ECOLOGICAL STUDIES AT LOUOH INE
249
large fluctuations in the amount of Codium present in successive years.
Stilophora is confined to the lough; it is a weakly anchored form and is
probably unsuitable for open waters.
Gibbula cineraria (Fig. 47) occurs throughout the lough and Barloge
Creek on laminarian fronds, where these are present, and on the shallow
bottom when they are not, though it is absent from laminarian fronds
a t open sea stations. Caryophyllia smithi, Marthasterias glacialis, Asterinu gibbosa and Paracentrotus lividus (Fig. 48) also prefer the lough, but
are not confined to it; occasional specimens of all these animals occur
in Barloge Creek, and Paracentrotus has been found in rock pools just
inside Carrigathorna. As a speculation it seems possible that Paracentrotus requires a combination of virtually permanent immersion with
safety from powerful predators. This would be afforded in rock pools
and sublittorally in certain landlocked areas (see Section VII). Paracentrotus is indeed common in rock pools on the west coast of Ireland.
It has also been suggested by Southward and Crisp (1954) that high
summer temperatures are necessary for breeding. There is, however, an
additional problem in that it is almost absent from Great Britain.
3. Species Found in All Parts of the Area
in Lough Ine and on the open coast.
Asterias rubens (Fig. 49) and Hiatella arctica occur commonly, both
E. WAVE ACTION I N COMPARISON WITH CURRENT
Of the three intertidal species, Porphym umbilicalis, Actinia equina
and Littorinu neritoides, which prefer open sea stations and penetrate
only to Bullock Narrows, none reappears in current in the Rapids. On
the other hand, all of the twelve species which prefer stations remote
from the sea and are not found outside of Bullock Narrows are present
in the Rapids. Thus the littoral species treat the Rapids as sheltered.
This one might expect, since there is little splash in the Rapids to protect vulnerable species from desiccation, and the current a t the bank
exerts much less mechanical pull than do the Atlantic waves on an open
shore.
Two of the sublittoral species which do not penetrate beyond Bullock
Narrows, namely Laminaria digitata and Saccmhiza polyschides, also
occur abundantly in the Rapids. As already stated, the third open coast
form, L. hyperborea, which is virtually absent &om the Rapids, may be
unable to compete there because of its stiff stipe. On the other hand, of
the species favouring the lough, only Marthasterias glacialis occurs in
the Rapids, and Stilophora rhizodes, Caryophyllia smithi and Paracentrotus lividus are all absent. Moreover, three species which occur both
249
large fluctuations in the amount of Codium present in successive years.
Stilophora is confined to the lough; it is a weakly anchored form and is
probably unsuitable for open waters.
Gibbula cineraria (Fig. 47) occurs throughout the lough and Barloge
Creek on laminarian fronds, where these are present, and on the shallow
bottom when they are not, though it is absent from laminarian fronds
a t open sea stations. Caryophyllia smithi, Marthasterias glacialis, Asterinu gibbosa and Paracentrotus lividus (Fig. 48) also prefer the lough, but
are not confined to it; occasional specimens of all these animals occur
in Barloge Creek, and Paracentrotus has been found in rock pools just
inside Carrigathorna. As a speculation it seems possible that Paracentrotus requires a combination of virtually permanent immersion with
safety from powerful predators. This would be afforded in rock pools
and sublittorally in certain landlocked areas (see Section VII). Paracentrotus is indeed common in rock pools on the west coast of Ireland.
It has also been suggested by Southward and Crisp (1954) that high
summer temperatures are necessary for breeding. There is, however, an
additional problem in that it is almost absent from Great Britain.
3. Species Found in All Parts of the Area
in Lough Ine and on the open coast.
Asterias rubens (Fig. 49) and Hiatella arctica occur commonly, both
E. WAVE ACTION I N COMPARISON WITH CURRENT
Of the three intertidal species, Porphym umbilicalis, Actinia equina
and Littorinu neritoides, which prefer open sea stations and penetrate
only to Bullock Narrows, none reappears in current in the Rapids. On
the other hand, all of the twelve species which prefer stations remote
from the sea and are not found outside of Bullock Narrows are present
in the Rapids. Thus the littoral species treat the Rapids as sheltered.
This one might expect, since there is little splash in the Rapids to protect vulnerable species from desiccation, and the current a t the bank
exerts much less mechanical pull than do the Atlantic waves on an open
shore.
Two of the sublittoral species which do not penetrate beyond Bullock
Narrows, namely Laminaria digitata and Saccmhiza polyschides, also
occur abundantly in the Rapids. As already stated, the third open coast
form, L. hyperborea, which is virtually absent &om the Rapids, may be
unable to compete there because of its stiff stipe. On the other hand, of
the species favouring the lough, only Marthasterias glacialis occurs in
the Rapids, and Stilophora rhizodes, Caryophyllia smithi and Paracentrotus lividus are all absent. Moreover, three species which occur both