Biome: Temperate shelf and seas ecoregions
Central latitude: 51.549250
Central longitude: 3.912051
Duration: 9 years, from 1982 to 1990
109 distinct species
Across the time series Cryptomonas is the most frequently occurring species
MethodsFor the phytoplankton analyses. only the easternmost and westernmostcompartments of the Oosterschelde were sampled (Figure 1). Eastern andwestern compartments will be further referred to as E and W respectively.Some hydrographical data. characteristic for both areas during the pre-barrier(1980-1983) and the barrier (1984-1986) period. are summarized in Table I andFigure 2. The eastern compartment differs from the western area by its muchlower mean depth and larger residence time. Current velocities decreased andresidence times increased during 1984-1986. the barrier period. Freshwaterinputs mainly entering the system from the northern branch via the Volkerak(Figure 1) amounted to 50-60 m3 s1 (Wetsteyn et al.. 1990). This was a verysmall fraction only (~l%0; Knoester et al.. 1984) of the amount of incomingseawater with each tide.In general. the Oosterschelde water is well mixed vertically. Salinitymeasurements of the surface. mid-depth and bottom water were regularlyperformed as a check on vertical mixing.In W. samples were taken at buoy R14 (main channel in the vicinity of thestorm-surge barrier. Figure 1). depth ?35 m; in E at the centrally located buoyLG-PK (Figure 1). depth ?20 m. All samples were taken at mid-depth duringhalf-tide periods when maximum current velocities caused vertical distributionsof the phytoplankton as homogeneous as possible. Sampling was carried outweekly from March to October (1982-1986) and incidentally during the rest ofthe year. In 1982 W was sampled biweekly. In 1985 only E was sampled.Water transparency was measured using a Secchi disc. Data about columnlight intensity. water temperature. suspended matter concentrations andmacronutrients (silicate. ammonium. nitrate and phosphate) were derived fromVegter and De Visscher (1987). Klepper (1989). Wetsteyn et al. (1990) andWetsteyn and Bakker (1990). Wind velocity data were obtained from the RoyalDutch Meteorological Institute.Phytoplankton analysisWater for phytoplankton analysis was sampled in 1 1 glass bottles. preservedbefore sedimentation with Lugol's solution. Phytoplankton cells were countedwith an inverted microscope.For the nomenclature of diatoms Hustedt (1930) and Drebes (1974) werefollowed. The Haptophycean flagellate Phaeocystis was not identified to specieslevel because Jahnke and Baumann (1987) suggested that Phaeocystis pouchetiicannot be considered conspecific with P.globosa; these species differ in colonyshapes. in distribution of cells within the colony and in temperature tolerances.Cell counts and volume measurements were converted to carbon using theequations of Eppley (in Smayda. 1978). For the presentation and thepreprocessing of the species data. logarithmic values of the carbon content ofeach species population per sampling date were calculated and plottedsymmetrically as kite diagrams along the horizontal (time) axis (Figures 4 and 5).Kite diagrams. first constructed by Lohmann (1908). are still considered topresent adequately phytoplankton species assemblages and succession (cf. Reidet al.. 1985). In these diagrams time is the horizontal axis. Species are arrangedvertically in a sequence that approximates their seasonal succession. Thissequence was derived from the divisive hierarchical clustering method TWINSPAN(Hill. 1979a). which performs a simultaneous ordering of samples and species.A number of diatoms and flagellates was not identified to species level anddiffered in dimensions. In order to estimate the carbon contents more precisely.these species were distinguished in size classes. indicated in Table III. Unit of abundance = IndCountInt, Unit of biomass = NA
Citation(s)Bakker, C., Herman, P.M.J. & Vink, M. (1990) Changes in seasonal succession of phytoplankton induced by the storm-surge barrier in the Oosterschelde (S.W. Netherlands). Journal of Plankton Research, 12, 947-972.
Bakker, C. & Herman, P.M.J. (1990) Phytoplankton in the Oosterschelde before, during and after the storm-surge barrier (1982-1990). Netherlands Institute of Ecology; Centre for Estuarine and Marine Ecology, Netherlands. EurOBIS Data. Available at: http://www.iobis.org/mapper/?dataset=505, accessed 2013.
Bakker, C., Herman, P. & Vink, M. (1994) A new trend in the development of the phytoplankton in the Oosterschelde (SW Netherlands) during and after the construction of a storm-surge barrier. The Oosterschelde Estuary (The Netherlands): a Case-Study of a Changing Ecosystem, pp. 79-100. Springer.