measurements and a diagenetic model

Scotland's forgotten carbon: a national assessment of mid-latitude fjord sedimentary carbon stocks

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

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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