382
I.M. Munda
The algal belts in the eulittoral zone shift with the seasons. A complete
zonation, as outlined above, was found in spring and was followed by
dense mats of Blidingia minima and Enteromorpha species, whereas
during the summer the eulittoral slopes used to be bare of algal growth.
Due to lack of competition with other macrophytes, Cyanobacteria
locally occupied the eulittoral slopes in dense mats during summer, for
example, Oscillatoria nigroviridis and other Oscillatoria species.
The level of the eulittorallsublittoral junction was devoid of the prolific red algae belts, viz. Ceramium, Polysiphonia, Chylocladia, Champia,
Griffithsia, Antithamnion and Callithamnion species during spring and
Laurencia obtusa with Wrangelia penicillata during summer. The latter
species extended, however, to the upper sublittoral. In moderately polluted sites, the vegetation was depleted of this characteristic intermediate
belt. This level was usually bare during summer, whereas in spring prolific stands of Scytosiphon lomentaria and Ulva rigida together with some
Enteromorpha species were common. This vernal association, characteristic of polluted habitats, extends locally into the upper sublittoral.
Scytosiphon lomentaria was likely to increase in size and density of the
settlements with increasing eutrophication, reaching its most prolific
growth in the harbour waters. Ulva rigida was found in patches throughout the sublittoral slopes also in moderately polluted habitats.
The main characteristic feature of moderately polluted sites in the
northern Adriatic are associations of Halopteris scoparia (Stypocaulon
scoparium) and of Dictyota dichotoma. They cover the sublittoral slopes
in a mosaic-like pattern, interrupting Cystoseira stands. In Rovinj, however, the sublittoral was devoid of fucoids during the period of the most
severe pollution impact, in the late 1970s and early 1980s. Later, a partial
restitution of both Cystoseira and Fucus virsoides populations took place,
although they were subordinate in the vegetation. In the Gulf of Trieste,
Cystoseira species, above all C. compressa and C. barbata, were still
relatively abundant. There, Halopythis incurvus was outstanding in the
sublittoral vegetation, forming dense stands. Erect corallines, such as
Corallina officinalis and Jania rubens, were likewise prolific in some
spots, while they were rare around Rovinj. Further floristic elements,
which occurred in notable amounts in moderately polluted habitats of
the northern Adriatic were Dictyopteris membranacea, Padina pavonica,
Ulva rigida, Pterocladia capillacea, Codium fragile var. tomentosoides,
Hypnea musciformis. The last species was locally belt-forming during
summer at the level of the eulittorallsublittoral junction.
The spring annual Nitophyllum punctatum was abundant at lower
water levels also during summer, while it deteriorated near the surface.
Also Ceramium cilia tum, which was found partly embedded in sand,
I.M. Munda
The algal belts in the eulittoral zone shift with the seasons. A complete
zonation, as outlined above, was found in spring and was followed by
dense mats of Blidingia minima and Enteromorpha species, whereas
during the summer the eulittoral slopes used to be bare of algal growth.
Due to lack of competition with other macrophytes, Cyanobacteria
locally occupied the eulittoral slopes in dense mats during summer, for
example, Oscillatoria nigroviridis and other Oscillatoria species.
The level of the eulittorallsublittoral junction was devoid of the prolific red algae belts, viz. Ceramium, Polysiphonia, Chylocladia, Champia,
Griffithsia, Antithamnion and Callithamnion species during spring and
Laurencia obtusa with Wrangelia penicillata during summer. The latter
species extended, however, to the upper sublittoral. In moderately polluted sites, the vegetation was depleted of this characteristic intermediate
belt. This level was usually bare during summer, whereas in spring prolific stands of Scytosiphon lomentaria and Ulva rigida together with some
Enteromorpha species were common. This vernal association, characteristic of polluted habitats, extends locally into the upper sublittoral.
Scytosiphon lomentaria was likely to increase in size and density of the
settlements with increasing eutrophication, reaching its most prolific
growth in the harbour waters. Ulva rigida was found in patches throughout the sublittoral slopes also in moderately polluted habitats.
The main characteristic feature of moderately polluted sites in the
northern Adriatic are associations of Halopteris scoparia (Stypocaulon
scoparium) and of Dictyota dichotoma. They cover the sublittoral slopes
in a mosaic-like pattern, interrupting Cystoseira stands. In Rovinj, however, the sublittoral was devoid of fucoids during the period of the most
severe pollution impact, in the late 1970s and early 1980s. Later, a partial
restitution of both Cystoseira and Fucus virsoides populations took place,
although they were subordinate in the vegetation. In the Gulf of Trieste,
Cystoseira species, above all C. compressa and C. barbata, were still
relatively abundant. There, Halopythis incurvus was outstanding in the
sublittoral vegetation, forming dense stands. Erect corallines, such as
Corallina officinalis and Jania rubens, were likewise prolific in some
spots, while they were rare around Rovinj. Further floristic elements,
which occurred in notable amounts in moderately polluted habitats of
the northern Adriatic were Dictyopteris membranacea, Padina pavonica,
Ulva rigida, Pterocladia capillacea, Codium fragile var. tomentosoides,
Hypnea musciformis. The last species was locally belt-forming during
summer at the level of the eulittorallsublittoral junction.
The spring annual Nitophyllum punctatum was abundant at lower
water levels also during summer, while it deteriorated near the surface.
Also Ceramium cilia tum, which was found partly embedded in sand,