236
R.L. Fletcher
Two notable exceptions to the above generalization are the brown
algae Fucus disticus subsp. edentatus and Ectocarpus siIicuiosus which
have been reported to thrive in nutrient-enriched waters. The former has
been reported to occur most abundantly in close proximity to sewage
outflows in the Shetland Isles, off the north coast of Scotland (Powell
1963; Russell 1974) whilst the latter has been reported to form
dense blooms in Dublin Bay, Ireland (Wilson et al. 1990; Jeffrey et al.
1992).
Whilst some of the above reports of increased algal growths refer to
attached populations, usually in the vicinity of sewage outfalls, many
refer to unattached, loose-lying mats of algae which accumulate on the
surface of sheltered mudflats. In Belfast Lough they occurred as a
flannelly or ropey mass known as "May Fog" or "Flannel Weed" and
comprised a mixture of species (Cotton 1911). In Langstone Harbour,
they were referred to as either "blanket-weed" (Southgate 1972) or
"slob" (Anonymous 1976a). These loose-lying mats of weed, which probably originated either from attached sporelings (Anonymous 1976a;
Jeffrey et al. 1992) or from vegetative plant portions buried within the
sediments (Anonymous 1976a), can be quite extensive. Cotton (1911), for
example, refers to wide stretches of the Belfast Lough "sloblands",
many hundreds of acres in extent, being covered with a green sward of
almost pure UIva, whilst Perkins and Abbott (1972) refer to
Enteromorpha mats occupying substantial areas (e.g. 21%) of some
shores in the Firth of Clyde, Scotland. Using aerial surveys, it was estimated that in 1983, 64% of the intertidal mudflats in Portsmouth
Harbour and in 1982, 43% of the intertidal mudflats in Langstone
Harbour were covered by algal mats (Coulson and Budd 1979; Soulsby
et al. 1985). In Langstone, the mats were described as particularlyextensive in the northern, more sheltered areas of the harbour, not too distant
from the sewage discharge pipe, forming a deep continuous cover of
green algae 10-12 cm deep (Montgomery and Soulsby 1980; Nicholls
et al. 1981; Lowthion et al. 1985) (Fig. 8.1). Comparable thick mats of
Enteromorpha, reaching 15-20 cm thick, were also reported for the Firth
of Clyde by Perkins and Abbott (1972). Maximum biomass figures for
these mats include 3 kg m -2 fresh weight (Ythan Estuary, Scotland; Hull
1987), 68 g m -2 dry weight (Langstone Harbour, England; Montgomery
and Soulsby 1980), 49 gm- 2 dry weight (Portsmouth Harbour, England;
Soulsby et al. 1978; Lowthion et al. 1985), 150 g m -2 dry weight (Loch
Forfar, Scotland; Coleman and Stewart 1979), 2 kg m -2 fresh weight
(Ythan Estuary, Scotland; Raffaelli et al. 1989), > 500 g m -2 dry weight
(Jeffrey et al. 1992) and 113 gm- 2 dry weight (Eden Estuary, Scotland;
Owens et al. 1979).
R.L. Fletcher
Two notable exceptions to the above generalization are the brown
algae Fucus disticus subsp. edentatus and Ectocarpus siIicuiosus which
have been reported to thrive in nutrient-enriched waters. The former has
been reported to occur most abundantly in close proximity to sewage
outflows in the Shetland Isles, off the north coast of Scotland (Powell
1963; Russell 1974) whilst the latter has been reported to form
dense blooms in Dublin Bay, Ireland (Wilson et al. 1990; Jeffrey et al.
1992).
Whilst some of the above reports of increased algal growths refer to
attached populations, usually in the vicinity of sewage outfalls, many
refer to unattached, loose-lying mats of algae which accumulate on the
surface of sheltered mudflats. In Belfast Lough they occurred as a
flannelly or ropey mass known as "May Fog" or "Flannel Weed" and
comprised a mixture of species (Cotton 1911). In Langstone Harbour,
they were referred to as either "blanket-weed" (Southgate 1972) or
"slob" (Anonymous 1976a). These loose-lying mats of weed, which probably originated either from attached sporelings (Anonymous 1976a;
Jeffrey et al. 1992) or from vegetative plant portions buried within the
sediments (Anonymous 1976a), can be quite extensive. Cotton (1911), for
example, refers to wide stretches of the Belfast Lough "sloblands",
many hundreds of acres in extent, being covered with a green sward of
almost pure UIva, whilst Perkins and Abbott (1972) refer to
Enteromorpha mats occupying substantial areas (e.g. 21%) of some
shores in the Firth of Clyde, Scotland. Using aerial surveys, it was estimated that in 1983, 64% of the intertidal mudflats in Portsmouth
Harbour and in 1982, 43% of the intertidal mudflats in Langstone
Harbour were covered by algal mats (Coulson and Budd 1979; Soulsby
et al. 1985). In Langstone, the mats were described as particularlyextensive in the northern, more sheltered areas of the harbour, not too distant
from the sewage discharge pipe, forming a deep continuous cover of
green algae 10-12 cm deep (Montgomery and Soulsby 1980; Nicholls
et al. 1981; Lowthion et al. 1985) (Fig. 8.1). Comparable thick mats of
Enteromorpha, reaching 15-20 cm thick, were also reported for the Firth
of Clyde by Perkins and Abbott (1972). Maximum biomass figures for
these mats include 3 kg m -2 fresh weight (Ythan Estuary, Scotland; Hull
1987), 68 g m -2 dry weight (Langstone Harbour, England; Montgomery
and Soulsby 1980), 49 gm- 2 dry weight (Portsmouth Harbour, England;
Soulsby et al. 1978; Lowthion et al. 1985), 150 g m -2 dry weight (Loch
Forfar, Scotland; Coleman and Stewart 1979), 2 kg m -2 fresh weight
(Ythan Estuary, Scotland; Raffaelli et al. 1989), > 500 g m -2 dry weight
(Jeffrey et al. 1992) and 113 gm- 2 dry weight (Eden Estuary, Scotland;
Owens et al. 1979).