The Occurrence of "Green Tides" - a Review
15
caught the attention of authors and caused concern to ecologists and
environmentalists.
Probably one of the most noticeable floristic changes associated with
eutrophication is a reported decline in the number of perennial macro algae
contributing to the so-called climax communities of both the intertidal and
subtidal regions throughout the world. Fucus communities appear to be
particularly vulnerable with several Fucus spp., and in particular Fucus
vesiculosus, being reported to be replaced or reduced in numbers in the
North Atlantic and Baltic as a result of waters being contaminated with
sewage effuent (Grenager 1957; Johnston 1971/72; Rueness 1973; Russell
1974; Bokn 1979; Hallfors et al. 1987; Vogt and Schramm 1991; Park 1992;
Kautsky et al. 1992). There are also some reports of a decline in North
Atlantic populations of the knotted wrack Ascophyllum nodosum as a result
of increased eutrophication (Rueness 1973; Bokn and Lein 1978; Bokn
1979). Work by Bokn and Lein (1978) and Rueness (1973) has indicated
that dense populations of green algae provide unfavourable competition to
these fucoids in Oslofjord, Norway, probably by hindering the establishment of germlings. A similar decline in fucoids has been reported in the
Mediterranean, notably species of the genus Cystoseira (BeHan-Santini
1969; Golubic 1970; Munda 1974, 1993; Sfriso 1987), e.g., Cystoseira fimbriata and C. barbata in the Venice Lagoon (Sfriso 1987), Cystoseira stricta
at Marseilles (BeHan and BeHan-Santini 1972; BeHan 1970) and Fucus
virsoides in the northern Adriatic (Munda 1974, 1993). There are also
reports of a decline in the number of Sargassum plants in Japan (Hirose
1978) and the northern Adriatic (Munda 1993). Some reports, however,
refer to a pollution-tolerant fucoid, Fucus distichus ssp. edentatus whose
occurrence and distribution in the North Atlantic appears to be associated
with sewage contaminated water (PoweHI963; Bokn and Lein 1978). Fucus
evanescens and Fucus spiralis were similarly reported by Bokn (1979) and
Bokn and Lein (1978) to be more common than other fucoids in the sewagepolluted inner part of Oslofjord, Norway. In this respect, it is noteworthy
that with improved sewage treatment and discharge practices, Bokn et al.
(1992) reported an improvement in the fucoid vegetation in the inner
o slofjord.
There are also several reports from around the world of a decline in
populations of seagrasses as a result of eutrophication (McNulty 1959;
North 1963; Bellan 1970; Munda 1974; Guist and Humm 1976; Harlin and
Thorne-Miller 1981; Murray and Littler 1983; Sfriso 1987; Ruiz et al. 1990).
This has been particularly weH documented for the Venice Lagoon, northern Adriatic which has seen a gradual decline in populations of the sea
grasses Cymodocea nodosa and Zostera noltii over recent years (Sfriso
1987). Other phanerograms reported to be reduced in abundance near
15
caught the attention of authors and caused concern to ecologists and
environmentalists.
Probably one of the most noticeable floristic changes associated with
eutrophication is a reported decline in the number of perennial macro algae
contributing to the so-called climax communities of both the intertidal and
subtidal regions throughout the world. Fucus communities appear to be
particularly vulnerable with several Fucus spp., and in particular Fucus
vesiculosus, being reported to be replaced or reduced in numbers in the
North Atlantic and Baltic as a result of waters being contaminated with
sewage effuent (Grenager 1957; Johnston 1971/72; Rueness 1973; Russell
1974; Bokn 1979; Hallfors et al. 1987; Vogt and Schramm 1991; Park 1992;
Kautsky et al. 1992). There are also some reports of a decline in North
Atlantic populations of the knotted wrack Ascophyllum nodosum as a result
of increased eutrophication (Rueness 1973; Bokn and Lein 1978; Bokn
1979). Work by Bokn and Lein (1978) and Rueness (1973) has indicated
that dense populations of green algae provide unfavourable competition to
these fucoids in Oslofjord, Norway, probably by hindering the establishment of germlings. A similar decline in fucoids has been reported in the
Mediterranean, notably species of the genus Cystoseira (BeHan-Santini
1969; Golubic 1970; Munda 1974, 1993; Sfriso 1987), e.g., Cystoseira fimbriata and C. barbata in the Venice Lagoon (Sfriso 1987), Cystoseira stricta
at Marseilles (BeHan and BeHan-Santini 1972; BeHan 1970) and Fucus
virsoides in the northern Adriatic (Munda 1974, 1993). There are also
reports of a decline in the number of Sargassum plants in Japan (Hirose
1978) and the northern Adriatic (Munda 1993). Some reports, however,
refer to a pollution-tolerant fucoid, Fucus distichus ssp. edentatus whose
occurrence and distribution in the North Atlantic appears to be associated
with sewage contaminated water (PoweHI963; Bokn and Lein 1978). Fucus
evanescens and Fucus spiralis were similarly reported by Bokn (1979) and
Bokn and Lein (1978) to be more common than other fucoids in the sewagepolluted inner part of Oslofjord, Norway. In this respect, it is noteworthy
that with improved sewage treatment and discharge practices, Bokn et al.
(1992) reported an improvement in the fucoid vegetation in the inner
o slofjord.
There are also several reports from around the world of a decline in
populations of seagrasses as a result of eutrophication (McNulty 1959;
North 1963; Bellan 1970; Munda 1974; Guist and Humm 1976; Harlin and
Thorne-Miller 1981; Murray and Littler 1983; Sfriso 1987; Ruiz et al. 1990).
This has been particularly weH documented for the Venice Lagoon, northern Adriatic which has seen a gradual decline in populations of the sea
grasses Cymodocea nodosa and Zostera noltii over recent years (Sfriso
1987). Other phanerograms reported to be reduced in abundance near