Seasonal budgets of the nutrient elements N and P at the surface of the German Bight during winter 1996, spring 1995, and summer 1994

Brockmann, U. H.; Raabe, Thomas; Hesse, Kirsten; Viehweger, Katrin; Rick, Silke; Starke, Andreas; Fabiszisky, B.; Topcu, Dilek; Heller, René

doi:10.1007/bf02764177

Cited by 22 publications

(9 citation statements)

References 28 publications

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“…11), which is in line with prior observations (e.g., Brockmann et al, 1999;Hydes et al, 2004). The maintenance of these gradients during winter is explained by the limited horizontal mixing due to the density gradients caused by the freshwater influx from the land (Simpson et al, 1993; Hydes et al, 2004) and the trapping of this nutrientrich freshwater at the coast due to the alongshore currents in the study system driven by predominantly westerly winds and the coriolis forcing (Becker et al, 1992;Simpson et al, 1993).…”

Section: Discussionsupporting

confidence: 88%

The acclimative biogeochemical model of the southern North Sea

Kerimoglu¹,

Hofmeister²,

Maerz³

et al. 2017

Biogeosciences

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Abstract. Ecosystem models often rely on heuristic descriptions of autotrophic growth that fail to reproduce various stationary and dynamic states of phytoplankton cellular composition observed in laboratory experiments. Here, we present the integration of an advanced phytoplankton growth model within a coupled three-dimensional physicalbiogeochemical model and the application of the model system to the southern North Sea (SNS) defined on a relatively high resolution ( ∼ 1.5-4.5 km) curvilinear grid. The autotrophic growth model, recently introduced by Wirtz and Kerimoglu (2016), is based on a set of novel concepts for the allocation of internal resources and operation of cellular metabolism. The coupled model system consists of the General Estuarine Transport Model (GETM) as the hydrodynamical driver, a lower-trophic-level model and a simple sediment diagenesis model. We force the model system with realistic atmospheric and riverine fluxes, background turbidity caused by suspended particulate matter (SPM) and open ocean boundary conditions. For a simulation for the period 2000-2010, we show that the model system satisfactorily reproduces the physical and biogeochemical states of the system within the German Bight characterized by steep salinity; nutrient and chlorophyll (Chl) gradients, as inferred from comparisons against observation data from long-term monitoring stations; sparse in situ measurements; continuous transects; and satellites. The model also displays skill in capturing the formation of thin chlorophyll layers at the pycnocline, which is frequently observed within the stratified regions during summer. A sensitivity analysis reveals that the vertical distributions of phytoplankton concentrations estimated by the model can be qualitatively sensitive to the description of the light climate and dependence of sinking rates on the internal nutrient reserves. A non-acclimative (fixed-physiology) version of the model predicted entirely different vertical profiles, suggesting that accounting for physiological flexibility might be relevant for a consistent representation of the vertical distribution of phytoplankton biomass. Our results point to significant variability in the cellular chlorophyll-to-carbon ratio (Chl : C) across seasons and the coastal to offshore transition. Up to 3-fold-higher Chl : C at the coastal areas in comparison to those at the offshore areas contribute to the steepness of the chlorophyll gradient. The model also predicts much higher phytoplankton concentrations at the coastal areas in comparison to its non-acclimative equivalent. Hence, findings of this study provide evidence for the relevance of physiological flexibility, here reflected by spatial and seasonal variations in Chl : C, for a realistic description of biogeochemical fluxes, particularly in the environments displaying strong resource gradients.

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Section: Discussionsupporting

confidence: 88%

The acclimative biogeochemical model of the southern North Sea

Kerimoglu¹,

Hofmeister²,

Maerz³

et al. 2017

Biogeosciences

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“…The combined DON + NH 4 + concentration decreased from 60 µM in the port of Hamburg to approximately 12 µM in the German Bight. These concentrations are in the same range as ours for the estuary, but lower for the saline water of the German Bight, which showed seasonal variability in other studies (Brockmann et al, 1999). Both previous studies Brockmann and Pfeiffer, 1990) and ours found decreasing DON + NH 4 + concentrations in the lower estuary due to dilution with marine water, consistent with conservative mixing.…”

Section: Long-term Changes In Don Loads and Ratiossupporting

confidence: 90%

Turnover of combined dissolved organic nitrogen and ammonium in the Elbe estuary/NW Europe: Results of nitrogen isotope investigations

Schlarbaum¹,

Dähnke²,

Emeis³

2010

Marine Chemistry

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“…4) mirror the admixture of nutrient-rich Elbe discharge (Rick, 1999). Other important nitrate sources include the Weser river and coastal water advected by the Rhine river (Brockmann et al, 1999) that all have high δ 15 N (8-9‰) in flux-weighted annual average loads (Johannsen et al,Fig. 4.…”

Section: Spatial Pattern In the δ 15 N Of Suspended Matter And Surfacmentioning

confidence: 98%

Organic matter degradation in the German Bight/SE North Sea: Implications from stable nitrogen isotopes and amino acids

Serna¹,

Lahajnar²,

Pätsch³

et al. 2014

Marine Chemistry

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Seasonal budgets of the nutrient elements N and P at the surface of the German Bight during winter 1996, spring 1995, and summer 1994

Cited by 22 publications

References 28 publications

The acclimative biogeochemical model of the southern North Sea

The acclimative biogeochemical model of the southern North Sea

Turnover of combined dissolved organic nitrogen and ammonium in the Elbe estuary/NW Europe: Results of nitrogen isotope investigations

Organic matter degradation in the German Bight/SE North Sea: Implications from stable nitrogen isotopes and amino acids

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