384
LM. Munda
Rovinj area Cladophora species occupied wide eulittoral surfaces in
heavily polluted habitats.
A characteristic feature of heavily polluted and rather exposed sites
was the dominance of macro-invertebrates, above all My til us
gaUoprovincialis Lam. A monopolization of eulittoral and upper sublittoral slopes by Mytilus displaced most of the macroalgae. Ulva rigida
and some Enteromorpha species were found attached to the shells.
Further down the sublittoral, bare slopes were encountered, grazed by
sea urchins, with only some remnants of crustose corallines.
On shores devoid of Mytilus, the above named Scytosiphon
lomentaria-Ulva rigida association was prolific and extended into the
sublittoral zone. Enteromorpha species were its only companions. In
several heavily polluted sites with increased turbidity, Enteromorpha
species formed dense stands, replacing Cystoseira species.
Looking at the schematic profiles of the vegetation in differently polluted habitats (Figs. 16.3. to 16.6), a rise of the lower vegetation limit
with increasing pollution is evident. Thus, increasing eutrophication is
likely to exclude perennial algae from the vegetation in favour of shortlived species with simpler thalli. Under extreme conditions an intensive
settling of macro-invertebrates exerts an additional deteriorating effect
on benthic macro algae. Intermediate conditions, however, favour the
development of dense settlements of nitrophilous species, which replace
or interrupt Cystoseira stands. As mentioned above, associations of
Dictyota dichotoma and Halopteris scoparia and locally also of
Halopythis incurvus are the main characteristic features of moderately
polluted habitats in the northern Adriatic.
16.5 Number of Species
The effect of eutrophication on the total number of species from a moderately polluted site near Piran is presented in Fig. 16.7A,B. The number
of species shifted with the seasons and differences between the littoral
levels were observed (Munda 1993a,b).
The pollution impact has eliminated several species from the vegetation and given preference to opportunistic species with a short life span
and a wide ecological valence. Sensitive species, which disappeared from
the vegetation, were deep-water fucoids (Sargassum acinarium, S. hornschouchii, Cystoseira fucoides, C. ercegovichii) along with Liebmannia
leveillei, Phyllophora palmetoides, Rytiphlaea tinctoria, Acrosymphytum
LM. Munda
Rovinj area Cladophora species occupied wide eulittoral surfaces in
heavily polluted habitats.
A characteristic feature of heavily polluted and rather exposed sites
was the dominance of macro-invertebrates, above all My til us
gaUoprovincialis Lam. A monopolization of eulittoral and upper sublittoral slopes by Mytilus displaced most of the macroalgae. Ulva rigida
and some Enteromorpha species were found attached to the shells.
Further down the sublittoral, bare slopes were encountered, grazed by
sea urchins, with only some remnants of crustose corallines.
On shores devoid of Mytilus, the above named Scytosiphon
lomentaria-Ulva rigida association was prolific and extended into the
sublittoral zone. Enteromorpha species were its only companions. In
several heavily polluted sites with increased turbidity, Enteromorpha
species formed dense stands, replacing Cystoseira species.
Looking at the schematic profiles of the vegetation in differently polluted habitats (Figs. 16.3. to 16.6), a rise of the lower vegetation limit
with increasing pollution is evident. Thus, increasing eutrophication is
likely to exclude perennial algae from the vegetation in favour of shortlived species with simpler thalli. Under extreme conditions an intensive
settling of macro-invertebrates exerts an additional deteriorating effect
on benthic macro algae. Intermediate conditions, however, favour the
development of dense settlements of nitrophilous species, which replace
or interrupt Cystoseira stands. As mentioned above, associations of
Dictyota dichotoma and Halopteris scoparia and locally also of
Halopythis incurvus are the main characteristic features of moderately
polluted habitats in the northern Adriatic.
16.5 Number of Species
The effect of eutrophication on the total number of species from a moderately polluted site near Piran is presented in Fig. 16.7A,B. The number
of species shifted with the seasons and differences between the littoral
levels were observed (Munda 1993a,b).
The pollution impact has eliminated several species from the vegetation and given preference to opportunistic species with a short life span
and a wide ecological valence. Sensitive species, which disappeared from
the vegetation, were deep-water fucoids (Sargassum acinarium, S. hornschouchii, Cystoseira fucoides, C. ercegovichii) along with Liebmannia
leveillei, Phyllophora palmetoides, Rytiphlaea tinctoria, Acrosymphytum