Does anoxia affect mercury cycling at the sediment–water interface in the Gulf of Trieste (northern Adriatic Sea)? Incubation experiments using benthic flux chambers

Emili, Andrea; Koron, Neža; Covelli, Stefano; Faganeli, Jadran; Acquavita, Alessandro; Predonzani, Sergio; Vittor, Cinzia De

doi:10.1016/j.apgeochem.2010.11.019

Cited by 50 publications

(26 citation statements)

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“…The sediments are recognized as both an important source and depository of MeHg, especially in the coastal and shelf waters [ Mason et al , ; Monperrus et al , ; Merritt and Amirbahman , ; Emili et al , ; Bratkič et al , ], but are not thought to be significant in terms of increasing concentrations in the open ocean [ Vetriani et al , ; Lamborg et al , ; Ogrinc et al , 2007; Mason et al , ; Amos et al , ]. The Argentinean basin is an area of enhanced sedimentation, influenced also by transport of Rio de la Plata; therefore, it is expected that sediments may be a source of MeHg to the water column, as our results indicate.…”

Section: Resultsmentioning

confidence: 99%

“…Mixing of salt and freshwater has been shown to increase DGM [Bratkič et al, 2013], and in addition, the Rio de la Plata transports much sedimentary matter, which contains on average up to 0.5 Hg mg/kg [Ronco et al, 2001]. As the environmental conditions change, particularly temperature, salinity, and redox potential, the bioavailability and reducibility of Hg change along with its partitioning between dissolved and solid phases [Coquery and Cossa, 1995;Barkay et al, 1997;Hines et al, 2006;Emili et al, 2011]. Figure 6.…”

Section: Dissolved Gaseous Mercurymentioning

confidence: 99%

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Mercury presence and speciation in the South Atlantic Ocean along the 40°S transect

Bratkič

Vahčič

Kotnik

et al. 2016

Global Biogeochemical Cycles

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Mercury (Hg) natural biogeochemical cycle is complex and a significant portion of biological and chemical transformation occurs in the marine environment. To better understand the presence and abundance of Hg species in the remote ocean regions, waters of South Atlantic Ocean along 40°S parallel were investigated during UK-GEOTRACES cruise GA10. Total mercury (THg), methylated mercury (MeHg), and dissolved gaseous mercury (DGM) concentrations were determined. The concentrations were very low in the range of pg/L (femtomolar). All Hg species had higher concentration in western than in eastern basin. THg did not appear to be a useful geotracer. Elevated methylated Hg species were commonly associated with low-oxygen water masses and occasionally with peaks of chlorophyll a, both involved with carbon (re)cycling. The overall highest MeHg concentrations were observed in the mixed layer (500 m) and in the vicinity of the Gough Island. Conversely, DGM concentrations showed distinct layering and differed between the water masses in a nutrient-like manner. DGM was lowest at surface, indicating degassing to the atmosphere, and was highest in the Upper Circumpolar Deep Water, where the oxygen concentration was lowest. DGM increased also in Antarctic Bottom Water. At one station, dimethylmercury was determined and showed increase in region with lowest oxygen saturation. Altogether, our data indicate that the South Atlantic Ocean could be a source of Hg to the atmosphere and that its biogeochemical transformations depend primarily upon carbon cycling and are thereby additionally prone to global ocean change.

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Section: Resultsmentioning

confidence: 99%

Section: Dissolved Gaseous Mercurymentioning

confidence: 99%

Mercury presence and speciation in the South Atlantic Ocean along the 40°S transect

Bratkič

Vahčič

Kotnik

et al. 2016

Global Biogeochemical Cycles

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“…3) MeHg diffuses into the water column from a larger area of the anoxic bottom, where MeHg was formed after the intrusion due to sulphate reduction and dissolution of Fe and Mn oxyhydroxides, and formation of sulphides [31,37,38], or 4) MeHg was formed in the water column under low hydrogen sulphide (or suboxic) conditions as a result of the intrusion.…”

Section: Resultsmentioning

confidence: 99%

Biogeochemical consequences of an oxygenated intrusion into an anoxic fjord

et al. 2014

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BackgroundThis paper is based on the studies of the biogeochemical structure of the water column in the anoxic Fjord Hunnbunn (south-eastern Norway) performed in 2009, 2011 and 2012. This Fjord is an enclosed basin of brackish water separated by a narrow and shallow outlet to the sea with a permanently anoxic layer. We show how an oxygenated intrusion could lead to both positive and negative effects on the ecosystem state in Hunnbunn due to a change in the biogeochemical structure.ResultsDuring the stratified periods in 2009 and 2012 the anoxic layer amounted to approximately 10% of the total water volume in the Fjord, while dissolved oxygen (DO) was present in 80-90% of the water. In the autumn of 2011 the water chemistry structure observed in Fjord Hunnbunn was clearly affected by a recent oxygenated intrusion defined by abnormal salinity patterns. This led to a shift of the DO boundary position to shallower depths, resulting in a thicker anoxic layer comprising approximately 40% of the total water volume, with DO present only in approximately 60% of the water. The oxygenated water intrusions led to a twofold decrease of the concentrations of hydrogen sulphide, ammonia, phosphate and silicate in the deep layers with a simultaneous increase of these nutrients and a decrease of the pH level in the surface layers. The concentrations of manganese, iron, and mercury species changed dramatically and in particular revealed a significant supply of iron and methylmercury to the water column.ConclusionsOxic water intrusions into anoxic fjords could lead not only to the flushing of the bottom anoxia, but to a dispersal of sulphidic and low oxygen conditions to the larger bottom area. The elevation of the hydrogen sulphide to the shallower layers (that can be rapidly oxidized) is accompanied by the appearance in the subsurface water of methylmercury, which is easily accumulated by organisms and can be transported to the surrounding waters, affecting the ecosystem over a larger area.

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“…Establishing the magnitude of benthic exchanges, especially in conditions of hypoxia/anoxia, is important because dissolved oxygen is a key regulator for many biogeochemical cycles, such as sulfur, nitrogen, and heavy metals; therefore, changes in sediment redox status could enhance the release of contaminants (e.g., mercury, iron, sulfur) (Santos-Escheandia et al 2009;Covelli et al 2011;Emili et al 2011;De Vittor et al 2012). Hence, the study of nutrient and carbon fluxes at the SWI is fundamental to define the functionality of coastal ecosystems and to provide indications for managing conservation and development land uses.…”

Section: Introductionmentioning

confidence: 99%

Oxygen, carbon, and nutrient exchanges at the sediment–water interface in the Mar Piccolo of Taranto (Ionian Sea, southern Italy)

Vittor

Relitti

Kralj

et al. 2015

Environ Sci Pollut Res

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In the shallow environment, the nutrient and carbon exchanges at the sediment-water interface contribute significantly to determine the trophic status of the whole water column. The intensity of the allochthonous input in a coastal environment subjected to strong anthropogenic pressures determines an increase in the benthic oxygen demand leading to depressed oxygen levels in the bottom waters. Anoxic conditions resulting from organic enrichment can enhance the exchange of nutrients between sediments and the overlying water. In the present study, carbon and nutrient fluxes at the sediment-water interface were measured at two experimental sites, one highly and one moderately contaminated, as reference point. In situ benthic flux measurements of dissolved species (O2, DIC, DOC, N-NO3 (-), N-NO2 (-), N-NH4 (+), P-PO4 (3-), Si-Si(OH)4, H2S) were conducted using benthic chambers. Furthermore, undisturbed sediment cores were collected for analyses of total and organic C, total N, and biopolymeric carbon (carbohydrates, proteins, and lipids) as well as of dissolved species in porewaters and supernatant in order to calculate the diffusive fluxes. The sediments were characterized by suboxic to anoxic conditions with redox values more negative in the highly contaminated site, which was also characterized by higher biopolymeric carbon content (most of all lipids), lower C/N ratios and generally higher diffusive fluxes, which could result in a higher release of contaminants. A great difference was observed between diffusive and in situ benthic fluxes suggesting the enhancing of fluxes by bioturbation and the occurrence of biogeochemically important processes at the sediment-water interface. The multi-contamination of both inorganic and organic pollutants, in the sediments of the Mar Piccolo of Taranto (declared SIN in 1998), potentially transferable to the water column and to the aquatic trophic chain, is of serious concern for its ecological relevance, also considering the widespread fishing and mussel farming activities in the area.

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Does anoxia affect mercury cycling at the sediment–water interface in the Gulf of Trieste (northern Adriatic Sea)? Incubation experiments using benthic flux chambers

Cited by 50 publications

References 50 publications

Mercury presence and speciation in the South Atlantic Ocean along the 40°S transect

Mercury presence and speciation in the South Atlantic Ocean along the 40°S transect

Biogeochemical consequences of an oxygenated intrusion into an anoxic fjord

Oxygen, carbon, and nutrient exchanges at the sediment–water interface in the Mar Piccolo of Taranto (Ionian Sea, southern Italy)

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