Biodiversity patterns of coralligenous outcrops over broad spatial and temporal scales in the NW Mediterranean Sea: baseline data for conservation
[eng] Increasing anthropogenic pressures and its effects on marine ecosystems urge enhanced knowledge and understanding of the current state of marine biodiversity. This baseline information is pivotal to establish the actual state, detect future changes, explore possible trends and propose adequate...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2016 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/104194 |
| Acceso en línea: | https://hdl.handle.net/2445/104194 http://hdl.handle.net/10803/398021 |
| Access Level: | acceso abierto |
| Palabra clave: | Coralls Conservació de la diversitat biològica Mediterrània (Mar) Corals Biodiversity conservation Mediterranean Sea |
| Sumario: | [eng] Increasing anthropogenic pressures and its effects on marine ecosystems urge enhanced knowledge and understanding of the current state of marine biodiversity. This baseline information is pivotal to establish the actual state, detect future changes, explore possible trends and propose adequate management actions for marine ecosystems. Coralligenous outcrops are a highly diverse and structurally complex habitat faced with major threats in the Mediterranean Sea. Despite its ecological, aesthetic and economic value, coralligenous biodiversity patterns are still poorly understood. Information on the spatial and temporal variability of the composition and structure of coralligenous assemblages is scarce for most regions. Specially, data on species diversity and structure in coralligenous outcrops dominated by Corallium rubrum and Paramuricea clavata are essentially lacking. Gathering these data is needed to build robust baselines in order to assess the responses of this highly threatened habitat to anthropogenic disturbances (e.g. mass mortality events, sedimentation and invasive species). There is currently no single sampling method that has been demonstrated to be sufficiently representative to ensure adequate community assessment and monitoring in this habitat. In Chapter 3, we propose a rapid non-destructive protocol for biodiversity assessment and monitoring of coralligenous outcrops providing good estimates of its structure and species composition, based on photographic sampling and the determination of presence/absence of macrobenthic species. We followed a hierarchical sampling survey, covering more than 400 km of rocky coasts in NW Mediterranean (Catalan coast –Spain-, Provence and NW Corsica –France). This approach allowed us to determine the minimal sampling area for each assemblage (5000 cm2 for P. clavata and 2500 cm2 for C. rubrum). In addition, we concluded that 3 replicates provided an optimal sampling effort in order to maximize the species number and to assess the main biodiversity patterns of studied assemblages in variability studies requiring replicates. We followed the mentioned hierarchical sampling survey in Chapter 3 to characterize the spatial and temporal variability of structure, composition, abundance and diversity of perennial species inhabiting coralligenous outcrops dominated by C. rubrum or P. clavata (Chapter 4 and Chapter 5 respectively). In Chapter 4 spatial variability of species composition, structure and diversity in coralligenous assemblages dominated by C. rubrum was assessed. We also pooled the identified species/taxa into morphofunctional groups according to their life-span and growth to characterize the structural complexity of the assemblages. Finally, we analyzed the number, size and shape of patches (landscape pattern indices) for each group in order to describe the spatial arrangement within the C. rubrum assemblage. Landscape pattern indices in C. rubrum assemblages exhibited important differences among sites in the same locality whereas localities showed similar values. In Chapter 5, the spatial and temporal variability of species composition, structure and diversity in coralligenous assemblages dominated by P. clavata was assessed. According to ordination analyses, species composition and the structural complexity of coralligenous assemblages differed consistently across all spatial scales considered. The lowest and the highest variability were found among localities (100 km) and within sites (1-5 km), respectively. Despite the differences, the sites displayed high similarity (average similarity 55.7 %) and shared approximately 50 % of the species. Similarly, differences in diversity indices (alpha, beta and gamma) were found. Furthermore, the study of P. clavata addressed diversity patterns over 5-year period. Overall, no temporal changes were detected in either species composition or the morphofunctional groups considered. In Chapter 6, we showed how an extreme storm event affected the dynamics of benthic coralligenous outcrops in the NW Mediterranean Sea using data acquired before (2006–2008) and after the impact (2009–2010) at four different sites. The loss of cover of benthic species resulted between 22% and 58%. The damage across these species (e.g. calcareous algae, sponges, anthozoans, bryozoans, tunicates) was uneven, and those with fragile forms were the most impacted, showing cover losses up to 50 to 100%. Interestingly, small patches survived after the storm and began to grow slightly during the following year. In contrast, sheltered sites showed no significant changes in all the studied parameters, indicating no variations due to the storm. Overall, the results presented in this thesis furnishes a basis for the implementation of monitoring schemes of coralligenous assemblages complementing the scarce available information on assemblage composition and structure of the emblematic Mediterranean coralligenous outcrops dominated by C. rubrum and P. clavata over large spatial scales. Our results demonstrate the moderate spatial and the extremely low temporal variability in biodiversity patterns in the NW Mediterranean region, providing the first baselines for detecting potential changes due to global change effects. We also provide new insights into the responses of these assemblages to a large and rare extreme event. The development of similar sampling schemes in other Mediterranean regions will provide a global view of the biodiversity of coralligenous outcrops. |
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