Carregant...
Tipus de document
TesiVersió
Versió publicadaData de publicació
Llicència de publicació
Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/204664
The importance of seasonality at different levels of ecological organization in the marine ecosystem of the Northwestern Mediterranean Sea
Títol de la revista
Autors
ISSN de la revista
Títol del volum
Resum
[eng] From an oceanographic perspective, seasonality has been widely studied, and abundant research exists about low trophic level organisms such as phytoplankton and zooplankton. Nevertheless, at a regional scale, this information is not always homogenous and certain areas lack longer time series to track seasonal cycles. This knowledge gap is emphasized as one moves to higher trophic level organisms, whose studies tend to focus on single seasons or inter-annual variation rather than on seasonal changes and intra-annual dynamics. This Ph.D. thesis aims to broaden the knowledge about the marine ecosystem of the Northwestern Mediterranean Sea incorporating the importance of seasonality in key ecological processes, such as body condition, fitness, spatial distribution, and trophic ecology of marine species, and, finally, the structure and functioning of marine food webs. Seasonality is approached at different levels of the marine community, including the demersal component focusing on commercially important species of fish (Merluccius merluccius, Lophius budegassa, Lophius piscatorius, Mullus barbatus), crustaceans (Liocarcinus depurator, Squilla mantis) and cephalopods (Illex coindetii, Eledone cirrhosa), the pelagic component targeting the most abundant and commercially important small pelagic fish species (Sardina pilchardus and Engraulis encrasicolus), and at the ecosystem level using system indicators. To attain these objectives, various methodological approaches have been combined, such as species distribution models, stable isotopes analysis, bayesian isotope mixing isotope models, analysis of biometrical/biophysical parameters (Kn, GSI, fat content), generalized additive models and ecosystem modelling. Results show seasonal variations in species distribution with species-specific patterns in the case of demersal species. Bathymetry, temperature and fishing effort are important drivers explaining biomass spatial distribution of these species. European hake is further studied in one of the chapters, and the predicted posterior mean weight distribution also presents spatial differences between winter and summer. Ontogenetic and seasonal variations are also detected in the diet of this species. Spatial and seasonal variations in fitness are found at the local scale for European sardines and anchovies. These changes are mostly explained by environmental variables while spatial and seasonal factors are also important. Moreover, trophic variables also contributed to the species dynamics, suggesting that variations in prey abundance, composition and quality can impact their fitness. At the ecosystem level, we investigate changes in indicators of ecosystem structure and functioning when using seasonal input data vs annual averages in marine ecosystem models for the characterization of our study area. We find several indicators showing significant variations in ecosystem structure and energy transfer. Overall, the findings of this Ph.D. show seasonal variation at different levels of biological organization and in various ecological processes, which highlights the relevance of seasonality in the marine realm, specifically in the Northwestern Mediterranean Sea. Therefore, we can conclude that considering seasonality in ecological studies can provide complementary insights into our understanding of species biological and ecological dynamics, which cascades up to the knowledge about ecosystem structure and functioning.
Descripció
Matèries (anglès)
Citació
Citació
LLORET LLORET, Elena. The importance of seasonality at different levels of ecological organization in the marine ecosystem of the Northwestern Mediterranean Sea. [consulta: 3 de desembre de 2025]. [Disponible a: https://hdl.handle.net/2445/204664]