366
AT,A IN HOIJlt NIA
The resiilts ohtaineti froin syndironous ciiltures in the laboratorywhich :u% often t.c+rrcd to i n this rrview--may not apply to natural
populations iis wc4I : i n siicli cxpciimrnts, cverything is attempted to
rcalize ideal growth conditions for n givcn species ; such an optimization
is only ~eldom attuinetl in thc opcn setis. Thus another question arises :
how do cornpctition, stxesx, or limiting factors affect the degree of
synchrony ~ i t l
the smplitiule of diel changes? Ryther et al. (1961)
stat>e that' " i t is under [. . .I im1)overished conditions that one might
expect the groatest response of organisms to daily [rather : diel] changes
in the cnvironmcntnl factors which critically limit their production ".
On the ot licr hand, Soetier ( 1965) has conipared ChZoreZZa behaviour
under t ~ t i f i ~ i i d
and natural light/dark cycles and found synchrony to be
inconiplete i i i the outdoor cultures, prcsunwtbly because light> grndients
thcn are gradual (dawn).
(1. Inferences for pro&ur.tiviQj studiee
'I'he implications of the photosynthetic rhythm for the measurement of prirnury production have been discussed above. More generally,
this phenomenon, i ~ s
well as all the other periodicities, has considerable
bearing on the various aspects of phytoplankton kinetics, as recognized
first by Eppley and Strickland (1968).
One should now eye the so-called constants more distrustfully. For
instance, the commonly used " iLssimilstion number '' and the photosynt'hesis/reslJiriLtiori or carbon/chloro~)hyll ratios are definitely not
constmt iri tho coursc of 24 hourx. No cttlculiition, no model of growth,
no trophod~ytiamic: rdiitkm ~ l i o u l d any more imply il straight-line
t h r o ~ g h o i ~ t
(lily ikritl night.
1). ('(111 fvr future work
As previously sttitd, I.'hStopliLnlrtologists have some leeway to
Iilikkc t i p with rCwpcCt to phyNiohgixtx : the forrner arc still CXJJl~JI'inK
tind describing whilc tlio btter begin to understanct the jhcnomenit . . . ,
its fiir ax it apptrs t'o u phytopltmktologist.
l h t of all, tin cfTort, must bo directed towards methodology. Too
riitiny st~clics Iicive been buscd o i i 11 loose sumpling strategy and morc
or less tied to t h e liIinii111 wal
~malysis, t i ciirrcnt, tool iri ch ronohiology, offers valuable hclp. Some
particnlar met,tiod,s nre iilso tjo be dcvelopcd, such as a biochemical or
tracer UpprbitCh to tho study of cell-division synchrony.
'~'IIcII, all t h e circntlian coiii pmimts of phytoplankton periodicities
AT,A IN HOIJlt NIA
The resiilts ohtaineti froin syndironous ciiltures in the laboratorywhich :u% often t.c+rrcd to i n this rrview--may not apply to natural
populations iis wc4I : i n siicli cxpciimrnts, cverything is attempted to
rcalize ideal growth conditions for n givcn species ; such an optimization
is only ~eldom attuinetl in thc opcn setis. Thus another question arises :
how do cornpctition, stxesx, or limiting factors affect the degree of
synchrony ~ i t l
the smplitiule of diel changes? Ryther et al. (1961)
stat>e that' " i t is under [. . .I im1)overished conditions that one might
expect the groatest response of organisms to daily [rather : diel] changes
in the cnvironmcntnl factors which critically limit their production ".
On the ot licr hand, Soetier ( 1965) has conipared ChZoreZZa behaviour
under t ~ t i f i ~ i i d
and natural light/dark cycles and found synchrony to be
inconiplete i i i the outdoor cultures, prcsunwtbly because light> grndients
thcn are gradual (dawn).
(1. Inferences for pro&ur.tiviQj studiee
'I'he implications of the photosynthetic rhythm for the measurement of prirnury production have been discussed above. More generally,
this phenomenon, i ~ s
well as all the other periodicities, has considerable
bearing on the various aspects of phytoplankton kinetics, as recognized
first by Eppley and Strickland (1968).
One should now eye the so-called constants more distrustfully. For
instance, the commonly used " iLssimilstion number '' and the photosynt'hesis/reslJiriLtiori or carbon/chloro~)hyll ratios are definitely not
constmt iri tho coursc of 24 hourx. No cttlculiition, no model of growth,
no trophod~ytiamic: rdiitkm ~ l i o u l d any more imply il straight-line
t h r o ~ g h o i ~ t
(lily ikritl night.
1). ('(111 fvr future work
As previously sttitd, I.'hStopliLnlrtologists have some leeway to
Iilikkc t i p with rCwpcCt to phyNiohgixtx : the forrner arc still CXJJl~JI'inK
tind describing whilc tlio btter begin to understanct the jhcnomenit . . . ,
its fiir ax it apptrs t'o u phytopltmktologist.
l h t of all, tin cfTort, must bo directed towards methodology. Too
riitiny st~clics Iicive been buscd o i i 11 loose sumpling strategy and morc
or less tied to t h e liIinii111 wal
~malysis, t i ciirrcnt, tool iri ch ronohiology, offers valuable hclp. Some
particnlar met,tiod,s nre iilso tjo be dcvelopcd, such as a biochemical or
tracer UpprbitCh to tho study of cell-division synchrony.
'~'IIcII, all t h e circntlian coiii pmimts of phytoplankton periodicities