:I44
ALAIN SOURNIA
but siriiilitr ol)sei*vtttions by Yentmh m d SciigeI (1958) did not reveal
itny clrar pc.r.iotlicity. The chlor. a/cttrotenoid ratio has been found to
decrcitwc from iiioriiing till cvening in surface waters (Ryther et aE.,
1‘368 ; Yentwh iilrtl higel, I ! ) h 8 ) i d increase in the middle of the day
irt, tloniv tloptli (Ycntxoh sntl S c i ~ g c l , 1958). Margalef’s pigment index,
I)4Ljo/l &, (?;ti1 show sonie piviodii.ity (Koblentz-Mishke, 1971). On the
otlicr Iiund, light/tlnrk cull’ures of the clinoflagellate Am,phidinium
klubnii Kof. cY. Bwc~zy indicutc a circittliitn rhythm of carotenoid interronvcrsion (MiLntlclli, 1 009).
Sirirx: ctilorophyll synthesis (:an bc continuous or discontinuous
w tiilc ))hot,osynt,tic.t,ic c i t r h i tl1)titlie is coiifinetf to the light period,
rwultiirg ihaiigw in thc cttrb(m/chlor. a ratio may turn out to be
rnotlrriite (Kpldcy and Coutsworth, 1966; Eppley at al., 1967) or quite
signiticiirit (Eppley et d., 1972; see also UIIO, 1971, Table 2).
v 1 I I . ‘I’H E I%HYTHM OF I’IIOTOSYNTHETIC CAPACITY
I’liotosynt hetic o;tyacity, ils generiilly iiccepted, is t’he potential
I)hotosyut hcsis of phytoplankton under constant (preferably, saturill ing) light coiitlitiontl. This proprt.v is measured, a t any time of
day ;end night, I)y short-terrti (one or 21 few hours) incubation period.
In addit ion to bcing ii useful tmd wi(1el.v used quantity in productivity
stidics, it, is :I biisic or “ refercnce ” property, the understanding cf
i:-hic.h is rcqiiircd when one studies the n a t m d course of in situ photosynthc~six. This second iispeot, will be dcnlt with in the next section.
A . Dqfinition, rind chnrrcctvriatics
‘I’hv short pripcr by 1)ot.y cind O p r i ( 1957) is (JIW of the moHt famous
rc.fiq*cwces in ttic p1iyto~)l:inkton litwnturc. In i hiH inst,nnoc, celebrity
has involvcd somv ii~isririderstr~ri~li~~g ; I h t y tind Oguri’s rhythm I~UR
hccn of’tcw iiiitl still is relied upon ILR i i sheet-anchor to explain Home
corifirsc~tl die1 vtmiations. A definition is thus neceesary :
‘‘ Dots w t l Ogiiri‘s rhythm ” -= (I circadian rhythm of phytoplankton
pho!osytrthdir int~rrsit!/ m nirasurd in shorl-term experiments under
PO n sla 11 t sat ti r(i t i n light ( pholosy nl hvt ie cnpacit?j) ; maxima and minima
(trv dtairtetl .for ~trvtrplvs fnken in the moming or around noon and in the
e w n i r y or anrly night re~~pertiva2g.
’I’hix phenomcnon is now substantiated by a considerable amount of
tlntn : It4 iis notc that photosynthetic rates have usually been measured
by the **(> met)hod, with the exception of u study by Lorenzen (1963)
wlio usrd ( h m l c r iind Gran’s oxygen method.
An “ anomnlous ” pattern, however, is known : coastal data from
ALAIN SOURNIA
but siriiilitr ol)sei*vtttions by Yentmh m d SciigeI (1958) did not reveal
itny clrar pc.r.iotlicity. The chlor. a/cttrotenoid ratio has been found to
decrcitwc from iiioriiing till cvening in surface waters (Ryther et aE.,
1‘368 ; Yentwh iilrtl higel, I ! ) h 8 ) i d increase in the middle of the day
irt, tloniv tloptli (Ycntxoh sntl S c i ~ g c l , 1958). Margalef’s pigment index,
I)4Ljo/l &, (?;ti1 show sonie piviodii.ity (Koblentz-Mishke, 1971). On the
otlicr Iiund, light/tlnrk cull’ures of the clinoflagellate Am,phidinium
klubnii Kof. cY. Bwc~zy indicutc a circittliitn rhythm of carotenoid interronvcrsion (MiLntlclli, 1 009).
Sirirx: ctilorophyll synthesis (:an bc continuous or discontinuous
w tiilc ))hot,osynt,tic.t,ic c i t r h i tl1)titlie is coiifinetf to the light period,
rwultiirg ihaiigw in thc cttrb(m/chlor. a ratio may turn out to be
rnotlrriite (Kpldcy and Coutsworth, 1966; Eppley at al., 1967) or quite
signiticiirit (Eppley et d., 1972; see also UIIO, 1971, Table 2).
v 1 I I . ‘I’H E I%HYTHM OF I’IIOTOSYNTHETIC CAPACITY
I’liotosynt hetic o;tyacity, ils generiilly iiccepted, is t’he potential
I)hotosyut hcsis of phytoplankton under constant (preferably, saturill ing) light coiitlitiontl. This proprt.v is measured, a t any time of
day ;end night, I)y short-terrti (one or 21 few hours) incubation period.
In addit ion to bcing ii useful tmd wi(1el.v used quantity in productivity
stidics, it, is :I biisic or “ refercnce ” property, the understanding cf
i:-hic.h is rcqiiircd when one studies the n a t m d course of in situ photosynthc~six. This second iispeot, will be dcnlt with in the next section.
A . Dqfinition, rind chnrrcctvriatics
‘I’hv short pripcr by 1)ot.y cind O p r i ( 1957) is (JIW of the moHt famous
rc.fiq*cwces in ttic p1iyto~)l:inkton litwnturc. In i hiH inst,nnoc, celebrity
has involvcd somv ii~isririderstr~ri~li~~g ; I h t y tind Oguri’s rhythm I~UR
hccn of’tcw iiiitl still is relied upon ILR i i sheet-anchor to explain Home
corifirsc~tl die1 vtmiations. A definition is thus neceesary :
‘‘ Dots w t l Ogiiri‘s rhythm ” -= (I circadian rhythm of phytoplankton
pho!osytrthdir int~rrsit!/ m nirasurd in shorl-term experiments under
PO n sla 11 t sat ti r(i t i n light ( pholosy nl hvt ie cnpacit?j) ; maxima and minima
(trv dtairtetl .for ~trvtrplvs fnken in the moming or around noon and in the
e w n i r y or anrly night re~~pertiva2g.
’I’hix phenomcnon is now substantiated by a considerable amount of
tlntn : It4 iis notc that photosynthetic rates have usually been measured
by the **(> met)hod, with the exception of u study by Lorenzen (1963)
wlio usrd ( h m l c r iind Gran’s oxygen method.
An “ anomnlous ” pattern, however, is known : coastal data from