Aquatic macrophytes as a habitat for free-living nematodes

Abstract The composition, trophic structure and diversity of nematode assemblages associated with three aquatic macrophyte species (Polygonum amphibium, Carex sp., Ceratophyllum demersum) were surveyed. Sampled stands were present at the three sites of the north bank in the Čonakut Channel (Nature Park Kopački rit, Croatia). They were all submerged during the period of investigation, which included two vegetation seasons. Nematode abundances (expressed as a number of individuals per 100 g of macrophyte dry weight) differ between the two vegetation seasons and between the sites, but not between the macrophyte species. In total, 19 nematode species were recorded. Chromadorina viridis, C. bioculata, Brevitobrilus stefanskii, Eutobrilus notus, Prodorylaimus longicaudatus and Ethmolaimus sp. were associated with all macrophyte species. Genera Eutobrilus, Brevitobrilus and Chromadorina were present at the highest relative abundances. Species diversity (H and Simpson's D) and evenness (Pielou's J), calculated on the nematode species level, display little or no change in relation to different macrophyte species. Ceratophyllum demersum associated nematode fauna had distinct dominance of one species (Eutobrilus notus) and consequently lower evenness, which was not statistically significant. Chewers (CH) represented the dominant trophic group of total nematode abundance for all three macrophyte species followed by epistrate feeders (EF). Detritus feeders (DF) and suction feeders (SF) were represented by low relative abundances. This paper is a contribution to ecology of aquatic nematodes associated with macrophyte species in mesoeutrophic to eutrophic slow flowing channel.