Shallowness may be a major factor generating nutrient gradients in the Wadden Sea

Ebenhöh, W.; Kohlmeier, Cora; Baretta, J. W.; Flöser, Götz

doi:10.1016/j.ecolmodel.2003.07.011

Cited by 19 publications

(26 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, the German rivers Ems, Weser and Elbe discharge into the German Bight. As a result of the riverine nutrient input, the German Bight features a generally high primary productivity (Joint and Pomroy, 1993) while it possesses pronounced heterogeneity with strong cross-shore gradients in (i) nutrients (Brockmann et al, 1990;Ebenhöh et al, 2004) and (ii) SPMC and composition (Eisma and Kalf, 1987). The near-coastal waters of the German Bight are characterized by relatively high SPMC of few to several hundred grams per cubic meter in near-bottom regions.…”

Section: Study Areamentioning

confidence: 99%

“…This probably causes a net SPM flux into the Wadden Sea (Burchard et al, 2008(Burchard et al, , 2013. The Wadden Sea is hypothesized to act as bioreactor, where organic components of SPM become remineralized and are exported in dissolved form (Postma, 1984;Ebenhöh et al, 2004;Grunwald et al, 2010) by the offshore-directed component of the estuarine circulation. Along this pathway, dissolved nutrients are assimilated by phytoplankton and thus transferred to bio particulates.…”

Section: Implications Of a Cross-coastal Maximum Of Sinking Velocity mentioning

confidence: 99%

See 1 more Smart Citation

Maximum sinking velocities of suspended particulate matter in a coastal transition zone

et al. 2016

View full text Add to dashboard Cite

Abstract. Marine coastal ecosystem functioning is crucially linked to the transport and fate of suspended particulate matter (SPM). Transport of SPM is controlled by, amongst other factors, sinking velocity w s . Since the w s of cohesive SPM aggregates varies significantly with size and composition of the mineral and organic origin, w s exhibits large spatial variability along gradients of turbulence, SPM concentration (SPMC) and SPM composition. In this study, we retrieved w s for the German Bight, North Sea, by combining measured vertical turbidity profiles with simulation results for turbulent eddy diffusivity. We analyzed w s with respect to modeled prevailing dissipation rates and found that mean w s were significantly enhanced around log 10 ( (m 2 s −3 )) ≈ −5.5. This region is typically found at water depths of approximately 15 to 20 m along cross-shore transects. Across this zone, SPMC declines towards the offshore waters and a change in particle composition occurs. This characterizes a transition zone with potentially enhanced vertical fluxes. Our findings contribute to the conceptual understanding of nutrient cycling in the coastal region which is as follows. Previous studies identified an estuarine circulation. Its residual landward-oriented bottom currents are loaded with SPM, particularly within the transition zone. This retains and traps fine sediments and particulate-bound nutrients in coastal waters where organic components of SPM become remineralized. Residual surface currents transport dissolved nutrients offshore, where they are again consumed by phytoplankton. Algae excrete extracellular polymeric substances which are known to mediate mineral aggregation and thus sedimentation. This probably takes place particularly in the transition zone and completes the coastal nutrient cycle. The efficiency of the transition zone for retention is thus suggested as an important mechanism that underlies the often observed nutrient gradients towards the coast.

show abstract

Section: Study Areamentioning

confidence: 99%

Section: Implications Of a Cross-coastal Maximum Of Sinking Velocity mentioning

confidence: 99%

Maximum sinking velocities of suspended particulate matter in a coastal transition zone

et al. 2016

View full text Add to dashboard Cite

show abstract

“…1). The southeastern portion of the SNS, known as the German Bight surrounded by the intertidal Wadden Sea, is especially characterized by steep gradients with respect to both nutrients (Hydes et al, 1999;Ebenhöh, 2004) and turbidity. The latter is largely determined by suspended particulate matter (SPM) concentrations (Tian et al, 2009;Su et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

The acclimative biogeochemical model of the southern North Sea

Kerimoglu¹,

Hofmeister²,

Maerz³

et al. 2017

Biogeosciences

View full text Add to dashboard Cite

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.

show abstract

“…Shankar and Manjunatha 1994;Woolfe et al 1998;Maldonado et al 1999;Zhou et al 2000;Manjunatha et al 2001;Audry et al 2006;He et al 2006;Karrasch et al 2006;Guo et al 2007), and ecological modelling (e.g. Lindstrom et al 1999;Håkanson et al 2000Håkanson et al , 2004Lindstrom 2001;Johansson et al 2001;Håkanson 2003, 2004;Ebenhöh et al 2004; Barros and Abril 2005;Håkanson and Eckhell 2005;Krivtsov et al 2008a).…”

Section: Introductionmentioning

confidence: 98%

Entropy analysis of SPM patterns: case study of Liverpool Bay

2011

View full text Add to dashboard Cite

were analyzed by means of entropy analysis and factor analysis in order to identify the meteorological and oceanographic variables of importance for the characterisation of the shape of SPM size spectra. Entropy analysis of in situ particle size spectra revealed five basic types, each attributable to different sets of environmental conditions. The results of correlation analysis showed that changes in the position of the main modal are significantly related to several environmental variables. One important class of these relationships is represented by wave-related variables (e.g. wave energy, maximum orbital velocity). Another important class of correlations (e.g. with salinity, density, water depth) can be associated with the inshore-offshore gradient in depth and physicochemical conditions existing in the bay. The strongest correlations, however, were with the air and water temperatures. Factor analysis (with Varimax rotation) of the overall dataset extracted four factors, together explaining over 70% of variance. Factor 1 explains >21% of the total variance, and appears to be related to wave activity. Factor 2, explaining 18.5% of the total variance, appears to be related to tidal currents. Factor 3 explains 16.4% of the total variance observed, and appears to be related to temperaturemodulated seasonal differences in oceanographic conditions. Factor 4 explains 15.2% of the total variance observed, and represents the inshore-offshore gradient in depth and physicochemical conditions. These findings are a step towards a better characterisation of floc size and, therefore, more precise calculations of sedimentation and transport rates needed for an improved understanding of ecosystem functioning in Liverpool Bay and, for that matter, other similar settings.

show abstract

Shallowness may be a major factor generating nutrient gradients in the Wadden Sea

Cited by 19 publications

References 31 publications

Maximum sinking velocities of suspended particulate matter in a coastal transition zone

Maximum sinking velocities of suspended particulate matter in a coastal transition zone

The acclimative biogeochemical model of the southern North Sea

Entropy analysis of SPM patterns: case study of Liverpool Bay

Contact Info

Product

Resources

About