392
LM. Munda
macroalgal settlements. The same holds true for the lower sublittoral.
There, Cystoseira species were dominant in undisturbed sites
(c. corniculata, C. crinita); and Dictyota dichotoma under the influence
of slight pollution. Further contributors to the fresh weight biomass at
this level were Halopteris scoparia and deep water green algae (Halimeda
tuna, Anadyomene 5 tellata, Udotea petiolata, Codium species). In
moderately polluted sites either Halopteris scoparia or Dictyota
dichotoma dominated in the total biomass with an admixture of the
above-mentioned green algae. In the schemes, only components which
were conspicuous in the total fresh weight biomass along the studied
transects were considered.
16.7 Possible Causes for the Extinction of Fucoids
in the Eutrophicated Habitats
A combination of environmental stresses, caused by the discharge of sewage, agricultural runoff or industrial effluents has profoundly changed
the benthic algal vegetation of the north Adriatic shelf area. An analysis
of the causality of these changes is a difficult and complicated task. Field
studies revealed that fucoids disappeared from areas affected by sewage
in accordance with their possibly genetically conditioned susceptibility.
On the basis of the distribution pattern of individual species, a sensitivity
scale was worked out (Munda 1982a). Fucus virsoides is probably the
most resistant among the fucoids from the Rovinj area and is able to
tolerate a certain degree of pollution. This might be in accordance with
its relatively wide ecological valence, as it tolerates lowered salinities as
well. Next to it were Cystoseira compressa and C. barbata, followed by C.
spicata, C. adriatica and C. crinita. The highest susceptibility towards
organic pollution was found in Sargassum species as well as in the deep
water Cystoseira species (c. fucoides, C. ercegovichii). It seems likely,
however, that sensitivity towards organic pollution and eutrophication
increases with the depth penetration of the fucoids, which means that
eulittoral fucoids are more tolerant compared to the sublittoral ones.
Chemical analyses of diverse benthic algae from polluted habitats have
revealed certain differences from those growing in unpolluted areas.
Changes in chemical composition under the influence of eutrophication
proved to be consistent with those induced by lowered salinities. A
pronounced increase in protein content was found in both brown and
LM. Munda
macroalgal settlements. The same holds true for the lower sublittoral.
There, Cystoseira species were dominant in undisturbed sites
(c. corniculata, C. crinita); and Dictyota dichotoma under the influence
of slight pollution. Further contributors to the fresh weight biomass at
this level were Halopteris scoparia and deep water green algae (Halimeda
tuna, Anadyomene 5 tellata, Udotea petiolata, Codium species). In
moderately polluted sites either Halopteris scoparia or Dictyota
dichotoma dominated in the total biomass with an admixture of the
above-mentioned green algae. In the schemes, only components which
were conspicuous in the total fresh weight biomass along the studied
transects were considered.
16.7 Possible Causes for the Extinction of Fucoids
in the Eutrophicated Habitats
A combination of environmental stresses, caused by the discharge of sewage, agricultural runoff or industrial effluents has profoundly changed
the benthic algal vegetation of the north Adriatic shelf area. An analysis
of the causality of these changes is a difficult and complicated task. Field
studies revealed that fucoids disappeared from areas affected by sewage
in accordance with their possibly genetically conditioned susceptibility.
On the basis of the distribution pattern of individual species, a sensitivity
scale was worked out (Munda 1982a). Fucus virsoides is probably the
most resistant among the fucoids from the Rovinj area and is able to
tolerate a certain degree of pollution. This might be in accordance with
its relatively wide ecological valence, as it tolerates lowered salinities as
well. Next to it were Cystoseira compressa and C. barbata, followed by C.
spicata, C. adriatica and C. crinita. The highest susceptibility towards
organic pollution was found in Sargassum species as well as in the deep
water Cystoseira species (c. fucoides, C. ercegovichii). It seems likely,
however, that sensitivity towards organic pollution and eutrophication
increases with the depth penetration of the fucoids, which means that
eulittoral fucoids are more tolerant compared to the sublittoral ones.
Chemical analyses of diverse benthic algae from polluted habitats have
revealed certain differences from those growing in unpolluted areas.
Changes in chemical composition under the influence of eutrophication
proved to be consistent with those induced by lowered salinities. A
pronounced increase in protein content was found in both brown and