Aquatic fungi and straminipilous organisms in lakes of the Augustowska Primeval Forest, Poland

We analyzed species composition of aquatic fungi and straminipilous organisms in six lakes located within the Augustowska Primeval Forest, Poland. Mycological observations conducted in the spring and autumn seasons together with hydrochemical analysis in the 2010-2012 revealed the presence of 44 species (10 aquatic fungi and 34 straminipilous organisms). Among the taxa detected, there were some potential pathogens of economically valuable fish species and spawn, including Achlya americana, Ac. polyandra, Saprolegnia ferax and S. parasitica. Some of the species were crustacean pathogens, such as Lagenidium giganteum, Myzocytium microsporum and M. zoophthorum. There were also some common human pathogens Aspergillus niger and Candida tropicalis. Some species, such as Achlya klebsiana, Ac. prolifera, Nowakowskiella elegans, N. macrospora, Pythium debaryanum, Py. inflatum, Rhizophlyctis rosea and Saprolegnia litoralis were common phytosaprobionts. The largest number of species of fungi and straminipilous organisms was identified in Lake Sajenek (22), the fewest in Lake Biae (12). The quantitative composition and qualitative differentiation of mycobiota were influenced by the content of biogenic compounds and the amount of organic substance. The elevated levels of these parameters (Lake Sajenek) stimulated the growth of fungi and straminipilous organisms, whereas very low concentrations of biogenic compounds and a small amount of organic matter (Lake Biae) had an inhibitory effect. Statistical analysis of the results was conducted to determine the correlations between the number of fungal and straminipilous species and the hydrochemical parameters, i.e. water temperature, the level of nitrogen compounds (nitrate nitrogen, ammonium nitrogen), calcium carbohydrate, magnesium carbohydrate, water oxidizability and the content of dry residue, dissolved substances and suspension.