The influence of macrophytes on the spatial distribution of littoral rotifers

1. The effect of macrophytes on the spatial distribution of littoral rotife rs was examined in Lake Rotomanuka, New Zealand (37 degrees 55'S, 175 degre es 19'E). Total rotifer abundances and those of abundant species, were comp ared between three macrophyte species, Myriophyllum propinquum, Eleocharis sphacelata and Egeria densa, and spatially across a littoral transect in re lation to these species. 2. The abundances of many species, for example Euchlanis dilatata, Lecane c losterocerca and L. lunaris, differed significantly between macrophyte spec ies. More planktonic forms, Ascomorpha saltans, Keratella cochlearis and Sy nchaeta oblonga, however, showed no significant preference for macrophyte s pecies. 3. Differences in rotifer abundances were evident even when different speci es of macrophyte grew in close proximity to one another, indicating that va riations in physical and chemical conditions, which occur in the littoral o f Lake Rotomanuka, could be largely discounted for much of the variation be tween macrophyte species. 4. Variation in rotifers between macrophytes was probably the result of a n umber of factors, including differences in macrophyte morphology, macrophyt e age, epiphytic algal growths and the differential effects of predation by invertebrates and fish between macrophytes. 5. Variability of rotifer abundances spatially across the ecotone was less marked than between macrophyte species. The species of macrophyte occurring , and therefore the community composition and distribution of macrophyte sp ecies in the littoral, appears to be a major influence in the spatial struc turing of rotifer communities in the littoral region of lakes.