scholarly journals Mg/Ca and Mn/Ca ratios in benthic foraminifera: the potential to reconstruct past variations in temperature and hypoxia in shelf regions

2013 ◽  
Vol 10 (7) ◽  
pp. 5125-5138 ◽  
Author(s):  
J. Groeneveld ◽  
H. L. Filipsson
Keyword(s):  
Dissolved Oxygen ◽  
Trace Metal ◽  
Benthic Foraminifera ◽  
Bottom Water ◽  
Oxygen Depletion ◽  
Open Ocean ◽  
Low Oxygen ◽  
Saturation State ◽  
Bottom Water Temperature ◽  
Fish And Shellfish

Abstract. Shelf and coastal regions are exceptionally important for many countries as they provide the main habitat for many economically important fish and shellfish species. With ongoing climate change and human-induced eutrophication the shelf regions are especially affected, resulting in increased temperatures and stratification as well as oxygen depletion of the bottom waters. In order to be able to predict the magnitude of these changes in the future, it is necessary to study how they varied in the past. Commonly used foraminiferal climate and environmental proxies, e.g., stable isotopes and trace metal/Ca ratios, that are applied in open-ocean settings are not necessarily applicable in shelf regions, either as faunas are significantly different or as conditions can change much faster compared to the open ocean. In this study we explore the use of Mg/Ca as paleothermometer and Mn/Ca as a potential proxy for changing dissolved oxygen conditions in bottom water on the benthic foraminifera Bulimina marginata and Globobulimina turgida. Living specimens were collected from the Skagerrak and the Gullmar Fjord (SW Sweden); the latter is hypoxic for several months a year. As the specimens were alive when collected, we assume it unlikely that any diagenetic coatings have already significantly affected the trace metal/Ca ratios. The Mg/Ca ratios are similar to previously published values but display much larger variation than would be expected from the annual temperature change of less than 2 °C. An additional impact of the difference in the calcite saturation state between the Skagerrak and the Gullmar Fjord could explain the results. Mn/Ca ratios from G. turgida can potentially be related to variations in dissolved oxygen of the habitat where the foraminifera calcify. Samples from the Skagerrak display increased Mn/Ca in specimens that lived deeper in the sediment than those that lived near the surface. G. turgida samples from the low-oxygen Gullmar Fjord showed significantly increased Mn/Ca, being highest when bottom water dissolved oxygen was at a minimum. Our study suggests that trace metal/Ca ratios in benthic foraminifera from shelf regions have the potential to record past variations in bottom water temperature and dissolved oxygen concentrations, but an additional impact of the inorganic carbonate chemistry cannot be excluded.

scholarly journals Trace metal/Ca ratios in benthic foraminifera: the potential to reconstruct past variations in temperature and hypoxia in shelf regions

2013 ◽  
Vol 10 (3) ◽  
pp. 4403-4438
Author(s):  
J. Groeneveld ◽  
H. L. Filipsson
Keyword(s):  
Dissolved Oxygen ◽  
Trace Metal ◽  
Benthic Foraminifera ◽  
Oxygen Depletion ◽  
Open Ocean ◽  
Care Needs ◽  
Saturation State ◽  
Bottom Water Temperature ◽  
The Difference ◽  
Fish And Shellfish

Abstract. Shelf and coastal regions are exceptionally important for many countries as they provide the main habitat for many economically important fish and shellfish species. With ongoing global warming and human-induced eutrophication the shelf regions are especially affected, resulting in increased temperatures and stratification as well as oxygen depletion of the bottom waters. In order to be able to predict the magnitude of these changes in the future it is necessary to study how they varied in the past. Commonly used foraminiferal climate and environmental proxies, e.g. stable isotopes and trace metal/Ca ratios, which are applied in open-ocean settings are not necessarily applicable in shelf regions, either as faunas are completely different or as conditions change a-typical compared to the open-ocean. In this study we explore the use of Mg/Ca as paleothermometer and Mn/Ca as a potential proxy for changing dissolved oxygen conditions on the benthic foraminifera Bulimina marginata and Globobulimina turgida. Living specimens were collected from the Skagerrak and the Gullmar Fjord (SW-Sweden); the latter is hypoxic for several months a year. As the specimens were alive when collected it can be excluded that any diagenetic coatings have affected the trace metal/Ca ratios. The Mg/Ca ratios are similar to previously published values from the literature but display much larger variation than would be expected from the annual temperature change of less than 2 °C. An additional impact of the difference in the carbonate ion saturation state between the Skagerrak and the Gullmar Fjord could explain the results. Mn/Ca ratios on Globobulimina turgida potentially record variations in dissolved oxygen of the habitat where the foraminifera calcify. Samples from the Skagerrak display increased Mn/Ca in specimens which lived deeper in the sediment than those that lived near the surface. Globobulimina turgida samples from the lower oxygen Gullmar Fjord showed significantly increased Mn/Ca, being highest when dissolved oxygen was at a minimum. Our study suggests that trace metal/Ca ratios in benthic foraminifera from shelf regions have the potential to record past variations in bottom water temperature and dissolved oxygen concentrations but care needs to be taken to constrain the carbonate system.

scholarly journals Exploring the controls on element ratios in middle Eocene samples of the benthic foraminifera <i>Oridorsalis umbonatus</i>

2012 ◽  
Vol 8 (6) ◽  
pp. 1957-1971 ◽  
Author(s):  
C. F. Dawber ◽  
A. K. Tripati
Keyword(s):  
Benthic Foraminifera ◽  
Bottom Water ◽  
Middle Eocene ◽  
Environmental Parameters ◽  
Intermediate Water ◽  
Saturation State ◽  
Bottom Water Temperature ◽  
Elemental Ratios ◽  
Elemental Ratio ◽  
Element Ratios

Abstract. Culturing studies and empirically based core top calibrations have been used to infer that elemental ratios in benthic foraminifera can be used as proxies to reconstruct past variations in bottom water temperature and saturation state (Δ [CO32−]). However the mechanisms linking elemental ratios to these parameters are poorly constrained. Here, we explore the environmental parameters influencing the incorporation of B, Li, Sr and Mg in Oridorsalis umbonatus in early Cenozoic sediments from Ocean Drilling Program Site 1209. We investigate the influence of middle Eocene variations in intermediate water Δ [CO32−] using relationships developed from core top samples. The fidelity of bottom water Δ[CO32−] reconstructions based on single element ratios is assessed by comparing the X/Ca-based reconstructions to each other and to carbon cycle proxy records (benthic foraminifera δ13C, organic carbon content, foraminifera dissolution indices), and a seawater δ18O reconstruction for Site 1209. Discrepancies in the reconstructed Δ[CO32−] values based on these different metal ratios suggest that there are still gaps in our understanding of the parameters influencing X/Ca and demonstrate that caution is required when interpreting palaeo-reconstructions that are derived from a single elemental ratio. The downcore record of O. umbonatus Mg/Ca does not exhibit any similarities with the Li/Ca, B/Ca and Sr/Ca records, suggesting that the environmental parameters influencing Mg/Ca may be different for this species, consistent with temperature as the strongest control on this elemental ratio. This hypothesis is supported by the coefficients of multiple linear regression models on published Mg/Ca data. An incomplete understanding of the controls on elemental incorporation into benthic foraminifera hinders our ability to confidently quantify changes in saturation state using single X/Ca reconstructions over a range of timescales.

scholarly journals Element/Calcium ratios in middle Eocene samples of <i>Oridorsalis umbonatus</i> from Ocean Drilling Program Site 1209

2011 ◽  
Vol 7 (6) ◽  
pp. 3795-3821 ◽  
Author(s):  
C. F. Dawber ◽  
A. K. Tripati
Keyword(s):  
Benthic Foraminifera ◽  
Bottom Water ◽  
Middle Eocene ◽  
Single Element ◽  
Intermediate Water ◽  
Ocean Drilling Program ◽  
Saturation State ◽  
Bottom Water Temperature ◽  
Elemental Ratios ◽  
Ocean Drilling

Abstract. Culturing studies and empirical-based calibrations suggest that elemental ratios in benthic foraminifera can be used as proxies to reconstruct past variations in bottom water temperature and saturation state (Δ[CO32−]). However the mechanism(s) linking elemental ratios to Δ[CO32−] are poorly constrained. We present middle Eocene records of Oridorsalis umbonatus Li/Ca, B/Ca, Mg/Ca and Sr/Ca from Ocean Drilling Program Site 1209. We apply calibrations developed from core top samples to estimate middle Eocene variations in intermediate water Δ[CO32−]. The fidelity of bottom water Δ[CO32−] reconstructions based on single element ratios are assessed by comparing the X/Ca-based reconstructions to each other and to carbon cycle proxy records (benthic foraminifera δ13C, organic carbon content, foraminifera dissolution indices), and a seawater δ18O reconstruction for Site 1209. Discrepancies in the reconstructed Δ[CO32−] values for the middle Eocene based on these different metal ratios suggests that there are still gaps in our understanding of the parameters influencing X/Ca. The downcore record of O. umbonatus Mg/Ca does not exhibit any similarities with the Li/Ca, B/Ca and Sr/Ca records, suggesting that bottom water Δ[CO32−] is not the dominant influence on Mg/Ca ratios for this species. This hypothesis is supported by the coefficients of multiple linear regression models on new and published Mg/Ca data.

scholarly journals The Relationship between Mollusks and Oxygen Concentrations in Todos Santos Bay, Baja California, Mexico

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
J. Gabriel Kuk-Dzul ◽  
Victoria Díaz-Castañeda
Keyword(s):  
Organic Matter ◽  
Dissolved Oxygen ◽  
Bottom Water ◽  
Organic Matter Content ◽  
Oxygen Depletion ◽  
Matter Content ◽  
The Other ◽  
Natural Conditions ◽  
The Relationship ◽  
Oxygen Concentrations

This study describes the relationship between mollusks, physicochemical properties of seawater, and sediments under natural conditions of low impact. Thirty-nine stations were sampled in October 1994 using a Van Veen grab (0.1 m−2). Temperature, salinity, and dissolved oxygen (DO) concentrations of bottom water were obtained with a CTD. Organic matter content and sediment grain analysis were determined. A total of 836 mollusks were collected. Gastropoda was the most abundant (52%) and diverse class with 27 genera, followed by Bivalvia with eight genera and Scaphopoda with only one genus. According to CCA analysis, dominant mollusks were significantly related with high DO concentrations.Donax,Natica,Acteocina,Bulla,Anachis,Odostomia, andCrucibulumcan be classified as sensitive genera because they were found mainly in high oxygen concentrations (3.1–5.6 mL L−1); on the other hand,Cardiomya,Nuculana,Laevicardium,Chione,Truncatella, andDentaliumcan be classified as tolerant genera (1.0–5.6 mL L−1). Todos Santos Bay hosts a diverse malacological fauna (36 genera); our results show that the dominant genera were mainly related to high dissolved oxygen concentrations. Mollusks can be a useful tool in environmental monitoring programs related with oxygen depletion in coastal areas.

scholarly journals Relationships between bottom water carbonate saturation and element/Ca ratios in coretop samples of the benthic foraminifera <i>Oridorsalis umbonatus</i>

2012 ◽  
Vol 9 (2) ◽  
pp. 1483-1510 ◽  
Author(s):  
C. F. Dawber ◽  
A. Tripati
Keyword(s):  
Benthic Foraminifera ◽  
Partition Coefficients ◽  
Bottom Water ◽  
Energetic Cost ◽  
Individual Element ◽  
Fractionation Factor ◽  
Bottom Water Temperature ◽  
Rayleigh Fractionation ◽  
Wide Range ◽  
Water Carbonate

Abstract. Elemental ratios in benthic foraminifera have been used to reconstruct bottom water temperature and carbonate saturation (Δ[CO32−]). We present elemental data for the long-ranging benthic foraminifera Oridorsalis umbonatus from sediment core tops that span a narrow range of temperatures and a wide range of saturation states. B/Ca, Li/Ca, Sr/Ca and Mg/Ca ratios exhibit positive correlations with bottom water carbonate saturation. The sensitivity of individual element/calcium ratios to bottom water Δ [CO32−] varies considerably, with B/Ca being most sensitive and Sr/Ca the least sensitive. The empirically derived sensitivity of B/Ca, Li/Ca, Mg/Ca and Sr/Ca to bottom water Δ [CO32−] are 0.433 ± 0.053 and 0.0561 ± 0.0084 μmol mol−1 per μmol kg−1 and 0.0164 ± 0.0015 and 0.00241 ± 0.0004 μmol mol−1 per μmol kg−1, respectively. To assess the fidelity of these relationships and the possibility of applying these relationships to earlier periods of Earth history, we examine the mechanisms governing elemental incorporation into foraminiferal calcite. Empirical partition coefficients for Li and Sr are consistent with Rayleigh fractionation from an internal pool used for calcification. For O. umbonatus and other benthic species, we show that the fraction of Ca remaining in the pool is a function of bottom water Δ [CO32−], and can be explained by either a growth rate effect and/or the energetic cost of raising vesicle pH at the site of calcification. Empirical partition coefficients for Mg and B may also be controlled by Rayleigh fractionation, but require that either the fractionation factor from the internal pool is smaller than the inorganic partition coefficient and/or additional fractionation mechanisms. O. umbonatus element ratio data may also be consistent with fractionation according to the surface entrapment model and/or the presence of discrete high- and low-Mg calcite phases. However at present we are limited in our ability to assess these mechanisms. The new X/Ca data for O. umbonatus provide constraints to test the role of these mechanisms in the future.

Impacts of open-ocean deep convection in the Weddell Sea on coastal and bottom water temperature

2016 ◽  
Vol 48 (9-10) ◽  
pp. 2967-2981 ◽  
Author(s):  
Zhaomin Wang ◽  
Yang Wu ◽  
Xia Lin ◽  
Chengyan Liu ◽  
Zelin Xie
Keyword(s):  
Water Temperature ◽  
Bottom Water ◽  
Deep Convection ◽  
Open Ocean ◽  
Weddell Sea ◽  
Bottom Water Temperature

scholarly journals Eastern Mediterranean Sea circulation inferred from the conditions of S1 sapropel deposition

2014 ◽  
Vol 10 (6) ◽  
pp. 4647-4681 ◽  
Author(s):  
K. Tachikawa ◽  
L. Vidal ◽  
M. Cornuault ◽  
M. Garcia ◽  
A. Pothin ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Benthic Foraminifera ◽  
Bottom Water ◽  
Thermohaline Circulation ◽  
Eastern Mediterranean ◽  
Oxygen Depletion ◽  
Last Deglaciation ◽  
Short Term ◽  
Total Recovery ◽  
Eastern Mediterranean Sea

Abstract. Holocene Eastern Mediterranean Sea sediments contain an organic-rich sapropel S1 layer that was formed in oxygen-depleted waters. The spatial distribution of this layer revealed that during S1 deposition deep waters were permanently anoxic below 1800 m in water depth. To provide further insight into past Eastern Mediterranean Sea circulation, a multi-proxy approach was applied to a core retrieved close to the 1800 m boundary (at 1780 m). We measured the bulk sediment elemental composition, the stable isotopic composition of the planktonic foraminifer Globigerinoides ruber, and the abundance of benthic foraminifera since the last deglaciation. The result indicates that authigenic U and Mo accumulation began around 13–12 cal ka BP, in concert with surface water freshening estimated from the G. ruber δ18O record. The onset of bottom/pore water oxygen depletion occurred prior to S1 deposition inferred from barium enrichment. In the middle of the S1 deposition period, between 9 and 8 cal ka BP, reduced authigenic V, Fe and As contents and Br / Cl ratio indicated short-term bottom water re-oxygenation. A sharp Mn peak and maximal abundance for benthic foraminifera marked a total recovery for circulation at approximately 7 cal ka BP. Based on our results and existing data, we suggest that S1 formation withinthe upper 1780 m of the Eastern Mediterranean Sea was preconditioned by reduced ventilation, resulting from excess fresh water inputs due to insolation changes under deglacial conditions, that initiated between 15 and 12 ka. Short-term re-oxygenation in the Levantine Basin is estimated to have affected bottom water below and above the anoxic boundary. We tentatively propose that complete ventilation recovery at the S1 termination was attained earlier within the upper 1780 m than at deeper water depths. Our results provided new constraints for eastern Mediterranean Sea thermohaline circulation.

scholarly journals Historical Shifts in Benthic Infaunal Diversity in the Northern Gulf of Mexico since the Appearance of Seasonally Severe Hypoxia

Diversity ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 49
Author(s):  
Nancy N. Rabalais ◽  
Melissa M. Baustian
Keyword(s):  
Species Richness ◽  
Dissolved Oxygen ◽  
Bottom Water ◽  
Benthic Communities ◽  
Penaeid Shrimp ◽  
Severe Hypoxia ◽  
Low Oxygen ◽  
Large Area ◽  
Surface Deposit ◽  
Deposit Feeders

Severe and persistent bottom-water hypoxia (≤2 mg O2 L−1) occurs on the Louisiana/Texas continental shelf from mid-May through mid-September over a large area (up to 23,000 km2 in mid-summer). Benthic infauna are less mobile than demersal organisms and become stressed by the low dissolved oxygen; benthic community composition, abundance, diversity, and biomass become altered. From the 1950s to the early 1970s, when sediment core indicators identified the initiation and subsequent worsening of dissolved oxygen conditions, there were no hydrographic data or benthic infaunal studies within the current area of frequent bottom-water hypoxia. This study highlights the impacts of severe hypoxia on benthic macroinfaunal communities and how they may have changed from less-hypoxic periods. Polychaetes were and are the dominant taxa in the available studies, but polychaete species richness in summer is now curtailed severely beginning with our 1985–1986 data. Species richness of polychaetes in summer hypoxia (1985–1986 and 1990–1991) was about 60% less than comparable taxa in 1972–1973. Abundance of polychaetes was much less in summer than spring, and recent infaunal biomass in summer was only 15% of what was found in spring. The result is less prey for demersal penaeid shrimp and fishes. Over the period of our comparison, infaunal feeding modes shifted from subsurface deposit feeders and surface deposit feeders to primarily surface deposit feeders (i.e., 95.5% of all polychaetes). Most were opportunistic, hypoxia tolerant, and recruited in high numbers following hypoxia abatement, some in fall and winter but most in spring. As benthic communities succumb to the stress of severe and continued seasonal low oxygen, they occupy the few upper centimeters of the sediment profile above the redox discontinuity layer with negative feedbacks to the water column by way of altered biogeochemical processes.

Some aspects of the sediment chemistry of Sullom Voe, Shetland

1981 ◽  
Vol 80 ◽  
pp. 91-100 ◽  
Author(s):  
S. O. Stanley ◽  
B. E. Grantham ◽  
J. W. Leftley ◽  
N. Robertson
Keyword(s):  
Dissolved Oxygen ◽  
Carbon Cycling ◽  
Bottom Water ◽  
Oxygen Depletion ◽  
Sediment Chemistry ◽  
Sedimentation Rates ◽  
Different Levels

SynopsisDeterminations of dissolved oxygen and nutrients in the water overlying the sediments, of sedimentation rates, and of redox values, acidity, dissolved sulphide, carbon, nitrogen and cellulose values at different levels in the sediments themselves have been carried out in various parts of Sullom Voe. The effects of oxygen depletion following intermittent stagnation of the bottom water in the inner basin on carbon cycling in the sediments are discussed and contrasted with the chemistry of oxygen-rich sediments elsewhere in the voe.

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