110
GORDON A. RILEY
0.4 mg C.m-2.day-l appears to be adequate to support a minimal
population of bacteria and animals, and the maximum estimate of
4.4 mg probably would take care of the largest populations ordinarily
found in the deep ocean. This still does not establish a reasonable
average value, and possibly it is premature to attempt to do so. However, if we accept Vinogradova’s approximate figure for average biomass
of the fauna, total utilization by these animals and associated bacteria
possibly would be of the order of 1 mg C.m-Z.day-l.
The rate of delivery of organic matter to the bottom can be estimated with some degree of confidence. The materials most frequently
seen in deep water samples are flakes and small particles. Under
laboratory conditions these have a sinking rate of about 0.2 m/day,
and in cold waters the rate might be reduced to around 0.1 m. Thus if
the bathypelagic concentration is of the order of 10-50 pg C/litre, the
rate of sedimentation would be 1-5 mg C.m-2.day-l. Quantitatively
this seems adequate to satisfy utilization rates described above, and
this may be a minimum estimate in view of the fact that there may
be some larger particles raining down faster.
The faunal assemblage has been reported by Vinogradova and others
to consist of seston feeders, indiscriminate detritus feeders, and carnivores. As far as seston feeders are concerned, the problem would
seem to be much the same as that posed earlier in connection with the
bathypelagic population. The rate of supply is adequate, but a concentration of 10-50 pg C/litre is minimal for filter feeders. However,
the published literature indicates that the relative proportions of mud
feeders and seston feeders are quite variable, and the latter are most
abundant in certain limited zones where suspended organic matter is
also most abundant. These zones are often located on or near continental rises or on the slopes of trenches, suggesting that the amount of
suspended material may be increased in such areas by turbidity currents
or the stirring action of deep water movements of a local nature. There
is little reason to suppose that the supply of organic matter from above
would vary in a way that would lead to strongly demarcated local zones
of abundance of sufficiently permanent nature to affect faunal distribution, and variations in the benthic environment are a more likely
explanation.
As indicated earlier, collection of sinking particles at the mudwater interface provides an abundant concentration of organic matter
there, in contrast to the scarcity in concentration per unit volume in
the overlying water. Thus it is not surprising to find that sediment
feeders are more important than seston feeders on much of the deep
ocean floor. There is not any good information as to what proportion
GORDON A. RILEY
0.4 mg C.m-2.day-l appears to be adequate to support a minimal
population of bacteria and animals, and the maximum estimate of
4.4 mg probably would take care of the largest populations ordinarily
found in the deep ocean. This still does not establish a reasonable
average value, and possibly it is premature to attempt to do so. However, if we accept Vinogradova’s approximate figure for average biomass
of the fauna, total utilization by these animals and associated bacteria
possibly would be of the order of 1 mg C.m-Z.day-l.
The rate of delivery of organic matter to the bottom can be estimated with some degree of confidence. The materials most frequently
seen in deep water samples are flakes and small particles. Under
laboratory conditions these have a sinking rate of about 0.2 m/day,
and in cold waters the rate might be reduced to around 0.1 m. Thus if
the bathypelagic concentration is of the order of 10-50 pg C/litre, the
rate of sedimentation would be 1-5 mg C.m-2.day-l. Quantitatively
this seems adequate to satisfy utilization rates described above, and
this may be a minimum estimate in view of the fact that there may
be some larger particles raining down faster.
The faunal assemblage has been reported by Vinogradova and others
to consist of seston feeders, indiscriminate detritus feeders, and carnivores. As far as seston feeders are concerned, the problem would
seem to be much the same as that posed earlier in connection with the
bathypelagic population. The rate of supply is adequate, but a concentration of 10-50 pg C/litre is minimal for filter feeders. However,
the published literature indicates that the relative proportions of mud
feeders and seston feeders are quite variable, and the latter are most
abundant in certain limited zones where suspended organic matter is
also most abundant. These zones are often located on or near continental rises or on the slopes of trenches, suggesting that the amount of
suspended material may be increased in such areas by turbidity currents
or the stirring action of deep water movements of a local nature. There
is little reason to suppose that the supply of organic matter from above
would vary in a way that would lead to strongly demarcated local zones
of abundance of sufficiently permanent nature to affect faunal distribution, and variations in the benthic environment are a more likely
explanation.
As indicated earlier, collection of sinking particles at the mudwater interface provides an abundant concentration of organic matter
there, in contrast to the scarcity in concentration per unit volume in
the overlying water. Thus it is not surprising to find that sediment
feeders are more important than seston feeders on much of the deep
ocean floor. There is not any good information as to what proportion