17031
Vlaams Instituut voor de Zee
FlandBia Marina Instituía
f t
¿ 1 5
O IKOS 2:2 1950
P H O T O T A C T I C VERTICAL M I G R A T IO N
IN M A R I N E
DIN O FLA G ELLA TES
BY
GRETHE RYTTER HASLE
(B iological laboratory, U n iv e rsity o f Oslo.)
1. I n t r o d u c t i o n
P re v io u s inv estig atio ns
W h en s tu d y in g th e v e rtic a l d is trib u tio n of p h y to p la n k to n , p ro n o u n ce d
m in im a a n d m a x im a a re o fte n re c o rd e d w ith in th e p h o to sy n th e tic zone. T his
m a y be d u e to v a ria tio n s in th e co n d itio n s for p h o to sy n th e sis a n d r a te of
m u ltip lic a tio n , o r it m a y also , as fo r fla g e lla te s, be the- re s u lt of p h o to ta c tic
m ov em en ts of th e p o p u la tio n .
A s m ig h t be e x p e c te d th e r a te of m u ltip lic a tio n is fo u n d to be d e p e n d e n t
u p o n th e s u p p ly of lig h t (e. g. in C e ra tiu m trip o s, B r a a r u d a n d N o r d l i u n p u b l.)
a n d in P ro ro c e n tru m m ica n s m ax im al r a te of m u ltip lic a tio n w as re a c h e d a t
re la tiv e ly h ig h lig h t in te n s itie s ( B a r k e r 1935. C pr. also R o s s a v ik 1943). On
th e o th e r h a n d e x p e rim e n ts on m ix ed p la n k to n p o p u la tio n s h a v e sh o w n th a t
in su m m er th e lig h t m a y be so in te n se a t th e su rfa c e th a t p h o to sy n th e sis is
in h ib ite d (M a r s h a l l a n d O r r 1928, S t e e m a n n N ie l s e n 1938).
T he la rg e s t p o p u la tio n s of c e ra tia a re u su a lly fo u n d 5 to 10 m etre s below
th e su rfa c e ( L o iim a n n 1908, G r a n 1915), w hile P ro ro c en tru m m ica n s is found
to h a v e a d iffe re n t d is trib u tio n ( L o iim a n n 1. c.). T h is d istrib u tio n of th e c e ratia
is m o stly e x p la in e d as p a r tly b e in g th e re s u lt of p h o to ta c tic m ovem ents
( G r a n 1915, B r a a r ijd a n d B u r s a 1939).
E x p e rim e n ts w ith C era tiu m fu s u s h a v e d e m o n stra te d th a t th is species is
p o sitiv e ly p h o to ta c tic a t lig h t in te n sitie s of 5000 L ux. L ik ew ise G oniaulax
p o ly e d ra is fo u n d to be p h o to ta c tic in c u ltu re s (B r a a r u d a n d N o r d l i , un p u b l.).
D in o fla g e lla te s h a v e b een fo u n d to m ove so q u ic k ly th a t a tra n slo c a tio n
c o rre sp o n d in g to 5 to 10 m e tre s in 12 h o u rs, h a s been re c o rd e d , w hile oth ers
w ere fo u n d to m ove m o re slo w ly ( L o iim a n n 1919, T s c iiir n 1920, P e t e r s 1929).
P h o to ta c tic V e r tic a l M ig ra tio n in M a rin e D in o fla g e lla te s
163
A c c o rd in g to th e se o b se rv a tio n s it w o u ld seem possible for d in o fla g e lla te s
to c a r r y o u t sim ila r d iu rn a l m ig ra tio n s as d e m o n stra te d in co p ep o d s a n d
c h a e to g n a ts ( R u s s e l l 1925— 34, K ik u c h i 1930, C l a r k e 1933, N ic h o l l s 1933,
J o h n so n 1938).
F o r A m p h id in iu m o p e rc u la tu m a n d E u g le n a deses, b o th of w hich a re
d ig g in g form s, d iu rn a l m o v em en ts h a v e been re c o rd e d , seem in g ly in d u c e d by
ch an g es in th e lig h t in te n s ity d u rin g th e d a y ( L a u r ie 1913, B r a c h e r 1919).
E u g le n a p ro x im a , o n th e o th e r h a n d , in sam p les c o llec ted e v e ry 4 h o u rs, w as
a lw a y s fo u n d in m ax im u m n u m b er a t th e sam e d e p th (M a r s h a l l a n d O r r
1948). G o n ia u la x ta m a re n sis, a c c o rd in g to o b se rv a tio n s b y C h a r l o t t e S u l l i ­
v a n , leav es th e su rfa c e d u rin g n ig h t a n d rise s a g a in in th e m o rn in g (quoted
b y B e r k e l e y N e e d l e r 1949, p a g e 500). A c o m p reh en siv e stu d y of th e
b e h a v io u r of th e c e ra tia seem s to h a v e been c a rrie d o u t in th e K iele r fjo rd
b y T s c h ir n , b u t th e re su lts a re no lo n g e r accessible e x c e p t for a s h o rt e x tra c t
w h ich h a s b e e n p u b lish e d ( T s c h ir n 1920). He a d v a n c e s th e v iew th a t the
c e ra tia b y m ean s o f th e ir fla g e lla e , a c tiv e ly seek th e d e p th w h ich su its them .
H e co n sid ers th e in te n s ity of d a y lig h t th e d ecisiv e fa c to r fo r th e m ig ra tio n ,
th e c e ra tia a v o id in g b rig h t lig h t a n d o n ly in o v e rc a st w e a th e r risin g to th e
u p p e rm o st la y e rs. B r a u n s (1942) h a s re c o rd e d a sim ila r v e rtic a l d istrib u tio n
of c e ra tia from th e F e h m a rn B elt.
T h e v e rtic a l d is trib u tio n of c e ra tia in in n e r Oslo fjo rd h a s been fo u n d to
d iffe r fro m th a t of o th e r c o a s ta l w a te rs a n d th e o u te r p a r t of th e fjo rd
(B r a a r u d a n d B u r s a 1939, B r a a r u d 1945), th e m axim um u su a lly o ccu rrin g
m uch n e a re r th e su rfa c e , th a n is re c o rd e d elsew here, o ften in th e sam ple
from 0 m ( B r a a r u d 1945, p a g e 82).
G r a n re p o rts v e rtic a l p h o to ta c tic a l m ig ra tio n of c e ra tia in th e Oslo fjo rd
( G r a n 1912 b, G r a n 1929) w ith o u t p re s e n tin g th e d e ta ile d m a te ria l for the
o b se rv a tio n .
T he a r e a of o b se rv atio n
In n e r Oslo fjo rd is re la tiv e ly sh allo w , m o stly w ith d e p th s less th a n 50 m
a n d w ith isla n d s a n d so u n d s. T h e w hole re g io n rec eiv e s se w ag e from Oslo
a n d s u rro u n d in g s a n d th is a ffe c ts th e h y d ro g ra p h ic a l co n d itio n s, c o n te n t of
n u trie n t sa lts, o p tic a l co n d itio n s a n d in d ire c tly e sp ec ially d u rin g sum m er the
p h y to p la n k to n p o p u la tio n . T h e su b m a rin e lig h t d istrib u tio n is e x c e p tio n al,
as show n b y B u v ig ( 1 9 4 1 ) a n d also b y th e o b se rv a tio n s p re se n te d in fig. 3
a n d 4 . L ig h t tra n sm issio n is re m a rk a b ly low a n d in c o n tra s t to o ceanic w a te rs
a n d c o a sta l w a te rs in g e n e ra l, th e b lu e lig h t b e in g firs t ab so rb e d , w hile red
a n d g re e n lig h t re a c h fu rth e r dow n to a b o u t th e sam e d e p th . S im ilar con­
d itio n s h a v e been re c o rd e d from Is e fjo rd in D e n m a rk d u rin g sum m er, w hen
p la n k to n a n d d isp e rse d p a rtic le s a re v e ry n u m ero u s ( S t e e m a n n N ie l s e n 1 9 4 4 ) .
164
G re th e R y t te r H a sle
T he to p o g ra p h y a n d h y d ro g ra p h y of th e reg io n as w ell as th e effect of
p o llu tio n a re e x te n siv e ly tre a te d b y B r a a r u d a n d R uud (1937), B r a a r u d an d
B u r s a (1939) a n d B r a a r u d (1945).
M e th o d s
W a te r sam p les fo r q u a n tita tiv e d e te rm in a tio n of p h y to p la n k to n w ith in the
0— 2 m la y e r w ere co llected d ire c tly in 100 m l b o ttles b y m ean s of a rod.
F ro m g re a te r d e p th s sam p les w ere co llected b y m eans of N an sen w a te r-b o ttle s
in series. T h e sam p les w ere p re s e rv e d w ith n e u tra liz e d form alin. C ounts w ere
m ade u s in g a n in v e rte d m icro sco p e as d escrib ed by U t e r m ö h l (1931). F o r
lig h t m e a su re m e n ts th e sam e a p p a r a tu s an d tech n iq u e w ere u se d as described
b y B u v ig (1941).
2. V e r t i c a l m i c r o - d i s t r i b u t i o n w i t h i n t h e u p p e r m o s t 2 m e t r e s
D u rin g p re v io u s in v e s tig a tio n s in th e in n er Oslo fjo rd sam p les h a d been
co llected a t e v e ry o th e r m eter a t som e of th e sta tio n s. M axim um for c e ra tia
w as th e n re c o rd e d fo r th e 0 m sam p le ( B r a a r u d 1945: C. trip o s a t P a ra d is
b a y , 19. J u ly 1938, 11.00 h r.). T h e p re s e n t o b se rv a tio n s in d ic a te a d iffe re n t
d istrib u tio n .
F o r 21 sta tio n s in sid e th e Oslo isla n d s sam p les w ere co llected a t the follow ­
ing d e p th s: 0 m, 25 cm , 5') cm, 1 m a n d 2 m. A ll o b serv atio n s w e re m ade'
b efore noon in calm a n d c le a r o r slig h tly clo u d ed w e a th e r d u rin g th e last
h a lf of J u ly . T h e s ta tio n s w ere w o rk e d in se v e ra l series. In one series the
sta tio n s w ere lo c a te d a t d iffe re n t d ista n c e s from la n d , in a n o th e r, sam ples
w ere ta k e n a t in te rv a ls of se v e ra l d a y s, w hile a th ird series com prised
sam p les c o llected from su n rise to a fte rn o o n . In th e firs t a n d la s t cases lig h t
c o n d itio n s w ere n o t th e sam e from one s ta tio n to th e o th er. T h is seem s to
influence th e d istrib u tio n d iffe re n tly in th e th re e species w h ich w ere in ­
v e s tig a te d : C era tiu m fu s u s , C. trip o s a n d P ro ro cen tru m m icans. N e v erth ele ss
th e o b se rv a tio n s d e m o n stra te c h a ra c te ris tic com m on fe a tu re s in th e v e rtic a l
d istrib u tio n , as sh o w n in th e follow ing tw o tables.
T ab le 1.
N um ber of observations w ith m axim um
p o pulation in
C eratium fu s u s
»
tripos
P rorocentrum m icans
0 m
25 cm
50 cm
1 m
2 m
0
0
0
0
1
1
0
4
5
3
10
i
18
6
8
P h o to ta c tic V e r tic a l M ig ra tio n in M a rin e D in o fla g e lla te s
165
T ab le 2.
N um ber of observations w ith m inim um
popu latio n in
C eratium fu su s
»
tripos
P rorocentrum m icans
0 m
25 cm
50 cm
1 m
2 m
12
13
16
4
6
0
5
0
1
0
1
2
0
1
2
According- to ta b le 1 th e m ax im u m n u m b e r of cells w as n e v e r re c o rd e d a t
the v e ry su rfa c e (0 m ). C o rre sp o n d in g ly th e m inim um n u m b er for all th re e
species w as re c o rd e d m o st fre q u e n tly a t th is d e p th (ta b le 2). T h e o b serv a tio n s
in d ic a te th a t th e tw o C era tiu m sp ecies re a c t d iffe re n tly u p o n th e sam e lig h t
in te n sity (cpr. ta b le 1).
T ab les fo r th e v e rtic a l d is trib u tio n of ea c h species d e m o n stra te a p r o ­
n o u n ced s tra tific a tio n w ith in th e u p p e rm o s t 2 m etres of th e su rfa c e la y e r
(e. g. ta b le 3).
T able 3. N um ber of cells p r. litre.
0
25
50
1
2
m
cm
cm
m
m
C. fusus
C. tripos
P r. micans
13 250
15 400
11 550
25 450
75 400
1 100
15 750
21 850
14 800
10 300
1 000
221 000
500 500
478 000
158 000
C. fu s u s in m o st cases show s a n even in c re a se do w n to 1 or 2 m, w hile
C. trip o s a n d e v e n m ore p ro n o u n c e d P ro ro c e n tru m m ic a n s, in m a n y cases
h a v e th e ir m ax im u m n u m b ers w ith in th e 2 m la y e r. T his fe a tu re is esp ecially
fo u n d a t sta tio n s w h e re lig h t on a c c o u n t of h ig h tu rb id ity , is q u ic k ly re d u ce d
w ith in c re a sin g d ep th .
W hile th e o b se rv a tio n s m e n tio n e d ab o v e from P a ra d is b a y , J u fy 1938, w ith
re c o rd s fo r e v e ry 2 m e tre s (B ra arud 1945), sh o w ed a m ax im u m p o p u la tio n
a t th e v e ry su rfa c e (0 m ), th ese 1 9 4 8 -o b serv atio n s from 21 sta tio n s w ith
in te rm e d ia te d e p th sam p les re c o rd e d th e m ax im u m below th e su rface.
3. V e r t i c a l d i s t r i b u t i o n d u r i n g d a y a n d n i g h t
M a te ria l fo r th e s tu d y of v e rtic a l d is trib u tio n in th e d in o fla g e lla te p o p u l­
a tio n d u rin g d a y a n d n ig h t w as c o llected fro m M/C “ G u n n a r K n u d se n ”
26— 27 a n d 28— 29 J u ly , 1948. T h e b o a t la y a t a n c h o r off O rm oya in in n e r
Oslo fjo rd . T h e d e p th w as 12— 14 m a n d th e o b se rv a tio n s w ere m ade
11 — Oikos
166
G re th e R y t t e r H a sle
F ig. 1. D iu rn al v a ria tio n of te m p e ra tu re a t d ifferen t d ep th s. Off O rm oya,
J u ly 26—27, 1948.
°c
"¡6°°
°"z0°°
°Z?a
^
^0
0
¡‘¿ ô r
F ig. 2. D iu rn al v a ria tio n of te m p e ra tu re a t d ifferen t dep th s. Off O rm oya,
J u ly 28—20, 1948.
fa irly close to la n d , w h ere th e b o a t h a d sh e lte r d u rin g th e w hole p e rio d of
o b se rv a tio n . T his w as of sp ecial im p o rta n c e fo r th e m e a su re m e n t of su b ­
m a rin e lig h t, w h ich w as c a rrie d o u t sim u lta n e o u sly w ith th e co llectio n of
w a te r sam p les. T h e tim e of o b se rv a tio n p ro v e d to be v e ry co n v e n ie n t, th e
d in o fla g e ila te p o p u la tio n b e in g v e ry n u m ero u s a n d th e w e a th e r sta b le. All
o b se rv a tio n s w ere m ad e d u rin g cle a r, h azy , or s lig h tly c lo u d y w e a th e r w ith
little o r no breeze. T e m p e ra tu re re c o rd s w ere m ade e v e ry seco n d h o u r.
T e m p e ra tu re co n d itio n s d u rin g th e tw o p e rio d s w ere so m ew h at d iffere n t
(figs. 1 a n d 2), th e te m p e ra tu re risin g so m ew h at in th e u p p e r la y e r a n d d u rin g
th e la s t p e rio d sh o w in g so m e w h a t la rg e r am p litu d es.
T h e lig h t d is trib u tio n w a s sim ila r d u rin g th e tw o p erio d s, a lth o u g h d u rin g
th e la s t one a s lig h t c h a n g e w as n o tic eab le (figs. 3 a n d '4 ), w h ich ac co rd s
w ell w ith th e ch an g es o b serv ed in th e d in o fla g e ila te p o p u la tio n .
T h e fo llo w in g d in o fla g e lla te s w ere s tu d ie d : C era tiu m fu s u s a n d C. tripos,
P h o to ta c tic V e r tic a l M ig ra tio n in M a rin e D in o fla g e lla te s
169
Cells
200
-
00
-
e '* >
50 -
20
-
0 - 0-
5UNSET
SUNRISE
F ig. 6. C hanges in th e 0 m (h eav y curve) a n d 2 m (stip p led cu rv e)-p o p u latio n s of
C eratium fu s u s in tw e n ty -fo u r h o u rs on J u ly 28— 29, 1948 off O rm oya. P o p u la tio n s
in n u m b er of cells in 2 ml.
b etw een th e tw o species in th e ir b e h a v io u r to w a rd s lig h t w o u ld h a rd ly be
n o tice ab le here.
G o nia u la x p o ly e d r a a n d P ro ro c e n tru m m ic a n s re p re s e n t th e second ty p e .
T h e cu rv e s fo r th e p o p u la tio n a t th e su rfa c e (0 m) a n d for th e in te n s ity of
d a y lig h t follow m u ch th e sam e tre n d . T h ese sp ecies le a v e th e su rfa c e d u rin g
th e n ig h t a n d rise d u rin g th e d a y . In P ro ro c e n tru m m ic a n s th e m axim um
n u m b er a t th e su rfa c e w as, h o w e v e r, re c o rd e d from a b o u t 12.00 h r., w hile
in G o n ia u la x p o ly e d ra it o c c u rre d c o n sid e ra b ly la te r, b etw een 16.00 a n d 18.00
h r., w h en m ax im u m of d a y lig h t in te n s ity h a d p a sse d som e tim e before.
In a sim ila r w a y th e c u rv e s fo r th e p o p u la tio n a t th e o th e r d e p th s m a y be
c o m p are d w ith th e lig h t cu rv e. F o r th e c e r a tia th e 1 m cu rv e ru n s p a ra lle l
to the 0 m c u rv e , w h ile th e 2 m c u rv e h a s a n in v e rse form , a n d th u s resem bles
th e cu rv e fo r d a y lig h t in te n sitie s (fig. 6). In th o se cases w h ere cu rv e s c a n be
d ra w n fo r 5 a n d 10 m, th e y h a v e a fo rm sim ila r to th a t of th e 2 m cu rv e.
F o r th e o th e r tw o species th e 0, 1 a n d 2 m c u rv es m ore or less conform ,
th e m a x im a a n d m in im a b e in g to som e e x te n t d isp la c e d ow ing to th e fa c t
th a t th e y o c c u r la te r a t d iffe re n t d ep th s.
T h ese c u rv e s d isclo se fe a tu re s of th e b e h a v io u r of th ese sp ecies to w a rd s
P h o to ta c tic V e rtic a l M ig ra tio n in M a rin e D in o fla g e lla te s
167
Blue
Green
R ed
Ormfiya . is 30- 1 6 00
2 8 - 7 , m e>
Total
F ig. 3. R elatio n b etw een d e p th a n d irra d ia tio n ex p ressed as p erce n ta g e of th e lig h t ju s t
over th e surface (lo g arith m ic scale). O b serv atio n s m ade off O rm oya a t 15.30— 16.00 hr.,
J u ly 28, 1948.
100
B lu e
Green
O r m o y a , 2000 - 2 0 25
2 8 -7 .4 8
Total
F ig. 4. R elatio n b etw een d e p th a n d irra d ia tio n ex p ressed as p erce n ta g e of th e lig h t ju s t
o v er the surface (logarith m ic scale). O b serv atio n s m ade off O rm oya a t 20.00'—20.25 h r.,
J u ly 28, 1948.
168
G re th e R y t t e r H a sle
C e l l s in 2 m l .
1000 Lux
1000
100
C .ÍU 5U 5
500 -
200 -
100 -
20 -
Light
Light
10 0
G.polyedra
Pr. m i c a n s
500 -
200
50 -
Li g h t
20 SUNSET
Fig. 5. C hanges in th e 0' m -p o p u latio n s of C eratium fu s u s a n d tripos, G oniaulax p o lyed ra
a n d P rorocentru m m icans (h ea v y curve) an d d a y lig h t in te n sitie s (thin curve), off
O rm oya, J u ly 26— 27, 1948. P o p u la tio n s in n u m b er of cells in 2 ml. L ig h t in ten sities
in 1000 L ux.
G o n ia u la x p o ly e d ra a n d P ro ro c e n tru m m ica n s. T hese w e re th e com m onest
d in o fla g e lla te s, a lth o u g h s e v e ra l o th e rs o cc u rre d , in co m p an y w ith a few
d iato m s a n d v a rio u s k in d s of fla g e lla te s. T h e n u m b ers re c o rd e d from th e 0 m
sam p les fo r a ll 4 sp ecies a re p re s e n te d in sm o o th ed c u rv es, in d ic a tin g th e
c h a n g e s w ith tim e. T h ese c u rv e s a re c o m p a re d w ith th e c u rv e fo r th e d a y lig h t
in te n sitie s as re c o rd e d o n th e d eck p h o to m e te r (fig. 5). T w o d istin c t ty p e s
a re fo u n d . T h e tw o C era tiu m sp ecies b e lo n g to one ty p e : T h e p o p u la tio n a t
th e su rfa c e (0 m) seem s to d e c re a se as th e lig h t in te n s ity in c rea ses, w hich
m eans th a t th e c e ra tia le a v e th e su rfa c e d u rin g th e d a y a n d rise a t n ig h t.
S in ce C. trip o s w as fo u n d in r e la tiv e ly sm all n u m b e rs, a po ssib le d ifference
169
P h o to ta c tic V e rtic a l M ig ra tio n in M a rin e D in o fla g e lla te s
Cells
in 2 m l .
200 -
oo
-
;z m
e '* >
50 -
20
-
SUNSET
SUNRISE
F ig. 6. C hanges in th e 0 m (heavy curve) a n d 2 m (stip p led cu rv e)-p o p u latio n s of
C eratium fu s u s in tw e n ty -fo u r h o u rs on J u ly 28—29, 1948 off O rm eya. P o p u latio n s
in nu m b er of cells in 2 ml.
b etw een th e tw o sp ecies in th e ir b e h a v io u r to w a rd s lig h t w o u ld h a rd ly be
n o tice ab le here.
G o n ia u la x p o ly e d ra a n d P ro ro c e n tru m m ica n s re p re s e n t th e seco n d ty p e .
T h e c u rv e s fo r th e p o p u la tio n a t th e su rfa c e (0 m) a n d fo r th e in te n s ity of
d a y lig h t follow m u ch th e sam e tre n d . T h e se sp ecies lea v e th e su rfa ce d u rin g
th e n ig h t a n d rise d u rin g th e d a y . In P ro ro c e n tru m m ica n s th e m axim um
n u m b er a t th e su rfa c e w as, h o w ev er, re c o rd e d from a b o u t 12.00 h r., w hile
in G o nia u la x p o ly e d ra it o c c u rre d c o n sid e ra b ly la te r, b etw een 16.00 a n d 18.00
hr., w hen m ax im u m of d a y lig h t in te n s ity h a d p a sse d som e tim e before.
In a sim ila r w a y th e c u rv e s fo r th e p o p u la tio n a t th e o th e r d e p th s m a y be
c o m p a re d w ith th e lig h t cu rv e. F o r th e c e ra tia th e 1 m c u rv e ru n s p a ra lle l
to th e 0 m cu rv e, w h ile th e 2 m c u rv e h a s a n in v e rse form , a n d th u s resem bles
th e cu rv e fo r d a y lig h t in te n sitie s (fig. 6). In th o se cases w h ere curv es c a n be
d ra w n fo r 5 a n d 10 m , th e y h a v e a fo rm sim ila r to th a t of th e 2 in cu rv e.
F o r th e o th e r tw o sp ecies th e 0, 1 a n d 2 m c u rv es m ore o r less conform ,
th e m a x im a a n d m in im a b e in g to som e e x te n t d isp la c e d ow ing to th e fa c t
th a t th e y o ccu r la te r a t d iffe re n t d ep th s.
T hese c u rv e s disclose fe a tu re s of th e b e h a v io u r of th e se sp ecies to w a rd s
170
G re th e R y t t e r H a sle
c h an g es in d a y lig h t. T h e c e ra tia e x h ib it a g re a te r se n sitiv ity to w a rd s high
lig h t in te n sitie s th a n th e o th e r tw o sp ecies. T h e lig h t in te n sitie s a t th e su rfa c e
(0 m) d u rin g these J u ly d a y s seem to h av e been so h ig h th a t th e y h av e in ­
duced n e g a tiv e p h o to ta c tic m o v em en ts in th e c e ra tia , w h ile a t a d e p th of 2 m
th e lig h t in te n sitie s a re so re d u c e d as n o t to hav e s u rp a sse d th e lim it of
p o sitiv e p h o to ta x is. T h e h ig h e s t 0 m v a lu e s w ere 100 000 L u x on th e firs t
d a y a n d 7 3 0 0 0 L u x on th e n e x t d a y , w h ile a t 2 m th e h ig h e st v a lu e w as
20000 Lux.
T he tw o sp ecies of C e ra tiu m , a lth o u g h follow ing th e sam e m ain p a tte rn ,
do n o t seem to h a v e id e n tic a l re a c tio n s to w a rd s v a rio u s lig h t in te n sitie s. T his
is in d ic a te d b y v a rio u s o b se rv a tio n s. O ur reco rd s on th e v e rtic a l m icro ­
d is trib u tio n p re s e n te d in ta b le 1 show th a t C. trip o s w as fo u n d close to the
su rfa c e m ore fre q u e n tly th a n w as C. fu su s. T h is is in a c c o rd a n c e w ith G r a n
(1912 b) w ho p o in ts o u t th a t C. fu s u s h as its m axim um a t lo w er d e p th s th a n
C. trip o s a n d th e sam e co n clu sio n w a s d ra w n b y T s c h ir n (1920) from his
o b se rv a tio n s. In c u ltu re s, a g r e a t n u m b e r of C. trip o s cells a re fo u n d u n d e r
th e su rfa c e film , w h ile C. fu s u s cells a re m ore ev en ly d is trib u te d in th e flu id
(E. N o r d l i u n p u b l.).
Table 4. Number of observed maxima at various levels for C. fusus and tripos.
26 — 27/7 — 48
0
1
2
5
10
m
m
m
m
m
28 — 29/7 — 48
C eratium fusus
C. tripos
C eratium fusus
C. tripos
3
4
1
1
;>
9
(i
7
4
5
7
2
3
1
3
9
3
2
0
0
I n th e m a te ria l p re s e n te d h e re C. fu s u s g e n e ra lly h a s its m axim um d eep er
dow n th a n C. trip o s (cpr. ta b le 4). T h u s C. trip o s in th e la s t series of o b se rv ­
atio n s h a d its m ax im u m a t 0 m from th e a fte rn o o n to su n rise (16.00 to
4.30 h r.), w h ile C. fu s u s d u rin g th e sam e p e rio d h a d its m axim um a t 5 m.
C o rre sp o n d in g ly from su n rise to a little before noon (4.30 to 10.40 hr.)
C. trip o s h a d its m ax im u m a t 1 m , a n d C. fu s u s a t 10 m.
A c c o rd in g to P e t e r s (1929) C. fu s u s w as able to m ove 1 mm in 4— 16 sec.,
w h ile C. trip o s m ad e th e sam e d ista n c e in 4— 8 sec. (8 sec, a c c o rd in g to
T s c h ir n 1920). T h is d ifferen ce b etw een th e tw o sp ecies is also of im p o rtan c e
fo r th e ir m ig ra tio n d u rin g d a y a n d n ig h t.
T he m ax im u m a t 0 m fo r G o n ia u la x p o ly e d ra occu rs a little la te r in th e
d a y th a n fo r P ro ro c e n tru m m ic a n s , a n d it seem s n a tu ra l to seek th e e x ­
171
P h o to ta c tic Y c r tic a l M ig ra tio n in M a rin e D in o fla g e lla te s
p l a n a t io n in a d if f e r e n c e in s w im m in g s p e e d in th e tw o s p e c ie s . N o o b s e r v ­
a tio n s a r e a v a ila b le o n th e s w im m in g s p e e d
but P
eters’
o f th e s e d in o f la g e ila te s p e c ie s ,
re c o rd s in d ic a te th a t th e s p e e d m a y d iffe r c o n s id e ra b ly fro m o n e
s p e c i e s t o a n o t h e r ( P e t e r s , 1. c . p a g e 3 0 7 ) .
T able 5. G oniaulax polyed ra , nu m b er of cells in 2 ml., off O rm oya, J u ly 26—27, 1948.
Sunrise
Sunset
Deptli
0
1
2
5
10
m
m
m
m
m
20:30
22:00
23:00
1:00
2:00
3:00
4:00
5:30
7:20
157
153
162
167
228
158
131
144
151
290
67
52
65
74
189
52
24
35
53
89
389
75
64
80
94
416
71
81
87
103
415
156
171
54
34
312
224
136
45
48
24
363
86
143
309
S unset
D epth
0
1
2
o
10
m
m
m
m
m
9:20
11:30
13:20
15:25
17:25
18:25
19:25
20:25
21:25
26
53
317
106
108
185
192
392
71
15
118
275
636
288
21
765
1049
1196
398
14
603
460
497
327
122
335
355
388
487
118
224
230
259
800
131
194
163
264
475
291
85
147
128
290
435
In ta b le o the v e rtic a l d is trib u tio n of G o n ia u lax p o ly e d ra th ro u g h o u t J u ly
26— 27, 1948 is show n. A t su n se t th e d is trib u tio n seem s to be r a th e r even.
G ra d u a lly th e m ax im u m a t 10 m becom es m ore p ro n o u n ce d . A t su n rise
a n o th e r te n d e n c y is n o tic e a b le . T h e m inim um la y e r a t th e su rfa c e is d e c re a s­
in g a n d a t n o o n th e la rg e s t p o p u la tio n s are to be fo u n d a t 2— 5 m a n d the
sm a lle st a t 10 m. A g a in th e d is trib u tio n becom es m ore ev en a n d a t la s t th e
situ a tio n is a b o u t th e sam e as a t the s ta r t 24 h o u rs earlier.
In P ro ro c e n tru m m ica n s th e s y ste m a tic a l c h a n g e in th e v e rtic a l d istrib u tio n
of th e p o p u la tio n is a b o u t th e sam e (fig. 7). W hen o b serv a tio n s s ta rte d , a
p ro n o u n c e d m ax im u m la y e r w as re c o rd e d in th e u p p e r 1 m eter. G ra d u a lly
th e d istrib u tio n b ecam e m ore even. O b se rv a tio n s from su n se t to su n rise show
an even d istrib u tio n . T he n e x t tw o o b se rv a tio n s show m ax im a a t 10 m. A g ain
th e d istrib u tio n becom es m ore even a n d a t la s t th e d istrib u tio n is ab o u t th e
sam e as a t th e s t a r t of th e o b se rv a tio n s w ith th e lo w est v a lu e s for 5 a n d 10 m
a n d th e h ig h e s t v a lu e s g r a d u a lly a p p ro a c h in g th e v e ry su rface.
T he d ifferen ce in te m p e ra tu re d u rin g th e tw o p e rio d s of o b serv atio n does
not seem to h a v e h a d a n y d efin ite in flu en ce u p o n th e v e rtic a l d istrib u tio n .
172
G re th e R y t t e r H a sle
m
2
5
loo
c el l s
io
55
0
2
5
IO
30
30
3 30
5UNRISL 4 30
0
2
5
IO
40
F ig . 7. V ertical d is trib u tio n of P ro ro cen tru m m icans a t d iffe re n t tim es in tw en ty -fo u r
hours on J u ly 28—-29, 1948 off O rm oya. O b serv atio n s of n u m b er of cells in 2 ml
a t 0, 1, 2, 5 a n d 10 m.
T h is m a te ria l from in n e r Oslo fjo rd c o m p risin g o b se rv a tio n s m a d e a t le a st
e v e ry seco n d h o u r d u rin g tw o d a y s a n d n ig h ts in la te J u ly , show s th a t
v e rtic a l m ig ra tio n o c c u rre d in th e C era tiu m fu su s, C. trip o s, G o niaulax
p o ly e d ra a n d P ro ro c e n tru m m ica n s p o p u la tio n s. T h e ch an g es in th e v e rtic a l
d is trib u tio n sh o w d iu rn a l p e rio d ic ity . T h e c o rre la tio n w ith v a ria tio n s in
d a y lig h t in te n s ity is so s tr ik in g th a t it seem s m o st p ro b a b le th a t p h o to ta c tic
m o v em en ts a re re sp o n sib le fo r th e ch anges w h ich ta k e p lac e. B e h a v io u r
d ifferen ces h a v e b een n o tic e d in th e sp ecies stu d ie d : C era tiu m fu s u s an d
trip o s re p re s e n t one ty p e , le a v in g th e su rfa c e d u rin g th e d a y a n d risin g a t
P h o to ta c tic V e rtic a l M ig ra tio n in M a rin e D in o fla g e lla te s
173
n ig h t; G o n ia u la x p o ly e d ra a n d P ro ro c e n tru m m ic a n s re p re s e n t th e o th e r,
risin g to th e su rfa c e d u rin g th e d a y a n d le a v in g it d u rin g th e n ig h t. The
tw o ty p e s m a y be c h a ra c te riz e d b y d iffe re n t lig h t sen sitiv itie s b u t d ifferen ces
in sw im m ing sp eed m a y also in flu en ce th e ir b e h a v io u r. T h e s lig h t d ifference
in b eh a v io u r of G o n ia u la x p o ly e d r a a n d P ro ro c e n tru m m ica n s m a y be d u e to
d ifferen ces in one of th ese fa c to rs o r in b o th , b u t th e p re se n t m a te ria l does
n o t suffice fo r a clo ser d iscu ssio n of th is qu estion.
T h e d iu rn a l m ig ra tio n w h ic h h a s b een d e sc rib ed ab ove is re c o rd e d fro m a
ra th e r u n iq u e a r e a a n d m a y n o t h o ld fo r d in o fla g e ila te p o p u la tio n s in g e n e ral.
In n e r Oslo fjo rd h a s ra th e r e x c e p tio n a l h j^d ro g rap h y a n d p h y to p la n k to n
co n d itio n s. I t is a sh e lte re d re g io n a n d th e p o llu tio n b y se w ag e re su lts in
re m a rk a b le p o p u la tio n s of d in o fla g e lla te s d u rin g su m m er a n d v e ry p ro n o u n ­
ced su b m a rin e lig h t co n d itio n s. P o p u la tio n s of sa y 800 000 P ro ro cen tru m
m ica n s a n d 100 000 C era tiu m fu s u s p e r litre com bined w ith a h ig h d eg ree of
tu rb id ity re d u c e lig h t tra n sm issio n . B u v i g (1941) fo u n d th a t in th e in n erm o st
p a r t of th e fjo rd (F ro g n e rk ile n ) o n ly 1 % of th e in c id e n t lig h t re a c h e d a
d e p th of 3 m, w h e re a s in th e o u te r p a r t (F e rd e r) th e d e p th re a c h e d w a s 23 m.
T h is fa c t sh o u ld be ta k e n in to a c c o u n t w h en c o n sid e rin g th e m ic ro stra tific ­
a tio n discu ssed above.
In sp ite of th e fa c t th a t th e d iu rn a l m ig ra tio n of th e fo u r d in o fla g e llates
w hich h a v e been s tu d ie d , h a s b een o b se rv e d u n d e r ra th e r sp ec ia l h y d ro g ra p h ic a l co n d itio n s, th e m a te ria l n e v e rth e le ss h as cle a rly d e m o n stra te d th a t
th ese sp ecies r e a c t to ch an g es in lig h t in te n s ity b y c a rry in g o u t p h o to ta c tic
m ovem ents. I n o th e r lo c a litie s th e e x te rn a l co n d itio n s m a y le a d to d iu rn a l
ch an g es in th e v e rtic a l d is trib u tio n of th e d in o fla g e ila te p o p u la tio n w hich
a re less c o n sp icu o u s th a n in th e p re s e n t case.
SUMMARY
1. Sam ples from a d e p th of 0 m, 25 cm, 50 cm, 1 m an d 2 m collected d u rin g
th e m o rn in g d em o n strate s tra tific a tio n in th e d in o flag eilate p o p u latio n w ith in
th e u p p e r 2 m etres. C era tiu m fu s u s , C. trip o s an d P rorocentrum m icans behave
d iffe re n tly , b u t in none of th e th re e species was th e m axim um p o p u la tio n
observed a t th e v ery su rfa c e (0 m ). (C p r. tab les 1 a n d 2 ).
2. V ertical m ig ra tio n w as observed in C era tiu m fustis, C. tripos, G oniaidax
p o lyedra a n d P ro ro cen tru m m icans. One m ig ra tio n period covers one d ay and
one n ig h t an d th e m ig ra tio n is considered to be p h o to tactic in origin.
3. The fo u r species in v estig ated re p re se n t tw o ty p e s w ith d iffe re n t lig h t
sensitivity.
a) C era tiu m fu s u s a n d trip o s leave th e su rface d u rin g th e d a y a n d rise again
d u rin g th e n ig h t.
b) G oniaidax p o lyed ra an d P ro rcen tru m m icans rise to th e su rfa c e d u rin g
th e d a y a n d leave i t a t n ig h t.
G re th e R y t t e r H a sle
174
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