Natascha Staats

University of Amsterdam, Amsterdamo, North Holland, Netherlands

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Publications (8)13.83 Total impact

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    ABSTRACT: The Ems-Dollard estuary, situated in the north of the Netherlands near to the German border, is covered for a large part by intertidal flats. Currents and wind- induced waves exert a shear stress on these flats, resulting in resuspension of the sediment. Fluctuations of the suspended sediment concentration in the Dollard are strongly affected by erosion due to wind-induced waves and by settling during calm weather conditions. However it is believed that benthic processes influence the amount of sediment that can be resuspended from the intertidal flats. Therefore suspended sediment concentration above the Heringsplaat, an intertidal flat in the Ems-Dollard estuary, was measured during two seasons and related to the dominant benthic biological features. The benthos and the abiotic sediment characteristics were monitored from 1995 till 1997, at two stations. At both stations a peak of chlorophyll-a concentration was found in spring, caused by a diatom bloom. Meiobenthos was dominated by nematodes, macrobenthos by the polychaete Marenzelleria viridis and the amphipod Corophium volutator.
    No preview · Article · Dec 2002
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    ABSTRACT: Three years of combined physical and biological measurements in the Dollard tidal basin showed that in the early spring of 1996, suspended particulate matter (SPM) concentrations were low compared to observations in spring 1995 and 1997. Since in 1996 the duration of ice formation on the tidal flats in winter was much longer than in 1995 or 1997 (until late February), it is proposed that ice cover reduced resuspension of bed material by enhancing consolidation of the sediment and thus increasing the critical shear stress for erosion (τcrit), and also by preventing the occurrence of high waves. Both phenomena led to low suspended particulate matter (SPM) concentrations. After the ice cover vanished, the clear water phase was followed by a microalgal bloom both in the water column and on the sediment. During the algal bloom, SPM concentrations remained low. Floc size measurements indicated that low SPM concentrations during the benthic and pelagic algal blooms were not caused by increased flocculation. On the sediment bed however benthic microalgae produced large amounts of extracellular carbohydrates, which led to an increase in bed strength (τcrit) and a reduction of resuspension, and thus kept SPM concentrations low during the algal bloom.
    No preview · Article · Sep 2001 · Estuarine Coastal and Shelf Science
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    ABSTRACT: The chlorophyll a content and two operational fractions of carbohydrate (water extractable and EDTA extractable) were measured every three months during one year along transects on a tidal flat in the Ems-Dollard estuary (The Netherlands). Chlorophyll a was used as an indicator of microphytobenthos biomass, which was composed predominantly of epipelic diatoms. Both carbohydrate fractions correlated significantly with chlorophyll a. EDTA extractable carbohydrates were more resistant towards degradation than the water extractable fraction. During most of the year, concentrations of chlorophyll a and carbohydrates were low, but in June, high concentrations of up to 90 g chlorophyll a/g sediment were found in a narrow zone running parallel to the channel. Maximum concentrations of water extractable carbohydrates and EDTA extractable carbohydrates ranged between 800–1200 and 600–800 g/g sediment, respectively. The mud content was high ( 90%) at the margin of the tidal flat. This was not limited to the growth season of the diatoms, but was observed throughout the year. This indicated that the high mud content at the mudflat margin was mainly caused by hydrodynamic factors, and not by biostabilization. In June, exceptionally high diatom densities were found in sediment with a high mud content. There was only minor evidence that biostabilization by epipelic diatoms lead to a further increase in the mud content of the sediment.
    Preview · Article · Mar 2001 · Hydrobiologia
  • Natascha Staats · LJ Stal · LR Mur
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    ABSTRACT: During the stationary phase of a batch culture of the epipelic diatom Cylindrotheca closterium, accumulation of exopolysaccharides and intracellular carbohydrates was observed. When nitrogen was added to the culture in the stationary phase, growth was resumed and the accumulation of exopolysaccharides was delayed. This indicated that nitrogen depletion caused cessation of growth, and stimulated exopolysaccharide accumulation. Exopolysaccharide accumulation was also stimulated when cells were either resuspended in medium lacking N or P, or when they were inoculated in medium with low concentrations of N or P. Growth was not immediately affected by low N or P concentrations. S depletion only resulted in exopolysaccharide accumulation when growth was affected. Si or Fe depletion did not stimulate exopolysaccharide accumulation, even when growth rates were lowered. Apparently, stimulation of exopolysaccharide accumulation is dependent on the type of nutrient depletion. Intracellular storage carbohydrates did not accumulate when cells were incubated at low N or P concentrations. Cells grown with ammonium as nitrogen source produced more carbohydrates (both extracellular and intracellular) than cells grown with nitrate as nitrogen source, indicating that both exopolysaccharides and intracellular carbohydrates accumulated as a result of overflow metabolism.
    No preview · Article · Jul 2000 · Journal of Experimental Marine Biology and Ecology
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    N. Staats · L. J. Stal · B. de Winder · L. R. Mur
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    ABSTRACT: The secretion of exopolysaccharide in an axenic culture of the marine benthic diatom Cylindrotheca closterium was investigated. The central question of the experiments was if polysaccharide secretion was dependent on light and photosynthesis. Cells were incubated in the Light, in the dark, or in the light with addition of the inhibitor of Photosystem II, 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU). These treatments were also applied to a population of benthic diatoms on an intertidal mudflat in the Westerschelde (Scheldt estuary, The Netherlands). In the light (60 mu mol photons m(-2) s(-1)) C, closterium showed high rates of polysaccharide secretion, while no secretion was observed in the dark or in the presence of DCMU. No intracellular carbohydrate was converted to exopolysaccharide in the dark or in the Light with DCMU added. This indicated that secretion of exopolysaccharide was dependent on oxygenic photosynthesis. Similarly, high rates of exopolysaccharide accumulation were observed during daytime emersion on the mudflat, but not in darkened or DCMU-treated sediment. This demonstrated that the pattern observed in cultures of C, closterium was reproducible in situ. It was observed that during daytime emersion patterns of vertical migration in the dark and DCMU-treated plots did not differ from those in the light. This implies that motility was not the steering factor for the observed accumulation of exopolysaccharide in the Light. When an axenic culture of C. closterium was incubated under an alternating 12 h Light:12 h dark cycle, exopolysaccharide concentrations decreased in the dark. Degradation of exopolysaccharide was also observed in the natural population on the mudflat during emersion at night. Because no bacteria were present in the C, closterium cultures, it was conceived that the degradation of exopolysaccharide observed in cultures was due to secretion of hydrolytic enzymes by C, closterium.
    Preview · Article · Feb 2000 · Marine Ecology Progress Series
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    B De Winder · N Staats · L.J Stal · D.M Paterson
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    ABSTRACT: Two different benthic phototrophic communities on tidal flats were investigated for their carbohydrate content and distribution. Carbohydrates were analysed as two operationally defined fractions, related to the difficulty of extraction from the sediment matrix. Water-soluble (colloidal) and EDTA-extractable (capsular) carbohydrates were measured in a cyanobacterial mat and a diatom biofilm. The chlorophyll-specific carbohydrate content of the two communities was very different. The diatom biofilm contained up to 100 times more colloidal carbohydrate than the cyanobacterial mat. The concentrations of colloidal carbohydrates in the diatom biofilm correlated with biomass (chlorophyll-a), but this was not the case with the carbohydrate in the EDTA extract. It is proposed that the capsular carbohydrates were probably recalcitrant to mineralisation and therefore accumulated in the sediment. Neither colloidal nor EDTA-extractable carbohydrate in the cyanobacterial mat correlated with chlorophyll-a. This was probably an artefact caused by the fact that approximately 50% of the chlorophyll-a in the mat was attributed to diatoms. The characteristics of extracellular polysaccharides were investigated in laboratory cultures of the dominant organisms. Extracellular polysaccharides of the cyanobacterium Microcoleus chthonoplastes and of the diatom Navicula menisculus did not contain uronic acids. However, carboxylated sugars were found in large quantities in the capsular polysaccharides of the cyanobacterium and were present in equal ratios in the extracellular and capsular carbohydrate of the diatom Cylindrotheca closterium. Both in laboratory model systems of diatom biofilms and in situ, enhanced colloidal carbohydrate production was observed in the light. No light-dependent increase in carbohydrate concentration was found for the cyanobacterial mat. The cyanobacteria formed a mat in which the filamentous organisms entangled sand grains and attached firmly to the substratum. The interparticle spaces were completely occluded by polymers, whereas in the diatom biofilm the organic matrix was less well developed and void spaces could still be discerned. It is conceived that the properties of extracellular polysaccharides influence the stability of the sediment bed. © 1999 Elsevier Science B.V. All rights reserved.
    Full-text · Article · Sep 1999 · Journal of Sea Research
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    Natascha Staats · Ben De Winder · LUCAS J. STAL · LUUC R. MUR
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    ABSTRACT: The production and composition of extracellular polymeric substances (EPS) in axenic batch cultures of the benthic marine epipelic diatoms Navicula salinarum and Cylindrotheca closterium were investigated. EPS was secreted into the medium and the bulk was loosely associated with the cells. Neither N. salinarum nor C. closterium formed a well-defined polysaccharide capsule. EPS of both N. salinarum and C. closterium consisted predominantly of polysaccharide but small quantities of protein were present as well. EPS also contained uronic acids and SO4 groups. Analysis of monosaccharides using gas chromatography showed that for both species glucose and xylose were the main constituents, but several other monosaccharides were present in smaller quantities. Two fractions of EPS were distinguished: a small amount was secreted into the medium and a second fraction was extracted in water at 30 °C. For both species the two fractions differed somewhat in composition, indicating that they represented two different types of EPS. The EPS produced by N. salinarum and by C. closterium differed in their composition. The rate of EPS production in batch culture was highest during the transition from exponential growth to stationary growth. Negatively charged groups such as uronic acids and sulphated sugars determine the adhesion capacity of EPS and probably play an important role in the stabilization of intertidal sediments on which these diatoms grow and produce biofilms.
    Preview · Article · May 1999 · European Journal of Phycology
  • N. Staats · LR Mur
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    ABSTRACT: The phosphorus-limited growth of cultures of the nitrogen-fixing cyanobacteria Aphanizomenon and Anabaena was investigated. In conditions of nutnent and light excess Anabaena has a competitive advantage. The lower the light intensity conditions at which Aphanizomenon populations dominate are indicated for future study.
    No preview · Article · Dec 1995 · Water Science & Technology