Variability of the planktonic cnidarian community at different spatio-temporal scales along the catalan coast (northwestern mediterranean)

• Autores: Elena Guerrero
• Directores de la Tesis: Josep Maria Gili Sardà (dir. tes.), Ana Sabatés (codir. tes.)
• Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2017
• Idioma: español
• Tribunal Calificador de la Tesis: Joan Domènec Ros (presid.), Vicente Gracia García (secret.), Gilian Mapstone (voc.)
• Programa de doctorado: Programa de Doctorado en Ciencias del Mar por la Universidad de Barcelona y la Universidad Politécnica de Catalunya
• Materias:
  • Ciencias de la vida
    • Biología animal (zoología)
      • Zoología marina
    • Biología vegetal (botánica)
      • Botánica marina
  • Ciencias de la tierra y del espacio
    • Oceanografía
      • Oceanografía biológica
      • Zoología marina
    • Ciencias del suelo
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• Resumen

  • Planktonic cnidarians are those species or their stages in the phylum Cnidaria that spent their life in the water column and therefore, are tightly linked to oceanographic dynamics and water mass structures, such as fronts and gyres. The objective of this thesis is to understand the variability of the planktonic cnidarian community inhabiting the Catalan coast (NW Mediterranean) at different spatio-temporal scales, and their relationships with the hydrography and environmental parameters that characterized the study area. At short time scales (10 days), in spring, important changes in the abundance and spatial distribution of the species were closely related to the shifting positions of a density front. The front acted as a barrier limiting offshore displacement of the two most dominant species. At an interannual scale, changes in the abundance, structure and latitudinal distribution of the summer community were observed when comparing extreme warm (July 2003) and standard conditions (July 2004). The exceptional warm conditions occurred in July 2003 due to a heat wave, lead to a reduction of the total abundance of the community and the latitudinal community distribution was reinforced. At an interdecadal scale, changes in species abundance, community composition and spatial distribution patterns were found during the month of June. Total Cnidaria abundance increased and the latitudinal community distribution patterns were reinforced when comparing three representative years (1983, 2004 and 2011) of the climatic and anthropogenic changes occurred during the last three decades in the NW Mediterranean. Temperature was the main environmental factor explaining these changes, representative of the climatic evolution from the colder 1980s to the warmer 2010s. Although, it is likely that others anthropogenic factors such us overfishing may have contributed to the observed changes over time. All these results are based in the study of a large and heterogeneous mesoscale area, characterized for different environmental gradients: bathymetry, temperature, salinity and primary production, as well as in the species level identification of the whole community. The planktonic cnidarian community along the Catalan coast presents a high variability both at temporal and spatial scales and is tightly related to hydrographic and environmental factors of the area, and to climatic and anthropogenic changes. These results show that it is extremely important to study and monitore planktonic cnidarians (considered as gelatinous zooplankton) in mesoscale spatial areas and at species level in order to assess possible changes at a temporal scales, since species and community spatial changes are sensitive indicators to climate change.