The Management of Eutrophicated Waters
63
and Hesse 1991). Because of oyster culture in some areas of the
Mediterranean, other species have spread, particularly in the Languedoc
ponds, and then drifted towards Spain on the open sea, e.g. Sargassum
muticum, Undaria japonica and Laminaria japonica. Meinesz (pers.
comm.) estimates that the speed of spreading reaches 5 cm/year. This
exponential proliferation threatens to cover the entire Mediterranean and
to modify all littoral ecosystems of the region. There seem to be no
scientific grounds to expect an end to the spreading.
Diatom blooms occurred in 1989 in the Adriatic Sea, with eutrophication suspected as the cause, even though similar blooms were already
observed in 1911. Another "slime" - producing diatom Ascino duscus
walesii moved into the Channel and the North Sea areas. It originates
from the Pacific Ocean (Smayda 1989).
Gyrodinium auredum, a newcomer to the North Sea and the
Norwegian coasts, is harmful for agriculture. Extensive blooms have been
reported on the French and British coasts and, it should be noted, at sites
far away from possible human influence.
2.4 Relationship Eutrophication - Environment
Eutrophication is thus enhanced by man-made discharges as well as by
natural input of nutrients, organic materials, and pollutants. It affects
particularly estuaries and coastal gulfs and bays that are rather shallow,
in narrow communication with main water bodies, and which are
polluted. Water, sediment, flora, and fauna undergo its effects. Sediments are modified and toxicity is increased. The fauna is subjected to
the presence of pollutants, additional organic matter and changes in
oxygen supply because of sediment modifications, which in turn influence toxicity (toxins). The sediments are also affected by nutrients
and carbon disulfide (CS z ). An increase in herbivorous dwellers is recorded, while algae including opportunistic species compete for substrate
and consume oxygen. The atmosphere is fouled by released hydrogen
sulfide (HzS).
The ensuing situation may be worsened by both a trend to overfish
herbivorous species, and by the introduction in the area of nonindigenous opportunistic algae. A process of successive steps sets in
because of easy nutrient assimilation, successful adaptation to existing
pollution and vegetative multiplication, proliferation occurs, leading to
strandings with consequent decomposition, or harvesting followed by
63
and Hesse 1991). Because of oyster culture in some areas of the
Mediterranean, other species have spread, particularly in the Languedoc
ponds, and then drifted towards Spain on the open sea, e.g. Sargassum
muticum, Undaria japonica and Laminaria japonica. Meinesz (pers.
comm.) estimates that the speed of spreading reaches 5 cm/year. This
exponential proliferation threatens to cover the entire Mediterranean and
to modify all littoral ecosystems of the region. There seem to be no
scientific grounds to expect an end to the spreading.
Diatom blooms occurred in 1989 in the Adriatic Sea, with eutrophication suspected as the cause, even though similar blooms were already
observed in 1911. Another "slime" - producing diatom Ascino duscus
walesii moved into the Channel and the North Sea areas. It originates
from the Pacific Ocean (Smayda 1989).
Gyrodinium auredum, a newcomer to the North Sea and the
Norwegian coasts, is harmful for agriculture. Extensive blooms have been
reported on the French and British coasts and, it should be noted, at sites
far away from possible human influence.
2.4 Relationship Eutrophication - Environment
Eutrophication is thus enhanced by man-made discharges as well as by
natural input of nutrients, organic materials, and pollutants. It affects
particularly estuaries and coastal gulfs and bays that are rather shallow,
in narrow communication with main water bodies, and which are
polluted. Water, sediment, flora, and fauna undergo its effects. Sediments are modified and toxicity is increased. The fauna is subjected to
the presence of pollutants, additional organic matter and changes in
oxygen supply because of sediment modifications, which in turn influence toxicity (toxins). The sediments are also affected by nutrients
and carbon disulfide (CS z ). An increase in herbivorous dwellers is recorded, while algae including opportunistic species compete for substrate
and consume oxygen. The atmosphere is fouled by released hydrogen
sulfide (HzS).
The ensuing situation may be worsened by both a trend to overfish
herbivorous species, and by the introduction in the area of nonindigenous opportunistic algae. A process of successive steps sets in
because of easy nutrient assimilation, successful adaptation to existing
pollution and vegetative multiplication, proliferation occurs, leading to
strandings with consequent decomposition, or harvesting followed by