(‘CRCAUZBN PERIODTCITl ES TN PHYTOP1,ANKTON
335
vtw. s~~bsnlsuni (Ost,elif.) I’aulscn divides iit~ night, so that regenertition
of horns in thiH genus CILIL be diaceriietl niainly during the second half
of thc night, (Cough, 19OA), or in the early morning (Jtjrgensen, 1911 ;
Nauwerck, 1963) ; similiw rnicrosccq)icttl ObRerVationS on other dinoflegelltites pointed to II division time of I’!p-cm?inium, around sunrise
(Riichtrntm, I !W) ttnd on(’ of f’yroc!/sti.q during thc night (Swift and
Durbiii, 1972). Sotno ditrtoms nlso were Nhown to divide preferentially
rtt, niglit (8nvcigt. rind Wimpenrry, 1 !i3(1; \I’impenny, 1938).
A paper by Staley (1971), though it deals with freshwiiter periphytic micro-nlgae, may be cited here 11s providing the first in situ
(truly in i t u ! ) dutri : using im immersed microscopc, the author noted
that cilgue incrcvrse their size during clnylight iuid diviclc ut night.
C: . Open y m ~ t i o n ~
I+om t h reported observations, one can only conclude its follows :
n-rtuiy picras of evidence indicate that cell division in natural p o p -
hitions of niarinc ~hytoplankton is synchronized a t lciist, to some
cxtcnt,. Iktails, hoth qrriilitative and quantitntivc, are lacking, arld
improved met,hodology is required.* Do phytoplsnkton organisms
in some ci~zles ctcpart from the generid teudency of algae t o divide at
night! 1s there t i succession of division times among the different
species and groups, similar to the succcssion observed in the course of a
yenr? Is s.ynchrony related, and in what way, to taxonomic position
of‘ the plunkters, to nutrients and physicnl conditions!
IV. RITOYANVY A N D SINKING
Before speaking of vertical migrations, i.e. sct’ive niov(mentR, thc:
question of passive vertical trailsports must be examined, as far as
“ active ” untl “ passive ” have sonic meaning ut, thc physiolopicd
level. For :L review of the mechanisms ant1 implications of phvtmplanktcm
suspension, one may refer to Srnayda ( 1970).
Luboratory observations, though few, d l show that buoyancy iH
better during the day and sinking rtttc faster a t night; organisms
testcd were two dinoflitgellstos : (J?/mnorlinium kourcclev,qkii Pitzik and
Yrorocentrrtm niicnns (Akinina, 1961)), and two diatoms : Ditylum
Hrightwellii (Eppley et al., 1967) and Thulurrsio.Yira ,jiuvktilis (Eppley
et d., L968a) ; in addition, Akininii (1969) report’s similar dat,a obtained
by Lrinslrayii (unspecified organisms). How is this periodicity related
to cell division, 11s Akininn (1969) contends? The two former species
*An attempt ~rrvolving pul8o-labding by tritiate thymidine, a DNA precursor. proved
to be technioally unsctcoeeaful (Sournie, unpubliuhed).
335
vtw. s~~bsnlsuni (Ost,elif.) I’aulscn divides iit~ night, so that regenertition
of horns in thiH genus CILIL be diaceriietl niainly during the second half
of thc night, (Cough, 19OA), or in the early morning (Jtjrgensen, 1911 ;
Nauwerck, 1963) ; similiw rnicrosccq)icttl ObRerVationS on other dinoflegelltites pointed to II division time of I’!p-cm?inium, around sunrise
(Riichtrntm, I !W) ttnd on(’ of f’yroc!/sti.q during thc night (Swift and
Durbiii, 1972). Sotno ditrtoms nlso were Nhown to divide preferentially
rtt, niglit (8nvcigt. rind Wimpenrry, 1 !i3(1; \I’impenny, 1938).
A paper by Staley (1971), though it deals with freshwiiter periphytic micro-nlgae, may be cited here 11s providing the first in situ
(truly in i t u ! ) dutri : using im immersed microscopc, the author noted
that cilgue incrcvrse their size during clnylight iuid diviclc ut night.
C: . Open y m ~ t i o n ~
I+om t h reported observations, one can only conclude its follows :
n-rtuiy picras of evidence indicate that cell division in natural p o p -
hitions of niarinc ~hytoplankton is synchronized a t lciist, to some
cxtcnt,. Iktails, hoth qrriilitative and quantitntivc, are lacking, arld
improved met,hodology is required.* Do phytoplsnkton organisms
in some ci~zles ctcpart from the generid teudency of algae t o divide at
night! 1s there t i succession of division times among the different
species and groups, similar to the succcssion observed in the course of a
yenr? Is s.ynchrony related, and in what way, to taxonomic position
of‘ the plunkters, to nutrients and physicnl conditions!
IV. RITOYANVY A N D SINKING
Before speaking of vertical migrations, i.e. sct’ive niov(mentR, thc:
question of passive vertical trailsports must be examined, as far as
“ active ” untl “ passive ” have sonic meaning ut, thc physiolopicd
level. For :L review of the mechanisms ant1 implications of phvtmplanktcm
suspension, one may refer to Srnayda ( 1970).
Luboratory observations, though few, d l show that buoyancy iH
better during the day and sinking rtttc faster a t night; organisms
testcd were two dinoflitgellstos : (J?/mnorlinium kourcclev,qkii Pitzik and
Yrorocentrrtm niicnns (Akinina, 1961)), and two diatoms : Ditylum
Hrightwellii (Eppley et al., 1967) and Thulurrsio.Yira ,jiuvktilis (Eppley
et d., L968a) ; in addition, Akininii (1969) report’s similar dat,a obtained
by Lrinslrayii (unspecified organisms). How is this periodicity related
to cell division, 11s Akininn (1969) contends? The two former species
*An attempt ~rrvolving pul8o-labding by tritiate thymidine, a DNA precursor. proved
to be technioally unsctcoeeaful (Sournie, unpubliuhed).