Turbidity, particle fluxes and mineralisation of carbon and nitrogen in a shallow coastal area

During a research programme carried out in a shallow coastal area (�rhus Bight, Denmark), short-term and long-term particle dynamics were measured continuously for a year in the water column and in the seabed. The research area is a homogeneous accumulation area for fine-grained sediment, with a water depth of 15 m. Fluxes in the water column were measured at nine depths with a time resolution of one to two weeks during one year, using duplicate sediment traps with an aspect ratio of 5. Significant correlation between turbidity and vertical particle fluxes was found. Continuous measurements close to the bottom gave an indirect measure of the concentration of suspended particles every 5 min. In this way, it was possible to measure resuspension dynamics with a detailed time resolution. A new method was developed for the separation of downward fluxes of primary and secondary (resuspended) sediment. The net deposition rate of total particulate matter (TPM) found by this method (DTPM = 1050 g m-2 year-1) is in good agreement with the accumulation rate found by 210Pb core datings (ATPM = 890 g m-2 year-1). The accumulation rate of particulate organic carbon (POC) and total particulate nitrogen (TPN) beneath the benthic mixing layer was five times smaller than the net deposition rate; this is assumed to be caused by mineralization mainly in the benthic mixing layer. Resuspension events are believed to play a major role in mineralization of organic matter and exchange of nutrients with the water column. Resuspension rates were 10 to 100 times greater than the net deposition rates in all measuring periods. Supply of new, easily resuspendable sediment during the spring phytoplankton bloom dramatically increased the possibility of resuspension.

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The mass impacts on chemosynthetic primary producers: potential implications on anammox communities and their consequences

International Journal of Astrobiology ◽

10.1017/s1473550418000411 ◽

2018 ◽

Vol 18 (05) ◽

pp. 440-444

Author(s):

Noel Pérez ◽

Jorge Luis Velazco-Vargas ◽

Osmel Martin ◽

Rolando Cardenas ◽

Jesús Martínez-Frías

Keyword(s):

Water Column ◽

Deposition Rate ◽

Extreme Case ◽

Chemical Compounds ◽

Global Scale ◽

Biogeochemical Cycle ◽

Potential Influence ◽

Asteroid Impact ◽

Global Cooling ◽

The Impact

AbstractThe potential of a mass asteroid impact on Earth to disturb the chemosynthetic communities at global scale is discussed. Special emphasis is made on the potential influence on anammox communities and their implications in the nitrogen biogeochemical cycle. According to our preliminary estimates, anammox communities could be seriously affected as a consequence of global cooling and the large process of acidification usually associated with the occurrence of this kind of event. The scale of affectations could vary in a scenario like the Chicxulub as a function of the amount of soot, depth of the water column and the deposition rate for sulphates assumed in each case. The most severe affectations take place where the amount of soot and sulphates produced during the event is higher and the scale of time of settlements for sulphates is short, of the order of 10 h. In this extreme case, the activity of anammox is considerably reduced, a condition that may persist for several years after the impact. Furthermore, the impact of high levels of other chemical compounds like sulphates and nitrates associated with the occurrence of this kind of event are also discussed.

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Mapping Benthic Substrate Type in a Shallow Coastal Area Using Airborne Hyperspectral Images

10.1109/igarss47720.2021.9553651 ◽

2021 ◽

Author(s):

Wonkook Kim ◽

Sung Hak Kim ◽

Sueng-Il Baek ◽

Hyunkyum Kim ◽

Jaehong Oh

Keyword(s):

Coastal Area ◽

Hyperspectral Images ◽

Substrate Type ◽

Shallow Coastal Area ◽

Benthic Substrate

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Control of the geomorphology and gas hydrate extent on widespread gas emissions offshore Romania

BSGF - Earth Sciences Bulletin ◽

10.1051/bsgf/2017182 ◽

2017 ◽

Vol 188 (4) ◽

pp. 26 ◽

Cited By ~ 11

Author(s):

Vincent Riboulot ◽

Antonio Cattaneo ◽

Carla Scalabrin ◽

Arnaud Gaillot ◽

Gwénaël Jouet ◽

...

Keyword(s):

Water Column ◽

Black Sea ◽

Gas Hydrate ◽

Accumulation Rate ◽

Sediment Accumulation ◽

The Black Sea ◽

North East ◽

Bottom Simulating Reflectors ◽

Gas Flares ◽

Sea Fan

The Romanian sector of the Black Sea deserves attention because the Danube deep-sea fan is one of the largest sediment depositional systems worldwide and is considered the world's most isolated sea, the largest anoxic water body on the planet and a unique energy-rich sea. Due to the high sediment accumulation rate, presence of organic matter and anoxic conditions, the Black sea sediments offshore the Danube delta is rich in gas and thus shows Bottom Simulating Reflectors (BSR). The cartography of the BSR over the last 20 years, exhibits its widespread occurrence, indicative of extensive development of hydrate accumulations and a huge gas hydrate potential. By combining old and new datasets acquired in 2015 during the GHASS expedition, we performed a geomorphological analysis of the continental slope north-east of the Danube canyon compared with the spatial distribution of gas seeps in the water column and the predicted extent of the gas hydrate stability zone. This analysis provides new evidence of the role of geomorphological setting and gas hydrate extent in controlling the location of the observed gas expulsions and gas flares in the water column. Gas flares are today considered an important source of the carbon budget of the oceans and, potentially, of the atmosphere.

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Effects of eutrophication on sedimentary organic carbon cycling in five temperate lakes

Biogeosciences ◽

10.5194/bg-16-3725-2019 ◽

2019 ◽

Vol 16 (19) ◽

pp. 3725-3746 ◽

Cited By ~ 3

Author(s):

Annika Fiskal ◽

Longhui Deng ◽

Anja Michel ◽

Philip Eickenbusch ◽

Xingguo Han ◽

...

Keyword(s):

Organic Carbon ◽

Water Column ◽

Trophic State ◽

Microbial Respiration ◽

Accumulation Rate ◽

Eutrophic Lake ◽

Accumulation Rates ◽

Artificial Lake ◽

Eutrophic Lakes ◽

Lake Ecosystems

Abstract. Even though human-induced eutrophication has severely impacted temperate lake ecosystems over the last centuries, the effects on total organic carbon (TOC) burial and mineralization are not well understood. We study these effects based on sedimentary records from the last 180 years in five Swiss lakes that differ in trophic state. We compare changes in TOC content and modeled TOC accumulation rates through time to historical data on algae blooms, water column anoxia, wastewater treatment, artificial lake ventilation, and water column phosphorus (P) concentrations. We furthermore investigate the effects of eutrophication on rates of microbial TOC mineralization and vertical distributions of microbial respiration reactions in sediments. Our results indicate that the history of eutrophication is well recorded in the sedimentary record. Overall, eutrophic lakes have higher TOC burial and accumulation rates, and subsurface peaks in TOC coincide with past periods of elevated P concentrations in lake water. Sediments of eutrophic lakes, moreover, have higher rates of total respiration and higher contributions of methanogenesis to total respiration. However, we found strong overlaps in the distributions of respiration reactions involving different electron acceptors in all lakes regardless of lake trophic state. Moreover, even though water column P concentrations have been reduced by ∼ 50 %–90 % since the period of peak eutrophication in the 1970s, TOC burial and accumulation rates have only decreased significantly, by ∼ 20 % and 25 %, in two of the five lakes. Hereby there is no clear relationship between the magnitude of the P concentration decrease and the change in TOC burial and accumulation rate. Instead, data from one eutrophic lake suggest that artificial ventilation, which has been used to prevent water column anoxia in this lake for 35 years, may help sustain high rates of TOC burial and accumulation in sediments despite water column P concentrations being strongly reduced. Our study provides novel insights into the influence of human activities in lakes and lake watersheds on lake sediments as carbon sinks and habitats for diverse microbial respiration processes.

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Variability of the Lithogenic Particle Fluxes Down Through the Water Column of the North-Eastern Subtropical Atlantic Ocean. Relations with Atmospheric Inputs

Mineralogical Magazine ◽

10.1180/minmag.1998.62a.1.106 ◽

1998 ◽

Vol 62A (1) ◽

pp. 199-200

Author(s):

A. Bory

Keyword(s):

Atlantic Ocean ◽

Water Column ◽

The North ◽

North Eastern ◽

Particle Fluxes ◽

Atmospheric Inputs

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Isotope constraints on particulate nitrogen source and dynamics in the upper water column of the oligotrophic South China Sea

Global Biogeochemical Cycles ◽

10.1029/2011gb004091 ◽

2012 ◽

Vol 26 (2) ◽

pp. n/a-n/a ◽

Cited By ~ 34

Author(s):

Shuh-Ji Kao ◽

Jin-Yu Terence Yang ◽

Kon-Kee Liu ◽

Minhan Dai ◽

Wen-Chen Chou ◽

...

Keyword(s):

South China Sea ◽

Nitrogen Source ◽

Water Column ◽

South China ◽

Particulate Nitrogen ◽

China Sea

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Isotopically Light Cd in Sediments Underlying Oxygen Deficient Zones

Frontiers in Earth Science ◽

10.3389/feart.2021.623720 ◽

2021 ◽

Vol 9 ◽

Author(s):

Lena Chen ◽

Susan H. Little ◽

Katharina Kreissig ◽

Silke Severmann ◽

James McManus

Keyword(s):

Water Column ◽

Continental Margin ◽

Solid Phase ◽

Isotope Composition ◽

Accumulation Rate ◽

Cadmium Sulphide ◽

Crustal Material ◽

Deep Seawater ◽

Complex Particle ◽

Cd Isotopes

Cadmium is a trace metal of interest in the ocean partly because its concentration mimics that of phosphate. However, deviations from the global mean dissolved Cd/PO4 relationship are present in oxygen deficient zones, where Cd is depleted relative to phosphate. This decoupling has been suggested to result from cadmium sulphide (CdS) precipitation in reducing microenvironments within sinking organic matter. We present Cd concentrations and Cd isotope compositions in organic-rich sediments deposited at several upwelling sites along the northeast Pacific continental margin. These sediments all have enriched Cd concentrations relative to crustal material. We calculate a net accumulation rate of Cd in margin settings of between 2.6 to 12.0 × 107 mol/yr, higher than previous estimates, but at the low end of a recently published estimate for the magnitude of the marine sink due to water column CdS precipitation. Cadmium in organic-rich sediments is isotopically light (δ114/110CdNIST-3108 = +0.02 ± 0.14‰, n = 26; 2 SD) compared to deep seawater (+0.3 ± 0.1‰). However, isotope fractionation during diagenesis in continental margin settings appears to be small. Therefore, the light Cd isotope composition of organic-rich sediments is likely to reflect an isotopically light source of Cd. Non-quantitative biological uptake of light Cd by phytoplankton is one possible means of supplying light Cd to the sediment, which would imply that Cd isotopes could be used as a tracer of past ocean productivity. However, water column CdS precipitation is also predicted to preferentially sequester light Cd isotopes from the water column, which could obfuscate Cd as a tracer. We also observe notably light Cd isotope compositions associated with elevated solid phase Fe concentrations, suggesting that scavenging of Cd by Fe oxide phases may contribute to the light Cd isotope composition of sediments. These multiple possible sources of isotopically light Cd to sediments, along with evidence for complex particle cycling of Cd in the water column, bring into question the straightforward application of Cd isotopes as a paleoproductivity proxy.

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Comprehensive studies of the Black Sea during the cruise 101 of the research vessel Professor Vodyanitskiy

Океанология ◽

10.31857/s0030-1574592315-318 ◽

2019 ◽

Vol 59 (2) ◽

pp. 315-318

Author(s):

A. A. Klyuvitkin ◽

A. V. Garmashov ◽

A. A. Latushkin ◽

N. A. Orekhova ◽

A. I. Kochenkova ◽

...

Keyword(s):

Water Column ◽

Black Sea ◽

Russian Federation ◽

Bottom Sediments ◽

Exclusive Economic Zone ◽

Research Vessel ◽

The Black Sea ◽

Biogeochemical Processes ◽

The Russian Federation ◽

Particle Fluxes

From 14 to 28 December 2017, in the central part of the Black Sea, within the exclusive economic zone of the Russian Federation, a joint interdepartmental comprehensive oceanological expedition was carried out on board the R/V «Professor Vodyanitsky». The main goal of the expedition was to study the characteristics of the hydrological, hydrochemical, hydro-optical and hydrobiological structure of the Black Sea waters during the winter, as well as to collect material for studying the sedimentation system of the sea, which allows assessing the particle fluxes in the water column, the rate of its sedimentation to the bottom and biogeochemical processes occurring in water and bottom sediments.

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