Periphyton density is similar on native and non-native plant species

International audience1. Non-native plants increasingly dominate the vegetation in aquatic ecosystemsand thrive in eutrophic conditions. In eutrophic conditions, submerged plants riskbeing overgrown by epiphytic algae; however, if non-native plants are less susceptibleto periphyton than natives, this would contribute to their dominance.Non-native plants may differ from natives in their susceptibility to periphytongrowth due to differences in nutrient release, allelopathy and architecture. Yet,there is mixed evidence for whether plants interact with periphyton growththrough nutrient release and allelopathy, or whether plants are neutral so thatonly their architecture matters for periphyton growth.2. We hypothesised that (1) non-native submerged vascular plants support lowerperiphyton density than native species, (2) native and non-native species are notneutral substrate for periphyton and interact with periphyton and (3) periphytondensity increases with the plant structural complexity of plant species.3. We conducted an experiment in a controlled climate chamber where we grew11 aquatic plant species and an artificial plant analogue in monocultures in buckets.These buckets were inoculated with periphyton that was collected locallyfrom plants and hard substrate. Of the 11 living species, seven are native to Europeand four are non-native. The periphyton density on these plants was quantifiedafter five weeks.4. We found that the periphyton density did not differ between non-native andnative plants and was not related to plant complexity. Three living plant speciessupported lower periphyton densities than the artificial plant, one supported ahigher periphyton density and the other plants supported similar densities. However,there was a strong negative correlation between plant growth and periphytondensity.5. We conclude that the periphyton density varies greatly among plant species,even when these were grown under similar conditions, but there was no indicationthat the interaction with periphyton differs between native and non-nativeplant species. Hence, non-native plants do not seem to benefit from reducedperiphyton colonisation compared to native species. Instead, certain native andnon-native species tolerate eutrophic conditions well and as a consequence, theyseem to host less periphyton than less tolerant species