HELGOL~NDER MEERESUNTERSUCHUNGEN Helgol~nder Meeresunters. 33, 401-414 (1980)
I n v e s t i g a t i o n on health conditions of flounder and smelt
in the Elbe estuary
A. K b h l e r 1 & F. H b l z e l 2
1Zoologisches Institut und Zoologisches Museum, Universit~t Hamburg; Martin-Luther-King-Platz 3, D-2000 Hamburg 13,
and
2 Universit~ts-Krankenhaus Hamburg-Eppendorf, Martinistr. 52; D-2000 Hamburg 20, Federal Republic of Germany
ABSTRACT: Since 1958 the occurrence of flounder (Platichthys flesus L.) and smelt (Osmerus eperlanus L.) in the lower River Elbe has shifted gradually toward the mouth of the river into the North Sea; this may be due to periodical deprivation of oxygen and fluctuating peaks of toxic nitrite concentrations. The interior organs of both fish species caught in the Elbe estuary were examined. Macroscopic inspections revealed discolouring of the liver to be most pronounced in specimens 2-3 years of age. Cross-sections of the liver demonstrated histepathological symptoms of oedematous degeneration in smelt, and extreme lipoid vacuolation in flounder increasing with size and age of the fishes. The intestine of both species investigated showed massive desquamation defects of the mucosa, occurring in smelts shortly after hatching, and in flounders after immigration into the estuary. The observations made suggest the influence of toxic compounds distributed in the aquatic environment on the health of both species.
I N T R O D U C T I O N
For the last 25 years, the River Elbe from H a m b u r g d o w n s t r e a m to its m o u t h h a s b e e n vastly affected b y the c o m m e r c i a l u s e of the w a t e r w a y as m a i n d r a i n a g e c h a n n e l . T h e i n c r e a s e i n t h e d e n s i t y of p o p u l a t i o n a n d of i n d u s t r i a l s e t t l e m e n t s l e d to s e v e r e d a m a g e to the n a t u r a l ecosystem, reflected b y c h a n g e s i n the o c c u r r e n c e a n d d i s t r i b u - t i o n p a t t e r n s of fish species t y p i c a l of the l o w e r Elbe a r e a (Podloucky, 1975; W i l k e n s & K6hler, 1977).
D u e to d a m m i n g a n d the d i s c h a r g e s from d e v e l o p i n g industries, the f l o u r i s h i n g fishery of c o m m e r c i a l l y u t i l i z e d p r i m e fish species s u c h as sturgeon, salmon, a n d h o u t i n g d i m i n i s h e d t o w a r d s t h e e n d of the last c e n t u r y (Bauch, 1958; D u n k e r & Ladiges, 1960). T h e o c c u r r e n c e of e e l - p o u t , l a m p r e y , a n d p e r c h h a s d e c r e a s e d c o n s i d e r a b l y i n the last 15 years (Wilkens & K6hler, 1977). O n l y d u r i n g p e r i o d s of l a r g e w a t e r s u p p l y from the u p p e r E l b e w a s the i n f l u e n c e of the i n d u s t r i a l s e t t l e m e n t s a n d the domestic s e w a g e o n the w a t e r q u a l i t y of the l o w e r Elbe r e d u c e d ; this l e d t e m p o r a r i l y to p a r t i a l r e s t o r a t i o n of p r e - i n d u s t r i a l e c o l o g i c a l c o n d i t i o n s (Wilkens & K6hler, 1977).
T h e p r e s e n t s t u d y w a s p e r f o r m e d i n 1978 w i t h the p u r p o s e of o b t a i n i n g i n f o r m a t i o n o n the state of h e a l t h of Elbe fish as a p o s s i b l e i n d i c a t o r for the w a t e r quality. Of the c o m m e r c i a l l y u s e d fish species w h o s e d i s t r i b u t i o n h a s b e e n i n v e s t i g a t e d i n r e c e n t years, f l o u n d e r (Platichthvs flesus) a n d s m e l t (Osmerus eperlanus) w e r e s e l e c t e d for this study.
402 A. K S h l e r & F. H S l z e l
Both a r e e s t u a r i n e s p e c i e s , d i f f e r i n g in t h e i r s p a w n i n g a n d m i g r a t o r y b e h a v i o u r . T h e s m e l t l i v e s p e l a g i c a l l y , a n d m i g r a t e s as a d o l e s c e n t from its s p a w n i n g a r e a in t h e l o w e r River E l b e d o w n s t r e a m t o w a r d t h e mouth. T h e f l o u n d e r , h o w e v e r , m i g r a t e s in e a r l y s u m m e r from its s p a w n i n g a r e a in t h e s o u t h e r n N o r t h S e a into t h e l o w e r River Elbe, to l i v e as a d e m e r s a l fish in t h e u p p e r l a y e r of t h e r i v e r s e d i m e n t .
T h e i n t e r i o r o r g a n s w e r e a n a l y s e d m a c r o s c o p i c a l l y a n d m i c r o s c o p i c a l l y in o r d e r to r e v e a l p a t h o l o g i c a l h e a l t h c o n d i t i o n s p r i o r to c h a n g e s d e t e c t a b l e b y e x t e r n a l i n s p e c t i o n of t h e fish. F i n e r o s i o n a n d ulcers, l y m p h o c y s t i s a n d e p i d e r m a l p a p i l l o m a s w e r e r e p o r t e d to occur i n fish of v a r i o u s a q u a t i c r e g i o n s h i g h l y p o l l u t e d b y h u m a n r e f u s e (M611er, 1979; S i n d e r m a r m , 1979). It w a s t h e p u r p o s e of this s t u d y to i n v e s t i g a t e t h e b e g i n n i n g a n d t h e c o u r s e of h i s t o p a t h o l o g i c a l a l t e r a t i o n s of t h e i n t e r i o r o r g a n s of f l o u n d e r a n d smelt. T h e e x p o s u r e to E l b e w a t e r at different s t a g e s of the d e v e l o p m e n t w a s a s s u m e d to affect f l o u n d e r a n d s m e l t differently.
M A T E R I A L S A N D M E T H O D S
T h e r e g i o n d o w n s t r e a m of F r e i b u r g , b e t w e e n s t r e a m k i l o m e t e r 695 a n d 723 w a s c h o s e n as c o l l e c t i o n site (see Fig. 2). S a m p l e s of fish w e r e t a k e n at t h r e e different locations: (I) at M e d e m S a n d across from C u x h a v e n , s t r e a m k i l o m e t e r 720; {2) in m i d s t r e a m , o p p o s i t e t h e n u c l e a r p o w e r p l a n t at Brunsbfittel, s t r e a m k i l o m e t e r 693; (3) at t h e fine r a k e of t h e i n f l u x of t h e c o o l i n g s y s t e m in t h e n u c l e a r p o w e r p l a n t of Brunsb/ittel. For c a t c h e s in t h e o p e n river, a d r a g n e t ( " B a u m k u r r e , " 3 m w i d e , m e s h size of 18 nm) w a s u s e d .
S a m p l e s w e r e c o l l e c t e d from M a y to N o v e m b e r ; this e x c l u d e d p h y s i o l o g i c a l a l t e r a - tions of t h e i n t e r i o r o r g a n s d u e to t h e s t a g e s of l o w food i n t a k e d u r i n g w i n t e r a n d to s e a s o n a l shifts of t h e g o n a d a l d e v e l o p m e n t in s p r i n g (Weis, 1972).
I m m e d i a t e l y after h a u l i n g , t h e fish w e r e k i l l e d a n d , u p o n d i s s e c t i o n , the i n t e r i o r o r g a n s w e r e e x a m i n e d b y m a c r o s c o p i c i n s p e c t i o n . S m a l l p i e c e s of liver, k i d n e y , s p l e e n , a n d t h e g a s t r o - i n t e s t i n a l tract w e r e r e m o v e d i m m e d i a t e l y from the f r e s h l y k i l l e d fish, a n d p r e s e r v e d in p h o s p h a t e - b u f f e r e d 4 % formalin. A f t e r fixation, t h e s p e c i m e n s w e r e p r o c e s s e d b y c o n v e n t i o n a l h i s t o l o g i c a l p r o c e d u r e s , a n d e m b e d d e d in p a r a f f i n (Para- plast, S h e r w o o d , M e d . I n d u s t r i e s , St. Louis, Mo.). S l i c e s (5 ~m) w e r e cut w i t h a r o t a t i o n a l m i c r o t o m e (Porter-Blum, S o r v a l l Inc., N e w t o w n , Conn.), s t a i n e d in M a y e r ' s H e m a l u m (Merck, D a r m s t a d t ) for 5 rain, i n 0.i % a q u e o u s Eosin (Merck) for 20 min, a n d f i n a l l y e m b e d d e d in E u k i t t (Kindler, F r e i b u r g ) . M i c r o p h o t o g r a p h s w e r e t a k e n on K o d a k P a n a t o m i c - X film.
In total, i 0 0 f l o u n d e r s a n d 90 s m e l t s w e r e e x a m i n e d b y m a c r o s c o p i c or m i c r o s c o p i c i n s p e c t i o n . F l o u n d e r s w e r e s o r t e d into 3 to 5, 6 to 8, I i to 19, a n d 20 to 31 c m l e n g t h groups. S m e l t s w e r e d i v i d e d into g r o u p s of 4 to 5, 6 to 8, i 0 to 15, a n d 16 to 24 cm. The first two g r o u p s r e p r e s e n t e d t h e y o u n g fish h a t c h e d in the y e a r of t h e i r c a p t u r e . T h e t h i r d a n d t h e fourth g r o u p s c o n t a i n e d fish of one year, a n d two y e a r s of a g e a n d older, r e s p e c t i v e l y .
H e a l t h c o n d i t i o n s of f l o u n d e r a n d s m e l t i n t h e Elbe e s t u a r y 403
RESULTS
Oxygen and nitrogen concentrations of the l=.lbe water
T h e w a t e r q u a l i t y of a river c a n b e r e c o g n i z e d e a s i l y b y d e t e r m i n a t i o n s of o x y g e n a n d i n o r g a n i c n i t r o g e n concentrations 9 By t h e s e criteria, a n d e s p e c i a l l y d u r i n g t i m e s of low w a t e r flow, the m u n i c i p a l a r e a of H a m b u r g exerts a n e n o r m o u s i n f l u e n c e o n the c o n d i t i o n s of the River Elbe. T h e r e s u l t i n g s e a s o n a l o x y g e n d e p r i v a t i o n s c a n b e l e t h a l to t h e m a j o r i t y of o r g a n i s m s .
D u r i n g p e r i o d s of l a r g e w a t e r s u p p l i e s from the u p p e r Elbe, the w a t e r q u a l i t y d o w n s t r e a m from H a m b u r g m a y b e i m p r o v e d . As e x a m p l e s , two w a t e r - q u a l i t y l e n g t h profiles are s h o w n i n F i g u r e 1. At a w a t e r flow of 398 m3/s, the River Elbe c o n v e y e d r e l a t i v e l y l a r g e c o n c e n t r a t i o n s of i n o r g a n i c n i t r o g e n at S c h n a c k e n b u r g . T h e o x y g e n c o n t e n t i m p r o v e d from 45 % to 63 ~ s a t u r a t i o n b e t w e e n s t r e a m k i l o m e t e r s 550 a n d 610. In the H a m b u r g port r e g i o n (St. Pauli), a d e c r e a s e of NH4 + - l e v e l s a n d a n i n c r e a s e of NO2- a n d NO3- w e r e o b s e r v e d o b v i o u s l y c a u s e d b y i n t e n s i f i e d n i t r i f i c a t i o n processes. NH4 + c a n b e o x i d i z e d to N O 2- b y b a c t e r i a of the N i t r o s o m o n a s group (Sch6berl & E n g e l , 1964). T h e e x t r e m e i n c r e a s e of u n s t a b l e nitrite, m e a s u r e d at H a m b u r g St. P a u l i (stream- k i l o m e t e r 625), w a s followed b y c o n t i n u o u s o x i d a t i o n to n i t r a t e i n v o l v i n g s i g n i f i c a n t o x y g e n c o n s u m p t i o n , p o s s i b l y c a u s e d b y the activity of Nitrobacter s p e c i e s (Boon & Laudelout, 1962; SchSberl & Engel, 19621). Thus, o x y g e n l e v e l s as low as 20 % of
KM 7 0 0 Z I.U > T X (.9
F
~ ~ ~ , . %i
i
650 600 550 500
I
o o T z z z
9 Q ) - 6
0 [ 0
mg/t
t ' %~.1 \ t ~ ",
J
650 600 550 500
~o
o
0
0
o KM 700 ':'/o 0 2
Z ILl < T X
0 i I D r~ ~- D D
D D I 0 ~ CO ~ D < 0 LU
v ~ ~ D ~ I
I 9 I ~ "I-
UD CO
Fig. 1. Oxygen and nitrogen profiles between Schnackenburg and Cuxhaven during high or better than average water influx from the upper Elbe Aver. Concentration of NH4 + - , N O 2 - - - -
NO3-- . . . . in mg/1. Oxygen content in % of saturation III . The water flow was measured at Darchau and at the temperature of 19.3 ~ Left: water flow of 1280 m3/s on July 10/11, 1958. Right: water flow of 398 m3/s on July 9/10, 1963 (data provided by "Untersuchungsstelle ffir die Wasser-
404 A. K 6 h l e r & F. H S l z e l
s a t u r a t i o n w e r e m e a s u r e d in t h e a r e a b e t w e e n H a m b u r g a n d G l i i c k s t a d t . D o w n s t r e a m t o w a r d t h e m o u t h of the river, the o x y g e n c o n t e n t r e g e n e r a t e d to 80 ~ s a t u r a t i o n , m e a s u r e d at C u x h a v e n .
In a d d i t i o n to t h e n i t r o g e n i n f l u x from t h e u p p e r Elbe, a n d e s p e c i a l l y d u r i n g low a m o u n t s of w a t e r s u p p l y , the c o n c e n t r a t i o n of i n o r g a n i c n i t r o g e n a p p e a r s to i n c r e a s e c o n s i d e r a b l y in the r e g i o n d o w n s t r e a m of H a m b u r g , i n d i c a t e d b y N O 3- l e v e l s e x c e e d i n g 20 rag/1. S i n c e t h e a v e r a g e of t h e m e d i a n l e v e l s of t h e w a t e r flow in s u m m e r of the y e a r s 1951 to 1970 w a s 270 m3/s, m e a s u r e d at D a r c h a u , o x y g e n s t a r v a t i o n p e r i o d i c a l l y t o o k p l a c e in t h e a r e a from H a m b u r g to G l f i c k s t a d t ( W a s s e r g i i t e s t e l l e H a m b u r g , p e r s o n a l c o m m u n i c a t i o n ) .
O n t h e left p a n e l of F i g u r e 1 o x y g e n a n d n i t r o g e n c o n c e n t r a t i o n s at a p e r i o d of h i g h w a t e r i n f l u x from t h e u p p e r E l b e r i v e r a r e p r e s e n t e d . T h e e n l a r g e m e n t of the w a t e r v o l u m e r e s t o r e d t h e o x y g e n l e v e l s to a b o u t 65 % s a t u r a t i o n in t h e H a m b u r g area. As e x p e c t e d , t h e N O 3- c o n c e n t r a t i o n i n c r e a s e d in t h e r e g i o n of H a m b u r g from 10 to 15 rag/1. But a d d i t i o n a l n i t r o g e n i n f l u x w a s o b v i o u s l y not e n o u g h to i n d u c e o x y g e n s t a r v a t i o n in the d o w n s t r e a m a r e a from H a m b u r g to Glfickstadt. T h e l e v e l s of NH4 + a n d N O 2- s t a y e d low at a r o u n d 2 a n d 0.2 mg/1, r e s p e c t i v e l y ; o n l y from s t r e a m k i l o m e t e r 640 to 670 w a s a c o n s i d e r a b l e p e a k of n i t r i t e o b s e r v e d ; this w a s p o s s i b l y i n d u c e d b y t h e i n f l u x of the h i g h l y p o l l u t e d t r i b u t a r i e s P i n n a u a n d Krfickau. O v e r the total l e n g t h of t h e l o w e r River Elbe, t h e o x y g e n c o n t e n t d i d not d e c r e a s e s i g n i f i c a n t l y . F r o m G l i i c k s t a d t to t h e m o u t h of the river, t h e o x y g e n l e v e l s e v e n i n c r e a s e d u p to 80 % s a t u r a t i o n .
T h e d a t a on t h e i n t e r d e p e n d e n c e of w a t e r flow a n d n i t r o g e n / o x y g e n c o r r e l a t i o n s are a v a i l a b l e for t h e last 28 y e a r s ( W a s s e r g i i t e s t e l l e H a m b u r g , 1950-1972; A R G E Elbe, 1972-1978). L o n g e r - l a s t i n g i m p r o v e m e n t s of t h e n i t r o g e n / o x y g e n c o n d i t i o n s w e r e con- c o m i t a n t w i t h a b a c k - s h i f t of t h e fish d i s t r i b u t i o n , r e f l e c t e d in a c o n s i d e r a b l e i n c r e a s e of the y i e l d s of f l o u n d e r a n d s m e l t c a u g h t at P a g e n s a n d (K6hler, u n p u b l i s h e d ) .
D i s t r i b u t i o n of f l o u n d e r a n d s m e l t
T h e m a i n l o c a t i o n s w h e r e f l o u n d e r a n d s m e l t w e r e c a u g h t in t h e l o w e r E l b e r e g i o n a n d the y i e l d s of the l a s t 28 y e a r s h a v e b e e n r e p o r t e d p r e v i o u s l y ( W i l k e n s & K6hler, 1977). T h e d i s t r i b u t i o n a r e a s w e r e d e r i v e d from t h e s e data. F i g u r e 2 s h o w s t h a t w i t h i n 20 y e a r s the u p p e r r a n g e s of d i s t r i b u t i o n of t h e two s p e c i e s s h i f t e d g r a d u a l l y t o w a r d t h e m o u t h of t h e River Elbe. T h e m a i n s p a w n i n g a r e a of t h e s m e l t u n t i l 1950 e x t e n d e d from D r a g e ( s t r e a m k i l o m e t e r 592) to P a g e n s a n d ( s t r e a m k i l o m e t e r 660) in the River E l b e ( E h r e n b a u m , 1896; L i l l e l u n d , 1961). F r o m 1958 on, this r e g i o n w a s less i n t e n s i v e l y u t i l i z e d for s p a w n i n g . Until 1965, the m a i n f i s h i n g sites for s p a w n i n g s m e l t w e r e in the a r e a b e t w e e n S c h u l a u a n d t h e m o u t h of t h e t r i b u t a r y Liihe ( s t r e a m k i l o m e t e r 655). T h e r e a f t e r , t h e y i e l d s of s m e l t d e c r e a s e d in this r e g i o n , w h e r e a s t h e y i n c r e a s e d in t h e Oste t r i b u t a r y a n d B r u n s b i i t t e l ( s t r e a m k i l o m e t e r 697). A t t h e p r e s e n t time, this is also t h e m a i n s p a w n i n g a r e a of t h e s m e l t w h i c h h a s s h i f t e d m o r e t h a n 100 k i l o m e t r e s d o w n w a r d from its o r i g i n a l site.
H e a l t h c o n d i t i o n s of f l o u n d e r a n d s m e l t i n the Elbe e s t u a r y 405 f l o u n d e r is c a p t u r e d i n c o m m e r c i a l l y still profitable a m o u n t s has shifted d o w n s t r e a m from Otterndorf, p r e d o m i n a n t l y at M e d e m S a n d i n t h e m o u t h of the River Elbe.
9 n-TERNDORF
:~/ Pagen~nd ~M~RG~
GEESTHACHT
19?9 19"/5 1965 UNTIL 1958
1979 u N T I L 1965 U N T t L 958
BRUNSBI]TTE~L
i'l'~"--''~
{'~
I
HAMBURG
~
GEESTHACHT
/ ~
~
~
R
G
~
~ I U AUto
L
~
~ r ~
1
. 9
.AGE
~J_.q r - ~ ~--," /'-"-.,v---..o. ~
~ v --..-.w,-~ , ~ ' ~ / /
"- ~
. ~
l ~ ' 1 ' ~ ' ~
S M E L T
~
OOTTERNDORF "~/[--.~A~'* t!TADE G
cux~,vEN
. ~
.~
cux~vE,
S
~
~
liLOCATiON
OF SAMPLiNGI
Fig. 2. Upper ranges (arrow) of the main areas of distribution for flounder and smelt in the lower Elbe river from 1958 to 1979
M a c r o s c o p i c e x a m i n a t i o n of t h e l i v e r
After d i s s e c t i o n of the freshly c a u g h t fish of both species, the i n s p e c t i o n of the i n t e r i o r o r g a n s - w h e n c o m p a r e d w i t h fish from t h e River E i d e r - r e v e a l e d a l t e r a t i o n s of the n o r m a l r e d - b r o w n colour of the liver i n a n i m a l s l o n g e r t h a n 6 cm (Table 1). T h e livers of fish older t h a n t h r e e m o n t h s (8 c m a n d longer) w e r e p a t h o l o g i c a l l y d i s c o l o u r e d u p to the stages of y e l l o w white, mostly f o u n d i n fish of 10/11 cm i n total l e n g t h e q u i v a l e n t to 1 y e a r of a g e a n d older. B l e a c h i n g of t h e liver of f l o u n d e r a n d smelt is r e g a r d e d as a v a l u a b l e i n d i c a t o r for severe liver d i s e a s e (Roberts, 1978). Smelt a n d f l o u n d e r c a u g h t i n a r e g i o n of low p o l l u t i o n , t h e E i d e r e s t u a r y i n t h e North Sea, k e p t the n o r m a l r e d - b r o w n colour of the liver to the a g e of 3 - 4 years, t h e t i m e u n t i l w h i c h w e i n v e s t i g a t e d them.
406 A. KShler & F. H S l z e l
Table 1. Age-dependent alterations of colour and infection with nematodes of the livers in flounder and smelt. Numbers of fishes examined are indicated
Flounder Total length (cm)
3-5 6-8 11-19 20-31
liver nematodes liver nematodes liver nematodes liver nematodes
0 red brown 13
1 light brown 1 1
2 orange brown 2 16 10
3 ochre yellow 5 20 8 1 1
4 yellow white 13 2 6 5
X 13 0 8 0 50 20 7 6
Smelt Total length (cm)
4-5 6-8 10-15 16-24
liver nematodes liver nematodes liver nematodes liver nematodes
0 red brown 3 1
1 light brown 1 3
2 orange brown 8 10 4 1 1
3 ochre yellow 1 8 2 1 1
4 yellow white 1 4 1 4 2
E 4 0 13 0 23 7 6 4
H i s t o l o g i c a l f i n d i n g s
T h e i n v e s t i g a t i o n of t h e i n t e r i o r o r g a n s r e v e a l e d that f l o u n d e r a n d s m e l t s h a r e d a n u m b e r of c o m m o n f e a t u r e s i n t h e h i s t o p a t h o l o g i c a l conditions. In t h e i n t e s t i n e , o n e of t h e m i l d e r forms of the h i s t o p a t h o l o g i c a l a l t e r a t i o n s s e e n i n y o u n g fish w a s a m a s s i v e d e s q u a m a t i o n of the e p i t h e l i u m (Fig. 3a). T h e s u b m u c o s a w a s i n f i l t r a t e d o c c a s i o n a l l y w i t h l y m p h o c y t e s , a n d t h e s m a l l i n t e s t i n a l v e s s e l s w e r e c o n g e s t e d . T h e most a g g r a v a t e d c o n d i t i o n s (total u l c e r o u s l e s i o n of the mucosa) w e r e f o u n d in fish o l d e r t h a n t w o months: the a r c h i t e c t u r e of t h e v i l l i w a s l a r g e l y destroyed, t h e i n t e s t i n a l e p i t h e l i u m h a d disap- p e a r e d , a n d b l e e d i n g into t h e l u m e n w a s n o t i c e d f r e q u e n t l y . T h e s e are s y m p t o m s of s e v e r e u l c e r o u s enteritis. E v e n m a c r o s c o p i c i n s p e c t i o n of t h e guts r e v e a l e d s y m p t o m s of t h e d i s e a s e i n d i c a t e d b y a v i s c o u s p u r u l e n t s e c r e t i o n into t h e i n t e s t i n a l l u m e n .
For c o m p a r i s o n , F i g u r e 3b s h o w s parts of t h e i n t e s t i n e of a 3 - y e a r - o l d f l o u n d e r c a u g h t in t h e r e l a t i v e l y u n p o l l u t e d E i d e r estuary. T h e e p i t h e l i a l l a y e r a n d the a r c h i t e c - ture of t h e v i l l i are in e x c e l l e n t condition, a n d g o b l e t cells c a n b e s e e n i n t e r d i s p e r s e d in t h e p r i s m a t i c e p i t h e l i u m .
H e a l t h c o n d i t i o n s of f l o u n d e r a n d s m e l t i n t h e E l b e e s t u a r y 4 0 7
Fig. 3. (a) Cross-section of the i n t e s t i n e of a y o u n g f l o u n d e r (7 cm i n total length), 8 - 1 0 w e e k s after i m m i g r a t i o n into the Elbe river (240 • ). (b) Intestine of a flounder (20 cm in total l e n g t h ) c a u g h t in
t h e E i d e r estuary (240 • }
408 A. K 6 h l e r & F. H61zel
Fig. 4. (a) Disintegration of the lobular structure, and extreme swelling of the liver in smelt (20 cm in total length; 240x). (b) Liver of a smelt caught in the Eider estuary, 21 cm of length equivalent to
3--4 years of age (240 X)
H e a l t h c o n d i t i o n s of f l o u n d e r a n d s m e l t i n t h e E l b e e s t u a r y 409
Fig. 5. (a) Cross-section of a liver of a young flounder (4 cm in total length) caught shortly after immigration into the Elbe river (945 X ). (b) Extreme intracytoplasmic lipoid vacuolation in the liver
of a flounder (21 cm in total length) caught at Brunsbiittel (945 x)
410 A. KShler & F. HSlzel
c y t o p l a s m a r e u n a f f e c t e d . O c c a s i o n a l l y , s i n g u l a r l i p o i d v a c u o l e s a r e s e e n in t h e cyto- p l a s m .
F i g u r e 5a s h o w s t h e l i v e r of a y o u n g f l o u n d e r (5 c m in total l e n g t h ) s h o r t l y after i m m i g r a t i o n into the l~.lbe estuary. T h e h e p a t o c y t e s a r e a r r a n g e d in a r e g u l a r m a n n e r . T h e c e l l u l a r b o r d e r l i n e s , t h e c y t o p l a s m , a n d t h e n u c l e i a r e s h a p e d i n c o n s p i c u o u s l y . A g a i n , few v a c u o l e s are f o u n d i n s i d e the l i v e r cells.
T h e l i v e r of E l b e f l o u n d e r s o l d e r t h a n 1 y e a r is e x t r e m e l y e n r i c h e d w i t h i n t r a c y t o - p l a s m i c v a c u o l e s . In F i g u r e 5b, the c r o s s - s e c t i o n of t h e l i v e r of a f l o u n d e r 21 c m l o n g is p r e s e n t e d . T h e c e l l u l a r structure is l a r g e l y p r e s e r v e d , t h e n u c l e i a n d t h e c e l l u l a r b o r d e r l i n e s a r e m a i n l y u n a f f e c t e d , b u t t h e c y t o p l a s m is d i s p l a c e d to a l a r g e e x t e n t b y v a c u o l e s w i t h d i s t i n c t l i n i n g s . S o m e of t h e v a c u o l e s a r e e v e n l a r g e r t h a n t h e n u c l e i . A s c o u l d b e d e m o n s t r a t e d b y s t a i n i n g w i t h S u d a n Black, all t h e v a c u o l e s w e r e c o m p o s e d of l i p o i d m a t e r i a l . T h e s y m p t o m s s h o w n a r e those of h o m o g e n e o u s l i p o i d v a c u o l a t i o n of t h e l i v e r cells.
D i s t r i b u t i o n of h i s t o p a t h o l o g i c a l a l t e r a t i o n s i n d i f f e r e n t s i z e g r o u p s
T h e i n v e s t i g a t i o n of h i s t o p a t h o l o g i c a l c h a n g e s of t h e i n t e r i o r o r g a n s of f l o u n d e r a n d s m e l t d e m o n s t r a t e d that the t i s s u e s w e r e a f f e c t e d d i f f e r e n t l y in t h e size g r o u p s e x a m i n e d . T h e i n t e r i o r o r g a n s of t h e y o u n g f l o u n d e r s r e v e a l e d no p a t h o l o g i c a l a l t e r a - tions at t h e t i m e of i m m i g r a t i o n from t h e s o u t h e r n N o r t h S e a into the E l b e estuary. E a r l y s t a g e s of t h e d i s e a s e w e r e m a n i f e s t e d in y o u n g f l o u n d e r s a p p r o x i m a t e l y 2 w e e k s after m i g r a t i o n into t h e River Elbe, a l t h o u g h o n l y in 10 ~ of t h e a n i m a l s . E i g h t to t e n w e e k s l a t e r (6-8 c m in total l e n g t h ) the i n t e s t i n e of t h e y o u n g f l o u n d e r s w a s s e v e r e l y d a m a g e d , w h i l e t h e l i v e r s h o w e d o n l y m i n o r h i s t o p a t h o l o g i c a l a l t e r a t i o n s .
In t h e y o u n g e s t a g e g r o u p of s m e l t s (4-5 cm in total l e n g t h ) h i s t o p a t h o l o g i c a l a l t e r a t i o n s in l i v e r a n d i n t e s t i n e w e r e d i a g n o s e d in a l l a n i m a l s , 10 w e e k s after h a t c h i n g ( e s t i m a t e d after L i l l e l u n d , 1961). W i t h a d e l a y of a b o u t 4 - 6 w e e k s {6-8 cm i n total l e n g t h ) m o r e s e r i o u s s y m p t o m s i n d i c a t i n g h i s t o p a t h o l o g i c a l c h a n g e s w e r e f o u n d in the s m e l t s ' l i v e r a n d i n t e s t i n e . In t h e guts, i n f l a m m a t i o n w i t h total u l c e r o u s d e s q u a m a t i o n of t h e e p i t h e l i u m w a s o b s e r v e d in 10 out of 12 a n i m a l s . In this a g e group, t h e l i v e r s of all a n i m a l s w e r e affected. In s m e l t s of two y e a r s a n d older, t h e m o s t s e v e r e d e g r e e of l i v e r d e g e n e r a t i o n , t h e c o a g u l a t i v e type, p r e d o m i n a t e d . S i m i l a r l y , i n f l o u n d e r s 1 y e a r of a g e (11-19 c m i n t o t a l l e n g t h ) t h e p a t h o l o g i c a l a l t e r a t i o n s of i n t e s t i n e , liver, a n d k i d n e y w e r e m o r e s e r i o u s t h a n in y o u n g e r fish. This d e v e l o p m e n t p r o g r e s s e d t o w a r d t h e o l d e s t a g e g r o u p i n v e s t i g a t e d u p to h o m o g e n e o u s v a c u o l a r l i p o i d d e g e n e r a t i o n of t h e liver. In this g r o u p (20-31 cm in total l e n g t h ) 86 % of t h e i n t e s t i n e s a n d 73 0/o of t h e l i v e r s s h o w e d t h e most s e v e r e s y m p t o m s o b s e r v e d .
D I S C U S S I O N
H e a l t h conditions of flounder and smelt in the Elbe estuary 411
addition, though u s u a l l y rather short-lived, the h i g h l y toxic nitrite (Roberts, 1978) which is p r o d u c e d in some parts of the river up to considerable levels m a y influence the distribution and the h e a l t h of the fishes. Presumably, it is the massive pollution b y the u r b a n discharges of the m u n i c i p a l area of H a m b u r g which l e a d s to the p e a k s of nitrite concentrations in the Elbe water. The location of the p e a k s can fluctuate d e p e n d i n g on the amount of w a t e r supply from the u p p e r Elbe (Fig. 1) and on the t i d a l conditions. During the outgoing tide, a nitrite p e a k at s t r e a m k i l o m e t e r 642 h a d b e e n r e p o r t e d by R h e i n h e i m e r (1959); this coincides with the m a x i m u m nitrite concentration during h i g h w a t e r influx (shown in Fig. 1). In addition, the oxidation of nitrite to nitrate b y Nitrobac- ter species m a y be i m p a i r e d b y chemical pollutants, or b y a l k a l i z a t i o n of the Elbe w a t e r (Ulken, 1963}. The stock of flounder and smelt u p s t r e a m of Gliickstadt fluctuates with variations in oxygen and n i t r o g e n concentrations. After massive i n c r e a s e in d e a t h rate, or d o w n s t r e a m migrations of fish several times during the year, the stock of both species b e t w e e n H a m b u r g and Glfickstadt is r e p e a t e d l y r e g e n e r a t e d b y i m m i g r a t i o n of fish from the lower regions of the estuary (KShler, unpublished).
For this reason, the s a m p l e collection for the p r e s e n t investigation was carried out b e t w e e n s t r e a m k i l o m e t e r 695 a n d 723 of the estuary w h e r e a constant occurrence and exposition of both species to the Elbe w a t e r could be expected. In this area, the o x y g e n content was satisfactory, and on a v e r a g e 60 to 80 % of saturation throughout the years 1950 to 1977 (Wassergfitestelle Hamburg, p e r s o n a l communication).
A p a r t from the oxygen conditions of the lower l~lbe, a d e c r e a s i n g g r a d i e n t of pollutants toward the mouth was d e s c r i b e d b y Lichtful~ & Brfimmer (1977). The w a t e r quality of the Elbe from Geesthacht to H a m b u r g Harbour is characterized b y h e a v y metal pollution of levels around 18 p p m for cadmium, 2100 p p m for zinc, and 13 p p m for mercury, m e a s u r e d in the top l a y e r of the Elbe sediment. Downstream from H a m b u r g Harbour, the d e c r e a s i n g levels of h e a v y metals rise a g a i n briefly in the area of Pagen- sand (streamkilometer 660). Then the h e a v y m e t a l pollution g r a d u a l l y diminishes to a p p r o x i m a t e l y 1/10 of the levels m e n t i o n e d above, p r e s u m a b l y b y mixing with less p o l l u t e d sea sediments, during the a l t e r n a t i n g tides (Lichtfult & Briimmer, 1977). Fur- thermore the river is c h a r g e d with seasonally fluctuating levels of p e s t i c i d e s s t e m m i n g from industrial production and agriculture. The extent to which flow of p o l y c h l o r i n a t e d b i p h e n y l s , PCB's, v a r y i n g up to 7.9 ~g/1 m e a s u r e d at s t r e a m k i l o m e t e r 670 (ARGI/l~lbe, 1978), m a y contribute to w a t e r pollution d e p e n d s on the quantity of w a t e r influx from the u p p e r River l~lbe, and p o s s i b l y on the industrial production rates.
412 A. Kbhler & F. H61zel
It is r e m a r k a b l e that in both species the p a t h o l o g i c a l alterations of the interior organs were first noticed in the intestine (K6hler, 1979). This suggests that toxic compounds of the food t a k e n up from the Elbe w a t e r m i g h t be the causative agents for the fish disease. The infestation with n e m a t o d e s was not r e s p o n s i b l e for the liver symptoms observed since the p a t h o l o g i c a l discolouring of the tissue d e v e l o p e d at an earlier age than the infection with parasites (Table 1). From the symptoms and the course of the d i s e a s e observed, a viral or bacterial origin of the d i s e a s e can be excluded.
A n u m b e r of laboratory e x p e r i m e n t s with different toxic compounds, a b u n d a n t l y occurring in aquatic ecosystems, were performed with fish (for review see Sprague, 1971). They were shown to induce p a t h o l o g i c a l c h a n g e s similar to those e s t a b l i s h e d by this investigation. In pinfish
(Lagodon rhomboides)
and spot(Leiostomus xanthurus) the
PCB Arochlor 1254 caused extreme lipoid vacuolation of the p a r e n c h y m a l cells of the liver, a c c o m p a n i e d b y sinusoidal congestion, focal necrosis, and inclusions of p i g m e n t (Hansen et al., 1971). The coagulative type of r a i n b o w trout liver d e g e n e r a t i o n could be i n d u c e d e x p e r i m e n t a l l y by the exposition to Lindane (Couch, 1975). The e x p e r i m e n t a l exposure of trout to levels of a m m o n i a of 1.6 p p m for 9 to 12 months l e d to d e g e n e r a t i v e alterations in the liver i n c l u d i n g cellular shrinkage, focal necrosis and dilatation of the sinusoids. In the intestinal mucosa, m i l d necrosis and sloughing were d e s c r i b e d (Smith & Piper, 1975). Levels of a m m o n i a around 2 p p m are m e a s u r e d in the River Elbe regularly~, (ARGE Elbe, 1978). The levels fluctuate, d e p e n d i n g on nitrification processes and seasonal influences. It remains to be seen in future studies w h e t h e r the a m m o n i a content of the Elbe w a t e r is r e s p o n s i b l e for the histopathological alterations of intestine and liver observed in our investigation. The histological e x a m i n a t i o n of the intestine of salmon following exposure to DDT in the w a t e r r e v e a l e d an inflammation with infiltration of lymphocytes into the submucosa (King, 1962; Marthur, 1962). N a p h t h a l e n e , a toxic compound of crude oil, caused necrosis and sloughing of the intestinal mucosa (DiMichele & Taylor, 1978). Pathological alterations of the liver can b e also i n d u c e d b y injection or oral a d m i n i s t r a t i o n of h e a v y metals. For example, the injection of methyl mercury caused necrosis in the liver of channel catfish
(Ictaluous punctatus)
(Kendall, 1977). The exposure to crude oil led to lipoid vacuolation of m o d e r a t e to h e a v y extent in sole(Solea solea)
liver (Hawkes, 1978). The p a t h o l o g i c a l effects were m o d u l a t e d by the p r e s e n c e of the trace metals l e a d and cadmium, occurring in p e t r o l e u m (Varanasi, 1978).The data c o m p i l e d b y S i n d e r m a n n (1979) and M611er (1979) were m a i n l y b a s e d on observations of external fish diseases caused b y the p o l l u t e d aquatic environment. Alterations of the interior organs m a y p r e c e d e externally visible diseases. However, during our investigation, macroscopical alterations of the skin and the cutaneous organs were not found. Thus, inspection of the interior organs even in young specimens using histological techniques obviously yields more sensitive results concerning fish diseases than macroscopical examination.
H e a l t h c o n d i t i o n s of f l o u n d e r a n d s m e l t i n t h e E l b e e s t u a r y 413
t w o s p e c i e s i n t h e i r p r e s e n t h a b i t a t s w i l l b e e n d a n g e r e d i n f u t u r e . T h e r e s u l t s o b t a i n e d i n d i c a t e t h a t t h e d i s t r i b u t i o n a n d t h e h e a l t h of t h e t w o f i s h s p e c i e s i n v e s t i g a t e d a r e
v a l u a b l e b i o l o g i c a l i n d i c a t o r s of t h e w a t e r q u a l i t y i n t h e R i v e r E l b e a n d i t s e s t u a r y .
Acknowledgements. We w i s h to t h a n k the "Wassergfitestelle H a m b u r g " for p r o v i d i n g the data on the o x y g e n a n d n i t r o g e n concentrations of the Elbe water. The m a n y e n c o u r a g i n g discussions w i t h H. Wilkens, Zoologisches Institut u n d Museum, a n d M. Dietel, Pathologisches Institut, Universit~its- K r a n k e n h a u s H a m b u r g - E p p e n d o r f , are gratefully a c k n o w l e d g e d . The f i s h e r m e n of the lower Elbe r e g i o n w e r e of great h e l p in p r o v i d i n g s a m p l e s of fish a n d exact data on the locations of fishery.
L I T E R A T U R E C I T E D
ARGE Elbe (Arbeitsgemeinschaff zur R e i n e r h a l t u n g der Elbe), 1978. W a s s e r g t i t e d a t e n der Elbe. Ed. by Wassergtitestelle Eibe, Hamburg, 44-84.
Bauch, G., 1958. U n t e r s u c h u n g e n tiber die Grtinde des Ertragsrfickganges der Elbfischerei zwi- s c h e n E l b s a n d s t e i n g e b i r g e u n d Boizenburg. - Z. Fisch. 7, 161-437.
Boon, B. & Laudelout, H., 1962. Kinetics of nitrate oxidation by Nitrobacter winogradskii. -
Biochem. J. 85, 440-447.
Couch, J. A., 1975. Histopathoiogical effects of p e s t i c i d e s a n d related chemicals in livers of fishes. In: The pathology of fishes. Ed. by W. E. Ribelin & G. Migaki. Univ. Wisconsin Press, Madison, Wisc., 559-584.
DiMichele, L. & Taylor, M. H., 1978. Histopathoiogical a n d physiological r e s p o n s e s of Fundulus heteroclitus to n a p h t h a l e n e exposure. - J. Fish. Res. Bd Can. 35, 1060-1066.
Dunker, G. & Ladiges, W., 1960. Die Fische der Nordmark. - Abh. Verb. naturw. Vet. H a m b u r g (Suppl.) 3, 1-432.
E h r e n b a u m , E., 1896. Beitr/ige zur Nafurgeschichte e i n i g e r Elbfische. - Wiss. Meeresunters. (Helgoland) I, 54-63.
Hansen, D. J., Parrish, P. R., Lowe, J. I., Wilson, A. J. Jr. & Wilson, P. D., 1971. Chronic toxicity, uptake, a n d retention of Arochlor 1254 in two estuarian fishes. - Bull. environ. Contain. Toxicol. 6, 113-119.
Hawkes, J. W., 1978. Morphology. In: Marine biological effects of OCS p e t r o l e u m d e v e l o p m e n t . Ed. by D. A. Wolfe. Boulder, Colorado, 87-94. (NOAA Technical M e m o r a n d u m ERL OCSEAP-1.) Kendall, M. W., 1977. Acute effects of methyl mercury toxicity in c h a n n e l catfish (Ictaiurus
punctatus) liver. - Bull. environ. Contain. Toxicol. 18, 143-151.
King, S. F., 1962. Some effects of DDT on t h e g u p p y a n d the b r o w n trout. - Spec. scient. Rep., Fish. Wildl. Serv. (Fisheries) 399, 1-22.
Kfhler, A., 1979. Pathologische Ver~inderungen der i n n e r e n O r g a n e von Fiunder (Platichthys flesus) u n d Stint (Osmerus eperlanus) in der Untereibe. - Verb. dtsch, zool. Ges. 1979, 245. LichtfuB, R. & Brfimmer, G., 1977. S c h w e r m e t a i l b e l a s t u n g yon E i b e - S e d i m e n t e n . - Naturwissen-
schaften 64, 122-125.
Lillelund, K., 1961. U n t e r s u c h u n g e n tiber die Bioiogie u n d Populationsdynamik des Stintes,
Osmerus eperlanus (L. 1758) d e r Elbe. - Arch. FischWiss. 12, 1-128.
Marthur, D. S., 1962. Studies on the histopathologic c h a n g e s i n d u c e d by DDT in liver, k i d n e y a n d intestine of certain fishes. - Experientia 18, 506-509.
M611er, H., 1979. G e o g r a p h i c a l distribution of fish diseases in the NE Atlantic. - Meeresforsch. 27,
217-235.
Mossewitsch, N. A., 1961. Sauerstoffdefizit an d e n Fitissen des w e s t s i b i r i s c h e n Tieflandes, seine U r s a c h e n u n d Einfltisse auf die aquafische Fauna. - Verh. int. Verein. theor, angew. Limnol. 14,
447-450.
Podloucky, R., 1975. Der N i e d e r e l b e r a u m - Industrie contra Natur. - H e i m a t 82, 181-190. Rheinheimer, G., 1959. Mikrobiologische U n t e r s u c h u n g e n tiber d e n Stickstoffhaushalt der Elbe. -
Arch. Mikrobiol. 34, 358-373.
Roberts, R. J., 1978. Fish pathology. Baillifre Tindall, London, 278.
414 A. K S h l e r & F. H 5 1 z e l
Sindermann, C. J., 1979. Pollution-associated diseases a n d abnormalities of fish a n d shellfish: A review. - Fish. Bull. 76, 717-749.
Smith, C. E. & Piper, R. G., 1975. Lesions associated with chronic exposure to ammonia. In: The pathology of fishes. Ed. by W. E. Ribelin & G. Migaki. Univ. Wisconsin Press, Madison, Wisc., 497--514.
Sprague, J. B., 1971. M e a s u r e m e n t of pollutant toxicity. 3. Sublethal effects a n d safe concentrations. - Water Res. 5, 245-266.
Ulken, A., 1963. Die I-terkunft des Nitrits in der Elbe. - Arch. Hydrobiol. 59, 486-501.
Varanasi, U., 1978. Biological fate of metals in fish. In: Marine biological effects of OCS p e t r o l e u m d e v e l o p m e n t . Ed. by D. A. Wolfe. Boulder, Colorado, 41-53. (NOAA Technical M e m o r a n d u m I~RL OCSEAP-I.)
Weis, P., 1972. Hepatic ultrastructure in two species of normal, fasted a n d gravid teleost fish. - A m . J. Anat. 133, 317--332.
