THE P R O D U C T I O N O F M A R I N E P L A N K T O N
189
The amount of food collected by these two methods may be very
different, and the extent to which each meclianism is used depends in
part on the type of food available. Carnivorous copepods (Anomahera,
Labidocera) use the sweeping movements of the maxillae to secure their
prey and this mechanism is also used by partly carnivorous species such
as Temora and Centropages. Cushing ( 1964) believes that considerable
superfluous feeding occurs with herbivorous copepods such as Calanus
(cf. Beklemishev, 1962). Active reproduction is limited to such periods
of excessive feeding. Even so, a considerable quantity of food is
“wasted”. Cushing believes that very high grazing rates are typical of
Calanu-s, but when there is extensive searching for limited food, egg
production ceases. Petipa (1959) believes tihat the average dietary
requirements of Acartia in the Black Sea, amounting to 4% of body
biomass per day, cannot normally be met without the inclusion of a
considerable amount of zooplankton food. Animal food plays a particularly important part during periods of activt: reproduction.
The investigations of Corner (1961) and of Cowey and Corner (1963)
tend to show that sufficient food material for Calanus is present in sea
water. They analysed the total amount of particulate matter in the
water and then related this to the maintenance requirements. During
winter, they suggest that Calanus needs to filter only 30 cm3/day, and
in summer some 50 cm3/day. Marshall and Orr (1964) have listed the
amounts of phytoplankton organic matter itnd the total particulate
organic matter in different marine areas. Although the quantities in
coastal waters are relatively high and appear to be sufficient for the
requirements of copepods, the amounts in open oceans and in deep
water are very much lower and would certainly seem to be inadequate
for herbivorous zooplankton. Even in inshore waters the seasonal variation in total particulate organic matter is not well known. Marshall and
Orr suggest that while during a spring diatom increase a great excess of
food is present, it is doubtful whether in winter the amount available
would cover requirements. The food requirements for a number of copepod species based on respiration rates are given. Some of the daily
requirements appear to be very high; moreover far more food will be
required for growth and reproduction. Further detailed metabolic
studies are needed before we can measure these additional food requirements. A comparison of the metabolic needs and the body reserves for
some zooplankton, however, has suggested that the requirements may be
exceedingly high (Conover and Raymont, unpublished; Anraku, 1964).
VII. CONCLUSION
Primary production in the oceans is mainly dependent on phytoplankton, though in shallow coastal waters the important contribution of the
Q.
189
The amount of food collected by these two methods may be very
different, and the extent to which each meclianism is used depends in
part on the type of food available. Carnivorous copepods (Anomahera,
Labidocera) use the sweeping movements of the maxillae to secure their
prey and this mechanism is also used by partly carnivorous species such
as Temora and Centropages. Cushing ( 1964) believes that considerable
superfluous feeding occurs with herbivorous copepods such as Calanus
(cf. Beklemishev, 1962). Active reproduction is limited to such periods
of excessive feeding. Even so, a considerable quantity of food is
“wasted”. Cushing believes that very high grazing rates are typical of
Calanu-s, but when there is extensive searching for limited food, egg
production ceases. Petipa (1959) believes tihat the average dietary
requirements of Acartia in the Black Sea, amounting to 4% of body
biomass per day, cannot normally be met without the inclusion of a
considerable amount of zooplankton food. Animal food plays a particularly important part during periods of activt: reproduction.
The investigations of Corner (1961) and of Cowey and Corner (1963)
tend to show that sufficient food material for Calanus is present in sea
water. They analysed the total amount of particulate matter in the
water and then related this to the maintenance requirements. During
winter, they suggest that Calanus needs to filter only 30 cm3/day, and
in summer some 50 cm3/day. Marshall and Orr (1964) have listed the
amounts of phytoplankton organic matter itnd the total particulate
organic matter in different marine areas. Although the quantities in
coastal waters are relatively high and appear to be sufficient for the
requirements of copepods, the amounts in open oceans and in deep
water are very much lower and would certainly seem to be inadequate
for herbivorous zooplankton. Even in inshore waters the seasonal variation in total particulate organic matter is not well known. Marshall and
Orr suggest that while during a spring diatom increase a great excess of
food is present, it is doubtful whether in winter the amount available
would cover requirements. The food requirements for a number of copepod species based on respiration rates are given. Some of the daily
requirements appear to be very high; moreover far more food will be
required for growth and reproduction. Further detailed metabolic
studies are needed before we can measure these additional food requirements. A comparison of the metabolic needs and the body reserves for
some zooplankton, however, has suggested that the requirements may be
exceedingly high (Conover and Raymont, unpublished; Anraku, 1964).
VII. CONCLUSION
Primary production in the oceans is mainly dependent on phytoplankton, though in shallow coastal waters the important contribution of the
Q.