ECOLOGICAL STUDIES AT LOUGH INE
253
Biotic factors may also be of great importance in determining sublittoral distribution. For example, in Lough Ine predation by crabs may
determine the lower limits of Mytilus edulis (Section VII), and Herring
Gulls may prevent the establishment of large Marthasterias glacialis in
water less than 1 m deep and thus permit the survival of Anomia
(Section VIII).
Problems of littoral zonation (reviewed by Lewis, 1964) have received
much attention from others; they have not formed any major part of
our studies a t Lough h e . Nevertheless certain problems of particular
relevance to the locality have interested us. We have, for example,
made detailed observations on the comparative zonation and characteristics of Patella species within and without the lough which also have
some taxonomic interest arising from the interplay of environmental
and genotypic characters. We are now studying the distribution of
organisms in the Western Trough in relation to the thermocline and
chemocline.
B. THE DISTRIBUTION A N D CHARACTERISTICS O F
P A T E L L A SPECIES
1. Zonation
Of the three species of Patella found in the British Isles, only two,
namely P. vulgata L. and P . aspera. Lamarck, occur in the Lough Ine
area or, indeed, anywhere on the Irish coast (Southward and Crisp,
1954; Crisp and Southward, 1958). Both these species are abundant on
the open coast of Carrigathorna, and occur somewhat more sparsely
throughout Barloge Creek and within Lough Ine (Ebling et al., 1962).
We have made a detailed study of the limpet population of a section
of coast exposed to the full tidal range and severe wave-action at
Carrigathorna, and compared with it the population in Lough h e , where
the tidal range is contracted and splash is negligible.
The relative proportions of Patella vulgata and Patella aspera were
determined from adequate samples at different levels in a section a t
Carrigathorna and are shown diagrammatically in Fig. 54. Limpets were
distributed fairly evenly throughout the intertidal region, although
occasional specimens occurred above our highest sample in crevices and
gullies outside the limits of the section. Samples were also taken from
two rock pools at the level of the uppermost band.
It is evident that P. aspera is t,he dominant species throughout the
intertidal region, extending up to but not beyond high water of spring
tides. P. vulgata exclusively occupies a narrow belt above this level, but
below it forms only a minor constituent of the limaet population. In
rock pools about 1 m above high-water mark the two species occur together in roughly equal proportions. These observations put the limits
253
Biotic factors may also be of great importance in determining sublittoral distribution. For example, in Lough Ine predation by crabs may
determine the lower limits of Mytilus edulis (Section VII), and Herring
Gulls may prevent the establishment of large Marthasterias glacialis in
water less than 1 m deep and thus permit the survival of Anomia
(Section VIII).
Problems of littoral zonation (reviewed by Lewis, 1964) have received
much attention from others; they have not formed any major part of
our studies a t Lough h e . Nevertheless certain problems of particular
relevance to the locality have interested us. We have, for example,
made detailed observations on the comparative zonation and characteristics of Patella species within and without the lough which also have
some taxonomic interest arising from the interplay of environmental
and genotypic characters. We are now studying the distribution of
organisms in the Western Trough in relation to the thermocline and
chemocline.
B. THE DISTRIBUTION A N D CHARACTERISTICS O F
P A T E L L A SPECIES
1. Zonation
Of the three species of Patella found in the British Isles, only two,
namely P. vulgata L. and P . aspera. Lamarck, occur in the Lough Ine
area or, indeed, anywhere on the Irish coast (Southward and Crisp,
1954; Crisp and Southward, 1958). Both these species are abundant on
the open coast of Carrigathorna, and occur somewhat more sparsely
throughout Barloge Creek and within Lough Ine (Ebling et al., 1962).
We have made a detailed study of the limpet population of a section
of coast exposed to the full tidal range and severe wave-action at
Carrigathorna, and compared with it the population in Lough h e , where
the tidal range is contracted and splash is negligible.
The relative proportions of Patella vulgata and Patella aspera were
determined from adequate samples at different levels in a section a t
Carrigathorna and are shown diagrammatically in Fig. 54. Limpets were
distributed fairly evenly throughout the intertidal region, although
occasional specimens occurred above our highest sample in crevices and
gullies outside the limits of the section. Samples were also taken from
two rock pools at the level of the uppermost band.
It is evident that P. aspera is t,he dominant species throughout the
intertidal region, extending up to but not beyond high water of spring
tides. P. vulgata exclusively occupies a narrow belt above this level, but
below it forms only a minor constituent of the limaet population. In
rock pools about 1 m above high-water mark the two species occur together in roughly equal proportions. These observations put the limits