Abstract
Abstract Non‐native plants increasingly dominate the vegetation in aquatic ecosystems and thrive in eutrophic conditions. In eutrophic conditions, submerged plants risk being overgrown by epiphytic algae; however, if non‐native plants are less susceptible to periphyton than natives, this would contribute to their dominance. Non‐native plants may differ from natives in their susceptibility to periphyton growth due to differences in nutrient release, allelopathy and architecture. Yet, there is mixed evidence for whether plants interact with periphyton growth through nutrient release and allelopathy, or whether plants are neutral so that only their architecture matters for periphyton growth. We hypothesised that (1) non‐native submerged vascular plants support lower periphyton density than native species, (2) native and non‐native species are not neutral substrate for periphyton and interact with periphyton and (3) periphyton density increases with the plant structural complexity of plant species. We conducted an experiment in a controlled climate chamber where we grew 11 aquatic plant species and an artificial plant analogue in monocultures in buckets. These buckets were inoculated with periphyton that was collected locally from plants and hard substrate. Of the 11 living species, seven are native to Europe and four are non‐native. The periphyton density on these plants was quantified after five weeks. We found that the periphyton density did not differ between non‐native and native plants and was not related to plant complexity. Three living plant species supported lower periphyton densities than the artificial plant, one supported a higher periphyton density and the other plants supported similar densities. However, there was a strong negative correlation between plant growth and periphyton density. We conclude that the periphyton density varies greatly among plant species, even when these were grown under similar conditions, but there was no indication that the interaction with periphyton differs between native and non‐native plant species. Hence, non‐native plants do not seem to benefit from reduced periphyton colonisation compared to native species. Instead, certain native and non‐native species tolerate eutrophic conditions well and as a consequence, they seem to host less periphyton than less tolerant species.
Highlights
Aquatic plants are a crucial component of aquatic ecosystems through their provision of habitat structure and food to fauna, which increases biodiversity (Carpenter & Lodge, 1986), and their enhancement of water quality through nutrient retention (Burks et al, 2006; Jeppesen, 1998; Scheffer, Carpenter, Foley, Folke, & Walker, 2001)
We conclude that the periphyton density varies greatly among plant species, even when these were grown under similar conditions, but there was no indication that the interaction with periphyton differs between native and non-native plant species
Comparing the periphyton density on young and old plant parts (Figure 2), we found a strong interaction between plant species and periphyton on top and bottom fragments, with more periphyton on older fragments for Ceratophyllum demersum (p < .001), Chara vulgaris (p = .016), E. nuttallii (p = .008), M. spicatum (p < .001), Potamogeton perfoliatus (p = .036) and R. circinatus (p = .021)
Summary
Aquatic plants are a crucial component of aquatic ecosystems through their provision of habitat structure and food to fauna, which increases biodiversity (Carpenter & Lodge, 1986), and their enhancement of water quality through nutrient retention (Burks et al, 2006; Jeppesen, 1998; Scheffer, Carpenter, Foley, Folke, & Walker, 2001). The success of non-natives has been attributed to many factors, including their rapid growth rate, release of enemies and ease of dispersion (Heger & Jeschke, 2014; Pysek & Richardson, 2007; Schultz & Dibble, 2012). It is unknown whether non-native plants are less prone to colonisation by periphyton, which would grant non-natives a competitive advantage over native submerged plants, especially under eutrophic conditions. There are several plant traits that may differ between non-native and native plants, which may provide the mechanism through which non-native plants may potentially be less susceptible to periphyton
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