Periphyton nematode assemblages in association with Myriophyllum spicatum L. in Lake Sakadas, Croatia.

摘要

This survey reports on periphyton nematode assemblages associated with the submersed macrophyte Myriophyllum spicatum sampled in Lake Sakadas, Croatia, at three stations. Nematode abundance and species diversity were examined during one vegetation season (July-September 2004). The measured environmental parameters within macrophyte stands were in the same range at all stations, but changed from the beginning to the end of the season. A significantly lower nematode abundance was recorded for stations I and II compared to station III. A low number of nematode species (maximum of twelve per station) was recorded, with no differences in diversity between stations. The variation in abiotic and biotic parameters allowed us to subdivide the period of investigation as the beginning of nematode colonization (July samples), stabilization (August samples) and stagnation (September samples). Statistically significant differences in chlorophyll A, dissolved oxygen concentration, depth and fresh macrophyte biomass occurred between all three months. Non-metric MDS based on square root transformed nematode abundance data separate the July and August nematode assemblages from the September assemblage. Nematode abundance increased from the beginning to the end of the vegetation season, coupled with a decrease in species number. Epistrate feeders as primary consumers dominated in nematode assemblages in all samples, increasing from July to September, followed by 'chewers' (predators and omnivores) as tertiary consumers. Environmental parameters affect the life span of Myriophyllum spicatum, and could have both direct and indirect effects on nematode abundance and species diversity.