Wassertransport und Wasseraustausch im nordfriesischen Wattenmeer — Ergebnisse numerischer Untersuchungen

Dick, S.; Schönfeld, W.

doi:10.1007/bf02794051

Cited by 23 publications

(22 citation statements)

References 10 publications

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“…The model is described elsewhere (Dick and Schönfeld 1996). Since we expected that stream velocity would be the best indication of the tidal phases, possible tidal variations of plankton data were checked by testing the significance of Pearson product-moment correlations between the data.…”

Section: Methodsmentioning

confidence: 99%

Tidal impact on planktonic primary and bacterial production in the German Wadden Sea

Poremba¹,

Tillmann²,

Hesse³

1999

Helgol Mar Res

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Tidal variation of biological parameters was studied at three anchor stations in selected inlet channels of the northern German Wadden Sea in May and July 1994. Concentrations of bacteria, chlorophyll a and suspended matter as well as primary and bacterial production were assessed over a period of 25 h in the surface and in the bottom water. Diurnal variation in primary production was found both under in situ light conditions and under constant illumination. Tidal turbulence caused the introduction of detritus, bacteria and pigments from the sediment into the water column. The impact of sediment resuspension was most evident in the bottom water, leading to tidally oscillating bacterial production rates which were high during high stream velocity and low during the slack times. Estimations of the areal daily phytoplankton production and corresponding bacterial carbon demands were unbalanced. Primary production accounted for only 25-45% of the total bacterial carbon requirement. This discrepancy is due to the shallow euphotic depth in the Wadden Sea, allowing net primary production only in the upper 2-3 m of the water column, while the relatively high levels of bacterial activity do not show a vertical decline. Assuming that the specific biological activities in the water columns over the tidal flats are similar to those found in the inlet channels, it was found that production processes dominate in shallow areas whereas decomposition processes dominate in the deep channels. Moreover, the predominance of heterotrophic processes in the inlet channels means that additional organic carbon sources must contribute to the heterotrophic metabolism in the deep parts of the Wadden Sea, and that the horizontal flux of material is important in this turbid mesotidal ecosystem.

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Section: Methodsmentioning

confidence: 99%

Tidal impact on planktonic primary and bacterial production in the German Wadden Sea

Poremba¹,

Tillmann²,

Hesse³

1999

Helgol Mar Res

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“…In the water column of the Wadden Sea, spatial variation due to the mixing of water from various sources was studied (Brasse et al 1999;Dick and Schönfeld 1996;Zimmerman and Rommets 1974). Major currents between North Sea, Wadden Sea and rivers partly determine the concentrations of Chl-a and SPM (Grossart et al 2004), and some researchers could optically distinguish water types and fronts (Hoge and Swift 1982;Reuter et al 1993).…”

Section: ¡1mentioning

confidence: 99%

“…Residence time is typically 11-12 tidal cycles (1 week) (Postma 1982) in the Wadden Sea but much shorter at areas directly connected with the North Sea (Dick and Schönfeld 1996). Therefore, the water column is usually well mixed (Tillmann et al 2000;Postma 1982).…”

Section: Tidal Variationmentioning

confidence: 99%

A review on substances and processes relevant for optical remote sensing of extremely turbid marine areas, with a focus on the Wadden Sea

et al. 2010

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The interpretation of optical remote sensing data of estuaries and tidal Xat areas is hampered by optical complexity and often extreme turbidity. Extremely high concentrations of suspended matter, chlorophyll and dissolved organic matter, local diVerences, seasonal and tidal variations and resuspension are important factors inXuencing the optical properties in such areas. This review gives an overview of the processes in estuaries and tidal Xat areas and the implications of these for remote sensing in such areas, using the Wadden Sea as a case study area. Results show that remote sensing research in extremely turbid estuaries and tidal areas is possible. However, this requires sensors with a large ground resolution, algorithms tuned for high concentrations of various substances and the local speciWc optical properties of these substances, a simultaneous detection of water colour and land-water boundaries, a very short time lag between acquisition of remote sensing and in situ data used for validation and suYcient geophysical and ecological knowledge of the area.

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“…For example, Dick and Schönfeld (1996) have recently estimated the flushing time within the tidal basins to be 2-9 days. Moreover, we also found indications that the development of bacteria lags behind that of the algae, which was even more unexpected since the hydrodynamic turbulence should not only prevent the establishment …”

Section: Distribution Patterns and Seasonal Succession Of The Planktomentioning

confidence: 99%

“…The work presented in this paper is the first comprehensive dataset of bacterioplankton in the German Wadden Sea, which provides information on whether there are spatial gradients even though the area is intensively hydrodynamically mixed. For example, the flushing times in the tidal basins of the study site (the time needed to renew the water by 60%) are 2-9 days (Dick and Schönfeld 1996), so that a homogeneous distribution could also be expected. Moreover, since the Wadden Sea usually possesses high nutrient loading, which facilitates algae growth, but also receives additional organic matter imported from the adjacent sea and from terrestrial runoff, we also compared bacterial abundance with chlorophyll-a, so that we could test whether the algae-bacteria link is different from those reported in the literature.…”

Section: Introductionmentioning

confidence: 99%

Distribution patterns of bacterioplankton and chlorophyll-a in the German Wadden Sea

Poremba¹,

Tillmann²,

Hesse³

1999

Helgol Mar Res

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In a first synoptic evaluation, the temporal and spatial distribution of bacterioplankton and chlorophyll-a were determined in the German Wadden Sea. Three surveys were undertaken in winter, spring, and summer of 1994 using up to eight ships simultaneously between the river Ems and Sylt island. Despite intensive hydrodynamic mixing of the Wadden Sea water, spatial gradients were obvious. The abundance of bacterioplankton ranged from 0.4 to 26×10 5 ml -1 and chlorophyll-a varied between <0.1 and 79 µg l -1 . In winter, relatively homogeneous distribution patterns of both parameters with small gradients were found. Highest chlorophyll-a values connected with a highly patchy structure were observed in spring, while in summer both total chlorophyll-a values and the complexity of the distribution pattern had decreased. In contrast, bacterial numbers increased steadily from January to July with the highest bacterial densities and greatest patchiness observed in summer. Moreover, in some regions of the Wadden Sea, a trophic succession of algae as carbon producers and bacteria as consumers was evident. Correlation analysis verified the relationship between bacteria and chlorophyll a, indicating bottom-up control of bacterial abundance in the northern part of the German Wadden Sea. Since the observed regression slope is remarkably low (0.12-0.46) compared to literature values (0.5-0.8), we suggest that the link between phytoplankton and bacteria found here is a special characteristic of the Wadden Sea as a transition zone between the coastal region and the outer North Sea.

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Wassertransport und Wasseraustausch im nordfriesischen Wattenmeer — Ergebnisse numerischer Untersuchungen

Cited by 23 publications

References 10 publications

Tidal impact on planktonic primary and bacterial production in the German Wadden Sea

Tidal impact on planktonic primary and bacterial production in the German Wadden Sea

A review on substances and processes relevant for optical remote sensing of extremely turbid marine areas, with a focus on the Wadden Sea

Distribution patterns of bacterioplankton and chlorophyll-a in the German Wadden Sea

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