The Effects of Hypoxia on Sediment Nitrogen Cycling in the Baltic Sea

Jäntti, Helena; Hietanen, Susanna

doi:10.1007/s13280-011-0233-6

Cited by 103 publications

(100 citation statements)

References 42 publications

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“…In addition, the hypoxic water volume displays a negative correlation with the total dissolved inorganic nitrogen pool: greater overall nitrogen removal with increased hypoxia (Vahtera et al, 2007). Hypoxia-related effects on the benthic ecosystem (e.g., Laine et al, 2007) and biogeochemical cycles of nutrients (e.g., Jäntti and Hietanen, 2012) are evident in the Gulf of Finland.…”

Section: Introductionmentioning

confidence: 96%

Estuarine circulation reversals and related rapid changes in winter near-bottom oxygen conditions in the Gulf of Finland, Baltic Sea

et al. 2013

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Abstract. The reversal of estuarine circulation caused by southwesterly wind forcing may lead to vanishing of stratification and subsequently to oxygenation of deep layers during the winter in the Gulf of Finland. Six conductivity, temperature, depth (CTD)+oxygen transects (130 km long, 10 stations) were conducted along the thalweg from the western boundary to the central gulf (21 December 2011-8 May 2012. Two bottom-mounted ADCP were installed, one near the western border and the second in the central gulf. A CTD with a dissolved oxygen sensor was deployed close to the western ADCP. Periods of typical estuarine circulation were characterized by strong stratification, high salinity, hypoxic conditions and inflow to the gulf in the near-bottom layer. Two circulation reversals were observed: one in DecemberJanuary and one in February. The first reversal event was well developed; it caused the disappearance of the stratification and an increase in the oxygen concentration from hypoxic values to 270 µmol L −1 (to 6 mL L −1 ) throughout the water column along the thalweg and lasted approximately 1.5 months. Shifts from estuarine circulation to reversed circulation and vice versa were both associated with strong longitudinal (east-west) gulf currents (up to 40 cm s −1 ) in the deep layer. The change from oxygenated to hypoxic conditions in the western near-entrance area of the gulf occurred very rapidly, within less than a day, due to the intrusion of the hypoxic salt wedge from the NE Baltic Proper. In the eastern part of the gulf, good oxygen conditions caused by reversals remained for a few months.

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Section: Introductionmentioning

confidence: 96%

Estuarine circulation reversals and related rapid changes in winter near-bottom oxygen conditions in the Gulf of Finland, Baltic Sea

et al. 2013

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“…For example, conversion of bioavailable nitrogen (N) into gaseous forms via canonical (heterotrophic) denitrification and anaerobic ammonium oxidation (anammox) are major sink mechanisms in the nitrogen cycle (Galloway et al 2004, Dalsgaard et al 2005. However, in organic-rich sediments overlain by hypoxic−anoxic but nitratecontaining bottom water, these processes are often replaced by dis similatory nitrate−nitrite reduction to ammonium (DNRA), in which bioavailable ammo-nium (NH 4 ), rather than gaseous forms of N, is the metabolic end product (McCarthy et al 2008, Thamdrup & Dalsgaard 2008 and references therein, Jäntti & Hietanen 2012, Bonaglia et al 2014). Furthermore, oxidation of NH 4 to NO 3 via nitrification does not take place in anoxic systems (Thamdrup & Dalsgaard 2000).…”

Section: Introductionmentioning

confidence: 99%

“…The spread of anoxic conditions have also increased eutrophication in the Baltic Sea by weakening the sedimentary sink mechanisms for N and P (Vahtera et al 2007, Jäntti & Hietanen 2012, Viktorsson et al 2012. For example, deoxygenation of oxic sediment areas in the Baltic proper in the 1990s mobilised some 160 000 t of P to the water column (Savchuk 2005).…”

Section: Introductionmentioning

confidence: 99%

Nutrient fluxes from reduced Baltic Sea sediment: effects of oxygenation and macrobenthos

Ekeroth¹,

Blomqvist²,

Hall³

2016

Mar. Ecol. Prog. Ser.

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Effects of bottom water oxygenation and macrofaunal colonisation on benthic fluxes of nitrogen (N), phosphorus (P) and silicon (Si) from long-term anoxic Baltic Sea bottom sediment were investigated. Sediment boxcosms from an anoxic site at 150 m depth in the open Baltic proper were incubated in the laboratory to follow the development of benthic nutrient fluxes during 74 d exposure to flow-through of oxygen-rich water. In contrast to traditional end-point experimental designs, our repeated measurement approach allowed for separation of transient and long-term effects of oxygenation and bioturbation on benthic nutrient recycling. The composition, but not the rate, of the benthic total dissolved N efflux changed by oxygenation from being dominated by NH 4 in situ to being mostly composed of NO 2 + NO 3 and dissolved organic N (DON) under oxic conditions. Oxygenation in the boxcosms decreased the benthic efflux of dissolved silicate (DSi) and essentially shut off the in situ flux of dissolved inorganic phosphorus (DIP). After 20 d of oxygenation, 2 bottom macrofauna taxa, the polychaete Marenzelleria spp. and the amphipod Monoporiea affinis, were introduced to a subset of the boxcosms. Bioturbation by either taxa increased the efflux of dissolved inorganic N (DIN), DON and DSi to the overlying water. The Prich benthic flux under in situ anoxic conditions roughly approached Redfield N:P stoichiometry after oxygenation in the sediment boxcosms. Upon addition of macrofauna, bioturbation generated even higher N:P flux ratios.

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“…The regional and spatial coverage of benthic flux data for the Baltic is low and most of the existing studies have not investigated the key regulators of benthic N cycling such as temperature, oxygen availability and demand, presence/absence of macrofauna, sedimentary organic matter content, or variable nutrient loading from human activities. Furthermore, for some of the most highly impacted areas of the Baltic Sea the published rates of N 2 production refer to a single campaign and do not have a temporal resolution that is high enough to catch the seasonal variability or the steep horizontal and vertical gradients of potentially regulating factors (Hietanen 2007;Deutsch et al 2010;Jäntti and Hietanen 2012).…”

Section: Introductionmentioning

confidence: 99%

“…In particular the proportion of recycled N as NH 4 ? versus the amount of lost N via denitrification or anammox need to be better quantified and related to the regenerated P pool (Vahtera et al 2007;Jäntti and Hietanen 2012).…”

Section: Introductionmentioning

confidence: 99%

Seasonal oxygen, nitrogen and phosphorus benthic cycling along an impacted Baltic Sea estuary: regulation and spatial patterns

et al. 2014

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The regulatory roles of temperature, eutrophication and oxygen availability on benthic nitrogen (N) cycling and the stoichiometry of regenerated nitrogen and phosphorus (P) were explored along a Baltic Sea estuary affected by treated sewage discharge. Rates of sediment denitrification, anammox, dissimilatory nitrate reduction to ammonium (DNRA), nutrient exchange, oxygen (O 2 ) uptake and penetration were measured seasonally. Sediments not affected by the nutrient plume released by the sewage treatment plant (STP) showed a strong seasonality in rates of O 2 uptake and coupled nitrification-denitrification, with anammox never accounting for more than 20 % of the total dinitrogen (N 2 ) production. N cycling in sediments close to the STP was highly dependent on oxygen availability, which masked temperaturerelated effects. These sediments switched from low N loss and high ammonium (NH 4 ? ) efflux under hypoxic conditions in the fall, to a major N loss system in the winter when the sediment surface was oxidized. In the fall DNRA outcompeted denitrification as the main nitrate (NO 3 -) reduction pathway, resulting in N recycling and potential spreading of eutrophication. A comparison with historical records of nutrient discharge and denitrification indicated that the total N loss in the estuary has been tightly coupled to the total amount of nutrient discharge from the STP. Changes in dissolved inorganic nitrogen (DIN) released from the STP agreed well with variations in sedimentary N 2 removal. This indicates that denitrification and anammox efficiently counterbalance N loading in the estuary across the range of historical and present-day anthropogenic nutrient discharge. Overall low N/P ratios of the regenerated nutrient fluxes impose strong N limitation for the pelagic system and generate a high potential for nuisance cyanobacterial blooms.

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The Effects of Hypoxia on Sediment Nitrogen Cycling in the Baltic Sea

Cited by 103 publications

References 42 publications

Estuarine circulation reversals and related rapid changes in winter near-bottom oxygen conditions in the Gulf of Finland, Baltic Sea

Estuarine circulation reversals and related rapid changes in winter near-bottom oxygen conditions in the Gulf of Finland, Baltic Sea

Nutrient fluxes from reduced Baltic Sea sediment: effects of oxygenation and macrobenthos

Seasonal oxygen, nitrogen and phosphorus benthic cycling along an impacted Baltic Sea estuary: regulation and spatial patterns

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