Phytoplankton size structure and species composition as an indicator of trophic status in transitional ecosystems: the case study of a Mediterranean fjord-like karstic bay**This study was funded by the Norwegian Cooperation Programme on Research and Higher Education with countries in the Western Balkans: ‘Marine Science and Coastal Management in the Adriatic, Western Balkans. An education and research network (2006–2009)’ and by the Ministry of Science, Education and Sport of the Republic of Croatia (Project Nos. 119-1191189-1228, 098-0982705-2729 and 001-0013077-0845).