Different zooplankton structures in the German Bight

(1)

HELGOI.~NDER MEERESUNTERSUCHUNGEN Helgol~nder Meeresunters. 47, 193-212 (1993)

Different zooplankton structures in the German Bight

P. M a r t e n s I & U. B r o c k m a n n 2

i Biologische Anstalt Helgoland (Litoralstation); D-25992 IA'st/Sylt, Federal Republic of G e r m a n y

2 Universit~t Hamburg, Institut ffir B i o c h e m i e und Lebensmittelchemie; M a r t i n - i u t h e r - IQ'ng-Platz 6, D-2014fi Hamburg, Federal Republic of G e r m a n y

ABSTRACT: In August 1982, a net of 48 stations with altogether 208 samples was investigated in the eastern German Bight with respect to temperature, salinity, as well as the amount and species composition of the mesozooplankton (> 80 [~m). The data were arranged into different structures by means of a cluster analysis. Four different clusters were found: (a) a "Wadden Sea water" with few holoplankton organisms but a higher amount of spionid larvae; (b) a "German Bight water" with a maximum occurrence of turbellaria (Alaurina composita) and medium concentrations of copepods; (c) a mixing area between these two water masses with highest amounts of Oikopleura dioica, Temora longicornis, Acartia sp., mussel larvae and larvae of the spionid worms; (d) a "North Sea water" mass with highest concentrations of Pseudocalanus elongatus, Paracalanus parvus und Oithona similis. The differences in the concentrations of the species mentioned between the four clusters were significant on the 0.1%-level.

I N T R O D U C T I O N

A n a l y s e s of z o o p l a n k t o n p o p u l a t i o n s h a v e b e e n r e p e a t e d l y p e r f o r m e d in t h e G e r - m a n B i g h t - o n e of t h e m o s t f r e q u e n t l y i n v e s t i g a t e d a r e a s b y G e r m a n m a r i n e r e s e a r - chers. At t h e b e g i n n i n g of this c e n t u r y , Kraefft (1908) r e p o r t e d a n e n r i c h m e n t of w o r m l a r v a e n e a r t h e coast. I n v e s t i g a t i o n s of z o o p l a n k t o n d i s t r i b u t i o n w e r e p e r f o r m e d b y K i i n n e (1937, 1952). M a r t e n s (1978) a s s o c i a t e d d i f f e r e n t z o o p l a n k t o n p o p u l a t i o n s w i t h d e f i n e d w a t e r m a s s e s .

T h e c o m p l e x h y d r o g r a p h i c s i t u a t i o n in t h e G e r m a n B i g h t is c a u s e d b y t h e m i x i n g of N o r t h S e a w a t e r , c o a s t a l w a t e r a n d E l b e R i v e r r u n o f f ( B e c k e r & P r a h m - R o d e w a l d , 1980; B e c k e r et al., 1983). T h e r e f o r e , e c o l o g i c a l i n v e s t i g a t i o n s r e q u i r e a h i g h s a m p l i n g r e s o l u - tion in o r d e r to d i s t i n g u i s h w a t e r m a s s e s of d i f f e r e n t origin.

M a r t e n s (1978) i n v e s t i g a t e d t h e d i s t r i b u t i o n of m e s o z o o p l a n k t o n d u r i n g w i n t e r , a l o n g a s a m p l i n g g r i d of 46 s t a t i o n s in t h e e a s t e r n G e r m a n Bight. T h i s p a p e r r e p o r t s o n t h e m e s o z o o p l a n k t o n d i s t r i b u t i o n in a p a r t i a l l y s t r a t i f i e d G e r m a n B i g h t in s u m m e r .

M A T E R I A L A N D M E T H O D S

F r o m A u g u s t 17 to 21, 1982, a n e t of 48 s t a t i o n s in t h e G e r m a n B i g h t ( N o r t h S e a ) w a s i n v e s t i g a t e d (Fig. 1);

(2)

194 P. Martens & U. Brockmann

5 5 ~

5 4 ~

o_ 9

9 9 9 9 9 s

i

9 9 9 o ~ 9 r

7 ~

8 ~

9 ~

Fig. 1. L o c a t i o n of t h e s a m p l i n g s t a t i o n s in t h e G e r m a n B i g h t (North S e a )

The following parameters measured during the cruise are dealt with in this paper:

Temperature (__ 0.01 ~ (Multi probe. System Meerestechnik Elektronik)

Salinity (_+ 0.01 SI (Multi probe. System Meerestechnik Elektronik) Mesozooplankton (5-1 PVS water samplers).

Temperature and salinity were profiled from the surface to the bottom. Zooplankton samples were taken in 0, 5, 10, 15, 20 and 30 m water depth (when possible). The plankton samples were sieved through 80 ~m gauze, preserved in 2 % formaldehyde-sea water solution and analysed to the species level under the microscope in the laboratory.

The larval stages of Pseudocalanus elongatus and Paracalanus parvus were not distin-

guished during the analyses.

Zooplankton dry weight was determined, using the results of the microscopic counts and empirical data sets of species mean dry weight (Hillebrandt, 1972; Martens, 1975).

Statistical m e t h o d s

(3)

Z o o p l a n k t o n in t h e G e r m a n B i g h t 195

o b s e r v e d d a t a into m e a n i n g f u l s t r u c t u r e s . T h e m e t h o d u s e d w a s a k - m e a n s - c l u s t e r i n g a l g o r i t h m .

T h e o b s e r v e d c l u s t e r s w_ere t e s t e d o n s i g n i f i c a n t d i f f e r e n c e s in t h e c o n c e n t r a t i o n of t h e p a r a m e t e r s in q u e s t i o n b y m e a n s of a K r u s k a l - W a l l i s A N O V A b y r a n k s a n d a m e d i a n - t e s t .

All c o m p u t a t i o n s w e r e p e r f o r m e d u s i n g t h e statistical p r o g r a m m e p a c k a g e C S S - Statistica (StatSoft 1991) u n d e r M S - D O S 5.0, on a M i l a n 386/40.

R E S U L T S

T h e T - S d i a g r a m (Fig. 2) s h o w s t h e e x i s t e n c e of d i f f e r e n t w a t e r m a s s e s . T h e b e s t fit to t h e d a t a sets, w i t h r e s p e c t to t e m p e r a t u r e a n d salinity, w a s a c h i e v e d b y m e a n s of a 4 - m e a n s c l u s t e r i n g a n a l y s i s r e s u l t i n g i n :

(1) a c o l d b o t t o m w a t e r of r e l a t i v e l y h i g h s a l i n i t y w i t h a m e a n t e m p e r a t u r e of 13.99 ~ a n d a m e a n s a l i n i t y of 33.58 S;

(2) a " G e r m a n B i g h t w a t e r " , m a r k e d l y w a r m e r t h a n t h e b o t t o m w a t e r a n d of l o w e r s a l i n i t y (17.24 ~ 33.51 S);

(3) a " W a d d e n S e a w a t e r " at t h e e a s t e r n b o r d e r of t h e r e s e a r c h a r e a , a w a r m w a t e r b o d y w i t h r e l a t i v e l y l o w salinity (18.06 ~ 30.75 S);

(4) a m i x i n g w a t e r b o d y w i t h a m e a n t e m p e r a t u r e of 17.14 ~ a n d a m e a n s a l i n i t y of 32.1 S. (see Fig. 2)

35

33

31

... : ... -...: ... .-. ... ~,..~,...'. ... : ... .- ...

I ! "i ," "'~ " i

9 9 9 : ~ : : ~

: : "im :'~

. . . ~ ' " - - , m m . . . "~-~, . . . ~ . . . ~ . . . ) ' d " ' ~ . . . ":" . . . m, . . .

: t 9

:- 9 . 9

H . " :" .m

I m m :-

i - k "

! ... 1 ... ~ . . . .: . . . ( . . . . . . ... . . .: . . . .

... ~ . . . ~ ... ~ ...

t : : 9 I t

13

15

17

19

t~

(4)

196 P. M a r t e n s & U. B r o c k m a n n

In o r d e r to a s c e r t a i n w h e t h e r this h y d r o g r a p h i c s t r u c t u r e is r e f l e c t e d b y t h e s p e c i e s c o m p o s i t i o n of t h e z o o p l a n k t o n , a c l u s t e r a n a l y s i s w a s p e r f o r m e d w i t h r e s p e c t n o t o n l y to t e m p e r a t u r e a n d sahnRy, b u t a l s o to t h e z o o p l a n k t o n s p e c i e s T e m o r a longicornis, C e n t r o p a g e s hamatus, Acartia sp. ( m a i n l y A c a r t / a clausi), Oithona similis, P s e u d o c a l a n u s elongatus, Paracalanus parvus, t h e l a r v a e of t h e O p h i u r o i d e a a n d t h e s p i o n i d w o r m s , t u r b e l l a r i a , Oikopleura dioica a n d m u s s e l l a r v a e .

T h e r e g i o n a l d i s t r i b u t i o n of t h e s e f o u r c l u s t e r s w a s c o m p a r a b l e to t h o s e of t h e p r e v i o u s c l u s t e r a n a l y s i s o n l y w i t h r e g a r d s to t e m p e r a t u r e a n d salinity.

Table 1. Descriptive statistics for cluster number 1 (23 cases)

Variable Mean Standard deviation Variance

Temperature 17.03 0.69 0.49

Salinity 31.67 0.49 0.24

Centropages 3.17 3.65 13.33

Temora 19.70 10.17 103.40

Acartia 27.91 12.33 151.99

Oithona 30.96 18.36 337.13

P.-Calanus 41.22 14.88 221.36

Ophioplutei 5.35 6.09 37.06

Spionid larvae 10.65 14.28 203,87

Turbellaria 1.57 1.41 1.98

Oikopleura 46,43 15.99 225.62

Bivalve larvae 8.65 6.87 47.24

Table 2. Descriptive statistics for cluster number 2 (39 cases)

Variable Mean Standard deviation Variance

Temperature 17.09 0.46 0.21

Salinity 32.81 0.56 0.32

Cen tropages 1.85 1.68 2.82

Temora 7.03 3.63 13.18

Acartia 22.13 7.82 61.17

Oithona 48.13 30.02 901.27

P.-Calanus 74.82 15.28 233.41

Spionid larvae 0.69 1.24 1.53

Oikopleura 6.64 6.99 48.87

T a b l e s 1 to 4 g i v e t h e d e s c r i p t i v e statistics for t h e f o u r clusters. T a b l e 5 g i v e s t h e c l u s t e r m e a n s for all f o u r c l u s t e r s .

(5)

Z o o p l a n k t o n i n t h e G e r m a n B i g h t

Table 3, Descriptive statistics for cluster n u m b e r 3 (94 cases)

197

Variable M e a n Standard deviation Variance

T e m p e r a t u r e 17.08 1.04 0.108

Salinity 33.08 0.87 0.75

Centropages 1.21 1.42 2.02

Temora 8.59 6.06 36.78

Acartia 22.81 11.83 140.03

Oithona 22,76 13.37 178,66

P.-Calanus 37.56 11.95 142.90

Oikopleura 6.62 6.25 39.12

Table 4. Descriptive statistics for cluster n u m b e r 4 (54 cases)

Variable M e a n S t a n d a r d deviation V a r i a n c e

T e m p e r a t u r e 16.71 2.10 4.41

Salinity 32.25 1.54 2.38

Centropages 3.56 5.28 27.90

Temora 8.01 4.86 23.63

Acartia 10.54 7.40 54.80

Oithona 8.19 8.68 75.26

P.-Calanus 11.94 7.63 58.29

Oikopleura 4.90 5.38 28.95

Bivalve larvae 2.33 3 . 3 7 11.36

Table 5. M e a n values for the variables in all four clusters

Variable Cluster 1 Cluster 2 Cluster 3 Cluster 4

T e m p e r a t u r e i7.03 17.09 17.08 16.71

Salinity 31.67 32.81 33.08 32.25

Centropages 3.17 1.85 1.21 3.56

Temora 19.70 7.03 8,59 8.01

Acartia 27.91 22.13 22.81 10.54

Oithona 30.96 48.13 22.76 8.19

P. -Calanus 41.22 74.82 37.56 11.94

Ophioplutei 5.35 8.51 3.13 1.00

Spionid larvae 10.65 0.69 2.72 9.52

Turbellaria 1.57 4.49 6.31 3.87

Oikopleura 46,43 6.64 6.62 4.90

(6)

55"

54"

D D O O O O

D O O D O D A

D O O r

D D O O O A A

D D D D O O A

D D D D O A A

A D D D D O A

r

f

O" b

7"

8"

9 =

Fig. 3a. The location of the different zooplankton clusters in the German Bight (North Sea). O = stations belonging to cluster 1, A = stations belonging to cluster 2, D = stations belonging to cluster

3, O = stations belonging to cluster 4

T h e 208 s a m p l e s t a k e n h a v e b e e n g r o u p e d into 4 clusters, with d i f f e r e n t c o n c e n - trations in salinity, a n d all of the 10 a n i m a l species a n d groups tested. No s i g n i f i c a n t d i f f e r e n c e w a s f o u n d in t e m p e r a t u r e (see T a b l e s 6, 7 a n d Figs 4-14). T h e d i f f e r e n c e s f o u n d in salinity a n d animals w e r e significant - at least at the 0 . 1 % - l e v e l .

T h e four clusters can b e biologically d e s c r i b e d in the following w a y :

C l u s t e r 1: M a x i m u m of O.

dioica, 7". ]ongicornis,

Acartia sp., m u s s e l l a r v a e a n d spionid larvae;

Cluster 1: H i g h e s t c o n c e n t r a t i o n s of

Pseudo-

and

Paracalanus

sp. a n d O.

similis

w i t h m i n i m u m of spionid l a r v a e ;

C l u s t e r 3: M a x i m u m o c c u r r e n c e of turbellaria (Alaur/na

composita)

w i t h m e d i u m con- c e n t r a t i o n s of c o p e p o d s ;

Cluster 4: R e l a t i v e l y h i g h c o n c e n t r a t i o n s of spionid larvae, all o t h e r a n i m a l g r o u p s s h o w m i n i m u m concentrations.

(7)

Z o o p l a n k t o n i n t h e G e r m a n B i g h t 1 9 9

55"

54"

D F 1 0

O O A

D O 0 0 0

O A

E ] O 0 0

O A

A

D F 1 O O

O A A

D D D . O

O A A

D D F I O

O O

A

E] E] E] D O O A

7"

8"

9"

Fig. 3b, T h e location of t h e different h y d r o g r a p h i c c l u s t e r s in t h e G e r m a n B i g h t (North Sea). O = s t a t i o n s b e l o n g i n g to c l u s t e r 1, A - s t a t i o n s b e l o n g i n g to c l u s t e r 2, [] = s t a t i o n s b e l o n g i n g to

c l u s t e r 3, O = s t a t i o n s b e l o n g i n g to c l u s t e r 4

T a b l e 6. R e s u l t s of t h e m e d i a n - t e s t s for t h e s i g n i f i c a n c e of t h e d i f f e r e n c e s in t e m p e r a t u r e , s a l i n i t y a n d z o o p l a n k t o n c o n c e n t r a t i o n s b e t w e e n t h e four c l u s t e r s

V a r i a b l e C a s e s a b o v e m e d i a n C h i - P r o b a b i l i t y ( o b s e r v e d m i n u s e x p e c t e d p e r cluster) s q u a r e l e v e l C l u s t e r 1 C l u s t e r 2 C l u s t e r 3 C l u s t e r 4

T e m p e r a t u r e - 6 . 5 4.5 4.5 - 2 . 5 7.91 0.05 Salinity - 1 4 . 9 4 5.31 11.39 - 1 . 7 6 35.49 < 0 . 0 0 0 1

Centropages 7.63 0.13 - 3 . 4 9 - 4 . 2 6 6.18 0.10

Temora 5.50 3.50 - 9 . 5 0 0.50 18.30 0.0004

Acartia - 8 . 2 5 - 7 . 2 5 - 5 . 9 4 21.44 48.03 < 0 . 0 0 0 1

Oithona - 0 . 9 4 - 1 4 . 6 9 - 3 . 6 1 19.24 51.35 < 0 . 0 0 0 1

P.-Calanus - 4 . 3 8 - 1 9 . 8 8 - 2 . 7 2 26.97 95.58 < 0 . 0 0 0 1

O p h i o p l u t e i 3.94 - 9 . 3 1 - 4 . 1 6 9.53 19.60 0.0002 S p i o n i d l a r v a e 10.88 10.38 - 1 3 . 9 3 - 7 . 3 2 56.42 < 0 . 0 0 0 1 T u r b e l l a r i a - 1 1 . 8 1 - 7 . 0 6 6.17 12.71 29.63 < 0 . 0 0 0 1

Oikopleura 3.00 1.00 - 1 2 . 3 8 8.38 32.48 < 0 . 0 0 0 1

(8)

Table 7. Results of the Kruskal-Wallis ANOVA by Ranks as test on the significance of differences in temperature, salinity and zooplankton concentrations b e t w e e n the four clusters

Variable H (3,N=208) Probability level

Temperature 3.061 0.3822

Salinity 32.000 <0.0001

Centropages 10.391 0.0155

Temora 32.891 <0.0001

Acartia 67,231 <0.0001

Oithona 82.050 <0.0001

P.-Calanus 156.387 < 0.0001

Ophioplutei 31.706 < 0.0001

Spionid larvae 46.140 < 0.0001

Turbellaria 26.118 < 0.0001

Oikopleura 62.642 < 0.0001

Bivalve larvae 28.546 < 0.0001

3 6

3 4

"E 3 2

30

8 . . . ,

1 2 3 4

c l u s t e r s

(9)

15

E

10

{3)

E

u~

5

0

~

0

Q .

2

r - -

~

- 5

0

Z o o p l a n k t o n i n t h e G e r m a n B i g h t

...

T ...

t" ...

. . . J

201

-10 I

.

1

2

3

4

clusters

Fig. 5. Companson of the four clusters with respect to dry weight of Cent.ropages hamatus (log

values; box-and-whisker plot); box: _+ 2 standard error; whisker: _ 2 standard deviation

40

E 30

{33

E

20

0

E 10

... m

m

| 9 |

2

3

4

clusters

(10)

60

40

0 3

E

0 3 O

~"

20

~

<

0

... i ...

mm

1

2

3

4

clusters

Fig. 7. Comparison of the four clusters with respect to dry weight of Acartia sp. (log values; box-and- whisker plot); box: -4- 2 standard error; whisker: +__ 2 standard deviation

E

O'}

E

0 3

O

v

t - O r

.D

O

120

8o 1 ...

t

~ ...

,01 ...

T ...

! ...

1 ...

0

1

2

3

4

clusters

(11)

Z o o p l a n k t o n in t h e G e r m a n B i g h t 203

E

O3

E

v

O

E

v

"-I c

l

n"

90

60

30

0

1

2

3

4

c l u s t e r s

Fig. 9. Comparison of the four clusters with respect to dry weight of Pseudo- and Paracalanus sp. (log values; b o x - a n d - w h i s k e r plot); box: + 2 standard error; whisker: + 2 standard deviation

30

E

15

E

O

--=

_Q.

0

0 c-

O

-15

i ... T ...

9 9 9 n

1

2

3

4

clusters

(12)

2 0 4 P. M a r t e n s & U. B r o c k m a n n

E

v

0

m v

~D

O~

>

_13

2,]

18 ... 1

T

12

6

0

-6

1

2

3

4

clusters

Fig. 11. Comparison of the four clusters with respect to dry weight of larvae of spionid worms (Polychaeta) (log values; box-and-whisker plot); box" + 2 standard error; whisker: -4- 2 standard

deviation

E

v

O

v

CD .-1

b--

20-

10-

1 0 I

1

2

3

4

clusters

(13)

Z o o p l a n k t o n i n t h e G e r m a n B i g h t 205

"-'.--

60"

E

v

~D

_go

v K . .

(D

Q . O

~

O

3o.0.

i i iiiiiiii iiiii! i i

9 | 9 |

1

2

3

4

clusters

Fig. 13. Comparison of the four clusters with respect to dry w e i g h t of Oikopleura dioica (log values; box-and-whisker plot); box: _+ 2 standard error; whisker: _+_ 2 standard deviation

5 0

. . • 2 5

... ,-, ...

~

0

...

~,

"~.

ffl

-25

1

2

3

4

clusters

(14)

2 0 6

S

3 4

3 3

3 2

31

3 0

P. M a r t e n s & U. B r o c k m a n n

A

& o 9 9

A A

A ~ 84 9

9 o

= .

S

54

33

32

31

30

13 ~ 14 ~ 1 5 o 16 ~ 17 ~ 18 ~

Fig. 15. Temperature-salinity-zooplankton diagram for Oikop]eura dioica

2X

A

19 ~ o C

13 ~ 14 ~ 15 ~ 16 ~ 17 ~ 18 ~

Fig. 16. Temperature-salinity-zooplankton diagram for Oithona similis

(15)

Z o o p l a n k t o n i n t h e G e r m a n B i g h t 207

S

3 4

3 3

3 2

31

3 0

4 A

&

s

A 8

A

m 9

A, A "A A8/I~

~k

A l l 9

A A & ~

9 4 A"

-- %

S

3 4

3 3

3 2

31

3 0

13 ~ 14 ~ 15 ~ 16 ~ 17 ~ 18 ~

Fig. 17. Temperature.salinity-zooplankton diagram for Alaurina composita

6 9

A . .

& * A

e

#

19 ~ o C

1.3 ~ 14 ~ 15 ~ 16 ~ 17 ~ 18 ~ 19 ~ o C

(16)

208 P. M a r t e n s & U. Brockmann

show u p in h i g h e s t q u a n t i t i e s i n t h e w a r m e s t w a t e r of lowest salinity, t h e w a t e r mass b e i n g i n f l u e n c e d b y the outflow of the W a d d e n Sea areas. T h e t u r b e l l a r i a are f o u n d i n relatively w a r m w a t e r of high sahnity, w h i c h was, at the b e g i n n i n g , c a l l e d a " G e r m a n Bight" water. O. dioica is f o u n d in the m i x i n g area b e t w e e n these two w a t e r masses. O. similis is, t o g e t h e r with P. elongatus a n d P. parvus, the only species f o u n d i n n u m e r o u s q u a n t i t i e s in the cold bottom w a t e r of high sahnity with lowest c o n c e n t r a t i o n s , i n the areas i n f l u e n c e d b y the W a d d e n S e a outflow.

This c a n b e s e e n w h e n l o o k i n g at the spatial distribution of the a b o v e - m e n t i o n e d species. Pigures 19-22 show the c o n c e n t r a t i o n of spionid larvae, t u r b e l l a r i a , O. dioica a n d O. similis i n the 10-m level. T h e spatial s e p a r a t i o n c a n b e c l e a r l y s e e n b y a comparison of b i o m a s s distribution.

5 5 ~

5 4 ~

"''t

9

m

9 ~ <

m m

~ " = 40 mg m-3

4, ~ 9

r

f

b

7 ~ 8 ~ 9 ~

(17)

Z o o p l a n k t o n i n the G e r m a n Bight 209

5 5 ~

5 4 ~ .

9

}1~

9 !1 tl I I t l

} i r a

9

I I

. 9

-}11•

= 6

mg

m -3

r

t

7 ~ 8 ~ 9 ~

Fig. 20. Abundance of Alaurina composita at the different sampling stations in 10 metre depth. 1 cm ~ = 6 mg dry weight m -3

DISCUSSION

(18)

55 ~

5 4 ~

9

m

9 m

m m 9 N( "

~ " = 40 mg m -3

~ ,

5==="~..~

r

b

7 ~ 8 ~ 9 0

Fig. 21. Abundance of Oikopleura dioica at the different sampling stations in 10 metre depth. 1 crn ~ --- 40 mg dry weight m -3

West of t h e W a d d e n Sea w a t e r lies a " m i x i n g a r e a " with a h i g h e r a m o u n t of neritic c o p e p o d species, a n d the m a x i m u m a b u n d a n c e of Oikopleura dioica. This w a s i d e n t i c a l in 1976 a n d 1982, e v e n t h o u g h the i n v e s t i g a t i o n in 1976 was p e r f o r m e d in N o v e m b e r a n d the latter in A u g u s t - a r e m a r k a b l y stable z o o p l a n k t o n structure in this h y d r o g r a p h i c a l l y v e r y t u r b u l e n t area.

T h e cold b o t t o m - w a t e r of cluster 2 has a r e l a t i v e l y h i g h e r a m o u n t of Oithona similis, Pseudocalanus elongatus a n d Paracalanus parvus. During the i n v e s t i g a t i o n period, the p r e v a i l i n g w i n d s w e r e of a w e s t e r l y direction, c a u s i n g an inflow of "North S e a w a t e r " . As s h o w n by K r a u s e & M a r t e n s (1990), the s p e c i e s in question can p r e f e r a b l y b e f o u n d in the central parts of the N o r t h S e a as o p p o s e d to m o r e neritic s p e c i e s l i k e Acartia sp.

(19)

Z o o p l a n k t o n in the G e r m a n Bight 211

5 5 ~

5 4 ~

9 9 9 m m] r

:

m

9

m

m ,m

m m r .,

" ~ ' = 40 mg m -3

(5"

r

f

o ,

7 ~ 8 ~ 90

Fig. 22. Abundance of Oithona similis at the different sampling stations in 10 metre depth. 1 cm ~ = 40 mg dry weight m -3

high c o n c e n t r a t i o n s i n the Dutch W a d d e n Sea (Giere, 1968). Its o c c u r r e n c e s e e m s to indicate a n inflow of s o u t h - w e s t e r n water into the G e r m a n Bight.

(20)

L I T E R A T U R E C I T E D

Barnes, H., Morris, R. J. & Achituv, Y., 1978. C h a n g e s in the biochemical composition of Balanus balanoides (L.) u n d e r experimental conditions: The effect of a starch diet. - J. exp. mar. Biol. Ecol. 31, 267-281.

Becker, G. A. & Prahm-Rodewald, G., 1980. Fronten im M e e r - Salzgehaltsfronten in der Deutschen Bucht. - Seewart 41, 12-21.

Becker, G. A., Fifiza, A. F. G. & James, I. D., 1983. Water mass analysis in the G e r m a n Bight during MARSEN, Phase I. - J. geophys. Res. CI4, 9865-9870.

Chervin, M. B., Malone, T. C. & Neale, P. J., 1981. Interactions b e t w e e n s u s p e n d e d organic matter a n d copepod grazing in the plume of the H u d s o n River. - Estuar. coast. Shelf Sci. 13, 169-183. Giere, O., 1968. Die Fluktuationen des m a r i n e n Zooplanktons im Elbe-Aestuar. - Arch. Hydrobiol.

(Suppl.) 3I, 379-546.

Hillebrandt, M., 1972. U n t e r s u c h u n g e n fiber die qualitative u n d quantitative Z u s a m m e n s e t z u n g des Zooplanktons in der Kieler Bucht w/ihrend der J a h r e 1966-1968. Diss., Univ. Kiel, 138 pp. Kraefft, F., 1908. Ober das Plankton in Ost- u n d Nordsee u n d d e n V e r b i n d u n g s g e b i e t e n , mit

b e s o n d e r e r Berficksichtigung der Copepoden. - Wiss. Meeresunters. (Abt. Kiel) 11, 29-109. Krause, M. & Martens, P., 1990. Distribution patterns of mesozooplankton biomass in the North Sea.

- Helgol/inder Meeresunters. 44, 295-327.

Kfinne, C., 1937. l)ber die Verbreitung der Leitformen des GroBplanktons in der sfidlichen Nordsee im Winter. - Ber. dt. wiss. Kommn. Meeresforsch. 8, 131-164,

Kfinne, C., 1952. U n t e r s u c h u n g e n fiber das GroBplankton in der D e u t s c h e n Bucht u n d im Nordsylter Wattenmeer. - Helgolfinder Meeresunters. 4, 1-54.

Martens, P., 1975. Ober die Qualitfit und Quantit/it d e r Sekundar- und Terti/irproduzenten in einem m a r i n e n Flachwasser6kosystem der westlichen Ostsee. Diss., Univ. Kiel, 111 pp.

Martens, P., 1978. Contributions to the hydrographical structure of the eastern G e r m a n Bight. - Helgolfinder Meeresunters. 31, 414-424.

Martens, P., 1980. Beitrfige zum Mesozooplankton des Nordsylter Wattenmeers. - Helgol/inder Meeresunters. 34, 41-53.