120
J . E . G. RAYMONT
bottom microflora was far more important than the phytoplankton. In
offshore waters, and especially in the open oceans, however, the phytoplankton must be all-important in production.
11. PHYTOPLANKTON PRODUCTION
The term production in the oceans is usually restricted to primary
production, the synthesis of organic matter by the phytoplankton. So
few parameters of production on the higher trophic levels (e.g. zooplankton, benthos, nekton) are as yet established, that estimates of
production are normally restricted to primary production alone. Even
here it is only comparatively recently that we have been able to gain a
reasonable appreciation of the rates of production of plant material.
Rate of production must be clearly distinguished from standing crop of
phytoplankton which is the amount of the living plant substance
existing under a unit area of sea (e.g. beneath mz) or per unit volume
(e.g. m3) a t a particular place at a point in time. Standing crop is itself
of great significance, but we shall first discuss rates of production.
A. METHODS O F ESTIMATING PRIMARY PRODUCTION
One of the first methods used for estimating primary production was
the so-called oxygen bottle method, which is still widely used. In this
kind of experiment a series of bottles filled with sea water and containing a phytoplankton population is suspended at various depths in the
sea starting at the surface. The rate of photosynthesis as a measure of
plant production is estimated by the rate of change of oxygen. concentration (measured by the Winkler method). Various precautions must
be taken such as avoiding shading by a bottle at a higher level in the I
water, and ensuring that no loss of gas occurs during the course of the
experiment. The change in concentration of oxygen in any bottle
(AO,) may be due to several factors which may be expressed as follows:
+ A O , = P -RI -RR, -Rb
where R, = Respiration of plant tissue originally present; R, = Respiration of newly formed plant tissue during the course of the experiment; Rb = Respiration of bacteria and any zooplankton. The change
in oxygen, apart from that due to bacterial and zooplankton respiration,
would thus be an estimate of net photosynthesis. But the amount of
oxygen consumed due to the respiration of the plant tissue originally
present (R,) and the amount of oxygen consumed by bacteria and zooplankton (Rb) can be estimated by suspending a series of so-called
“dark” bottles at the same time and at the same depths as the normal
“light” bottles. If the amount of oxygen consumed in a “dark” bottle
J . E . G. RAYMONT
bottom microflora was far more important than the phytoplankton. In
offshore waters, and especially in the open oceans, however, the phytoplankton must be all-important in production.
11. PHYTOPLANKTON PRODUCTION
The term production in the oceans is usually restricted to primary
production, the synthesis of organic matter by the phytoplankton. So
few parameters of production on the higher trophic levels (e.g. zooplankton, benthos, nekton) are as yet established, that estimates of
production are normally restricted to primary production alone. Even
here it is only comparatively recently that we have been able to gain a
reasonable appreciation of the rates of production of plant material.
Rate of production must be clearly distinguished from standing crop of
phytoplankton which is the amount of the living plant substance
existing under a unit area of sea (e.g. beneath mz) or per unit volume
(e.g. m3) a t a particular place at a point in time. Standing crop is itself
of great significance, but we shall first discuss rates of production.
A. METHODS O F ESTIMATING PRIMARY PRODUCTION
One of the first methods used for estimating primary production was
the so-called oxygen bottle method, which is still widely used. In this
kind of experiment a series of bottles filled with sea water and containing a phytoplankton population is suspended at various depths in the
sea starting at the surface. The rate of photosynthesis as a measure of
plant production is estimated by the rate of change of oxygen. concentration (measured by the Winkler method). Various precautions must
be taken such as avoiding shading by a bottle at a higher level in the I
water, and ensuring that no loss of gas occurs during the course of the
experiment. The change in concentration of oxygen in any bottle
(AO,) may be due to several factors which may be expressed as follows:
+ A O , = P -RI -RR, -Rb
where R, = Respiration of plant tissue originally present; R, = Respiration of newly formed plant tissue during the course of the experiment; Rb = Respiration of bacteria and any zooplankton. The change
in oxygen, apart from that due to bacterial and zooplankton respiration,
would thus be an estimate of net photosynthesis. But the amount of
oxygen consumed due to the respiration of the plant tissue originally
present (R,) and the amount of oxygen consumed by bacteria and zooplankton (Rb) can be estimated by suspending a series of so-called
“dark” bottles at the same time and at the same depths as the normal
“light” bottles. If the amount of oxygen consumed in a “dark” bottle