ECOLOGICAL STUDIES AT LOUGH INE
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to wave action. Himanthalia (Fig. 43) replaces Alaria towards increasing
shelter and may perhaps compete with it in the entrance to Barloge
Creek; the two species overlap along the south-west shore of Bullock
Island. Himanthalia itself grows only very sparsely in the lough, and
looks unhealthy except where it is washed by the inflowing tide; it is
absent from the North Basin. I n stations of moderate wave exposure
Gigantina stellata and Chondrus crispus form an undergrowth in the
sublittoral fringe; at this level within Lough Ine and extending the
length of Barloge Creek but not into open sea, the brown bubbly
vesicles of Leathesia difformis and Colpmenia sinuosa are found on
horizontal or gently sloping rock surfaces.
D. THE SUBLITTORAL REGION
1. Species Preferring Open-sea and Intermediate Stations
Along the open coast the upper margin of the Laminaria forest is
formed by Laminaria digitata, which can escape undue exposure to air
a t low tides by lying flat; below the reach of all tides, however, it cannot compete with the erect L. hyperborea (Etching, 1941). Both species
penetrate the Bullock Narrows, and Saccorhiza polyschides (Fig. 44)
penetrates slightly further. L. digitata and Saccorhiza polyschides reappear to form a dense forest in the Rapids, where L. hyperborea is very
uncommon; it appears that the two species with flexible stipes are
superior in current. In contrast, L. saccharina is found a t sheltered stations from Bullock Narrows to the South Basin, but is absent from
most of the North Basin, even though the area includes seemingly suitable substrates. Experimental transfers carried out by Dr. E. M.
Burrows and Dr. T. Norton indicate that the sea urchin Paracentrotus,
which is abundant along much of the shore of the North Basin, readily
destroys Laminaria saccharina; other factors also may operate against
this alga.
The laminarian seaweeds form the chief substrate for Patina pellucida
and an important one for two other gastropods, Calliostoma zizyphinum
and Gibbula cineraria. Patina (Fig. 45) is found at all seaward stations
and extends up Barloge Creek to the Rapids, where it flourishes in
moderate current. It is almost absent from the lough, though occasional
specimens occur in the Castle Narrows. Calliostma has a similar type of
distribution, but not Gibbula cineraria which is discussed below.
2. Species Preferring Stations Remote from the Open Sen
The most conspicuous algae of the shallow sublittoral within the
lough are Stilophora rhizodes (Fig. 46), Enteromorpha clathrata, and
Codium fragile subsp. tomentosoides (Silva, 1955), although there are
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to wave action. Himanthalia (Fig. 43) replaces Alaria towards increasing
shelter and may perhaps compete with it in the entrance to Barloge
Creek; the two species overlap along the south-west shore of Bullock
Island. Himanthalia itself grows only very sparsely in the lough, and
looks unhealthy except where it is washed by the inflowing tide; it is
absent from the North Basin. I n stations of moderate wave exposure
Gigantina stellata and Chondrus crispus form an undergrowth in the
sublittoral fringe; at this level within Lough Ine and extending the
length of Barloge Creek but not into open sea, the brown bubbly
vesicles of Leathesia difformis and Colpmenia sinuosa are found on
horizontal or gently sloping rock surfaces.
D. THE SUBLITTORAL REGION
1. Species Preferring Open-sea and Intermediate Stations
Along the open coast the upper margin of the Laminaria forest is
formed by Laminaria digitata, which can escape undue exposure to air
a t low tides by lying flat; below the reach of all tides, however, it cannot compete with the erect L. hyperborea (Etching, 1941). Both species
penetrate the Bullock Narrows, and Saccorhiza polyschides (Fig. 44)
penetrates slightly further. L. digitata and Saccorhiza polyschides reappear to form a dense forest in the Rapids, where L. hyperborea is very
uncommon; it appears that the two species with flexible stipes are
superior in current. In contrast, L. saccharina is found a t sheltered stations from Bullock Narrows to the South Basin, but is absent from
most of the North Basin, even though the area includes seemingly suitable substrates. Experimental transfers carried out by Dr. E. M.
Burrows and Dr. T. Norton indicate that the sea urchin Paracentrotus,
which is abundant along much of the shore of the North Basin, readily
destroys Laminaria saccharina; other factors also may operate against
this alga.
The laminarian seaweeds form the chief substrate for Patina pellucida
and an important one for two other gastropods, Calliostoma zizyphinum
and Gibbula cineraria. Patina (Fig. 45) is found at all seaward stations
and extends up Barloge Creek to the Rapids, where it flourishes in
moderate current. It is almost absent from the lough, though occasional
specimens occur in the Castle Narrows. Calliostma has a similar type of
distribution, but not Gibbula cineraria which is discussed below.
2. Species Preferring Stations Remote from the Open Sen
The most conspicuous algae of the shallow sublittoral within the
lough are Stilophora rhizodes (Fig. 46), Enteromorpha clathrata, and
Codium fragile subsp. tomentosoides (Silva, 1955), although there are