33s
Al'AIN S O l I H N l h
I~iist. for 24 ii iindcr oontinous tldmess ( i d to some extent under
constit tit light), Sperifio responses of niigrution to nitrogen limitation
w(ve nott4. Anotlicr :tspcct shoulil be empliasized : in Cuchonirm nearly
all tliv ot*lls wen' implictrtctl in thc diitrnal ascent, while approximately
hidf of thmi inovcd tiown i h t night ; considering that daily division
nbta U'W Iihout 0.5, t hr iLut,hors wondercd if the organisms which
n i i g i ~ b t r h tlo\vn t ~ r o tlioec whic:h divide or those which do not. In addition,
t l i r I ~ O I * ~ I I I * I I ~ L I
rnovcwicnt8 w~is shown to be 20 times filstcr t , h m would
be thr (us(' it' only sinking w m opernting.
ICC>LV ( l i i t i i MC ;iv;Lilnble about the other tiLxonomic groups, but
thcy ~ ~ g r c c
too with the pittern of a diurnal upwnrrl migration (&atonis i n c l \ u i c ~ l , though they do not possess fli~gellt~). Also, while the
ttattb for tlitiotlt~~c~llut~~..i hapl)(m tso exhibit but n motlcriite I " I ~ (a few
inetrcs or teti nictrrs), tlie follou ing examples will widen this intcrval
consic1cribl)ly : thc. diittom ('oscinodiscus bouvet Karsten movod ( M y
bctwccm siirf;ic.e tint1 250 m depth (however, grazing, rhythinic division or atlvcction 1liLve been often put forward as alternative ex~ ~ ~ ; ~ l l i l t ~ i O i l S )
;LS reported by Hardy ( 1935) ; Marshall's (1 968) coccolithoplioricb m o v d i1ppiLreritly through ;L vertical distiince of i h u t
2'00 in.
Sonic. ot1u.i. works rnii? 1~ cited a, s " miscellaneous ". Lanslraya,
qttoted in Akininn ( 1 nW), observed phytoplankt~on (species not indiciLtetl) concentrating in surfacc layers usually during the morning.
Froni two wries of stirface stimples, Silva ( 1 960) deduced, not quite
concliisively, that Home diatoms " appear a t t,he surface, electively,
a t ib ckterininute timc on thr two days ". A few other studies failed
to cstublish :Lny c1e:wcut picttmn (c.g. Ycntsch et ul., 1084 ; Mawhall,
1nt;c;).
AN for fwsh water, Hutchinson (1967) give8 three reference8 to
works which reveal the typi(;iIl morning iiscent. Two subsequent
p i i b I i ~ 4 o n s can bc ntldetl : t hrcv cryptIomon;Ltls were ehown to undergo
a sin~ili~r gilttrl.11 while i~ niotionless grwn i ~ l g i ~
showed no tlisp1;icerncnt
(Swdcr, l9ti7) ; somc flagelli~tcs snenietl to hchave in the opposite way
wcwding to Tilztr ( I !)73) whose datii are hardly conclusive (see his
Fig. 2 i l l i d 'I'iiblt? 1). FiniLll*y the behnviour of the semi-benthic diatom
Sikschicr p i k a (Kiitz.) W. Smith in ti polluted stream should be
rtyortetl : it I)ecanie ab~incir~nt in surftice plankton from late morning
till inid-iifternoon, ;~lle~gedly due to increiised buoyancy consequent
on ~nliuiictd oxygen 1)roduction (Rlum, 1954) ; Miiller-Haeckel (1967,
1971 ) (*Stcti(ld this observation to a number of freshwatcr diatoms,
whioh \wrc showti to lctive tlie bottom and colonize new substrates
during dihylight, wcording to an active rhythmical process.
Al'AIN S O l I H N l h
I~iist. for 24 ii iindcr oontinous tldmess ( i d to some extent under
constit tit light), Sperifio responses of niigrution to nitrogen limitation
w(ve nott4. Anotlicr :tspcct shoulil be empliasized : in Cuchonirm nearly
all tliv ot*lls wen' implictrtctl in thc diitrnal ascent, while approximately
hidf of thmi inovcd tiown i h t night ; considering that daily division
nbta U'W Iihout 0.5, t hr iLut,hors wondercd if the organisms which
n i i g i ~ b t r h tlo\vn t ~ r o tlioec whic:h divide or those which do not. In addition,
t l i r I ~ O I * ~ I I I * I I ~ L I
rnovcwicnt8 w~is shown to be 20 times filstcr t , h m would
be thr (us(' it' only sinking w m opernting.
ICC>LV ( l i i t i i MC ;iv;Lilnble about the other tiLxonomic groups, but
thcy ~ ~ g r c c
too with the pittern of a diurnal upwnrrl migration (&atonis i n c l \ u i c ~ l , though they do not possess fli~gellt~). Also, while the
ttattb for tlitiotlt~~c~llut~~..i hapl)(m tso exhibit but n motlcriite I " I ~ (a few
inetrcs or teti nictrrs), tlie follou ing examples will widen this intcrval
consic1cribl)ly : thc. diittom ('oscinodiscus bouvet Karsten movod ( M y
bctwccm siirf;ic.e tint1 250 m depth (however, grazing, rhythinic division or atlvcction 1liLve been often put forward as alternative ex~ ~ ~ ; ~ l l i l t ~ i O i l S )
;LS reported by Hardy ( 1935) ; Marshall's (1 968) coccolithoplioricb m o v d i1ppiLreritly through ;L vertical distiince of i h u t
2'00 in.
Sonic. ot1u.i. works rnii? 1~ cited a, s " miscellaneous ". Lanslraya,
qttoted in Akininn ( 1 nW), observed phytoplankt~on (species not indiciLtetl) concentrating in surfacc layers usually during the morning.
Froni two wries of stirface stimples, Silva ( 1 960) deduced, not quite
concliisively, that Home diatoms " appear a t t,he surface, electively,
a t ib ckterininute timc on thr two days ". A few other studies failed
to cstublish :Lny c1e:wcut picttmn (c.g. Ycntsch et ul., 1084 ; Mawhall,
1nt;c;).
AN for fwsh water, Hutchinson (1967) give8 three reference8 to
works which reveal the typi(;iIl morning iiscent. Two subsequent
p i i b I i ~ 4 o n s can bc ntldetl : t hrcv cryptIomon;Ltls were ehown to undergo
a sin~ili~r gilttrl.11 while i~ niotionless grwn i ~ l g i ~
showed no tlisp1;icerncnt
(Swdcr, l9ti7) ; somc flagelli~tcs snenietl to hchave in the opposite way
wcwding to Tilztr ( I !)73) whose datii are hardly conclusive (see his
Fig. 2 i l l i d 'I'iiblt? 1). FiniLll*y the behnviour of the semi-benthic diatom
Sikschicr p i k a (Kiitz.) W. Smith in ti polluted stream should be
rtyortetl : it I)ecanie ab~incir~nt in surftice plankton from late morning
till inid-iifternoon, ;~lle~gedly due to increiised buoyancy consequent
on ~nliuiictd oxygen 1)roduction (Rlum, 1954) ; Miiller-Haeckel (1967,
1971 ) (*Stcti(ld this observation to a number of freshwatcr diatoms,
whioh \wrc showti to lctive tlie bottom and colonize new substrates
during dihylight, wcording to an active rhythmical process.