The Northern Adriatic Sea
395
impact in the northern Adriatic, were eradicated from the vegetation
close to the sources of pollution. They are, however, still found in
relatively unpolluted sites, though with some modifications in their floristic composition and degree of cover.
There is, however, a consistency of algal associations with environmental conditions. In particular Fucacean association rather clearly reflect the pollution gradients and are able to record environmental conditions or stress over time, such as the nutrient input by sewage and the
nitrate/phosphate cycles, which are again conditioned by pelagic events
(cf. Schramm et al. 1988).
The Fucus virsoides association disappeared from polluted sites and
was succeeded by diverse spring annuals and algal turfs, containing
Gelidium pusillum, interwoven with Gelidiella and Laurencia species.
Under extreme conditions, the eulittorallevel was occupied by mats of
Blidingia minima, Enteromorpha intestinalis or Cladophora species. The
eulittoral slopes were usually bare of macro algae during mid-summer
(Munda 1972, 1980a).
Cystoseira associations were either reduced or excluded from the
vegetation. Their distribution pattern in the investigated areas of the
northern Adriatic revealed a scale of susceptibility towards pollution
by sewage (Munda 1982a). Cystoseira compressa and C. barbata are the
least susceptible among other representatives of this genus. As such, they
can at first replace as vicariates other Cystoseira associations, when
pollution is not yet too severe. Similar changes of the benthic algal
associations were observed in the middle and southern Adriatic (Span
et al. 1989; Cormaci and Furnari 1991). Also in these areas of the
Adriatic sea, a decrease or disappearance of Cystoseira associations,
reduction in species number and admixture of nitrophilous species were
found.
The succession in relation to pollution gradients was demonstrated for
benthic communities by Pearson and Rosenberg (1978). For benthic
marine algae, some characteristic associations were found in moderately
polluted habitats, representing intermediate conditions between extreme
pollution-induced changes and an undisturbed vegetation pattern.
Associations of the nitrophilous species Dictyota dichotoma and
Halopteris scoparia, which either interrupt or replace Cystoseira stands,
are the most conspicuous characteristic of moderately polluted habitats
all over the northern Adriatic (Munda 1980a, 1993a,b). Further characteristic species in these associations were Dictyopteris membranacea,
Padina pavonica, Cladophora rupestris, Halopythis incurvus, Pterocladia
capillacea, Ulva rigida and Hypnea musciformis. It is noteworthy that
erect corallines, for example Jania rubens and Corallina officinalis, were
395
impact in the northern Adriatic, were eradicated from the vegetation
close to the sources of pollution. They are, however, still found in
relatively unpolluted sites, though with some modifications in their floristic composition and degree of cover.
There is, however, a consistency of algal associations with environmental conditions. In particular Fucacean association rather clearly reflect the pollution gradients and are able to record environmental conditions or stress over time, such as the nutrient input by sewage and the
nitrate/phosphate cycles, which are again conditioned by pelagic events
(cf. Schramm et al. 1988).
The Fucus virsoides association disappeared from polluted sites and
was succeeded by diverse spring annuals and algal turfs, containing
Gelidium pusillum, interwoven with Gelidiella and Laurencia species.
Under extreme conditions, the eulittorallevel was occupied by mats of
Blidingia minima, Enteromorpha intestinalis or Cladophora species. The
eulittoral slopes were usually bare of macro algae during mid-summer
(Munda 1972, 1980a).
Cystoseira associations were either reduced or excluded from the
vegetation. Their distribution pattern in the investigated areas of the
northern Adriatic revealed a scale of susceptibility towards pollution
by sewage (Munda 1982a). Cystoseira compressa and C. barbata are the
least susceptible among other representatives of this genus. As such, they
can at first replace as vicariates other Cystoseira associations, when
pollution is not yet too severe. Similar changes of the benthic algal
associations were observed in the middle and southern Adriatic (Span
et al. 1989; Cormaci and Furnari 1991). Also in these areas of the
Adriatic sea, a decrease or disappearance of Cystoseira associations,
reduction in species number and admixture of nitrophilous species were
found.
The succession in relation to pollution gradients was demonstrated for
benthic communities by Pearson and Rosenberg (1978). For benthic
marine algae, some characteristic associations were found in moderately
polluted habitats, representing intermediate conditions between extreme
pollution-induced changes and an undisturbed vegetation pattern.
Associations of the nitrophilous species Dictyota dichotoma and
Halopteris scoparia, which either interrupt or replace Cystoseira stands,
are the most conspicuous characteristic of moderately polluted habitats
all over the northern Adriatic (Munda 1980a, 1993a,b). Further characteristic species in these associations were Dictyopteris membranacea,
Padina pavonica, Cladophora rupestris, Halopythis incurvus, Pterocladia
capillacea, Ulva rigida and Hypnea musciformis. It is noteworthy that
erect corallines, for example Jania rubens and Corallina officinalis, were