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axonomic composition, depth distribution and phytogeographic characteristics of marine benthic macroflora from Rijeka bay (North Adriatic sea, Croatia)

Here we give a review of taxonomic composition, depth distribution, and phytogeographic characteristics of benthic marine macroflora from Rijeka Bay. It is based on our researches from 1950 to 2000, and on both nomenclatural and taxonomic critical revision of previous records from that region. The list contains 380 taxa belonging to the Rhodophyta (231), the Ochrophyta (74), the Chlorophyta (71) and the Magnoliophyta (4), of which 338 are at specific level and 42 are infraspecific (4 subspecies, 31 varieties, 7 forms, 1 stage). The established ratio between the number of Rhodophyta and Phaeophyceae (R/P Index ; FELDMANN, 1937) was 3.1, and relation between the number of Rhodophyta + Chlorophyta and Phaeophyceae (R+C/P Index ; CHENEY, 1977) was 4.1. Both the above values show a subtropical character of benthic macroalgal flora in the surveyed area. With regard to its origin, the Rijeka Bay benthic flora is not homogenous. It comprises floral elements from several phytogeographic regions. Predominant by number and percentage are Atlantic (86 taxa - 23%), subcosmopolitan (75 taxa - 20%), Mediterranean (70 taxa - 19%), and Indo-Atlantic (53 taxa - 14%) floral elements. Other phytogeographic regions contribute to Rijeka marine algal flora by only 96 taxa - 25% of total 380 taxa recorded. Only 3 species (1%) are included in Adriatic endemic category (Polysiphonia adriatica, Feldmannia irregularis var. Lebeliides and Fucus virsoides). The analysis of benthic flora in relation to littoral bionomical zones reveals that the highest number of algal taxa is recorded in the upper infralittoral zone (325), and the lowest (the supralittoral excepted) in the eulittoral zone (109). With regard to depth distribution, the marine benthic flora of Rijeka Bay consists of a very small number of algal taxa which live only deeper than 6 m (36 taxa - 9.4%), in comparison with the relatively high number of algal taxa which live only up to 6 m depth (153 taxa - 40.3%), and those living above and below 6 m depth (191 taxa – 50.1%).

marine benthic macroalgae and seagrasses; check-list; taxonomic composition; depth distribution; phytogeographic characteristics; Rijeka Bay; north Adriatic Sea

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