186
J. E. G . RAYMONT
know the specific requirements of these protozoans, but some Radiolaria might consume bacteria. Murray (1963) suggests that Foraminifera
can feed on dead material and possibly on detritus and bacteria, though
living phytoplankton appears to be preferred. However, the recent
work of Freudenthal and his colleagues (unpublished),* using labelled
food cultures, shows that planktonic Foraminifera prefer Nitzschia and
some flagellates; bacteria although ingested apparently do not contribute to the nutrition.
Vinogradov (1962b) suggests that zooplankton from intermediate
depths by extensive diurnal vertical migrations obtains food from the
upper water layers. Faecal pellets produced by this migrating plankton
may assist with the nutrition of the plankton of the deeper layers. Apart
from these coarse filter feeders, the majority of the deep-sea plankton
will be carnivorous.
E. ALTERNATIVE FOOD SOURCES FOR ZOOPLANKTON
The kdings of Bernard, Wood, and others that various Protophyta
may occur in the deep layers of the ocean, far below the euphotic zone,
implies that these plant cells may also serve as food for deep-sea zooplankton. However, the amount of food available to deep-sea plankton
must be extremely limited. There is little doubt as Zenkevitch and
Birstein (1956) have suggested that deep-sea plankton is very reduced
in density. Vinogradov (1962a) has commented on the extraordinarily
rapid reduction of biomass of zooplankton in really deep water. At high
latitudes, for example, he suggests that the biomass below 6 0001 metrea
is only l/lOOOth that of the uppermost water layers. Although Vinogradov believes that few deep-sea animals feed mainly on detritus, this
may be an important accessory food. Investigations, especially summarized by Krey (1961), suggest that detritus can account for a very
large fraction of the total organic suspended matter; this is true even of
the surface layers where the contribution from living plankton may be
expected to be high. In deeper water the actual quantity of orgmio
matter is much lower, but the proportion of detritus may reach almost
100%. In a later study, Krey (1964) shows that despite considerable
fluctuations in the amount of suspended matter, there is a marked tendency for the amount to fall with depth and in very deep water extremely little material is present. This Krey attributes partly to the
eating of material by organisms in the upper layers, but above all to the
mineralization processes occurring in deep water. The fraction of living
material in the total suspended matter shows, as would be expected, 8
remarkably sharp fall in really deep water.
Although the very small amount of suspended material in deep waters
* I em much indebted to the authors for permission to use their data.
J. E. G . RAYMONT
know the specific requirements of these protozoans, but some Radiolaria might consume bacteria. Murray (1963) suggests that Foraminifera
can feed on dead material and possibly on detritus and bacteria, though
living phytoplankton appears to be preferred. However, the recent
work of Freudenthal and his colleagues (unpublished),* using labelled
food cultures, shows that planktonic Foraminifera prefer Nitzschia and
some flagellates; bacteria although ingested apparently do not contribute to the nutrition.
Vinogradov (1962b) suggests that zooplankton from intermediate
depths by extensive diurnal vertical migrations obtains food from the
upper water layers. Faecal pellets produced by this migrating plankton
may assist with the nutrition of the plankton of the deeper layers. Apart
from these coarse filter feeders, the majority of the deep-sea plankton
will be carnivorous.
E. ALTERNATIVE FOOD SOURCES FOR ZOOPLANKTON
The kdings of Bernard, Wood, and others that various Protophyta
may occur in the deep layers of the ocean, far below the euphotic zone,
implies that these plant cells may also serve as food for deep-sea zooplankton. However, the amount of food available to deep-sea plankton
must be extremely limited. There is little doubt as Zenkevitch and
Birstein (1956) have suggested that deep-sea plankton is very reduced
in density. Vinogradov (1962a) has commented on the extraordinarily
rapid reduction of biomass of zooplankton in really deep water. At high
latitudes, for example, he suggests that the biomass below 6 0001 metrea
is only l/lOOOth that of the uppermost water layers. Although Vinogradov believes that few deep-sea animals feed mainly on detritus, this
may be an important accessory food. Investigations, especially summarized by Krey (1961), suggest that detritus can account for a very
large fraction of the total organic suspended matter; this is true even of
the surface layers where the contribution from living plankton may be
expected to be high. In deeper water the actual quantity of orgmio
matter is much lower, but the proportion of detritus may reach almost
100%. In a later study, Krey (1964) shows that despite considerable
fluctuations in the amount of suspended matter, there is a marked tendency for the amount to fall with depth and in very deep water extremely little material is present. This Krey attributes partly to the
eating of material by organisms in the upper layers, but above all to the
mineralization processes occurring in deep water. The fraction of living
material in the total suspended matter shows, as would be expected, 8
remarkably sharp fall in really deep water.
Although the very small amount of suspended material in deep waters
* I em much indebted to the authors for permission to use their data.