178
J . E . C,. RAYMONT
the enormous burst, of phytoplankton typical of high latitudes. Steemann Nielsen believes that such “explosions” of phytoplankton occur
only if a very rapid burst of algal growth precedes the reproduction of
the zooplankton. Thus with particularly good light conditions and the
rapid stabilization of the upper water layers, the rapid algal bloom
typical of neritic areas may get ahead of zooplankton growth. More
generally the relationship between phytoplankton and zooplankton is
probably more stable. This “wastefulness” in production at higher
latitudes may be only apparent; material not consumed or only partly
digested by the zooplankton may be used effectively by other members
of the marine eco-system. Vinogradov (196213) has suggested that excessively rich algal crops may also supply food to deep layers through
extensive vertical migrations of the zooplankton. Although some
bathypelagic zooplankton may feed on detritus, many will be filter
feeders migrating periodically towards the surface. When such plankton
descends again their faeces and their bodies may be preyed on by zooplankton of the mid-water strata. The total biomass of the intermediate
layers may thus be greater since these can be made up not only of filter
feeders which migrate but of predators and detrital feeders. The amount
of detritus descending to deeper levels is probably very small and is
relatively resistant, so that the biomass of zooplankt,on at great depths
is much reduced. In the deep sea as in oligotrophic shallower layers
there is presumably a delicate balance between the herbivorous and
carnivorous population.
At high latitudes the breeding, especially of herbivorous copepods, is
largely influenced by phytoplankton outbursts though Heinrich (1 962)
states that some copepods breed before the phytoplankton outburst.
Grainger (1959) suggests that while the herbivorous copepods at high
latitudes breed essentially near the time of the major phytoplankton
growth and show enormous fluctuations in population, the carnivorous
forms do not show nearly as great numerical changes seasonally and
may breed at different times of the year. This is perhaps borne out by the
observations of Dunbar (1946, 1962) on chaetognaths and amphipods;
for example, Sagitta elegans arctica appears to have a very long spawning
period (July to February) in Arctic waters and the spawning time does
not depend on food availability.
c. RATE O F ZOOPLANKTON PRODUCTION
So far discussion has been limited to the standing crop of zooplankton;
estimation is difficult and our knowledge is limited. But estimates of tfhe
rates of production of zooplankton are even more difficult. One of the
earliest attempts was that of Riley (1947). Over the region of Georgea
Bank, Riley proposed that the size of the herbivore population (H)
J . E . C,. RAYMONT
the enormous burst, of phytoplankton typical of high latitudes. Steemann Nielsen believes that such “explosions” of phytoplankton occur
only if a very rapid burst of algal growth precedes the reproduction of
the zooplankton. Thus with particularly good light conditions and the
rapid stabilization of the upper water layers, the rapid algal bloom
typical of neritic areas may get ahead of zooplankton growth. More
generally the relationship between phytoplankton and zooplankton is
probably more stable. This “wastefulness” in production at higher
latitudes may be only apparent; material not consumed or only partly
digested by the zooplankton may be used effectively by other members
of the marine eco-system. Vinogradov (196213) has suggested that excessively rich algal crops may also supply food to deep layers through
extensive vertical migrations of the zooplankton. Although some
bathypelagic zooplankton may feed on detritus, many will be filter
feeders migrating periodically towards the surface. When such plankton
descends again their faeces and their bodies may be preyed on by zooplankton of the mid-water strata. The total biomass of the intermediate
layers may thus be greater since these can be made up not only of filter
feeders which migrate but of predators and detrital feeders. The amount
of detritus descending to deeper levels is probably very small and is
relatively resistant, so that the biomass of zooplankt,on at great depths
is much reduced. In the deep sea as in oligotrophic shallower layers
there is presumably a delicate balance between the herbivorous and
carnivorous population.
At high latitudes the breeding, especially of herbivorous copepods, is
largely influenced by phytoplankton outbursts though Heinrich (1 962)
states that some copepods breed before the phytoplankton outburst.
Grainger (1959) suggests that while the herbivorous copepods at high
latitudes breed essentially near the time of the major phytoplankton
growth and show enormous fluctuations in population, the carnivorous
forms do not show nearly as great numerical changes seasonally and
may breed at different times of the year. This is perhaps borne out by the
observations of Dunbar (1946, 1962) on chaetognaths and amphipods;
for example, Sagitta elegans arctica appears to have a very long spawning
period (July to February) in Arctic waters and the spawning time does
not depend on food availability.
c. RATE O F ZOOPLANKTON PRODUCTION
So far discussion has been limited to the standing crop of zooplankton;
estimation is difficult and our knowledge is limited. But estimates of tfhe
rates of production of zooplankton are even more difficult. One of the
earliest attempts was that of Riley (1947). Over the region of Georgea
Bank, Riley proposed that the size of the herbivore population (H)