362
ALAlN SOUILNIA
tlic 7;inge of die1 viwi;itions varivs setisonally together with thc abundaiice of diirtsotii pop11:it~ions : oiw nlily idso note that the differences
between morniug iuid cveniiig concentrations are the highest when the
tiveriip love1 of silica contc.nt is the lowest; this point lends one to
tliiiik thnt, tlic poorer the nivtiiunr , tlit. grwter is the tendency towards
an exhnustion/rc~plcnisli rnentJ cyclc on the diaily basis.
A (lie1 cyolo of dissolved o~wl)ohytlratcs content was reported by
W;alsti ( 1 965) from i L coitstill pond : minimum occurred at 05.00 hours
i ~ n d rwxirn urn was re:~chcd brtween 14.00 and 17.00, the phytoplankt,on bring ;Lssurneti t o pro(1uctr carhohydrates in the daytime and
consumc tho n~ nt night .
KibRhiwtida ~1 al. ( 1957) investigated the possibility of did fluctuations in vit,rrmin
content of sen water, but no regular trend was
detected .
15. Ph~~foplnnktott~zooplnv~lclon interrelationships
As is t h c a gcncrlil rule with int,ctrrcIationships, two opposite points of
view tire involvcd. %ooplaiiktologists are interested in any influence
of ~ ) I i ~ t ~ ~ ) l i ~ ~ ~ k t o ~ l
priodicitios on the growth and behaviour of animal
plmliton (nbovch all, the uvailability of food). The scope of this review
is directed rather t o w d s the other side : how far is phytoplankton
subjected to zooplmkton rhythmicity? I n this connection two points,
at least, rdse.
Excretion by zooplankton is p;Lrtly responsible for the die1 periodicity of nutrient concentrations (Goering et nl., 1964; Beers and Kelly,
1968).
The otller problem conccrns grazing, which appears in turn to
depend on two components : ( 1 ) the hypothesis of a proper feeding
rhythm (Puller, 1937 : furtlicr references in Petipa, 19.58) ; though
gencrully discarded ((hiild, 1!)53 ; 1Cichmim hind Rogers, 1969), it cannot
be definitely excluded (in the caw of chwetognaths, this component is
indispntublc, as first shown by Reeve, 1964) ; (2) the evidence of vertical
migrations (for recent, progress and reviews in this field, see Enright
anti Hammer, 1967 ; Hudjtlkov, 1!)70; Vinogrdov, 1968, and others).
I)ifi.rent1 put,tcrns might thus take plscc, according to whether grazing
pressuiv is :issunled to br constant night and d;~y, or noc%urnal-con&ant,
or ~iortu~nul-dec.reasing (Gtiitld, 195.7 ; Petipa and Makarova, 1969;
MoAllister, 1971); this matter has bcen dealt with a t some length by
McAllister (1971) using the three major tools of modern oceanography :
field studies, laboratory experiments and computer modelling.
Wirnpcnny ( I 938) was struck by the opposing bchttviour of phytoplankton m d zooplankton during the course of the tlay/ni& cycle,
ALAlN SOUILNIA
tlic 7;inge of die1 viwi;itions varivs setisonally together with thc abundaiice of diirtsotii pop11:it~ions : oiw nlily idso note that the differences
between morniug iuid cveniiig concentrations are the highest when the
tiveriip love1 of silica contc.nt is the lowest; this point lends one to
tliiiik thnt, tlic poorer the nivtiiunr , tlit. grwter is the tendency towards
an exhnustion/rc~plcnisli rnentJ cyclc on the diaily basis.
A (lie1 cyolo of dissolved o~wl)ohytlratcs content was reported by
W;alsti ( 1 965) from i L coitstill pond : minimum occurred at 05.00 hours
i ~ n d rwxirn urn was re:~chcd brtween 14.00 and 17.00, the phytoplankt,on bring ;Lssurneti t o pro(1uctr carhohydrates in the daytime and
consumc tho n~ nt night .
KibRhiwtida ~1 al. ( 1957) investigated the possibility of did fluctuations in vit,rrmin
content of sen water, but no regular trend was
detected .
15. Ph~~foplnnktott~zooplnv~lclon interrelationships
As is t h c a gcncrlil rule with int,ctrrcIationships, two opposite points of
view tire involvcd. %ooplaiiktologists are interested in any influence
of ~ ) I i ~ t ~ ~ ) l i ~ ~ ~ k t o ~ l
priodicitios on the growth and behaviour of animal
plmliton (nbovch all, the uvailability of food). The scope of this review
is directed rather t o w d s the other side : how far is phytoplankton
subjected to zooplmkton rhythmicity? I n this connection two points,
at least, rdse.
Excretion by zooplankton is p;Lrtly responsible for the die1 periodicity of nutrient concentrations (Goering et nl., 1964; Beers and Kelly,
1968).
The otller problem conccrns grazing, which appears in turn to
depend on two components : ( 1 ) the hypothesis of a proper feeding
rhythm (Puller, 1937 : furtlicr references in Petipa, 19.58) ; though
gencrully discarded ((hiild, 1!)53 ; 1Cichmim hind Rogers, 1969), it cannot
be definitely excluded (in the caw of chwetognaths, this component is
indispntublc, as first shown by Reeve, 1964) ; (2) the evidence of vertical
migrations (for recent, progress and reviews in this field, see Enright
anti Hammer, 1967 ; Hudjtlkov, 1!)70; Vinogrdov, 1968, and others).
I)ifi.rent1 put,tcrns might thus take plscc, according to whether grazing
pressuiv is :issunled to br constant night and d;~y, or noc%urnal-con&ant,
or ~iortu~nul-dec.reasing (Gtiitld, 195.7 ; Petipa and Makarova, 1969;
MoAllister, 1971); this matter has bcen dealt with a t some length by
McAllister (1971) using the three major tools of modern oceanography :
field studies, laboratory experiments and computer modelling.
Wirnpcnny ( I 938) was struck by the opposing bchttviour of phytoplankton m d zooplankton during the course of the tlay/ni& cycle,