Deep-water inflow event increases sedimentary phosphorus release on a multi-year scale

Abstract. Phosphorus fertilisation (eutrophication) is expanding oxygen depletion in coastal systems worldwide. Under low-oxygen bottom water conditions, phosphorus release from the sediment is elevated, which further stimulates primary production. It is commonly assumed that re-oxygenation could break this “vicious cycle” by increasing the sedimentary phosphorus retention. Recently, a deep-water inflow into the Baltic Sea created a natural in situ experiment that allowed us to investigate if temporary re-oxygenation stimulates sedimentary retention of dissolved inorganic phosphorus (DIP). Surprisingly, during this 3-year study, we observed a transient but considerable increase, rather than a decrease, in the sediment efflux of DIP and other dissolved biogenic compounds. This suggested that the oxygenated inflow elevated the organic matter degradation in the sediment, likely due to an increase in organic matter supply to the deeper basins, potentially combined with a transient stimulation of the mineralisation efficiency. As a result, the net sedimentary DIP release per m2 was 56 %–112 % higher over the years following the re-oxygenation than before. In contrast to previous assumptions, our results show that inflows of oxygenated water to anoxic bottom waters can increase the sedimentary phosphorus release.

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Deep-water inflow event increases sedimentary phosphorus release on a multi-year scale

10.5194/bg-2021-5 ◽

2021 ◽

Author(s):

Astrid Hylén ◽

Sebastiaan J. van de Velde ◽

Mikhail Kononets ◽

Mingyue Luo ◽

Elin Almroth-Rosell ◽

...

Keyword(s):

Deep Water ◽

Oxygen Depletion ◽

Inorganic Phosphorus ◽

Phosphorus Release ◽

Water Inflow ◽

Low Oxygen ◽

In Situ Experiment ◽

Inflow Event ◽

Bottom Waters ◽

The Baltic

Abstract. Phosphorus fertilisation (eutrophication) is expanding oxygen depletion in coastal systems worldwide. Under low-oxygen bottom-water conditions, phosphorus release from the sediment is elevated which further stimulates primary production. It is commonly assumed that re-oxygenation could break this ‘vicious cycle’ by increasing sedimentary phosphorus retention. Recently, a deep-water inflow into the Baltic Sea created a natural in-situ experiment that allowed us to investigate if temporary re-oxygenation stimulates sedimentary retention of dissolved inorganic phosphorus (DIP). Surprisingly, during this three-year-long study, we observed a transient but considerable increase, rather than a decrease, in the sediment efflux of DIP and other dissolved biogenic compounds. This suggested that the oxygenated inflow elevated the organic matter degradation in the sediment. As a result, the net sedimentary DIP release per m2 was 35–70 % higher over the years following the re-oxygenation than before. In contrast to previous assumptions, our results show that inflows of oxygenated water to anoxic bottom waters can increase the sedimentary phosphorus release.

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Origin and assessment of deep groundwater inflow in the Ca' Lita landslide using hydrochemistry and in situ monitoring

Hydrology and Earth System Sciences ◽

10.5194/hess-16-4205-2012 ◽

2012 ◽

Vol 16 (11) ◽

pp. 4205-4221 ◽

Cited By ~ 18

Author(s):

F. Cervi ◽

F. Ronchetti ◽

G. Martinelli ◽

T. A. Bogaard ◽

A. Corsini

Keyword(s):

Groundwater Flow ◽

Deep Water ◽

Major Ions ◽

Pore Water Pressure ◽

Water Pressure ◽

Slope Instability ◽

In Situ Monitoring ◽

Water Inflow ◽

Groundwater Levels

Abstract. Changes in soil water content, groundwater flow and a rise in pore water pressure are well-known causal or triggering factors for hillslope instability. Rainfall and snowmelt are generally assumed as the main sources of groundwater recharge. This assumption neglects the role of deep water inflow in highly tectonized areas, a factor that can influence long-term pore-pressure regimes and play a role on local slope instability. This paper aims to assess the origin of groundwater in the Ca' Lita landslide (northern Italian Apennines) and to qualify and quantify the aliquot attributable to deep water inflow. The research is essentially based on in situ monitoring and hydrochemical analyses. It involved 5 yr of continuous monitoring of groundwater levels, electrical conductivity and temperature and with groundwater sampling followed by determination of major ions (Na+, K+, Mg2+, Ca2+, Cl−, HCO3−, SO42−), tracers (such as Btot and Sr2+), and isotopes (δ18O, δ2H and 3H). Leaching experiments on soil samples, hydrochemical modelling and water recharge estimation were also carried out. Results show that the groundwater balance in the Ca' Lita landslide must take into account an inflow of deep and highly mineralised Na-SO4 water (more than 9500 μS cm−1) with non-negligible amounts of Cl− (up to 800 mg l−1). The chemical and isotopic fingerprint of this water points to oilfield water hosted at large depths in the Apennine chain and that uprises through a regional fault line crossing the landslide area. It recharges the aquifer hosted in the bedrock underlying the sliding surface (at a rate of about 49 000–85 700 m3 yr−1) and it also partly recharges the landslide body. In both the aquifers, the hydrochemical imprint of deep water mixed with rainfall and snowmelt water was observed. This indicates a probable influence of deep water inflow on the mobility of the Ca' Lita landslide, a finding that could be applicable to other large landslides occurring in highly tectonized areas in the northern Apennines or in other mountain chains. The paper demonstrates that hydrochemistry should, therefore, be considered as a valuable investigation method to define hydrogeological limits and the groundwater sources in hillslope and to assess groundwater flow patterns in deep-seated landslides.

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A note on the deep-water inflow to the Bothnian Sea

Journal of Marine Systems ◽

10.1016/j.jmarsys.2006.12.004 ◽

2007 ◽

Vol 68 (1-2) ◽

pp. 255-264 ◽

Cited By ~ 8

Author(s):

Riikka Hietala ◽

Peter Lundberg ◽

Jenny A.U. Nilsson

Keyword(s):

Deep Water ◽

Water Inflow ◽

Bothnian Sea

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Temporal variability of the Circumpolar Deep Water inflow onto the Ross Sea continental shelf

Journal of Marine Systems ◽

10.1016/j.jmarsys.2016.05.006 ◽

2017 ◽

Vol 166 ◽

pp. 37-49 ◽

Cited By ~ 14

Author(s):

Pasquale Castagno ◽

Pierpaolo Falco ◽

Michael S. Dinniman ◽

Giancarlo Spezie ◽

Giorgio Budillon

Keyword(s):

Continental Shelf ◽

Deep Water ◽

Temporal Variability ◽

Ross Sea ◽

Water Inflow ◽

Circumpolar Deep Water

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Evidence of deep-water inflow in a tectonic window of the northern Apennines (Italy)

Environmental Earth Sciences ◽

10.1007/s12665-014-3149-1 ◽

2014 ◽

Vol 72 (7) ◽

pp. 2389-2409 ◽

Cited By ~ 7

Author(s):

F. Cervi ◽

L. Borgatti ◽

G. Martinelli ◽

F. Ronchetti

Keyword(s):

Deep Water ◽

Northern Apennines ◽

Water Inflow ◽

Tectonic Window

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Origin and assessment of deep groundwater inflow in the Ca' Lita landslide using hydrochemistry and in situ monitoring

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-9-7699-2012 ◽

2012 ◽

Vol 9 (6) ◽

pp. 7699-7738

Author(s):

F. Cervi ◽

F. Ronchetti ◽

G. Martinelli ◽

T. A. Bogaard ◽

A. Corsini

Keyword(s):

Deep Water ◽

Major Ions ◽

Pore Water Pressure ◽

Water Pressure ◽

Slope Instability ◽

In Situ Monitoring ◽

Water Inflow ◽

Groundwater Levels ◽

Italian Apennines

Abstract. Changes in soil water content, groundwater flow and a rise in pore water pressure are well-known causal or triggering factors for hillslope instability. Rainfall and snowmelt are generally assumed as the only sources of groundwater recharge. This assumption neglects the role of deep water inflow in highly tectonized areas, a factor that can influence long-term pore-pressure regimes and play a role on local slope instability. This paper aims to assess the origin of groundwater in the Ca' Lita landslide (northern Italian Apennines) and to qualify and quantify the aliquot attributable to deep water inflow. The research is essentially based on in situ monitoring and hydrochemical analyses. It involved 5 yr of continuous monitoring of groundwater levels, electrical conductivity and temperature, and with groundwater sampling followed by determination of major ions, tracers (such as Boron and Strontium), and isotopes (Oxygen, Deuterium, Tritium). Leaching experiments on soil samples and water recharge estimation were also carried out. Results show that the groundwater balance in the Ca' Lita landslide must take into account an inflow of highly mineralized Na-SO4 water (more than 9500 μS cm−1) with non-negligible amounts of Chloride (up to 800 mg l−1). The deep water inflow recharges the aquifer hosted in the bedrock underlying the sliding surface (at a rate of about 7800–17 500 m3 yr−1). It also partly recharges the landslide body, where the hydrochemical imprint of deep water mixed with rainfall and snowmelt water was observed. This points to a probable influence of deep water inflow on the mobility of the Ca' Lita landslide, a finding that could be applicable to other large landslides occurring in highly tectonized areas in the northern Apennines or in other mountain chains.

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Benthic foraminiferal zonation in deep-water carbonate platform margin environments, northern Little Bahama Bank

Journal of Paleontology ◽

10.1017/s0022336000058819 ◽

1988 ◽

Vol 62 (01) ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

Ronald E. Martin

Keyword(s):

Deep Water ◽

Benthic Foraminifera ◽

Carbonate Platform ◽

Sedimentary Facies ◽

Depositional Environments ◽

Near Surface ◽

Sediment Gravity Flows ◽

Gravity Flows ◽

Platform Margin ◽

Water Carbonate

The utility of benthic foraminifera in bathymetric interpretation of clastic depositional environments is well established. In contrast, bathymetric distribution of benthic foraminifera in deep-water carbonate environments has been largely neglected. Approximately 260 species and morphotypes of benthic foraminifera were identified from 12 piston core tops and grab samples collected along two traverses 25 km apart across the northern windward margin of Little Bahama Bank at depths of 275-1,135 m. Certain species and operational taxonomic groups of benthic foraminifera correspond to major near-surface sedimentary facies of the windward margin of Little Bahama Bank and serve as reliable depth indicators. Globocassidulina subglobosa, Cibicides rugosus, and Cibicides wuellerstorfi are all reliable depth indicators, being most abundant at depths >1,000 m, and are found in lower slope periplatform aprons, which are primarily comprised of sediment gravity flows. Reef-dwelling peneroplids and soritids (suborder Miliolina) and rotaliines (suborder Rotaliina) are most abundant at depths <300 m, reflecting downslope bottom transport in proximity to bank-margin reefs. Small miliolines, rosalinids, and discorbids are abundant in periplatform ooze at depths <300 m and are winnowed from the carbonate platform. Increased variation in assemblage diversity below 900 m reflects mixing of shallow- and deep-water species by sediment gravity flows.

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