The Occurrence of "Green Tides" - a Review
23
features of these "green tide" -forming algae include vegetative fragmentation/propagation and the ability to form free-floating or loose-lying populations capable of almost unlimited vegetative growth (Gordon et al. 1985).
Certainly vegetative fragmentation is characteristic of plants living in
calm-water conditions (Norton and Mathieson 1983), whilst Langton et aL
(1977) observed that fragmentation in Hypnea musciformis was related to
high ammonium-N concentrations. Some reports also suggest that
sporulation is relatively uncommon in unattached plants (Cotton 1911;
Gordon et al. 1985; Park 1992) which might be related to ambient nutrient
levels (Park 1992).
Probably one of the most important attributes of these algae, however, is
their competitive response to the high nutrient content of the surrounding
waters. Apart from an ability to tolerate high nutrient levels, many authors,
have reported these algae to be capable of high and rapid inorganic nitrogen
uptake and storage, i.e. they have a high nitrogen saturation level (Letts and
Richards 1911; Wilkinson 1963; Subbaramaiah and Parekh 1966; Baalsrud
1967; North et aL 1972; Chapman and Craigie 1977; Wallentinus 1981;
Gerard 1982; Kautsky 1982; Rosenberg et aL 1984; Fujita 1985; Lapointe
1985; Soulsby et al. 1985; Ramus and Venable 1987; Fujita et aL 1988, 1989;
Smith and Horne 1988; Pugnetti et al. 1990; Vogt and Schramm 1991).
Indeed, Rosenberg and Ramus (1982) concluded that fast N uptake rates are
a necessary strategy for fast growing, opportunistic macro algae and that
this must be followed by rapid growth before losses occur from grazing and
abrasion. Very small increases in nutrients have also been reported to cause
massive growth increases in Ulva (Harlin and Thorne-Miller 1981). Ulva is
also opportunistic in that it is highly adapted for rapid uptake and storage
of nutrients received intermittently (Rosenberg and Ramus 1984; Fujita
1985; Ramus and Venable 1987; Fujita et al. 1988, 1989; Duke et al. 1989;
Lundberg et al. 1989). It is essential, however, that the nutrients are supplied
continuously to such algae: long-term storage is not possible compared to
the degree which occurs in the slower-growing, longer-living, climax
components of algal communities, e.g. the high N0 3 concentration factor
mentioned above for Laminaria longicruris which sustains growth
throughout the nitrogen-deficient summer periods (Chapman and Craigie
1977; Chapman et al. 1978).
Although it is generally recognized that NO 3 is the main available source
ofN for macroalgae (Anderson 1942; Fries 1963; Prince 1974; Wallentinus
1991), some genera such as Ulva, Enteromorpha and Gracilaria can also
rapidly take up and utilize ammonia (Wilkinson 1963; Waite and Gregory
1969; Neish and Fox 1971; Waite and Mitchell 1972a,b; Guist and Humm
1976; Harlin et al. 1978; Rosenberg and Ramus 1984; Duke et aL 1989). In
some experimental studies, for example, many green algae have been
23
features of these "green tide" -forming algae include vegetative fragmentation/propagation and the ability to form free-floating or loose-lying populations capable of almost unlimited vegetative growth (Gordon et al. 1985).
Certainly vegetative fragmentation is characteristic of plants living in
calm-water conditions (Norton and Mathieson 1983), whilst Langton et aL
(1977) observed that fragmentation in Hypnea musciformis was related to
high ammonium-N concentrations. Some reports also suggest that
sporulation is relatively uncommon in unattached plants (Cotton 1911;
Gordon et al. 1985; Park 1992) which might be related to ambient nutrient
levels (Park 1992).
Probably one of the most important attributes of these algae, however, is
their competitive response to the high nutrient content of the surrounding
waters. Apart from an ability to tolerate high nutrient levels, many authors,
have reported these algae to be capable of high and rapid inorganic nitrogen
uptake and storage, i.e. they have a high nitrogen saturation level (Letts and
Richards 1911; Wilkinson 1963; Subbaramaiah and Parekh 1966; Baalsrud
1967; North et aL 1972; Chapman and Craigie 1977; Wallentinus 1981;
Gerard 1982; Kautsky 1982; Rosenberg et aL 1984; Fujita 1985; Lapointe
1985; Soulsby et al. 1985; Ramus and Venable 1987; Fujita et aL 1988, 1989;
Smith and Horne 1988; Pugnetti et al. 1990; Vogt and Schramm 1991).
Indeed, Rosenberg and Ramus (1982) concluded that fast N uptake rates are
a necessary strategy for fast growing, opportunistic macro algae and that
this must be followed by rapid growth before losses occur from grazing and
abrasion. Very small increases in nutrients have also been reported to cause
massive growth increases in Ulva (Harlin and Thorne-Miller 1981). Ulva is
also opportunistic in that it is highly adapted for rapid uptake and storage
of nutrients received intermittently (Rosenberg and Ramus 1984; Fujita
1985; Ramus and Venable 1987; Fujita et al. 1988, 1989; Duke et al. 1989;
Lundberg et al. 1989). It is essential, however, that the nutrients are supplied
continuously to such algae: long-term storage is not possible compared to
the degree which occurs in the slower-growing, longer-living, climax
components of algal communities, e.g. the high N0 3 concentration factor
mentioned above for Laminaria longicruris which sustains growth
throughout the nitrogen-deficient summer periods (Chapman and Craigie
1977; Chapman et al. 1978).
Although it is generally recognized that NO 3 is the main available source
ofN for macroalgae (Anderson 1942; Fries 1963; Prince 1974; Wallentinus
1991), some genera such as Ulva, Enteromorpha and Gracilaria can also
rapidly take up and utilize ammonia (Wilkinson 1963; Waite and Gregory
1969; Neish and Fox 1971; Waite and Mitchell 1972a,b; Guist and Humm
1976; Harlin et al. 1978; Rosenberg and Ramus 1984; Duke et aL 1989). In
some experimental studies, for example, many green algae have been