Montrose Alpha oil platform was installed in the North Sea during August 1975. Samples and photographs of marine growth on the platform jacket have been analysed since 1977. Marine growth is depth related, with particular organisms or group of organisms dominant at various depths. Seaweeds dominate the sunlit surfaces extending down to a depth of -10m. On shaded surfaces in the sunlit zone, arborescent bryozoans cover most of the substrate and continue down to -31 m. In the range -31 m to -51 nl calcareous bryozoans cover large areas of the available substrate but hydroids are also common. Between -51 m and -71 m, encrusting bryozoans dominate the community but below -71 m the aggregate tubeworm Filograna implexa and deep-water barnacle Balanus hameriare common. Changes have taken place in the dominant species over the years. There have been relatively rapid changes in the depth range M.L.W. to -31 m and a more gradual change in the mid-water levels. Reasons for these changes are discussed. Marine growth on Montrose is compared with that on contemporary jackets in the Forties field, 40 km to the north-west. Causes for the observed differences are discussed.
Oxygen consumption (Mo 2) of
P. cygnus was measured in intermittent flow
respirometers. A log–log relationship with body weight
(W ) remained constant over the range 15–31
°C. Mo 2 was related to
body weight and temperature (T) : log
10 Mo 2
=0.814log 10W +0.051
T – 2.075.I n 400 –500 g lobsters it showed
a strong response to acute temperature changes (23 –19 –15
–11 and 23 –27 –31 °C): log 10
Mo 2 = 0.045
T – 2.38. Activity caused a significant
(P <0.001) increase in
Mo 2, with the response being
modulated by temperature and body weight. Lobsters took 5–8 h to recover
from exposure to handling and emersion, the duration of the recovery period
being longer at higher temperatures. A nocturnal rhythm to oxygen consumption
was evident. There was a large and sustained specific dynamic action, with a
peak Mo 2 of 2.19 times the
standard rate occurring 7 h after feeding.
Mo 2 at 23 °C was
independent of the oxygen tension down to a critical oxygen tension
(P c) of 46.2 Torr, be low which
Mo 2 varied directly with the
oxygen tension. P c varied with
temperature and activity state. The data allow the design of live-holding
systems and practices that provide the oxygen requirements of captive
P. cygnus .
Extra keyword: live holding.
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