Inter-annual variation in macroinvertebrate communities in a shallow forest lake in eastern Finland during 1990–2001

Cylindrospermopsis raciborskii undergoes characteristic morphological changes during its annual population development. Primary filaments (those that derive directly from the akinetes) possess the following morphological features: the trichomes have one or two acuminate ends; they are narrower (2.4–2.6 μm) tfhan older filaments, their lengths vary in a wide range (from 40 to 300 μm); some of them are straight but others are slightly coiled even in populations that later consist exclusively of straight filaments; cell walls between the cells are not or only hardly visible; the filaments have a fine granulation but no gas-vacuoles, polyphosphate- or any other contrasting bodies are seen. The secondary filaments deriving from the first division of primary filaments are similar but with only one acuminate end. This way, the number of germinating akinetes can be estimated as the number of primary filaments + 1/2 number of secondary filaments. The described morphological method to estimate inoculum size of C. raciborskii has limitations. (1) The number of akinetes that we get in this way is only a minimum number since germination is not synchronous under field conditions and probably not each akinete germinates that is present in the sediments. (2) The method is applicable only if germination occurs suddenly (relatively synchronously). This is often the case in a temperate region where germination is triggered by temperature. (3) The method cannot be used in tropical or subtropical lakes where water temperature is permanently rather high and akinetes do not develop or develop only very rarely. (4) Being an a posteriori method it cannot be used as predictive tool. Estimations for Lake Balaton are in a good agreement with results of studies with other methods (germination in laboratory cultures and direct counting) and have the advantage that they do not need time-consuming experimenting or difficult direct countings.     

Perch (Perca fluviatilis L.) parasites reflect ecosystem conditions: a comparison of a natural lake and two acidic reservoirs in Finland

Parasite communities of perch were studied in a natural lake (Vetämäjärvi) and two reservoirs (the Kyrkösjärvi and Liikapuro reservoirs) located in Western Finland. All water bodies studied are small, shallow and humic. However, the reservoirs are more acidic than the lake (pH 5.9 and 5.3 vs. 6.4). Altogether, 18 parasite species were found, but the component communities were reduced in the harsh conditions of the reservoirs (12 and six species) as compared with the lake (17 species). In addition, the mean number of metazoan parasite specimens per fish was markedly lower in the reservoirs (64.3 and 14.3 specimens) than in the lake (116.1 specimens). Our prediction on the depauperation of parasite communities in reservoirs as compared with the lake was confirmed. Many ectoparasite groups were rare and most of the digenean parasites using molluscs as their intermediate host were absent from the reservoirs due to the inability of molluscs to tolerate the acidic water. The only digenean parasite found in the less acidic reservoir was Bunodera luciopercae. There were also species that preferred reservoirs as was expected. The protozoan ciliate Capriniana piscium benefiting acidic water and Acanthocephalus lucii, due to the abundance of its intermediate host, were most prevalent in the reservoir conditions.     

Prediction of product formation as an aid to decision-making in pilot plant experiments on batch fermentations

A mathematical model for the prediction of product formation in batch processes is presented. The suggested procedure allows production of a prognose at any given moment of a run concerning the product concentration at any future moment of the same experiment. The series of subsequent prognoses thus produce a trend, and it is assumed that an analysis of the trend may provide information, which is useful in the evaluation of different decision alternatives in pilot plant batch experiments.