Biological control of phytoplankton by the subtropical submerged macrophytes Egeria densa and Potamogeton illinoensis: a mesocosm study

摘要: 1. In temperate regions, submerged macrophytes can hamper phytoplankton blooms. Such an effect could arise directly, for instance via allelopathy, or indirectly, competition nutrients the positive interaction between and zooplankton grazing. However, there is some evidence that grazing less marked in warmer where well studied, negative effects of higher water plants on biomass are weaker. 2. We carried out two consecutive mesocosm experiments Uruguay (subtropical South America) to study common from this region (Egeria densa Potamogeton illinoensis) biomass, absence We compared development different macrophyte treatments (no macrophytes, artificial real Egeria Potamogeton). used differentiate physical (i.e. shading, sedimentation with periphyton) biological nutrient allelopathy). 3. In Experiment 1, we found no but both species seemed exert strong biomass. Only affected community structure, particularly tempering dominance Scenedesmus. Nutrient addition assays revealed only suppressed through competition. 4. We performed a second experiment same design, applying saturating conditions as way excluding nutrients. This showed were still able suppress mechanisms, providing allelopathic effects. Our results indicate keep low, even