Alteração da concentração de nutrientes causada por P. ambrosettii afeta relação entre macrófita invasora H. verticillata e nativa E. najas : uma abordagem experimental .

Abstract

Non native species can negatively affect the invaded environment. Often, these species have biological characteristics that benefit other non natives and facilitate their invasion, so knowing the facilitation mechanisms between invaders are useful to mitigate their damage to the ecosystem. Thus, in this study we tested the hypothesis that Pterygoplichthys ambrosettii, a non native catfish, has habits that can alter nutrient concentrations (phosphorus and nitrogen) in the water column, and positively affect the growth of an invasive macrophyte species in detriment of a native one, characterizing ecological facilitation among invasive species. Therefore, an experiment was conducted with six treatments and four replicas, using the invasive macrophyte Hydrilla verticillata and the native Egeria najas, in the presence and absence of P. ambrosettii, all with occurrence recorded in the upper Paraná River floodplain. The results showed that the treatments with P. ambrosettii had a lower amount of dissolved oxygen, higher electrical conductivity, higher concentration of chlorophyll-a, total phosphorus (TP) and inorganic nitrogen (NI). Macrophyte biomass was significantly higher in monoculture treatments with fish, with this effect being more intense for H. verticillata. When in the same treatment, in the absence of P. ambrosettii, H. verticillata showed greater biomass than E. najas, but with the fish presence, the macrophyte species did not differ in their biomass, indicating that the high concentration of nutrients makes the coexistence of these macrophytes possible. The results found will be useful for future actions to manage invasive species, especially in habitats where they co-occur.