A link in the chain of the Cambrian zooplankton: bradoriid arthropods invade the water column

2015 ◽  
Vol 152 (5) ◽  
pp. 923-934 ◽  
Author(s):  
MARK WILLIAMS ◽  
THIJS R. A. VANDENBROUCKE ◽  
VINCENT PERRIER ◽  
DAVID J. SIVETER ◽  
THOMAS SERVAIS
Keyword(s):  
Sea Level Rise ◽  
Water Column ◽  
Sea Level ◽  
Global Distribution ◽  
Geographical Range ◽  
Low Oxygen ◽  
Active Lifestyle ◽  
Environmental Controls ◽  
Continental Shelves ◽  
Oxygen Conditions

AbstractBradoriids are small bivalved arthropods that had global distribution for about 20 million years beginning at Cambrian Epoch 2 (c. 521 Ma). The majority of bradoriids are considered to be benthic, favouring oxygenated waters, as suggested by their anatomy, lithofacies distribution, faunal associates and provinciality. Most bradoriids were extinct by the end of the Drumian Age (middle of Cambrian Epoch 3). The post-Drumian is characterized by widespread dysoxic shelf lithofacies in southern Britain and Scandinavia and by the abundance of phosphatocopid arthropods. This interval is also associated with two bradoriid species with wide intercontinental distribution: Anabarochilina primordialis, which had a geographical range from the palaeo-tropics to high southern palaeo-latitude, and Anabarochilina australis, which extended through the palaeo-tropics from Laurentia to Gondwana. The wide environmental and geographical range of these species, coupled with a carapace anatomy that suggests an active lifestyle, is used to infer a zooplanktonic lifestyle. A possible driver of this widespread Cambrian bradoriid zooplankton was sea-level rise coupled to the periodic spread of low oxygen conditions onto continental shelves, acting in tandem with anatomical pre-adaptations for swimming. Parallels exist with the myodocope ostracod colonization of the water column during Silurian time, which may also have been influenced by extrinsic environmental controls acting on anatomical pre-adaptations for swimming. Similar biological and environmental mechanisms may have facilitated arthropod zooplankton colonizations across Phanerozoic time.

Benthic foraminiferal response to relative sea-level changes in the Maastrichtian–Danian succession at the Dakhla Oasis, Western Desert, Egypt

2016 ◽  
Vol 155 (3) ◽  
pp. 729-746 ◽  
Author(s):  
SHERIF FAROUK ◽  
SREEPAT JAIN
Keyword(s):  
Sea Level ◽  
Western Desert ◽  
Level Curve ◽  
Sea Level Changes ◽  
Low Oxygen ◽  
Benthic Environment ◽  
Oxygen Conditions ◽  
Early Paleocene ◽  
Dakhla Oasis ◽  
Regional Tectonics

AbstractThe Maastrichtian–Danian benthic foraminiferal diversity and assemblages through sequence stratigraphy were studied at Dakhla Oasis, Egypt. Benthic foraminifera numbers (BFN), high-flux species and characteristic benthic foraminiferal species and genera distribution are also incorporated to assess palaeobathymetry, palaeoenvironment and palaeoproductivity. All these proxies are then taken together to construct a sea-level curve and interpreted in terms of regional tectonics, climate and eustasy. Data suggest a remarkably highly equitable benthic environment deposited in a brackish littoral and/or marsh setting with moderate (?) to low oxygen conditions and reduced salinity (oligotrophic), possibly due to increased precipitation and terrestrial runoff. The interrupted dominance of calcareous forms and high-organic-flux species suggests occasional marine incursions and high palaeoproductivity, due to local upwelling. The inferred sea-level curve replicates the global eustatic curve and suggests that the curve is more influenced by the prevailing climate and global eustasy rather than by regional tectonics. The post-Cretaceous–Palaeogene boundary displays improvement in the environment in terms of diversity and number of species and specimens, with a marked reduction in the abundance of high-organic-flux species during early Paleocene (Danian) time, indicating a shift from a more mesotrophic open marine environment to much reduced oligotrophic conditions.

scholarly journals A Sediment Diagenesis Model of Seasonal Nitrate and Ammonium Flux Spatial Variation Contributing to Eutrophication at Taihu, China

2020 ◽  
Vol 17 (11) ◽  
pp. 4158 ◽  
Author(s):  
Linda Sarpong ◽  
Yiping Li ◽  
Eyram Norgbey ◽  
Amechi S. Nwankwegu ◽  
Yue Cheng ◽  
...  
Keyword(s):  
Water Quality ◽  
Water Column ◽  
Algal Blooms ◽  
Latin Hypercube Sampling ◽  
Sediment Flux ◽  
Low Oxygen ◽  
Four Seasons ◽  
Sediment Diagenesis ◽  
Oxygen Conditions ◽  
Autumn And Winter

Algal blooms have thrived on the third-largest shallow lake in China, Taihu over the past decade. Due to the recycling of nutrients such as nitrate and ammonium, this problem has been difficult to eradicate. Sediment flux, a product of diagenesis, explains the recycling of nutrients. The objective was to simulate the seasonal spatial variations of nitrate and ammonium flux. In this paper, sediment diagenesis modeling was applied to Taihu with Environmental Fluid Dynamics Code (EFDC). Latin hypercube sampling was used to create an input file from twelve (12) nitrogen related parameters of sediment diagenesis and incorporated into the EFDC. The results were analyzed under four seasons: summer, autumn, winter, and spring. The concentration of NH4–N in the sediment–water column increased from 2.744903 to 22.38613 (g/m3). In summer, there was an accumulation of ammonium in the water column. In autumn and winter, the sediment was progressively oxidized. In spring, low-oxygen conditions intensify denitrification. This allows algal blooms to continue to thrive, creating a threat to water quality sustainability. The sediment diagenesis model, coupled with water quality measured data, showed an average relative error for Total Nitrogen (TN) of 38.137%, making the model suitable. Future studies should simulate phosphate flux and measure sediment fluxes on the lake.

scholarly journals Global Distribution of Sea-Level Rise and its Risk Index based on the latest Climate Scenario

2012 ◽  
Vol 68 (2) ◽  
pp. I_1256-I_1260
Author(s):  
Hiromune YOKOKI ◽  
Mai NEMOTO ◽  
Yuji KUWAHARA ◽  
Daisaku SATO ◽  
Hideki OKAJIMA ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Risk Index ◽  
Climate Scenario ◽  
Global Distribution

scholarly journals Effects of low oxygen concentrations on aerobic methane oxidation in seasonally hypoxic coastal waters

2016 ◽  
Author(s):  
Lea Steinle ◽  
Johanna Maltby ◽  
Tina Treude ◽  
Annette Kock ◽  
Hermann W. Bange ◽  
...  
Keyword(s):  
Water Column ◽  
Methane Oxidation ◽  
Coastal Waters ◽  
Bacterial Biomass ◽  
Low Oxygen ◽  
Overlying Water ◽  
Hypoxic Conditions ◽  
Environmental Controls ◽  
Effect Of Oxygen ◽  
Oxygen Concentrations

Abstract. Coastal seas may account for more than 75 % of global oceanic methane emissions. There, methane is mainly produced microbially in anoxic sediments from where it can escape to the overlying water column. Aerobic methane oxidation (MOx) in the water column acts as a biological filter reducing the amount of methane that eventually evades to the atmosphere. The efficiency of the MOx filter is potentially controlled by the availability of dissolved methane and oxygen, as well as temperature, salinity, and hydrographic dynamics, and all of these factors undergo strong temporal fluctuations in coastal ecosystems. In order to elucidate the key environmental controls, specifically the effect of oxygen availability, on MOx in a seasonally stratified and hypoxic coastal marine setting, we conducted a 2-year time-series study with measurements of MOx and physico-chemical water column parameters in a coastal inlet in the southwestern Baltic Sea (Eckernförde Bay). We found that MOx rates always increased toward the seafloor, but were not directly linked to methane concentrations. MOx exhibited a strong seasonal variability, with maximum rates (up to 11.6 nmol l−1 d−1) during summer stratification when oxygen concentrations were lowest and bottom-water temperatures were highest. Under these conditions, 70–95 % of the sediment-released methane was oxidized, whereas only 40–60 % were consumed during the mixed and oxygenated periods. Laboratory experiments with manipulated oxygen concentrations in the range of 0.2–220 µmol l−1 revealed a sub-micromolar oxygen-optimum for MOx at the study site. In contrast, the fraction of methane-carbon incorporation into the bacterial biomass (compared to the total amount of oxidised methane) was up to 38-fold higher at saturated oxygen concentrations, suggesting a different partitioning of catabolic and anabolic processes under oxygen-replete and oxygen-starved conditions, respectively. Our results underscore the importance of MOx in mitigating methane emission from coastal waters and indicate an organism-level adaptation of the water column methanotrophs to hypoxic conditions.

Decadal Sea Level Changes in the 50-Year GECCO Ocean Synthesis

2008 ◽  
Vol 21 (9) ◽  
pp. 1876-1890 ◽  
Author(s):  
Armin Köhl ◽  
Detlef Stammer
Keyword(s):  
Heat Flux ◽  
Sea Level Rise ◽  
Water Column ◽  
Sea Level ◽  
Ocean Circulation ◽  
Heat Content ◽  
Total Water ◽  
Sea Level Changes ◽  
Recent Estimate ◽  
Over The Top

Abstract An estimate of the time-varying ocean circulation, obtained over the period 1952–2001, is analyzed here with respect to its decadal and longer-term changes in sea level. The estimate results from a synthesis of most of the ocean datasets available during this 50-yr period with the Estimating the Circulation and Climate of the Ocean/Massachusetts Institute of Technology (ECCO/MIT) ocean circulation model. Over the period 1992 through 2001, the increase in thermosteric sea level rise on average amounts to 1.2 mm yr−1 over the top 750 m and 1.8 mm yr−1 over the total water column. This corresponds to an increase in upper-ocean heat content of 1.5 × 1022 J yr−1 and is in agreement with the estimates of Willis et al. However, over the period 1962 through 2001 the global net thermosteric sea level rise is estimated as 0.66 mm yr−1 over the top 750 m, which is twice the recent estimate from Antonov et al. (0.33 mm yr−1). The corresponding trend over the total water column of 0.92 mm yr−1 is also about twice their value for the layer of 0–3000 m (0.40 mm yr−1). For the last decade, the global heat flux into the ocean of 1.5 W m−2 is twice as large as the recent estimate by Willis et al. due to the heat content change in deeper layers. Regional changes in sea level are predominantly associated with an intensification of the subtropical gyre circulation and a corresponding redistribution of heat. The horizontal advection of heat due to an increase in wind stress curl is found to explain a major fraction of the estimated regional sea level trends over the last 40 years. However, the mechanisms appear different during the last decade when in some regions changes in surface heat flux may explain as much as 50% of the sea level changes.

scholarly journals Iodine speciation and cycling in limnic systems: observations from a humic rich headwater lake (Mummelsee)

2008 ◽  
Vol 5 (1) ◽  
pp. 25-64 ◽  
Author(s):  
B. S. Gilfedder ◽  
M. Petri ◽  
H. Biester
Keyword(s):  
Water Column ◽  
Sediment Core ◽  
Redox Conditions ◽  
Low Oxygen ◽  
Total Iodine ◽  
Iodine Species ◽  
Hypoxic Conditions ◽  
Iodine Speciation ◽  
Oxygen Conditions ◽  
Co Precipitation

Abstract. Iodine undergoes several redox changes in the natural environment, existing as iodate, iodide, and covalently bound to organic matter. While considerable attention has been given to iodine speciation and cycling in the marine environment, very little is known about iodine cycling and speciation in terrestrial fresh water systems. Here we show iodine speciation (measured by IC-ICP-MS) data from one year of monthly sampling of a small humic rich lake in the Black Forest (Mummelsee) under varying redox conditions. The aim was to elucidate the seasonal cycles of iodine species in the lake water column and to quantify both inorganic and organic iodine species. A sediment core was also collected for iodine analysis. Total iodine levels in the Mummelsee averaged 1.93±0.3 μg l−1. Organo-I was the dominant species in the lake, making up on average 85±7% of the total iodine. No strong seasonal variation in organo-I was observed, with only small variations occurring in the epi- and hypolimnion. Iodide was scavenged from the epilimnion during the summer and autumn, which could be related to (micro)biological uptake and co-precipitation. This was also suggested by the high iodine levels in the sediment core (av. 11.8±1.7 mg kg −1). In the hypolimnion, a strong flux of iodide was observed from the sediments into the water column during anoxic and hypoxic conditions, observed during the summer, autumn and, in the bottom 2 m, the winter. This iodide flux and is thought to occur during decomposition of biological material. Iodate levels in the epilimnion increased consistently over the year, whereas it was reduced below detection limits in the hypolimnion during low oxygen conditions. The winter partial turnover lead to reintroduction of oxygen into the hypolimnion and the formation of iodate and organo-I, as well as removal of iodide. In conclusions, iodine cycling in the Mummelsee was controlled by organo-I, although redox conditions and perhaps biological activity were also important, particularly in the hypolimnion during stratification.

scholarly journals Effects of low oxygen concentrations on aerobic methane oxidation in seasonally hypoxic coastal waters

2017 ◽  
Vol 14 (6) ◽  
pp. 1631-1645 ◽  
Author(s):  
Lea Steinle ◽  
Johanna Maltby ◽  
Tina Treude ◽  
Annette Kock ◽  
Hermann W. Bange ◽  
...  
Keyword(s):  
Water Column ◽  
Methane Oxidation ◽  
Coastal Waters ◽  
Bacterial Biomass ◽  
Low Oxygen ◽  
Overlying Water ◽  
Hypoxic Conditions ◽  
Environmental Controls ◽  
Effect Of Oxygen ◽  
Oxygen Concentrations

Abstract. Coastal seas may account for more than 75 % of global oceanic methane emissions. There, methane is mainly produced microbially in anoxic sediments from which it can escape to the overlying water column. Aerobic methane oxidation (MOx) in the water column acts as a biological filter, reducing the amount of methane that eventually evades to the atmosphere. The efficiency of the MOx filter is potentially controlled by the availability of dissolved methane and oxygen, as well as temperature, salinity, and hydrographic dynamics, and all of these factors undergo strong temporal fluctuations in coastal ecosystems. In order to elucidate the key environmental controls, specifically the effect of oxygen availability, on MOx in a seasonally stratified and hypoxic coastal marine setting, we conducted a 2-year time-series study with measurements of MOx and physico-chemical water column parameters in a coastal inlet in the south-western Baltic Sea (Eckernförde Bay). We found that MOx rates generally increased toward the seafloor, but were not directly linked to methane concentrations. MOx exhibited a strong seasonal variability, with maximum rates (up to 11.6 nmol L−1 d−1) during summer stratification when oxygen concentrations were lowest and bottom-water temperatures were highest. Under these conditions, 2.4–19.0 times more methane was oxidized than emitted to the atmosphere, whereas about the same amount was consumed and emitted during the mixed and oxygenated periods. Laboratory experiments with manipulated oxygen concentrations in the range of 0.2–220 µmol L−1 revealed a submicromolar oxygen optimum for MOx at the study site. In contrast, the fraction of methane–carbon incorporation into the bacterial biomass (compared to the total amount of oxidized methane) was up to 38-fold higher at saturated oxygen concentrations, suggesting a different partitioning of catabolic and anabolic processes under oxygen-replete and oxygen-starved conditions, respectively. Our results underscore the importance of MOx in mitigating methane emission from coastal waters and indicate an organism-level adaptation of the water column methanotrophs to hypoxic conditions.

scholarly journals Global Distribution of Risk due to Sea-Level Rise Including its Seasonal Variation Based on Climate Scenario

2013 ◽  
Vol 69 (2) ◽  
pp. I_1271-I_1275
Author(s):  
Hiromune YOKOKI ◽  
Madoka NAKAMURA ◽  
Daisaku SATO ◽  
Yuji KUWAHARA ◽  
Michio KAWAMIYA
Keyword(s):  
Seasonal Variation ◽  
Sea Level Rise ◽  
Sea Level ◽  
Climate Scenario ◽  
Global Distribution

scholarly journals Benthic phosphorus cycling in the Peruvian oxygen minimum zone

2016 ◽  
Vol 13 (5) ◽  
pp. 1367-1386 ◽  
Author(s):  
Ulrike Lomnitz ◽  
Stefan Sommer ◽  
Andrew W. Dale ◽  
Carolin R. Löscher ◽  
Anna Noffke ◽  
...  
Keyword(s):  
Water Column ◽  
Surface Sediments ◽  
Solid Phase ◽  
Continental Margins ◽  
Low Oxygen ◽  
Anoxic Waters ◽  
Oxygen Conditions ◽  
Bottom Waters ◽  
Minimum Zone ◽  
Oxygen Minimum

Abstract. Oxygen minimum zones (OMZs) that impinge on continental margins favor the release of phosphorus (P) from the sediments to the water column, enhancing primary productivity and the maintenance or expansion of low-oxygen waters. A comprehensive field program in the Peruvian OMZ was undertaken to identify the sources of benthic P at six stations, including the analysis of particles from the water column, surface sediments, and pore fluids, as well as in situ benthic flux measurements. A major fraction of solid-phase P was bound as particulate inorganic P (PIP) both in the water column and in sediments. Sedimentary PIP increased with depth in the sediment at the expense of particulate organic P (POP). The ratio of particulate organic carbon (POC) to POP exceeded the Redfield ratio both in the water column (202 ± 29) and in surface sediments (303 ± 77). However, the POC to total particulate P (TPP = POP + PIP) ratio was close to Redfield in the water column (103 ± 9) and in sediment samples (102 ± 15). This suggests that the relative burial efficiencies of POC and TPP are similar under low-oxygen conditions and that the sediments underlying the anoxic waters on the Peru margin are not depleted in P compared to Redfield. Benthic fluxes of dissolved P were extremely high (up to 1.04 ± 0.31 mmol m−2 d−1), however, showing that a lack of oxygen promotes the intensified release of dissolved P from sediments, whilst preserving the POC / TPP burial ratio. Benthic dissolved P fluxes were always higher than the TPP rain rate to the seabed, which is proposed to be caused by transient P release by bacterial mats that had stored P during previous periods when bottom waters were less reducing. At one station located at the lower rim of the OMZ, dissolved P was taken up by the sediments, indicating ongoing phosphorite formation. This is further supported by decreasing porewater phosphate concentrations with sediment depth, whereas solid-phase P concentrations were comparatively high.

scholarly journals Benthic phosphorus cycling in the Peruvian oxygen minimum zone

2015 ◽  
Vol 12 (20) ◽  
pp. 16755-16801 ◽  
Author(s):  
U. Lomnitz ◽  
S. Sommer ◽  
A. W. Dale ◽  
C. R. Löscher ◽  
A. Noffke ◽  
...  
Keyword(s):  
Water Column ◽  
Surface Sediments ◽  
Solid Phase ◽  
Continental Margins ◽  
Low Oxygen ◽  
Oxygen Minimum Zones ◽  
Oxygen Conditions ◽  
Bottom Waters ◽  
Minimum Zone ◽  
Oxygen Minimum

Abstract. Oxygen minimum zones (OMZs) that impinge on continental margins favor the release of phosphorus (P) from the sediments to the water column, enhancing primary productivity and the maintenance or expansion of low-oxygen waters. A comprehensive field program in the Peruvian OMZ was undertaken to identify the sources of benthic P, including the analysis of particles from the water column, surface sediments and pore fluids as well as in situ benthic flux measurements. A major fraction of solid phase P was bound as particulate inorganic P (PIP) both in the water column and in sediments. Sedimentary PIP increased with depth in the sediment at the expense of particulate organic P (POP). The ratio of particulate organic carbon (POC) to POP exceeded the Redfield Ratio both in the water column (202 ± 29) and in surface sediments (303 ± 77). However, the POC to total particulate P (TPP = POP + PIP) ratio was close to Redfield in the water column (103 ± 9) and in sediment samples (102 ± 15) taken from the core of the OMZ. This observation suggests that the burial efficiencies of POC and TPP are similar under the low oxygen conditions prevailing in the Peruvian OMZ. Benthic fluxes of dissolved P were extremely high (up to 1.04 ± 0.31 mmol m−2 d−1) and exceeded the fluxes resulting from the degradation of particulate organic matter raining to the seabed. Most of the excess P may have been released by bacterial mats that had stored P during previous periods when bottom waters were less reducing. At one station located at the lower rim of the OMZ, dissolved P was taken up by the sediments indicating recent phosphorite formation.

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