Both particle abundance and free-living and particle-attached bacterial abundance have been studied in many recent studies as the responsible of a crucial role in the cycle of particulate organic matter (POM) and dissolved organic matter (DOM). In spite of their important role in this cycle, neither particle abundance nor bacterial abundance have been studied together. This paper synthesizes the results of our investigation on the spatial variations of bacterial abundance of free-living bacteria and particle-attached bacteria and particle abundance and composition as blue, yellow or mixed particles at different depth from surface to bottom depths from the coast of Blanes (NW Mediterranean) to open sea. Bacteria and particles were found to be more abundant in surface, especially where nutrient concentrations and phytoplankton are also high. Particles are also enriched in the nepheloid layer of deep layers. Blue particles are the most abundant type of particles in surface and in the open ocean, though concentration of yellow particles is higher in the deep layers and in the coastal stations. Particle-attached bacteria represent 0.4-1% of the total bacteria, and they are more abundant in the open ocean

Trabajo final presentado por Susana Sánchez Del Río para el grado de Ciencias Ambientales en la Universitat de Barcelona (UB), realizado bajo la dirección de la Dra.Josefina Martínez de la Universitat de Barcelona (UB) y la Dra. Maria Montserrat Solé Rovira del Institut de Ciències del Mar (ICM-CSIC).-- 30 pages, 17 figures, 3 tables

Peer Reviewed