228
J. A. KITCHING AND F. J. EBLING
Sill to Codium Bay, a sheltered situation inside the lough, the Sertularia
became clogged with fine sediment within a week, and most colonies
died within nine weeks. A large population of diatoms settled on the
perisarc; and the amphipod Caprella acutifrons, a normal inhabitant of
the Sertularia and transferred with it from the Rapids, also became
clogged with sediment and perished along with the Sertularia. Clogging
with sediment is the most probable cause of death, both for the Sertularia and for the Caprella, but again it is not possible to exclude other
agents. It is interesting that Sertularia on boulders raised up on spikes in
Codium Bay, whether facing upwards or downwards, and even Sertularia suspended over relatively deep water from buoys, all rapidly became clogged and perished. These colonies must have been quite out of
reach of any adverse chemical influence of the bottom mud. The
branches of the hydroid filtered sediment from the water moving past
in the South Basin Vortex, At the same time the water movement was
insufficient to prevent the spread of diatoms upon the hydroid, and a
considerable population of these developed during the course of a few
weeks (Round et al., 1961).
We have made similar investigations on the anemone Corynactis
viridis, which is somewhat more tolerant of sheltered conditions than
is Sertularia operculata. Rocks bearing this anemone were transferred
from the Rapids to Codium Bay. Corynactis on rocks raised upon spikes,
and mounted facing downwards, survived for two years and multiplied.
On the other hand, Corynactis on rocks facing upwards, whether upon
spikes or on the bottom, survived for only about one year or less.
Settling of sediment upon Corynactis facing upwards might account for
this observation. Nevertheless, there remains the possibility that full
exposure to light, in the absence of a canopy of Saccorhiza fronds, might
be deleterious, either directly or by the encouragement of competitive
algae. Rocks with Corynactis were therefore transferred to floating wire
cages, some open to the light and some covered, in the Rapids and in
sheltered water. Corynactis tended to close and to remain closed when
exposed to full daylight, but to open in covered cages or by night. The
distribution of Corynactis in the Lough Ine area is consistent with the
hypothesis that these animals require clean conditions and restricted
illumination.
We have not yet investigated any of the numerous species which prefer shelter from current. We do not know whether they are restricted by
the mechanical effects of current or by some secondary effect.
J. A. KITCHING AND F. J. EBLING
Sill to Codium Bay, a sheltered situation inside the lough, the Sertularia
became clogged with fine sediment within a week, and most colonies
died within nine weeks. A large population of diatoms settled on the
perisarc; and the amphipod Caprella acutifrons, a normal inhabitant of
the Sertularia and transferred with it from the Rapids, also became
clogged with sediment and perished along with the Sertularia. Clogging
with sediment is the most probable cause of death, both for the Sertularia and for the Caprella, but again it is not possible to exclude other
agents. It is interesting that Sertularia on boulders raised up on spikes in
Codium Bay, whether facing upwards or downwards, and even Sertularia suspended over relatively deep water from buoys, all rapidly became clogged and perished. These colonies must have been quite out of
reach of any adverse chemical influence of the bottom mud. The
branches of the hydroid filtered sediment from the water moving past
in the South Basin Vortex, At the same time the water movement was
insufficient to prevent the spread of diatoms upon the hydroid, and a
considerable population of these developed during the course of a few
weeks (Round et al., 1961).
We have made similar investigations on the anemone Corynactis
viridis, which is somewhat more tolerant of sheltered conditions than
is Sertularia operculata. Rocks bearing this anemone were transferred
from the Rapids to Codium Bay. Corynactis on rocks raised upon spikes,
and mounted facing downwards, survived for two years and multiplied.
On the other hand, Corynactis on rocks facing upwards, whether upon
spikes or on the bottom, survived for only about one year or less.
Settling of sediment upon Corynactis facing upwards might account for
this observation. Nevertheless, there remains the possibility that full
exposure to light, in the absence of a canopy of Saccorhiza fronds, might
be deleterious, either directly or by the encouragement of competitive
algae. Rocks with Corynactis were therefore transferred to floating wire
cages, some open to the light and some covered, in the Rapids and in
sheltered water. Corynactis tended to close and to remain closed when
exposed to full daylight, but to open in covered cages or by night. The
distribution of Corynactis in the Lough Ine area is consistent with the
hypothesis that these animals require clean conditions and restricted
illumination.
We have not yet investigated any of the numerous species which prefer shelter from current. We do not know whether they are restricted by
the mechanical effects of current or by some secondary effect.