Long-term development of the crustacean plankton in the Saidenbach Reservoir (Germany) – changes, causes, consequences

Hörn, W.

doi:10.1023/b:hydr.0000008518.30455.5e

Cited by 25 publications

(26 citation statements)

References 10 publications

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“…The statistical analyses revealed that the highest abundances of crustaceans often occurred simultaneously with high abundances of A. formosa in the eutrophic years until 1990. The significant decrease in the total mean crustacean biovolume in all seasons after 1990 is largely attributed to important changes in the fish population structure (Horn, 2003b). Sars, Eudiaptomus gracilis G.O.…”

Section: Other Factorsmentioning

confidence: 99%

Long-term trends in the diatom composition of the spring bloom of a German reservoir: is Aulacoseira subarctica favoured by warm winters?

et al. 2011

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Summary 1. Long‐term data on the meteorology, hydrology, physicochemistry and plankton of a reservoir and its tributaries in SE Germany run from 1976 until now. This dimictic reservoir changed from mesotrophic to eutrophic in the 1970s, remained eutrophic in the 1980s and returned to the mesotrophic state after a sharp reduction in P loading in 1990. 2. Phytoplankton biomass reaches an annual maximum in spring and consists almost entirely of diatoms. While Asterionella formosa was dominant until 1990, Aulacoseira subarctica became more frequent at the end of the 1990s and was particularly abundant in years with short winters. 3. Statistical analyses suggested that these changes were triggered primarily by the mild winters that were frequent after 1988. Climate‐related hydrophysical variables and the initial biomass of the diatoms at the beginning of the year, considered as an ‘inoculum’, were identified as most important. These variables explained 39% of the total variance of the relative abundance, whereas the change in trophic conditions was responsible for about 20%. 4. The absolute and relative abundance of A. subarctica was positively related to short ice cover, early ice‐out and a long‐lasting spring circulation. Owing to its physiological traits, and particularly its ability to survive under low‐light conditions, A. subarctica benefitted from short, mild winters. Under such conditions, it could sustain or establish a high initial biomass, whereas the concentrations of the other diatoms decreased over winter. However, this advantage may be lost if further warming causes an early onset of summer stratification. Because of its low population growth rate and requirement for high turbulence, A. subarctica needs long, cold springs to exploit the improved starting conditions and to become abundant. 5. In contrast to A. subarctica, A. formosa required a substantial soluble reactive phosphorus supply to compete successfully. The eutrophic conditions until 1990 were the prerequisite for its mass growth under low‐light and low‐temperature conditions during the spring. After reduction in P concentration from 1990, A. formosa declined and other diatom species became more abundant. 6. These other diatoms may be viewed as ‘stopgaps’ when conditions were not favourable for A. subarctica or A. formosa. Diatoma elongatum exploited brief circulation periods in years with low P loading. Synedra acus and Fragilaria crotonensis, because of their poor competitive ability at low light intensity, reached high density in the upper water column in the transitional period between spring circulation and summer stratification. 7. Our study suggests that climate‐related variables have crucial impacts on the spring phytoplankton dynamics of deep stratified waterbodies. They can mask the consequences of changes in the trophic conditions and, corresponding to the functional traits of the different phytoplankton species, also decisively control their relative abundances. In this reservoir, the warmer winters and prolonged spring circulation...

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Section: Other Factorsmentioning

confidence: 99%

Long-term trends in the diatom composition of the spring bloom of a German reservoir: is Aulacoseira subarctica favoured by warm winters?

et al. 2011

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“…It has been investigated continuously every week or every other week since 1975 (e.g. Horn 2003aHorn , 2003b in terms of biological (phytoplankton and zooplankton to species level), chemical (e.g. nutrients, oxygen, pH) and physical variables (temperature, turbidity among others).…”

Section: Study Sitementioning

confidence: 99%

“…Several methods were tested on long-term series of diatoms from the Saidenbach Reservoir (Saxony, Germany) Horn 2003aHorn , 2003b, which have undergone climatic as well as trophic changes in the last 31 years. During this 31-year period, the yield and duration of the phytoplankton spring blooms have varied considerably, so these data may provide a basis for comparing methods (Horn et al 1994;.…”

Section: Introductionmentioning

confidence: 99%

Identifying cardinal dates in phytoplankton time series to enable the analysis of long-term trends

et al. 2007

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Phenology and seasonal succession in aquatic ecosystems are strongly dependent on physical factors. In order to promote investigations into this coupling, methods of characterising annual time series of phytoplankton were derived and applied to a 31-year data set from Saidenbach Reservoir (Saxony, Germany). Field data are often scarce and irregularly sampled, particularly in the transition period from winter to spring, so reliable methods of determining cardinal dates in the time series are necessary. The proposed methods were used to determine the beginning, maximum and end of the spring mass development of phytoplankton by estimating the inflexion points (A), fitting a Weibull-type function (B) and fitting linear segments to the logarithmic values (C). For the data set from Saidenbach Reservoir, all three methods proved to be relevant to the analysis of long-term trends. Differences between the maxima determined by the different methods seemed small, but there were deviations when the maximum was related to physical factors such as ice-out. The Weibull-type fit gave the most reliable and comprehensible results and is recommended for trend analyses. For all methods, long-term analysis of the duration of the spring mass development and the duration of the spring full circulation revealed a period of consistently low values (1975-1990) followed by a period of higher values (1990-2005). These periods were also identified for the date of ice-out, although in this case there was a period of high values followed by a period of low values. A sensitivity analysis that compared results from subsampled time series with increasing time intervals indicated that a minimum of one sample every three weeks is needed to obtain reliable results.

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“…One might argue that the year classes after 2001 were negatively influenced by the exceptionally strong year class of 2001. But the zooplankton dynamics in Saidenbach Reservoir are not comparable to that reported from Alderfen Broad, showing remarkably stable seasonal patterns each year since the early 1990s (Horn, 2003). Moreover, zooplankton densities rather tended to be higher in 2002 and 2003 compared to earlier years (Table 1, compare Hu¨lsmann et al, 2006).…”

Section: Discussionmentioning

confidence: 70%

“…Data were provided by W. Horn, partly reported in Hu¨lsmann et al (2006). Sampling and processing was done according to Horn (2003), considering only epilimnetic samples, since roach preferentially dwell close to the surface (Kahl and Radke, 2006a). The duration of the winter stagnation was determined as the period with ice cover.…”

Section: Methodsmentioning

confidence: 99%

The impact of water level fluctuations on the year class strength of roach: Implications for fish stock management

et al. 2008

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Water level fluctuations in a drinking water reservoir (Saidenbach Reservoir, Saxony, Germany) and length-frequency data of roach (Rutilus rutilus) derived from gillnet catches were studied over a period of eight succeeding years and subsequently analysed with respect to level change and cohort establishment. The results indicate a strong impact of water level on the year class strength of roach. Constantly high water level with large areas of inundated plants led to a very strong roach year class. Conversely, decreasing water level shortly after the spawning period was found to result in a total loss of the new roach year class. Any other possible factors influencing year class strength of roach (such as food, temperature, winter duration) may only play a role if the water level after spawning remained relatively stable. Consequently, water quantity management in reservoirs can be used as a biomanipulation tool to reduce the planktivorous fish stock and to improve water quality, which should be an interesting option especially in drinking water reservoirs.

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Long-term development of the crustacean plankton in the Saidenbach Reservoir (Germany) – changes, causes, consequences

Cited by 25 publications

References 10 publications

Long-term trends in the diatom composition of the spring bloom of a German reservoir: is Aulacoseira subarctica favoured by warm winters?

Long-term trends in the diatom composition of the spring bloom of a German reservoir: is Aulacoseira subarctica favoured by warm winters?

Identifying cardinal dates in phytoplankton time series to enable the analysis of long-term trends

The impact of water level fluctuations on the year class strength of roach: Implications for fish stock management

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