240
R.L. Fletcher
attributed to the exceptional high temperatures and sunshine levels recorded in the summer months. Note, however, that under less extreme
conditions (dry conditions, light winds) dense mats of algae were reported for the same harbour (den Hartog 1994). Anonymous (1976a) also
concluded that the "optimal" conditions of 1973 (previous winter
warmer than average, steady temperature rise during February, March
and April, calm conditions etc. all providing low turbidity and high
irradiance) were responsible for the excellent growth of Enteromorpha
below low water neap tide level in Langstone Harbour. Jeffrey et al.
(1992) also drew attention to the important role played by climatic conditions in controlling algal growths in Dublin Bay; they suggested that a
prolonged high summer temperature would result in a lower biomass. Based on studies in Langstone Harbour, Anonymous (1976a) and
Montgomery and Soulsby (1980) further suggested that another important
factor that determines algal cover is the direction and speed of prevailing
winds during the growing season. Such studies led Soulsby et al. (1985) to
the conclusion that the distribution and biomass of algae in Langstone
Harbour was controlled by the availability of habitats, physical! climatic
factors and grazing activity; they suggested, therefore, that any further
increase in the nutrient loading would go undetected in the harbour.
Particularly significant to this discussion, however, is the recent work
of Jeffrey et al. (1992) in Dublin Bay. They refute the importance of
metereological conditions and draw attention to the sediments underlying the algal mats as a significant source of nutrients; they suggested that
the decline in the algal crop in August bore no relationship with environmental factors such as temperature and light (which were still favourable) but, more notably, corresponded with a comparatively low nutrient
release rate from the sediments. They also suggested that nutrients released from the sediments playa major role in determining spatial variations in algal biomass in Dublin Bay (Fig. 8.4).
8.6 Effect of Excessive Growth of Algae
Whilst some authors conclude that the extensive green algal mats can
sometimes be beneficial by insulating the intertidal invertebrates from
the heat of the sun, that they cause no major ecological or environmental
problems, or that the effects are not acute enough to warrent corrective
action (Montgomery et al. 1985), more commonly the mats are considered a nuisance and that they lower the quality of the ecosystem. For
R.L. Fletcher
attributed to the exceptional high temperatures and sunshine levels recorded in the summer months. Note, however, that under less extreme
conditions (dry conditions, light winds) dense mats of algae were reported for the same harbour (den Hartog 1994). Anonymous (1976a) also
concluded that the "optimal" conditions of 1973 (previous winter
warmer than average, steady temperature rise during February, March
and April, calm conditions etc. all providing low turbidity and high
irradiance) were responsible for the excellent growth of Enteromorpha
below low water neap tide level in Langstone Harbour. Jeffrey et al.
(1992) also drew attention to the important role played by climatic conditions in controlling algal growths in Dublin Bay; they suggested that a
prolonged high summer temperature would result in a lower biomass. Based on studies in Langstone Harbour, Anonymous (1976a) and
Montgomery and Soulsby (1980) further suggested that another important
factor that determines algal cover is the direction and speed of prevailing
winds during the growing season. Such studies led Soulsby et al. (1985) to
the conclusion that the distribution and biomass of algae in Langstone
Harbour was controlled by the availability of habitats, physical! climatic
factors and grazing activity; they suggested, therefore, that any further
increase in the nutrient loading would go undetected in the harbour.
Particularly significant to this discussion, however, is the recent work
of Jeffrey et al. (1992) in Dublin Bay. They refute the importance of
metereological conditions and draw attention to the sediments underlying the algal mats as a significant source of nutrients; they suggested that
the decline in the algal crop in August bore no relationship with environmental factors such as temperature and light (which were still favourable) but, more notably, corresponded with a comparatively low nutrient
release rate from the sediments. They also suggested that nutrients released from the sediments playa major role in determining spatial variations in algal biomass in Dublin Bay (Fig. 8.4).
8.6 Effect of Excessive Growth of Algae
Whilst some authors conclude that the extensive green algal mats can
sometimes be beneficial by insulating the intertidal invertebrates from
the heat of the sun, that they cause no major ecological or environmental
problems, or that the effects are not acute enough to warrent corrective
action (Montgomery et al. 1985), more commonly the mats are considered a nuisance and that they lower the quality of the ecosystem. For