336
AIATN BOURNTA
mantioned were assumed to divide in the niorning, while the two diatoins divided at, the end of the light period. Excretion and permoability
ure also to be tiilten into considerittion (Eppley et al., 1967). On the other
hctnd, it, is well known t,hat sinking rates in phytoplankton cultures are
niinimiiin for young and dividing cells (“ log ’’ phase) provided with
an atlequatc supply of light and nutrients (Munk and Riley, 1952;
Stoele and Yentsch, 1960; Smayda and Boleyn, 1966; Akinina, 1967,
1969) ; in the ooiirse of 24 hours, the light phase may represent such
“ nourishing ” conditions, as compared to the dark phase.
As for field data, we know only of the particular case of a surf
zone diatom, Chmtoceros armatum West, which concentrates a t the
surftioe during the day and is presumably dispersed throughout the
writer column at night (Lewin i d Hruby, 1973). Although the authors
(10 not use tlw word “ migration ”, their paper might have been included in thc ncxt section as well.
V. VERTICAL MIGRATION
Phytop1:Lnkton counting on samples taken from two or more
discret,e depMis ut, different timeR of day and night has suggested in
several cases that cells migrtitc from one level to another according to
the illuminution cycle. Whether this is fact, or illusion will be discussed
fiirthcr below ; let 1 1 s first review the data, starting with dinoflagellates
which ;Ire the more documented tiLxonomic group.
A . Obsurvntiom
h d e ( 1 f)60), who reviewed wrlichr investigations, has given what
is probably tlic tirst clear picturc of the phenomenon in dinoflagellates.
Among the four species studied, two of them migrated upward during
the dny mid the two others behaved in the opposite way ; however, in a
liktaer work, Hiisle (1954) showed thitt the first puttern is the usual one,
being subject to occasional tilteration by light condition8 and qmific
sensitivitray. Z’?/rodiniurn bahumense Plate, in a shallow bay, concentrated
twice daily towards the surface, mound 14.00 and around 22-00 h
(Soli, 1966) : the nocturnal ancent is denied, however, by Carpenter
anti Seliger ( 1!)68) and Scliger :md McElroy (1 968) as discxwed below,
while the diurnal rise I i i ~ s been confirmed by Soliger and McJ!!lroy
( 1968) anti Seliger et nE. (1969, 1970). A serni-benthic species, Pwidirtiunc grqurium Lombwd &, Capon, leaves the bottom of tida pool.^
during the morning hours (Lombard and Capon, 1971).
The above observations, together with some dat>a on a Cerutium
furcn bloom (Eppley el al., I!bOtlb) and with work on freshwater dinoflagellates (Nauwerck, 1963; Berman and Rodhe, 1971 ; Soeder, 1967),
AIATN BOURNTA
mantioned were assumed to divide in the niorning, while the two diatoins divided at, the end of the light period. Excretion and permoability
ure also to be tiilten into considerittion (Eppley et al., 1967). On the other
hctnd, it, is well known t,hat sinking rates in phytoplankton cultures are
niinimiiin for young and dividing cells (“ log ’’ phase) provided with
an atlequatc supply of light and nutrients (Munk and Riley, 1952;
Stoele and Yentsch, 1960; Smayda and Boleyn, 1966; Akinina, 1967,
1969) ; in the ooiirse of 24 hours, the light phase may represent such
“ nourishing ” conditions, as compared to the dark phase.
As for field data, we know only of the particular case of a surf
zone diatom, Chmtoceros armatum West, which concentrates a t the
surftioe during the day and is presumably dispersed throughout the
writer column at night (Lewin i d Hruby, 1973). Although the authors
(10 not use tlw word “ migration ”, their paper might have been included in thc ncxt section as well.
V. VERTICAL MIGRATION
Phytop1:Lnkton counting on samples taken from two or more
discret,e depMis ut, different timeR of day and night has suggested in
several cases that cells migrtitc from one level to another according to
the illuminution cycle. Whether this is fact, or illusion will be discussed
fiirthcr below ; let 1 1 s first review the data, starting with dinoflagellates
which ;Ire the more documented tiLxonomic group.
A . Obsurvntiom
h d e ( 1 f)60), who reviewed wrlichr investigations, has given what
is probably tlic tirst clear picturc of the phenomenon in dinoflagellates.
Among the four species studied, two of them migrated upward during
the dny mid the two others behaved in the opposite way ; however, in a
liktaer work, Hiisle (1954) showed thitt the first puttern is the usual one,
being subject to occasional tilteration by light condition8 and qmific
sensitivitray. Z’?/rodiniurn bahumense Plate, in a shallow bay, concentrated
twice daily towards the surface, mound 14.00 and around 22-00 h
(Soli, 1966) : the nocturnal ancent is denied, however, by Carpenter
anti Seliger ( 1!)68) and Scliger :md McElroy (1 968) as discxwed below,
while the diurnal rise I i i ~ s been confirmed by Soliger and McJ!!lroy
( 1968) anti Seliger et nE. (1969, 1970). A serni-benthic species, Pwidirtiunc grqurium Lombwd &, Capon, leaves the bottom of tida pool.^
during the morning hours (Lombard and Capon, 1971).
The above observations, together with some dat>a on a Cerutium
furcn bloom (Eppley el al., I!bOtlb) and with work on freshwater dinoflagellates (Nauwerck, 1963; Berman and Rodhe, 1971 ; Soeder, 1967),