Realm: Freshwater
Climate: Temperate
Biome: Small Lake Ecosystems Central latitude: 52.440000
Central longitude: 13.650000
Duration: 21 years, from 1992 to 2012
Climate: Temperate
Biome: Small Lake Ecosystems Central latitude: 52.440000
Central longitude: 13.650000
Duration: 21 years, from 1992 to 2012
4563 records
153 distinct species
Across the time series Cryptomonas is the most frequently occurring speciesMethods
The lake is sampled at weekly intervals during the growing season and at biweekly intervals during periods with ice cover. Between 1979 and 1986, phytoplankton samples were drawn weekly (in winter biweekly) at the deepest section of the lake (M7 in Table 1; integrated from 0.5, 4, and 7m). A detailed description of the sampling strategy is given in Driescher et al. (1993). Since 1987, integrated samples were collected weekly at five different lake stations (see description below). We assume that change in the sampling strategy did not cause a significant bias in the plankton series, as analysis of synchronous zooplankton counts in 1987 (n-15) revealed no significant differences (Wilcoxon-Mann-Whitney: p>0.1). Moreover, Schellenberger and Stellmacher (1986) found that seston concentrations were quasi homogeneously distributed across the lake. On each sampling date a non fixed concentrated water sample (concentrated through a 5 ?m mesh size) is screened for actual species composition in order to guarantee an accurate species determination in the fixed sample. An aliquot of this concentrated sample is preserved in formaldehyde and stored. Since mid 2016 a photo is taken from this concentrated sample on each sampling date. Cell number and biovolume are determined using an inverted microscope (Utermöhl 1958). We use sedimentation tube volumes between 2100 ml with a diameter of 2.5 cm. We use original Hydro-Bios (Kiel) tubes or tubes following the Hydro-Bios prototype that were built in the IGB workshop. Counting procedure: Transects are counted across the middle of the chamber. If two transects are counted the chamber is turned by 180° for the analysis of a second transect. At least 400 individuals per sample are counted. For large (e.g. Ceratium) and rare species the entire chamber area is screened and counted. Data are documented in a counting protocol according to the programme developed by HAMILTON (1996); Version 3.1 B. Determination of cell dimensions: Cell dimensions are determined via an ocular micrometer or a microscope camera. At least 20 individuals per species are measured if individual numbers are n>20. Used magnifications are: 200 x; 400 x; 1000 x. If measuring of the third dimension (including cells in colonies) is not possible we use length - width - depth relationships from the literature. For centric diatoms and cryptophytes we assume that cell length equals half of the cell diameter. Biovolume determination: Cell biovolume estimates are based on simple geometric forms such as cuboid, sphere, cylinder, cone, spheroid (PADISÀK & ADRIAN 1999, pages 334-351). Cell biovolume estimates for e.g. Ceratium, Staurastrum, Peridinium, Gymnodinium are based on a mix of several different geometric forms, which make the best fit to the cell shape. A list of the specific geometric forms used for each species is given in Appendix 3. Calculation of phytoplankton biomass: The biomass of a single species equals the product of the cell number in the sample and the determined biovolume assuming that: 109 ?m3=1mm3=1mg(specificweight=1g/cm3)=106 ?m3=1?g The biomass of all single species is added up to gain the total biomass of the sample. Biomass is given in ?g/liter respectively mg/m3. For more detail of the biovolume - biomass relationships see MISCHKE & BEHREND (2007). Density is given in individuals per LCitation(s)
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