River plume and bottom boundary layer – Hotspots for nitrification in a coastal bay?

Bartl, Ines; Liskow, Iris; Schulz, Kirstin; Umlauf, Lars; Voß, Maren

doi:10.1016/j.ecss.2018.04.023

Cited by 25 publications

(30 citation statements)

References 64 publications

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“…In addition, assimilation and degradation, including ammonification and nitrification, in the coastal surface waters for the entire spring period can be assumed. Indeed, mean nitrification rates of 59 nmol L −1 d −1 were detected during a spring bloom in the surface waters of the BG, and further offshore they were much higher 258 nmol L −1 d −1 (Bartl et al, 2018). This observation is consistent with the high N:P ratio in the nutrient load, which is ∼140 in winter and spring but only ∼10 in summer (Voss et al, 2006).…”

Section: Nutrient Cycle and Filter Functionsupporting

confidence: 66%

“…2016), determined very high ratios, up to 7.8 times higher than the Redfield ratio of 16 (Figure 3). Further data obtained during the cruise are reported in Bartl et al (2018Bartl et al ( , 2019. The high and unbalanced Redfield ratios in the coastal zone may alter nitrate cycling (Lunau et al, 2012).…”

Section: Introductionmentioning

confidence: 93%

“…While under normal conditions the VR plume propagates eastward, parallel to the coast, during easterly or northeasterly winds it detaches from the coast and meanders in the center of the BG. The resulting eddies have a seasonal varying radius of deformation of 850 m during winter, 4500 m during spring and 6500 m during summer (Voss et al, 2005;Bartl et al, 2018) and a spin-down time of approximately 4.5 days (Voss et al, 2005). These non-linear processes can be taken into account if the residence time is computed using an eddy-resolving model within a Lagrangian framework.…”

Section: Introductionmentioning

confidence: 99%

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Lagrangian Residence Time in the Bay of Gdańsk, Baltic Sea

et al. 2019

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The impact of synoptic scale and mesoscale variability on the Lagrangian residence time (LRT) of the surface water in the Bay of Gdańsk was investigated using the results from an eddy-resolving model. The computed LRT of 53-60 days was up to four times longer than the estimated flushing time reported by Witek et al. (2003). The highest residence times were those of Puck Bay and near the coast, shallower than 50 m water depth, especially during the winter. These sites also had the highest annual mean in LRT. During the summer, when the level of biological activity is high, the LRT distribution was very heterogeneous and patchy, possibly due to the dynamics of varying eddy field and to variable wind forcing. Long-term run tracking of the inflowing water from the Vistula River (VR) showed a broad spectrum of tracer distribution. The potential impact of a much higher LRT on the near-coastal nitrogen cycle, coastal filter function and genetic differentiation is discussed, and the consequences for coastal zone management are considered. Since residence time is the most important factor regulating nutrient cycling, the incorporation of residence time into the Marine Strategy Framework Directive descriptors would result in an improved, unbiased evaluation of good environmental status.

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Section: Nutrient Cycle and Filter Functionsupporting

confidence: 66%

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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Lagrangian Residence Time in the Bay of Gdańsk, Baltic Sea

et al. 2019

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“…Such pressure gradients mainly originate from waves or from the interaction of near-bottom flow and the bottom topography (Santos et al, 2012). To examine whether the interaction of near-bottom flow with a topographic object could, at least theoretically, create pressure gradients sufficient to drive advection, we used modelled near-bottom flow velocity data of our sampling period and estimated pressure gradients and the Peclet number (Bear, 1972;see Supplement). The modelled near-bottom flow velocity was very low (< 2.5 cm s −1 ) and resulted only in minor pressure gradients (< 0.15 Pa) at a 3 cm high mound (Table S3).…”

Section: Permeable Sediments Of the Vistula Estuarymentioning

confidence: 99%

Particulate organic matter controls benthic microbial N retention and N removal in contrasting estuaries of the Baltic Sea

et al. 2019

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Abstract. Estuaries worldwide act as “filters” of land-derived nitrogen (N) loads, yet differences in coastal environmental settings can affect the N filter function. We investigated microbial N retention (nitrification, ammonium assimilation) and N removal (denitrification, anammox) processes in the aphotic benthic system (bottom boundary layer (BBL) and sediment) of two Baltic Sea estuaries differing in riverine N loads, trophic state, geomorphology, and sediment type. In the BBL, rates of nitrification (5–227 nmol N L−1 d−1) and ammonium assimilation (9–704 nmol N L−1 d−1) were not enhanced in the eutrophied Vistula Estuary compared to the oligotrophic Öre Estuary. No anammox was detected in the sediment of either estuary, while denitrification rates were twice as high in the eutrophied (352±123 µmol N m−2 d−1) as in the oligotrophic estuary. Particulate organic matter (POM) was mainly of phytoplankton origin in the benthic systems of both estuaries. It seemed to control heterotrophic denitrification and ammonium assimilation as well as autotrophic nitrification by functioning as a substrate source of N and organic carbon. Our data suggest that in stratified estuaries, POM is an essential link between riverine N loads and benthic N turnover and may furthermore function as a temporary N reservoir. During long particle residence times or alongshore transport pathways, increased time is available for the recycling of N until its eventual removal, allowing effective coastal filtering even at low process rates. Understanding the key controls and microbial N processes in the coastal N filter therefore requires to also consider the effects of geomorphological and hydrological features.

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“…Nitrification rates were determined using the 15 N-NH + 4 tracer method (Ward, 2005;Veuger et al, 2013;Damashek et al, 2016), as described in detail by Bartl et al (2018). Briefly, polycarbonate bottles were filled with water, avoiding air bubbles, and sealed with a butyl septum.…”

Section: Nitrificationmentioning

confidence: 99%

Extensive nitrification and active ammonia oxidizers in two contrasting coastal systems of the Baltic Sea

Happel

Bartl

Voß

et al. 2018

Environmental Microbiology

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Nitrification is important in nitrogen (N) cycling of aquatic environments, but knowledge about its regulation and importance is sparse. Here we examined nitrification and ammonia oxidizers in the Baltic Sea. We investigated two sites with different catchment characteristics (agricultural and forest), the Bay of Gdánsk (south) and the Öre Estuary (north), and measured pelagic nitrification rates and abundance, composition and expression of ammonia monooxygenase (amoA) genes. Highest nitrification rates were found in the nutrient rich Bay of Gdańsk. Interestingly, abundances of ammonia-oxidizing archaea (AOA) and bacteria (AOB) were orders of magnitude lower than reported from other sites. Although AOA were most abundant at both sites, the highest expression levels were from AOB. Interestingly, few AOA and AOB taxa dominated amoA gene expression, with a Nitrosomarinus related phylotype showing widespread expression. AOA and AOB communities differed between sites and depths, respectively, with the composition in rivers being distinct. A storm event, causing an even depth distribution of nitrification and particles in the Bay of Gdańsk, indicated that the presence of particles stimulate nitrification. The study highlights coastal regions as dynamic sites of extensive pelagic nitrification, which may affect local food web dynamics and loss of N mediated by denitrification.

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River plume and bottom boundary layer – Hotspots for nitrification in a coastal bay?

Cited by 25 publications

References 64 publications

Lagrangian Residence Time in the Bay of Gdańsk, Baltic Sea

Lagrangian Residence Time in the Bay of Gdańsk, Baltic Sea

Particulate organic matter controls benthic microbial N retention and N removal in contrasting estuaries of the Baltic Sea

Extensive nitrification and active ammonia oxidizers in two contrasting coastal systems of the Baltic Sea

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