Taxonomic composition, depth distribution and phytogeographic characteristics of marine benthic macroflora from Rijeka Bay (north Adriatic Sea, Croatia)

Here we give a review of the taxonomic composition, depth distribution, and phytogeographic characteristics of benthic marine macroflora from Rijeka Bay. It is based on our research from 1950 to 2000, and on both a nomenclatural and a 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), 338of which are at the species level while 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 the relation between the number of Rhodophyta + Chlorophyta and Phaeophyceae (R+C/P Index; CHENEY, 1977) was 4.1. Both the above values show the 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 only 96 taxa to Rijeka marine algal flora – 25% of total the 380 taxa recorded. Only 3 species (1%) are included in the category of Adriatic endemic (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, 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 as far as 6 m deep (153 taxa – 40.3%), and
U radu se iznosi popis bentoskih morskih makroalga i morskih cvjetnica Riječkog zaljeva koji se temelji na istraživanjima izvedenim od 1950. do 2000. godine, te starijim i novijim bibliografskim podacima. Popis sadrži ukupno 376 svojte bentoskih alga (231 svojti ili 60,8% Rhodophyta, 74 svojte ili 19,5% Ochrophyta, 71 svojta ili 18,7% Chlorophyta) i 4 vrste morskih cvjetnica (Magnoliophyta). Prema vrijednostima kvocijenata R/P (FELDMANN, 1937) i R+C/P (CHENEY, 1977) bentoska flora Riječkog zaljeva ima suptropski karakter. U fitogeografskom sastavu brojem i postotkom prevladavaju atlantski (86 svojti ili 22,5%), subkozmopolitski (75 svojte ili 19,8%), mediteranski (70 svojte ili 18,5%) i indo-atlantski (53 svojte ili 14%) florni elementi. Od endemskih jadranskih vrsta zabilježene su samo tri (Polysiphonia adriatica, Feldmannia irregularis var. Lebeliides i Fucus virsoides). Najveći je broj svojti zabilježen u gornjem infralitoralu (325), dosta manje u srednjem (213) i donjem infralitoralu (190), a najmanje (izuzevši supralitoral gdje je određena samo jedna vrsta) u eulitoralu (109). Razmjerno mali broj svojti bentoske flore (36 ili 9,4% od ukupnog broja) živi na većim dubinama od 6 m, u odnosu na razmjerno velikog broja svojti koje žive samo do 6 m dubine (153 ili 40,3%), odnosno svojti koje su zastupljene u obje kategorije (191 ili 50,1%).