increases. At the same time, the physical dissolubility of oxygen in warm water is less
than in cold water. For this reason, the probability of anaerobic conditions and the
dying of fish in the summer becomes greater due to the introduction of warmth into
an organically stressed estuary. If warm water is going to be introduced without additional damage to the ecosystem, care must be taken through treatment plants that
the organic load is lessened in domestic effluents.
There is, by the way, a harmful side-effect of cooling water passing through a power
plant. High flow-through speeds require effective pumps; plankton is partially destroyed by these pumps. Supposedly, it is best to use larger quantities of water for
cooling so that they can flow more slowly through the cooling system, because many
estuary organisms can tolerate a brief period in water up to 10°C warmer than
ambient water.
2.9 Gradual Coastal Changes
An impoverishment of the animal and plant population in the vicinity of coastal
cities is being reported all over the world, predominantly in shallow areas. The disappearance in the Adriatic of the brown algae of the genus Cystoseira, which forms
a belt of up to I m, is especially noticeable. But in the Norwegian fjords as well, seaweed is disappearing from the areas near towns. Other algae are spreading in their
place: Cladophora, Enteromorpha, and blue-green algae. In the Mediterranean, various
somewhat deeper regions in which eel-grass (Posidonia) formed lush meadows, are
also being affected. In the areas around Marseilles as well as in the Adriatic, eel-grass
has disappeared from the vicinity of many towns. In its place the Ulva and Haiopteris
algae have increased. Changes have occurred in the benthos fauna as well (Avcin et al.
1974; Katzmann 1974; Munda 1974). In the 0resund between Malmo and Copenhagen, 20 species of large algae have disappeared in recent decades. Others have
increased in their place; for instance, Cladophora,Enteromorpha, Ectocarpus,Pylaeila,
and Poiysiphonia (Wachenfeldt 1971). The branching green plant Chara aspera, which
formerly was common in the belt of skerries around Stockholm, is no longer present
there. At most, pitiful specimens are occasionally observed. 25 to 30 km from Stockholm, these plants develop normally (Pekkari 1973).
Even very small communities of humans disrupt the coastal vegetation. The island of
San Clemente, occupied by 300 marines, lies 76 km off the California coast. Only
around 100 m 3 of domestic effluents reach the ocean daily from the island. Despite
this, several species of algae have disappeared from the shore areas near the drain
pipe: Egregia, Hydrolithon, Halidrys, Phyllospadix, and Sargassum. One hundred
meters from the drain point, these algae are present, as they are everywhere else, and
represent around a third of the plant cover. But around the drain area, they have been
replaced by Ulva, Ge/idium, and blue-green algae (Littler and Murray 1975).
Although a change of algal communities is being observed along those coasts all over
the world that are affected by effluents, no single cause has been found to be responsible for it up till now. The mixture of domestic and industrial effluents, which are
introduced into the sea by many coastal towns, can have various effects: the water is
warmed; drain water contains suspensions of the most varied sorts which settle on
33
than in cold water. For this reason, the probability of anaerobic conditions and the
dying of fish in the summer becomes greater due to the introduction of warmth into
an organically stressed estuary. If warm water is going to be introduced without additional damage to the ecosystem, care must be taken through treatment plants that
the organic load is lessened in domestic effluents.
There is, by the way, a harmful side-effect of cooling water passing through a power
plant. High flow-through speeds require effective pumps; plankton is partially destroyed by these pumps. Supposedly, it is best to use larger quantities of water for
cooling so that they can flow more slowly through the cooling system, because many
estuary organisms can tolerate a brief period in water up to 10°C warmer than
ambient water.
2.9 Gradual Coastal Changes
An impoverishment of the animal and plant population in the vicinity of coastal
cities is being reported all over the world, predominantly in shallow areas. The disappearance in the Adriatic of the brown algae of the genus Cystoseira, which forms
a belt of up to I m, is especially noticeable. But in the Norwegian fjords as well, seaweed is disappearing from the areas near towns. Other algae are spreading in their
place: Cladophora, Enteromorpha, and blue-green algae. In the Mediterranean, various
somewhat deeper regions in which eel-grass (Posidonia) formed lush meadows, are
also being affected. In the areas around Marseilles as well as in the Adriatic, eel-grass
has disappeared from the vicinity of many towns. In its place the Ulva and Haiopteris
algae have increased. Changes have occurred in the benthos fauna as well (Avcin et al.
1974; Katzmann 1974; Munda 1974). In the 0resund between Malmo and Copenhagen, 20 species of large algae have disappeared in recent decades. Others have
increased in their place; for instance, Cladophora,Enteromorpha, Ectocarpus,Pylaeila,
and Poiysiphonia (Wachenfeldt 1971). The branching green plant Chara aspera, which
formerly was common in the belt of skerries around Stockholm, is no longer present
there. At most, pitiful specimens are occasionally observed. 25 to 30 km from Stockholm, these plants develop normally (Pekkari 1973).
Even very small communities of humans disrupt the coastal vegetation. The island of
San Clemente, occupied by 300 marines, lies 76 km off the California coast. Only
around 100 m 3 of domestic effluents reach the ocean daily from the island. Despite
this, several species of algae have disappeared from the shore areas near the drain
pipe: Egregia, Hydrolithon, Halidrys, Phyllospadix, and Sargassum. One hundred
meters from the drain point, these algae are present, as they are everywhere else, and
represent around a third of the plant cover. But around the drain area, they have been
replaced by Ulva, Ge/idium, and blue-green algae (Littler and Murray 1975).
Although a change of algal communities is being observed along those coasts all over
the world that are affected by effluents, no single cause has been found to be responsible for it up till now. The mixture of domestic and industrial effluents, which are
introduced into the sea by many coastal towns, can have various effects: the water is
warmed; drain water contains suspensions of the most varied sorts which settle on
33