Browsing by Author "Hartmann, Tim Felix"
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- Loss of biodiversity in sea urchin patches in the Ria Formosa, due to the invasive behaviour of caulerpa?Publication . Hartmann, Tim Felix; Duarte, Duarte; Gamito, SofiaRia Formosa, a shallow, multi-barrier lagoon system located along Portugal's southern coast between Loulé and Vila Real de Santo António, is recognized as an ecologically significant wetland with substantial economic value. Protected as a natural park since 1987, the lagoon serves as a vital nursery ground for various species of fish, crustaceans, and molluscs. Despite its importance, certain habitats within the lagoon, particularly with high biodiversity, known as sea urchin patches, have remained understudied. Spread in the less vegetated bottoms, spatially restricted patches of seagrass can be found, marked by the dominance of sea urchins and are here referred to as sea urchin patches. However, this habitat isincreasingly threatened by the invasion of non-native species, such as Caulerpa prolifera, which has become an emerging concern for biodiversity conservation and ecosystem functioning in the region. Extensive fieldwork was conducted, including diving campaigns and sample analysis, to access the changes in fauna composition and distribution in the sea urchin patches dominated by sea urchins and those invaded by Caulerpa prolifera. The results revealed that C. prolifera invaded patches support a distinct assemblage of species compared to sea urchin-dominated areas. The sampled fauna included Annelida species, which were predominantly found in C. prolifera invaded patches. In contrast, arthropods were more frequently encountered in sea urchin patches, with a notable absence in C. prolifera invaded areas. Chordates were primarily present in sea urchin patches. Molluscs, including various orders, were distributed across all patches without a clear pattern. Echinoderms were also predominantly found in sea urchin patches, with only a one exception in C. prolifera invaded areas. The flora samples revealed that not only the patches dominated by C. prolifera are affected by an invasion. Unexpectedly, the remaining patches mainly presented an invasive alga, the recently described Rugulopteryx okamurae, instead of the expected native algae species Ulva sp. and Codium sp. This complicates the evaluation of biodiversity changes due to multiple overlapping invasions and highlights the lack of data for this specific habitat of the Ria Formosa lagoon. The analyses indicate the significant ecological impact of Caulerpa prolifera invasion that alters the species composition and abundance in marine habitats, possibly affecting the diversity and distribution of organisms. The observed alteration in flora and fauna highlights the ecological vi impact of invasive species on local biodiversity and the need for further research on this habitat. Moreover, the simultaneous presence of multiple invasive species complicates efforts to manage and protect the native biodiversity of this ecosystem.
- Sea urchins’ patches in Ria Formosa coastal lagoon altered under invasion pressure of Caulerpa prolifera and Rugulopteryx okamuraePublication . Hartmann, Tim Felix; P. Moreira Ribeiro, Ines; Ramos Duarte, Duarte Nuno; Gamito, SofiaThis study investigates specific epibenthic community in sea urchin patches from Ria Formosa lagoon, near the Armona Inlet in southern Portugal. These patches are concentrated in distinct spatially isolated areas surrounded by unvegetated, bare sediment bottom and support diverse organisms, dominated by a high density and biomass of Paracentrotus lividus and ascidians. Field surveys conducted between 2014 and 2023 revealed a shift in flora composition, with the replacement of native seagrasses and seaweed by the invasive macroalgae Caulerpa pro lifera. The main aim of this study was to evaluate the effects of this invasive alga in the epibenthic communities of the patches. However, in 2024 surveys, another invasive macroalgae, Rugulopteryx okamurae, was detected in the patches. Sphaerechinus granularis was the dominant sea urchin species in biomass, in R. okamurae patches. In the patches invaded by Caulerpa prolifera, sea urchins were generally absent, as were ascidians’ species. Faunal analyses indicate a significant decline in macroinvertebrate taxa richness, abundance and biomass within Cau lerpa-invaded patches, when compared with patches invaded by R. okamurae. Non-metric multidimensional scaling, confirm the observed differences between the two invaded patches. The invasion by R. okamurae complicates the ecological balance, potentially leading to species replacement and eventual biodiversity loss. Additionally, the disappearance of shell layers in these patches, observed in previous years, raises concerns about habitat stability and resilience. The findings highlight the urgent need for continuous monitoring and man agement strategies to mitigate the ecological consequences of macroalgal invasions in the Ria Formosa.