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Trophic interactions and marine invasions
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This dissertation investigates marine biological invasions, focusing on the trophic interactions between non-indigenous species (NIS) and native predators/foragers. The research, conducted in situ across various locations of the Portuguese coastline, provides insights into the impacts of NIS and their interactions with native predators.
The studies within this thesis examine marinas and their adjacent areas, identified as key gateways for NIS introduction and crucial battlegrounds for preventing NIS establishment, examining predation effects on both NIS invertebrates and NIS macroalgae. Utilising innovative methodologies, the research investigates the influence of predation on NIS abundance using predation-exclusion and predation-observation experiments. The dissertation introduces a novel tool, the Remote Video Foraging System (RVFS), for identifying potential defenders — predators capable of resisting NIS establishment.
Our predation exclusion experiment indicate that predation increased the relative abundance of NIS, particularly Watersipora subatra, in estuarine marinas in mainland Portugal, indicating a facilitation effect. Conversely, in Madeira Island, using the RVFS, native species, specifically Sparisoma cretense, consumed NIS, indicating biotic resistance. Canthigaster capistrata in Madeira preferred NIS over native species, with ascidians being the most favoured among the NIS. Additionally, local fish communities in Madeira showed reluctance to consume the invasive macroalga Asparagopsis taxiformis, highlighting its potential threat to biodiversity. Notably, irrespective of the experiment conducted, a discernible trend emerged, indicating site-specific and species-specific predation effects on NIS abundance.
In conclusion, this dissertation significantly advances our understanding on NIS invasion dynamics and the complex interactions between NIS and native predators/foragers, specifically in terms of trophic relationships. The developed methodology offers means for predicting local biotic resistance against NIS, potentially extending its applications across geographical areas and marine NIS communities. These insights can inform management strategies and conservation efforts for the global combat against NIS, ultimately safeguarding coastal ecosystems and their native species.
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Marine biological invasions Trophic interactions Biotic resistance Non-indigenous marine species Invasion impact Invasões biológicas marinhas Interações tróficas Resistência biótica Espécies marinhas não indígenas Impacto da invasão