PE EIE[R-Rg RESEARCH ON - HJ Andrews Experimental Forest

contribute to detrital compartment as a resul t
of their fecal deposits or their death and decomposition.
Ultimately DOC and detrital
carbon are decomposed by bacteria or zoo -
plankton feeding on bacteria/detritus mixtures,
to dissolved inorganic carbon as a result
of respiratory oxidative decompositio n
processes .
In nature the standing stock in each compartment
is the dynamic equilibrium level
attained as a result of input/output rate s
about the compartment . The quality of th e
standing stock will also vary as the input /
output mechanisms change .
With the advent of the carbon-14 tracer
techniques, the transports of carbon to and
from each compartment in an aquatic ecosystem
is possible . For example, Steemann-
Nielsen (1952) initiated such studies with C' 4
bicarbonate to estimate the rate of primar y
production in the ocean . Goldman (1963 )
outlined the use of this method in fres h
water .
Sorokin (1966), Shuskina and Monako v
(1969), and Johannes and Satomi (1967) use d
labeled phytoplankton to determine the rat e
at which zooplankton feed and process thei r
waste . The production of dissolved organic
carbon (DOC) by phytoplankton (Fogg 1965,
Saunders and Storch 1971) and uptake by
zooplankton and bacteria have been success -
fully measured using carbon-14 tracers.
Hobbie and Wright (1965) and Wright an d
Hobbie (1966) refined the enzyme saturatio n
technique of Parson and Strickland (1962) a s
measured by a carbon-14 tracer, to evaluat e
the pool size and potential flux of dissolve d
organics through the bacterial (heterotrophic )
compartment in the aquatic web . With
carbon-14 labeled detritus Sorokin (1966 )
measured assimilation by zooplankton . H e
prepared the detritus by homogenizing radio -
actively labeled algal cultures . Others hav e
used autoclaved, labeled natural and culture d
algal populations 2 (Bell and Ward 1970) .
Labeled detritus may also be prepared, b y
foam separating C-14 labeled dissolve d
organics from the liquid phase (Baylor an d
Sutcliff 1963) . However, there is evidenc e
2 G . W. Saunders, personal communication .
that this method will work only in sea water .
For the first time, Saunders 3 recently combined
the aforementioned methods to measure
simultaneously all of the previously liste d
carbon fractions and their fluxes in a "Compartment
Analysis" scheme (Patten 1968 ,
Atkins 1969). He has made this type of
analysis at one location and one instant in
time at several lakes .
Compartment Analysis, in essence, is performed
by establishing a series of known fractions
or compartments in an experimenta l
confine (e .g., glass carboy or plastic bag) and
following a tracer such as carbon-14 as a func -
tion of time as it proceeds through each compartment
in the confined system . Measurement
of the radioactive carbon as it passe s
through each compartment can be used t o
evaluate the rate of incorporation of carbo n
into each compartment in succession, and b y
isotopic dilution or total carbon conten t
analysis, the pool size estimated . These data
may be used to describe mathematically th e
carbon change in compartments as a functio n
of time, e .g .,
d( q 1) _ - k l q l and
dt
d( q 2 )
dt =k l q 1 -k 2 q 2
where (4 1 and q 2 are the specific activities o f
the first and second compartments and k l
and k2 are the rate constants into each compartment.
The compartments could very wel l
be phytoplankton and zooplankton or DOC ,
bacteria and zooplankton, etc. The specifi c
activities rather than tracer amounts will b e
used in mathematical models .
It must be emphasized that the confinement
of an aliquot of the sampled water during
the compartment analysis will yield value s
prevailing for (1) standing stock at the time o f
sample confinement, and (2) uptake value s
for that particular sample during the incubation
period . Thus, it is very important whe n
and where test water samples are chosen . For
example, if lake water were collected for a
compartment analysis of the carbon fraction s
during maximum expected respiratory and
3 Unpublished data .
291