394
I.M. Munda
in a cobweb-like form. Such phenomena were common in the Gulf of
Trieste during summer months of the last few years and have caused
modifications as well as mortality within benthic communities (Stachowitsch 1984; Stachowitsch and Avcin 1988; Stachowitsch et al. 1990).
Further deteriorations of the sublittoral vegetation during summer
months of the years, when extensive mucus aggregations were formed,
were observed locally in the Gulf of Trieste, around Piran (M. Richter,
pers. comm.).
Eulittoral surfaces covered solely by mats of Cyanobacteria, mainly
Oscillatoria species, were followed downwards to the depth of approximately 1 m by Licmophora gracilis mats, in sites where the coast slopes
moderately. Below the Licmophora mats, stones were covered with
patches of a low-growing form of Cladophora sp. with partly decayed
thalli. It seems that Cyanobacteria and diatoms thrive in sites affected by
mucus aggregations.
In polluted sites, a monopolization of the substrata by macroinvertebrates in the eulittoral and upper sublittoral had excluded most of the
macro algae (cf. Figs. 16.6 and 16.8), with only Ulva rigida and
Enteromorpha species growing attached to the mussels. Lower sublittoral
slopes, grazed by sea urchins, were bare of macro algae. Surfaces covered
by patches of Spirulina species were frequently observed there during the
last few years, indicating polysaprobic conditions and also anoxia. Remnants of the previous undergrowth of crustose corallines were still
observed. Mats of Mytilus galloprovincialis were common especially in
polluted sites of the Rovinj area, and also on the adjacent islands. Comparable conditions have been reported for other areas, such as the Baltic and
the Oslofjord (e.g. Lundalv and Christie 1986; Rueness and Fredriksen
1991).
16.8 Conclusions
Increased eutrophication in the marine environment leads to excessive
algal growth in the pelagic system, including unusually large phytoplankton blooms, whereas only a few opportunistic benthic algal species are
capable of mass development under such conditions( e.g. Ulva rigida in
the lagoon of Venice}.
Perennial, more sensitive species with rather complicated thalli, such
as fucoids and most of the red algae, either die away or decline in
quantity. Main algal associations, found before the severe pollution
I.M. Munda
in a cobweb-like form. Such phenomena were common in the Gulf of
Trieste during summer months of the last few years and have caused
modifications as well as mortality within benthic communities (Stachowitsch 1984; Stachowitsch and Avcin 1988; Stachowitsch et al. 1990).
Further deteriorations of the sublittoral vegetation during summer
months of the years, when extensive mucus aggregations were formed,
were observed locally in the Gulf of Trieste, around Piran (M. Richter,
pers. comm.).
Eulittoral surfaces covered solely by mats of Cyanobacteria, mainly
Oscillatoria species, were followed downwards to the depth of approximately 1 m by Licmophora gracilis mats, in sites where the coast slopes
moderately. Below the Licmophora mats, stones were covered with
patches of a low-growing form of Cladophora sp. with partly decayed
thalli. It seems that Cyanobacteria and diatoms thrive in sites affected by
mucus aggregations.
In polluted sites, a monopolization of the substrata by macroinvertebrates in the eulittoral and upper sublittoral had excluded most of the
macro algae (cf. Figs. 16.6 and 16.8), with only Ulva rigida and
Enteromorpha species growing attached to the mussels. Lower sublittoral
slopes, grazed by sea urchins, were bare of macro algae. Surfaces covered
by patches of Spirulina species were frequently observed there during the
last few years, indicating polysaprobic conditions and also anoxia. Remnants of the previous undergrowth of crustose corallines were still
observed. Mats of Mytilus galloprovincialis were common especially in
polluted sites of the Rovinj area, and also on the adjacent islands. Comparable conditions have been reported for other areas, such as the Baltic and
the Oslofjord (e.g. Lundalv and Christie 1986; Rueness and Fredriksen
1991).
16.8 Conclusions
Increased eutrophication in the marine environment leads to excessive
algal growth in the pelagic system, including unusually large phytoplankton blooms, whereas only a few opportunistic benthic algal species are
capable of mass development under such conditions( e.g. Ulva rigida in
the lagoon of Venice}.
Perennial, more sensitive species with rather complicated thalli, such
as fucoids and most of the red algae, either die away or decline in
quantity. Main algal associations, found before the severe pollution