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Polychlorinated biphenyls in oystercatchers (Haematopus ostralegus) from the oosterschelde (Dutch Delta area) and the Western Wadden Sea, that died from starvation during severe winter weather
Environmental Pollution 71 ( 1991 ) 1-16 ~'~. ~'/~1
Polychlorinated Biphenyls in Oystercatchers (Haematopus ostra/egus) from the Oosterschelde (Dutch Delta area) and the Western Wadden Sea, that Died from Starvation During Severe Winter Weather*
R. H. D. Lambeck, J. Nieuwenhuize & J. M. van Liere Delta Institute for Hydrobiological Research, Vierstraat 28, 4401 EA Yerseke, The Netherlands (Received 17 July 1990; revised version received 19 October 1990; accepted 25 October 1990)
ABSTRACT Wintering oystercatchers ( H a e m a t o p u s ostralegus), charadriid shorebirds that chiefly feed on intertidal bivalves, suffered mass mortality in The Netherlands during severe frosts in 1986 and 1987. PCBs were analysed in liver and (partially) brain lipids of 96 birds to examine the influence of age (three categories), sex and wintering area (the Oosterschelde estuao' versus the westernmost Wadden Sea) on levels, and the risk of intoxication due to starvation. Victims had lost nearly 40% of their normal winter weight. PCBstructures were similar in aU age/sex categories, and in both areas. Sex did not affect total PCB-concentrations. First-winter Wadden birds had lower levels than subadults and adults, but an age-d(fference was absent in the Oosterschelde birds. Some juvenile outliers possibly originated from polluted breeding areas. Individual variation was considerable in most categories. Relevant ecological factors are discussed. A lthough a dam has considerabO' reduced the direct transport of PCBs into the Oosterschelde since 1969, contamination qf local birds was hardly lower than in Wadden winterers. Influx of riverine PCBs into the Oosterschelde from coastal water may have been underrated. Starvation increased liver concentrations by a factor of 35: factors Jbr the hrahl were 56for juveniles and approximately 120for older birds. Considering published lethal levels.for other species, it is doubtful (f PCBs contributed to this winter mortality. * Communication No. 511 of the Delta Institute for Hydrobiological Research. 1
Environ. Pollut. 0269-7491/91/$03"50 © 1991 Elsevier Science Publishers Ltd, England Printed in Great Britain
2
R . H . D . Lambeck, J. Nieuwenhuize, J. M. van Liere
INTRODUCTION Persistent chemicals, such as PCBs, are potentially toxic to animals. Many of the analytical studies of marine biota concentrate on fish and bivalves, in particular mussels, as human food (cf. Phillips, 1978; Holden, 1981; Franklin, 1987; Tanabe et al., 1987). In most estuaries and coastal bays, birds are the main predators of these two animal groups. A comparison of congener composition and total burden of PCBs in these birds on the one hand, and in their food on the other, may provide an insight into metabolism and biomagnification processes. A relatively large effort has been put into studies of fish-eating birds (Koeman et al., 1972; Parslow & Jefferies, 1973; Falandysz & Szefer, 1984; Hoffman et al., 1986; Borlakoglu et al., 1988), but little is known about PCBs in marine waders (Charadrii) that feed on macrozoobenthos along shorelines and, particularly, on tidal flats exposed during ebb tides (e.g. de Voogt et al., 1985). A problem of studies on most wader species, however, is their extensive migratory movements, with prolonged stops in many estuaries en route (Pienkowski & Evans, 1984). In contrast, the proportion of long-distance migrants among the c. 400000 oystercatchers (Haematopus ostralegus) that winter in The Netherlands is small (Hulscher, 1981; Lambeck et al., unpublished). After the breeding season adults usually return to the same feeding area in the same estuary each year. They stay there for the next 6-8 months (Lambeck et al., unpublished; see also Symonds et al., 1984). Contaminant levels in oystercatchers are, therefore, more easily attributable to specific feeding areas than is the case for most other wader species (cf. de Voogt et al., 1985). IX
Fig. 1.
WADDEN SEA ~ . . , ~
Location of the two study areas. Arrow indicates the Volkerakdam, mentioned in the text.
PCBs in starved oystercatehers
3
During harsh frost, waders can be forced to metabolize part of their fat reserves, which raises the concentrations of PCBs in vital organs, such as liver and brain. A large mortality of oystercatchers during the severe winters of 1986 and 1987 allowed us to consider: (1) the possibility of intoxication under such circumstances, (2) the impact of age category and sex on PCB burdens, and (3) the significance of local conditions by comparing victims from the Oosterschelde in the so-called Delta area (SW Netherlands) with those of the westernmost Dutch Wadden Sea. The Oosterschelde used to be one of the estuarine branches of the rivers Rhine and Meuse; a dam broke the direct connection in 1969. The impact of these rivers on the Wadden Sea, via a tributary (River IJssel and Lake IJssel) on the one hand, and via the residual northwards current along the Dutch coast on the other, remained unchanged over recent decades. Such a comparison may provide more insight into the persistence of PCBs in the estuarine environment.
MATERIAL AND METHODS
Collection of oystercatchers Corpses used in this study were collected at high-water roosts along the central and eastern Oosterschelde in February 1986 and the western Wadden Sea in January 1987 (Fig. l). At least 5100 of the 90000 Oosterschelde oystercatchers died in February 1986. This large mortality was a strictly local phenomenon, due to a combination of prolonged icy weather and a reduced tidal amplitude during the construction of a stormsurge barrier (Lambeck, 1989). To study the effects of this barrier on waders, c. 17 000 oystercatchers had been ringed between August 1984 and February 1986. Of the 288 that starved to death in our collection area, 84% were found near the place of ringing. Only a few birds left the Oosterschelde, as shown by ring recoveries and counts. Data support, therefore, the assumption that our sample of victims reflects the contamination conditions in the Oosterschelde. The cold spell in mid-January 1987 induced a large 'winter rush' out of the Wadden Sea, mainly to France (Hulscher, 1989). As shown by ring data (Swennen, C., 1989, pers. comm.), migrants died at North Sea Beaches and not at roosts near normal feeding areas where our birds were collected. So, victims from the Wadden Sea can be presumed to reflect the local contaminant conditions too. Collected birds were split into six categories based upon differences of sex (assessed by dissection) and age (three classes that can be distinguished by plumage and colour of eyes, bill and legs: (1)juveniles are first-winter birds,
4
R . H . D . Lambeck, J. Nieuwenhuize, J. M. van Liere
so about 7 months old, (2) subadults are birds in their second and third winter, and (3) adults are birds in their fourth winter or older). Eight oystercatchers of each category were analysed, giving a total of 96 birds for the two areas combined.
Analytical treatment A thawed corpse was weighed before liver and brain (only in Wadden Sea birds) were dissected with pre-cleaned stainless steel knives. Organs were freeze-dried, ground and homogenized in an agate grinder, and subsequently extracted with n-pentane in a rnicro-soxhlet. After evaporation at 50°C to constant weight, the extractable lipids were determined. After dissolution in hexane and a dual-step clean-up over A1203, a gas chromatography analysis was carried out on a United Instruments Packard 438A with ECDs, automatic injection and fused silica capillary columns CPSil 8CB of 50 m × 0.22 mm with a film of 0-12/~m. Congeners, indicated by their IUPAC number, are defined according to Ballschmiter & Zell (1980). Identification of chromatogram peaks was based on the retention time of standard congeners. Use of a conditioned room contributed to very stable retention times (variation within 0.02 rain). Recovery of a test congener, added at the start of the processing procedure of a sample, was 95-6 + SD 3.1% (N=5). The repeatability and accuracy of assessed congener concentrations were confirmed in an international intercomparison exercise. PCB concentrations are expressed in #g g- 1 pentane-extractable lipids. The efficiency of fat extraction by n-pentane and other methodological details are discussed in Duursma et al. (1986). RESULTS
Weight losses Body weights of the winter victims in the Oosterschelde (Delta) and the Wadden Sea were similar, about 310 g for the smaller-sized juveniles, 350 g for subadult and adult females and 330g for the males. Given a normal midwinter weight of approximately 570 g for adults, 530 g for subadults and 495 g for juveniles (Swennen & Duiven, 1983; Lambeck et al., in prep.), oystercatchers that starved to death lost nearly 40% of their normal weight. In none of the birds was there any visible depot fat left.
Individual congeners The average congener structure in brain and liver were similar in all Wadden categories, as illustrated for adults by Fig. 2. The patterns in livers of
PCBs in starved oystercatchers 10-
* male o female
c ~o c_
c_ 4J c oJ u c o u
5
o /
8-
or
,
4
2
0
~
.
i
i0
,
r
20 3'0 CB concentration
4'0 lzver
5'0
Fig. 2. The relation between the concentration (in/~gg- ' pentane-extractable lipid) of each of the PCB congeners in liver and brain of starved adult male and female oystercatchers (mcan values of eight birds) from the western Wadden Sea; also drawn calculated regression 3'=0'169 x-0.18 (r = 0"99). W a d d e n and Delta birds also showed a large resemblance. Two hexachlorobiphenyls (IUPAC numbers 138 and 153) were by far the most important congeners, each comprising about 20% of the total PCB concentration. Next came the penta-CB 118 and the hepta-CBs 180 and 187, each fluctuating around 10% of total PCB concentration. With the exception of the juvenile Delta males, these five congeners made up, on average, 75% (70-79%) of the PCB burden in the different oystercatcher categories (Table 1). In the Delta birds, the share of the two major congeners CB-138 and CB-153 increased from 34% in juveniles to 45% in older individuals (Mann-Whitney U-test, two-sided p < 0.01). This is the reverse of the pattern in W a d d e n birds, which had 47% in juveniles and 37"5% in subadults and adults (p < 0.01; Table 1). The contribution of the CBs 118, 180 and 187 was fairly stable in the Delta birds (c. 32%) and, moreover, was similar to that in the W a d d e n subadults and adults (Table i). In the Wadden juveniles, their level was slightly reduced (c. 28%). Mono-tetra CBs hardly occurred in the oystercatcher (Table 2). Only the tri-CB 26 had a significant contribution, about 3% o f the total PCB concentration, in the Delta juveniles. It dropped to 0-7% in older specimens, however. The overall importance of this congener was negligible in the W a d d e n birds. Distinct patterns in other congeners were absent. Considering the good resemblance in PCB-patterns between Wadden and Delta birds, total PCB values can be used as an index of the degree of contamination in the different categories.
Liver Log-transformed total PCB values (to obtain a normal distribution) for the individual birds were subjected to an analysis o f variance to assess the
0
R . H . D . Lambeck, J. Nieuwenhuize, J. M. van Liere
TABLE I
Composition of Major Congeners (in % of total PCB) in the Liver Lipids of Three Age Categories (n = 8) of Starved Oystercatchers from the Oosterschelde in the Dutch Delta Area (D) and from the Western Wadden Sea (W) IUPA C ttttmber
Age categorr Jueeniles
138 153 180 187 118
170 183 128 26 209 105 95 194 101 Total 0%
Adults
D
W
D
W
D
W
17'9 16"0 12"8 10"2 9"4 6"2 5"2 3"9 2"9 2"8 2"3 2"1 1"1 1"0
23"7 23"2 7"0 10"9 9"9 3"0 3"6 3"9 0"9 1"1 2"4 1"8 0"5 0'7
21"8 21"9 12"0 10'0 9"9 4'5 6"1 4"2 0"7 1"4 2"3 0'8 0'7 0"4
19"7 18"6 9"9 11"6
22"4 24"6 10"4 10-0 8-2 4-3 5-6 3"6 0"5 2"0 2'0 0"9 1'2 0"5
18"6 18"4 11-4 11"8
93.8
600
-
92.6
96'7
12"2
5"3 5"5 4-9 0'4 1'8 2"7 1"2 0"9 0'5 95.2
96.2
11 "7
4'8 5'2 5"0 0"4 1"8 2"8 1"3 1-0 0-5 94-7
L i vet o
50O
"7
Subadults
o •
40O o
@
•
JUV
F SUB
M
o o
20oD,_ l-4
loo OdUV
M
SUB
AD
AO F
Fig. 3. Mean total PCB liver concentrations in six age/sex categories (M =male, F - female, Juv=juvenile, Sub=subadult, A d = a d u l t ) of starved oystercatchers from the Oosterschelde (hatched column) and the western Wadden Sea (open column); vertical bar = SE. Concentrations for individual birds indicated (A Wadden; O Oosterschelde).
PCBs in starved oystercatchers
7
TABLE 2
Percentage Contribution of Congener Categories to the total PCB Burden in the Liver Lipids of Three Age Categories of Starved Oystercatchers from the Oosterschelde, and in Body Lipids of Local Mussel (Mytilus edulis) in August and Winter (Average of November and January) and Tellin (Macoma balthica) from November. Mollusc Data after Hummel et al. (1990 and unpubl.) Trichloro
Tetrachloro
Oystercatcher juvenile subadult adult
3.2 0"8 0.7
1.3 0.4 0-5
15-2 13-6 11.6
39.7 48.6 51 "3
34.4 32"6 30-3
6'2 3.9 5.5
Mytilus August Winter
6.2 3'5
15-7 11.1
20.5 21.8
45.2 52.3
12.4 11.1
0 0"3
13.4
16-8
24.9
37-1
7.9
Macoma November
Pentachloro Hexachloro Heptachloro
Octadecachloro
0
impact of area, age class and sex. The average total PCB concentration in the livers amounted to ~ 250/~g g-1 pentane-extractable lipids (PEL). There were no overall differences between sexes, and between the Delta and Wadden birds (Fig. 3); significant differences (p < 0.05) were found between age classes, but interpretation is hampered because of interactions (p < 0-05) between sex and area, as well as age class and area. Two factors are involved. First, juveniles from the Wadden Sea had a lower total PCB level than older birds. No such difference was found with oystercatchers from the Delta, where juvenile females contained similar residues to older birds (Fig. 3). Mean values for juvenile males were strongly influenced by two Delta and one Wadden outlier: their concentrations of 470-600/~g g- 1 PEL were the highest found in this study (Fig. 3). Excluding these outliers, mean levels for the Delta juvenile males and the Wadden juvenile males and females were nearly identical at about 135/~g g - i . Secondly, subadult and adult Delta males showed relatively low levels without much variation (mean 209g, range 145-275/lg g-1 PEL). The majority (10 out of 16) of Wadden (sub)adult males had higher concentrations, resulting in a mean of 295/~g g-1 PEL. In contrast, both mean (261 and 247/~g respectively) and range were quite similar for Delta and Wadden (sub)adult females (Fig. 3). Brain
Total PCB levels in the brain lipids of the Wadden Sea oystercatchers were about one sixth of those in the liver lipids (Fig. 4). With an average of
8
R . H . D . Lambeck, J. Nieuwenhuize, J. M. van Liere Brain I00
-3 BO "7
60
--
40
•
t
.
20-
JUV M JUV F SUB M SUB F
AD M
AD F
Fig. 4. Mean (column) and individual total PCB brain concentrations (in #g g- Lpentaneextractable lipids) in six age/sex categories of starved oystercatchers from the western Wadden Sea. See further Fig. 3.
24 llg g- l PEL, juvenile concentrations were lower (Mann-Whitney U-test, p < 0.05) than the 44/tgg -1 in subadults and adults. There were no differences between sexes: the somewhat higher average for juvenile males compared to juvenile females can be completely ascribed to one outlier (Fig. 4). In all categories, a good correlation (r = 0"79; p < 0-001) existed between total PCB values in liver and brain of a single bird (Fig. 5). Data suggest a proportional partitioning between liver and brain over the entire concentration range in juveniles (Fig. 5a). In older birds, the brain held a higher proportion of the body burden at low concentrations (Fig. 5b). laY .
t00 "n '
male • female 0
male female
sub. • []
ad. • A
80
[] A
z[
c
•~
60
o 40
•
m 20
zx
13.. r.-4
o
3Go 4Go ZPCB l i v e r (a)
( ~ g g-i PEL)
6Go
3 o,4o 5Go ZPCB l i v e r
(~g
6OO
g-i PEL)
(b)
Fig. 5. The relation between the total PCB concentration (in pg g-1 pentane-extractable lipid) in the brain and in the liver of (a) starved juvenile O' = 0.139 x + 1.1; r = 0"94) and (b) starved subadult and adult oystercatchers (y=0-096 x + 17"4; r=0"76) from the western Wadden Sea.
PCBs in starvedoystercatchers
9
DISCUSSION The analysis of whole bodies, as carried out in a study of some small wader species (Schick et al., 1987), is not practicable in a large bird such as the oystercatcher. Our results suggest that congener composition and total PCB level in one organ may provide a reliable index of the contamination of the entire individual. This confirms findings of de Voogt et al. (1985) for two small waders, dunlin (Calidris alpina) and knot (C. canutus), and Larsson & Lindegren (1987) for a duck, the red-breasted merganser (Mergus serrator). Congener patterns in bivalves more or less reflect those in the ambient water (Boon et al., 1989). A crude comparison between patterns in oystercatchers and two bivalve prey species (see below) from the Oosterschelde study area shows a distinct shift towards higher chlorinated CBs in the birds (Table2). The major CBs in oystercatcher (Table 1) are persistent, they are characterized by a lack of unsubstituted adjacent metapara H-atoms in the biphenyl skeleton. Details on metabolic aspects are provided by Borlakoglu et al. (1988) and Boon et al. (1989). Individual variation in PCB concentrations
In most categories, PCB concentrations varied considerably between individuals. This is also reported for other bird species (e.g. Borlakoglu et al., 1988). Variation may originate from the breeding area, the wintering area, and the staging areas used en route. Dutch breeders (90000 pairs: nearly 60% of the European mainland population (Piersma, 1986)) and their offspring comprise the majority of the wintering birds in our study areas; the rest originate from an area ranging from Belgium to northern Norway and the White Sea (Hulscher, 1981). Remote northern areas will, in general, be less contaminated than industrialized western Europe. PCB levels in juvenile dunlin and knot, hatched in boreal and arctic habitats indeed rapidly increase during the first months in the Wadden Sea (de Voogt et al., 1985). Our oystercatcher data show an increase in burden between the first and second winter for most individuals. This also results from uptake via marine zoobenthos, because the birds spend their second year entirely in tidal habitats. Apparently, inland prey, predominantly earthworms (Lumbricidae) and insects, are mostly a less important source of contamination. In contrast to inland birds, coastal breeders and their chicks depend partly or entirely on estuarine food. Consequently, besides latitude, the breeding biotope will also contribute to individual variation. The proportion of juveniles hatched in contaminated habitats, such as industrialized port areas and the water-meadows of the River Rhine, is much higher in the Delta than in the Wadden Sea (Lambeck et al., unpublished). If
10
R. H. D. Lambeek, J. Nieuwenhuize, J. M. van Liere
all our Delta juvenile females originated, by chance, from such areas, the higher burdens in this category might be explained. Local pollution of a breeding area is, in fact, the only plausible explanation for the extremely high burdens found in some juveniles (see also Becker, 1989). In a wintering area, there are two potential sources for variation in PCBsuptake: (1) differences in prey choice by individual oystercatchers (cf GossCustard & Durell, 1983) and (2) variability in contamination between individuals of the same prey in different sectors of a feeding area. The mussel M y t i l u s edulis, the cockle Cerastoderma edule and the tellin M a e o m a balthiea are the main food species in our study areas. Locally or temporarily, other molluscs, polychaetes and crustaceans may also be important. Prey species indeed differ in PCB-structure and total burden (Goerke et al., t979; Duinker et al., 1983; de Voogt et al., 1985; Boon et al., 1989; see also Duursma et al., 1986), due to species-dependent differences in the amount of body lipids (Phillips, 1978) or a different potential to metabolize PCBs (Langston, 1978; Boon et al., 1989). When uptake of PCBs by a benthic invertebrate results from equilibrium partitioning between body lipids and the ambient water (Schneider, 1982; Duursma et al., 1986), intraspecific spatial variation may be mediated via a pollution gradient or via systematic differences in feeding conditions and hence lipid contents between subareas, because of, for example, differences in length of the immersion period or in population densities. These aspects deserve more attention. Differences between Oosterschelde and western Wadden Sea
The large resemblance in congener patterns reconfirms the common origin of PCBs in the two study areas, the rivers Rhine and Meuse. About 20% of their discharge, on average 450 m 3 s- 1, enters the Wadden Sea (Duinker et al., 1984). The resultant PCB contamination has deleterious effects, for example on seal reproduction (Reijnders, 1986). Conditions in the Oosterschelde have improved since the construction of the Volkerakdam (Fig. 1) in 1969. The former average Rhine-Meuse discharge of 50m 3 swas reduced by 20% (Anon., 1986) and, of more importance, the transport of suspended matter has largely ended. Adsorbed PCBs constitute 75% of the riverine input (cf Duinker et al,, 1984). This has not resulted in distinctly lower burdens in oystercatchers as compared to the Wadden Sea. There are three possible explanations: (1) (bio)degradation in the sediment pool is very slow, (2) decreasing PCB loads in the rivers during the 1980s (Kerkhoff et al., 1986) have overruled a developing difference between the two areas, and (3) coastal water was, and is, the principal source of contaminants for the Oosterschelde. Rhine-Meuse water constitutes, on average, 10% of the tidal volume in its mouth (Anon.,
PCBs in starved oystercatchers
11
1986); mussels from that sector have indeed higher burdens than mussels elsewhere in the Oosterschelde (Hummel et al., 1990). This aspect warrants further study. Differences between sexes and loss rate
As in our oystercatcher data, a sex difference in PCB-burden is also absent in herring gull (Larus argentatus) (Lemmetyinen et al., 1982) and Adelie penguin (Subramanian et al., 1986). In other species, for example red-breasted merganser (Larsson & Lindegren, 1987; Duursma et al., 1989), arctic tern (Sterna paradisea) (Lemmetyinen et al., 1982) and sparrowhawk (Accipiter nisus) (Newton et al., 1981), adult females have lower levels than males. Although a difference in migration between sexes should be considered too, release via eggs is the obvious explanation for lower female levels. The total clutch weight in relation to body weight is of relevance, but Lemmetyinen et al. (1982) showed, besides, considerable interspecific differences in the efficiency of transferring PCBs into eggs. The amount of PCBs in oystercatcher eggs (e.g. Becker, 1989) is apparently insignificant in the annual budget of this species. Water birds can also excrete PCBs, mainly lower chlorinated congeners, via the lipids of the uropygeal gland (Subramanian et al., 1987; Larsson & Lindegren, 1987). Metabolism and elimination via faeces is the principal mechanism of loss. Loss rates have mainly been studied in experiments based on a short-term administration of a high dosage of a commercial PCB mixture (e.g. Stickel et al., 1984). Conditions are hence unnatural and results will depend also on the composition of the mixture. Little is known about natural loss rates. An estimate for Adelie penguins, that are characterized by low burdens, arrived at 0-26% day -a, implying a half-life of 270 days (Subramanian et al., 1987). From our oystercatcher data a rough estimate of the natural loss rate can be derived when some simplifying assumptions are made: (1) contamination of juveniles starts as soon as they arrive in the estuaries (an average date is taken as 1 August), (2) daily uptake is constant over the year, and (3) a constant fraction of the total body burden is excreted per day. We then have, in general: Ca = C~(1 - e/'la- 60~) where, C~ is the asymptotic total PCB concentration in/tg g- 1 PEL; 2 is the daily loss rate (day- 1); a is the age (days); and 60 is the average age of(Dutch) juveniles at 1 August (Beintema, A. J., 1990, pers. comm.). The average age of subadults at the assumed day of death (1 Feb.) was estimated as 2 years. For adults an approximation must be used; with an annual mortality of 10% (cf Goss-Custard et al., 1982) and a maximal life
12
R. H. D. Lambeck, J. Nieuwenhuize, J. M. van Liere
span of 30years, the average age of an adult in a stable population is 11 years. By applying a non-linear regression (Wilkinson, 1988) to the set of individual Wadden liver data, the daily loss rate was estimated as 0"50% day-x (a half-life of 139 days). For the brain data 0.45% day-1 (153 days) was found. Because the total PCB levels in most of the Delta juveniles were as high as in older birds, which is a violation of our assumptions, no reasonable estimate could be obtained for the Delta birds. Starvation effects
A weight loss of nearly 40% has also been found in other oystercatcher winter mortalities (Swennen & Duiven, 1983). It results from depletion of fat and, partly, protein reserves (Davidson, 1981). In the oystercatcher (Heidmann et al., 1987) as well as in other species (Parslow & Jefferies, 1973; Newton et al., 1981; Fossi et al., 1986; Subramanian et aL, 1986), the bulk of the PCBs in a healthy bird is deposited in the subcutaneous fat. Subramanian et al. (1986) demonstrated a redistribution of PCBs from this adipose tissue to some organs in fasting Adelie penguins. In guillemots (Uria aalge), depletion of reserves hardly changed the total body burden, but the share in the liver increased from a normal 0"9 to 22-5% (Parslow & Jefferies, 1973). A similar twentyfold increase was found in the brain of emaciated loons (Gavia immer) (Frank et al., 1983). In March 1984, a few hundred oystercatchers drowned in the western Wadden Sea. Victims were in good condition; per age/sex category, 4-5 were analyzed. Total PCB levels in the liver were, on average, 4-5 #g g- ~ PEL in juveniles and 8 #g g- 1 in subadults and adults (Everaarts et al., 1991, original data). Figures for our starved Wadden birds were thus 35 times higher in each of the six categories. Levels in the brain of the drowned birds were, on average, 0.42#gg-~ PEL in juveniles and 0.36#g in older individuals, implying concentration factors of 56, 134 and 113, respectively, for juveniles, subadults and adults. Lipids constitute an important structural component in the nervous system. Starvation did indeed not affect the proportion of lipids in the brain of our oystercatchers, while a decrease of 70% was found in the liver (see also Parslow & Jefferies, 1973). Such a difference will contribute to the higher concentration factors found in the brain compared to the liver. Data for healthy birds agree with the different relationship between brain and liver levels found in starved juveniles and (sub)adults (Fig. 5). It is plausible that in juveniles proportionally more of the total body burden goes to the brain, because they have considerably lower fat reserves than older birds. High concentration factors for the latter show that this difference in allocation is partially counterbalanced during starvation.
PCBsinstarved oystercatchers
13
Heidmann et al. (1987) suggest that PCBs contributed to the large winter mortality of oystercatchers in the German Wadden Sea in 1987. Since neither concentrations in extractable lipids and in fresh adipose tissue, nor weight loss and loss of fat, are simple equivalents, they probably overestimated body burdens by at least a factor of two, however. A comparison between our data and burdens found in victims of winter mortalities, in which PCBs were claimed to have played a part (Koeman et al., 1972; Parslow & Jefferies, 1973), and those in experimentally poisoned birds (e.g. Stickel et al., 1984), is difficult, due to methodological differences (see also Phillips, 1978; Duinker et al., 1983). Because of differences in toxicity between individual congeners (Safe, 1984), the PCB-structure is also important. Bird species may furthermore differ in sensitivity (Koeman et al., 1972; Stickel et al., 1984). Healthy wintering grebes (Podiceps cristatus) and mergansers from the Dutch Delta area, with a PCB-structure resembling that of oystercatchers, had about six times higher burdens in the liver than healthy Wadden oystercatchers (Duursma, E. K. & Nieuwenhuize, J., unpublished). Levels of around 500 ppm fresh weight in poisoned passerine birds (Stickel et al., 1984) correspond with at least a few thousand #g g- 1 PEL, an order of magnitude higher than in our starved oystercatchers. It is therefore doubtful that PCBs contributed to the oystercatcher winter mortality. ACKNOWLEDGEMENTS We would like to thank our colleagues from The Netherlands Institute for Sea Research, Texel, for collecting and dissecting the Wadden Sea oystercatchers. A team composed of collaborators from the Delta Institute and the former 'Deltadienst of Rijkswaterstaat', plus some volunteers, collected the frost victims in the Oosterschelde. We especially like to mention E. B. M. Brummelhuis who dissected the selected birds. E. G. J. Wessel was of great help during part of the data processing; he also made the computer graphs. Dr P. M. J. Herman gave statistical advice; special thanks are due for his loss rate calculations. Dr J. P. Boon, Dr J. M. Everaarts and two referees made useful comments on an earlier draft of the manuscript. Dr P. G. Harrison corrected the English. REFERENCES Anon. (1986). De waterkwaliteit van de Oosterschelde. Driemaand. Berichten Deltawerken, 116, 263-71. Ballschmitter, K. & Zell, M. (1980). Analysis of polychlorinated biphenyis (PCBs) by glass capillary gas chromatography. Composition of technical Aroclor- and Clophen-PCB mixtures. Fresen. Z. Anal Chem., 302, 20-31.
14
R. H. D. Lambeck, J. Nieuwenhuize, J. M. van Liere
Becker, P. H. (1989). Seabirds as monitor organisms of contaminants along the German North Sea coast. Helgoldnder Meeresunters., 43, 395-403. Boon, J. P., Eijgenraam, F. & Everaarts, J. M. (1989). A structure-activity relationship (SAR) approach towards metabolism of PCBs in marine animals from different trophic levels. Mar. Environ. Res., 27, 159-76. Borlakoglu, J. T., Wilkins, J. P. G. & Walker, C. H. (1988). Polychlorinated biphenyls in fish-eating seabirds--Molecular features and metabolic interpretations. Mar. Environ. Res., 24, 15-19. Davidson, N. C. (1981). Survival of shorebirds (Charadrii) during severe weather: The role of nutritional reserves. In Feeding and Survival Strategies of Estuarine Organisms, ed. N. V. Jones & W. J. Wolff, Plenum Press, New York, pp. 231-49. Duinker, J. C., Hillebrand, M. T. J. & Boon, J. P. (1983). Organochlorines in benthic invertebrates and sediments from the Dutch Wadden Sea; Identification of individual PCB components. Neth. J. Sea Res., 17, 19-38. Duinker, J. C., Boon, J. P. & Hillebrand, M. T. J. (1984). Organochlorines in the Dutch Wadden Sea. Neth. Inst. for Sea Research Publ. Ser., 10, 211-28. Duursma, E. K., Nieuwenhuize, J., van Liere, J. M. & Hillebrand, M. T. J. (1986). Partitioning of organochlorines between water, particulate matter and some organisms in estuarine and marine systems of The Netherlands. Neth. J. Sea Res., 20, 239-51. Duursma, E. K., Nieuwenhuize, J. & van Liere, J. M. (1989). Polychlorinated biphenyl equilibria in an estuarine system. Sci. Total Environ., 79, 141-55. Everaarts, J. M., de Buck, A., Hillebrand, M. T. J. & Boon, J. P. (1991). Residues of chlorinated biphenyl congeners and pesticides in brain and liver of the oystercatcher (Haematopus ostralegus) in relation to age, sex and biotransformation capacity. Sci. Total Environ., 100, 483-99. Falandysz, J. & Szefer, P. (1984). Chlorinated hydrocarbons in fish-eating birds wintering in the Gdansk Bay, 1981-82 and 1982-83. Mar. Pollut. Bull., 15, 298-301. Fossi, C., Leonzio, C. & Focardi, S. (1986). Mixed-function oxidase activity and cytochrome P-450 forms in Black-headed gulls feeding in different areas. Mar. Pollut. Bull., 17, 546-8. Frank, R., Lumsden, H., Bars, J. F. & Braun, H. E. (1983). Residues of organochlorine insecticides, industrial chemicals, and mercury in eggs and tissues taken from healthy and emaciated common loons, Ontario, Canada, 1968 1983. Arch. Environ. Contam. Toxicol., 12, 641-53. Franklin, A. (1987). The concentrations of metals, organochlorine pesticides and PCB residues in marine fish and shellfish: Results from MAFF fish and shellfish monitoring programmes, 1977-1981. Aquat. Environ. Monitoring Report, MAFF Direct. Fish Res., Lowestoft (UK). Goerke, H., Eder, G., Weber, K. & Ernst, W. (1979). Patterns of organochlorine residues in animals of different trophic levels from the Weser estuary. Mar. Pollut. Bull., 10, 127 33. Goss-Custard, J. D., Durell, S. E. A. le V. dit, Sitters, H. P. & Swinfen, R. (1982). Age structure and survival of a wintering population of oystercatchers. Bird Study, 29, 83-98. Goss-Custard, J. D. & Durell, S. E. A. le V. dit (1983). Individual and age differences in the feeding ecology of oystercatchers Haematopus ostralegus wintering in the Exe estuary, Devon. Ibis, 125, 155-71. Heidmann, W. A., Biithe, A., Peterat, B. & Kntiwer, H. (1987). Zur Frage des
PCBs in starved oystercatchers
15
Einflusses chemischer Riickst~nde auf das Sterben von Austernfischern (Haematopus ostralegus) an der nieders/ichsischen Kfiste im Winter 1986/87. Vogelwarte, 34, 73-9. Hoffman, D. J., Rattner, B. A., Bunck, C. M., Krynitsky, A., Ohlendorf, H. M. & Lowe, R. W. (1986). Associations between PCBs and lower embryonic weight in black-crowned night-herons in San Francisco Bay. J. Toxicol. Environ. Health, 19, 383-91. Holden, A. V. (1981). Organochlorines--An overview. Mar. Pollut. Bull., 12, 110-5. Huischer, J. B. (1981). Oystercatcher (Haematopus ostralegus L.). In Birds of the Wadden Sea, ed. C. J. Smit & W. J. Wolff, Balkema, Rotterdam, pp. 92-104. Hulscher, J. B. (1989). Sterfte en overleving van scholeksters Haematopus ostralegus bij strenge vorst. Limosa, 62, 177-81. Hummel, H., Bogaards, R. H., Nieuwenhuize, J., de Wolf, L. & van Liere, J. M. (1990). Spatial and seasonal differences in the PCB content of the mussel Mytilus edulis. Sci. Total Environm., 92, 155-63. Kerkhoff, M. A. T., de Boer, J., de Vries, A., Otte, P. F., Warnaar, D. & Masereeuw, P. (1986). De PCB verontreiniging van rode aal: Trends in chloorbiphenylgehalten (1977-1985). Report Rijksinstituut voor Visserijonderzoek M O 86-01, IJmuiden (Netherlands). Koeman, J. H., Bothof, T., de Vries, R., van Velsen-Blad, H. & Vos, J. G. (1972). The impact of persistent pollutants on piscivorous and molluscivorous birds. TNOnieuws, 27, 561-9. Lambeck, R. H. D. (1989). Beroven de Deltawerken de steltlopers van hun voedsel? Vogels, 49, 8-12. Langston, W. J. (1978). Accumulation of polychlorinated biphenyls in the cockle Cerastoderma edule and the tellin Macoma balthica. Mar. Biol., 45, 265-72. Larsson, P. & Lindegren, A. (1987). Animals need not be killed to reveal their body burdens of chlorinated hydrocarbons. Environ. Pollut., 45, 73-8. Lemmetyinen, R., Rantam~iki, P. & Karlin, A. (1982). Levels of DDT and PCB's in different stages of life cycle of the arctic tern Sterna paradisea and the herring gull Larus argentatus. Chemosphere, 11, 1059-68. Newton, I., Bogan, J. & Marquiss, M. (1981). Organochiorine contamination and age in sparrowhawks. Environ. Pollut. Ser. A., 2fi, 155-60. Parslow, J. C. F. & Jefferies, D. J. (1973). I~elationship between organochlorine residues in livers and whole bodies of guillemots. Environ. Pollut., 5, 87-101. Phillips, D. J. H. (1978). Use of biological indicator organisms to quantitate organochlorine pollutants in aquatic environments--A review. Environ. Pollut., 16, 167-229. Pienkowski, M. W. & Evans, P. R. (1984). Migratory behavior of shorebirds in the Western Palearctic. In Shorebirds--Migration and Foraging Behavior, ed. J. Burger & D. L. Olla, Plenum Press, New York, pp. 73-123. Piersma, T. (1986). Breeding waders in Europe: A review of population size estimates and a bibliography of information sources. Wader Study Group Bull., 48 Suppl., 1-116. Reijnders, P. J. H. (1986). Reproductive failure in common seals feeding on fish from polluted waters. Nature, 324, 456-7. Safe, S. (1984). Polychlorinated biphenyls (PCBs) and polybrominated biphenyls (PBBs): Biochemistry, toxicology, and mechanism of action. CRC Crit. Rev. Toxicol., 13, 319-93. Schick, C. T., Brennan, L. A., Buchanan, J. B., Finger, M. A., Johnson, T. M. &
16
R. H. D. Lambeck, J. Nieuwenhuize, J. M. van Liere
Herman, S. G. (1987). Organochlorine contamination in shorebirds from Washington State and the significance for their falcon predators. Environ. Monit. Assessm., 9, 115-31. Schneider, R. (1982). Polychiorinated biphenyls (PCBs) in cod tissue from the western Baltic: Significance of equilibrium partioning and lipid composition in the bioaccumulation of lipophilic pollutants in gill-breathing animals. Meeresforsch., 29, 69-79. Stickel, W. H., Stickel, L. F., Dyrland, R. A. & Hughes, D. L. (1984). Aroclor 1254 residues in birds: Lethal levels and loss rates. Arch. Environ. Contam. Toxicol., 13, 7-13. Subramanian, A. N., Tanabe, S., Hidaka, H. & Tatsukawa, R. (1986). Bioaccumulation of organochlorines (PCBs and p,p'-DDE) in Antarctic Adelie penguins Pygoscelis adeliae collected during a breeding season. Environ. Pollut. Ser. A., 40, 173-89. Subramanian, A. N., Tanabe, S., Tanaka, H., Hidaka, H. & Tatsukawa, R. (1987). Gain and loss rates and biological half-life of PCBs and DDE in the bodies of Adelie penguins. Environ. Pollut., 43, 39-46. Swennen, C. & Duiven, P. (1983). Characteristics of oystercatchers killed by coldstress in the Dutch Wadden Sea area. Ardea, 71, 155-9. Symonds, F. C., Langslow, D. R. & Pienkowski, M. W. (1984). Movements of wintering shorebirds within the Firth of Forth: Species differences in usage of an intertidal complex. Biol. Conserv., 28, 187-215. Tanabe, S., Tatsukawa, R. & Phillips, D. J. H. (1987). Mussels as bioindicators of PCB pollution: A case study on uptake and release of PCB isomers and congeners in green-lipped mussels (Perna viridis) in Hong Kong waters. Environ. Pollut., 47, 41-62. Voogt, P. de, Klamer, J. C., Goede, A. A. & Govers, H. (1985). Accumulation of organochlorine compounds in waders from the Dutch Wadden Sea. Report Inst. Environ. Stud. Free University Amsterdam, R85/7. Wilkinson, L. (1988). SYSTAT: The system for statistics. SYSTAT Inc., Evanston, USA.
Polychlorinated Biphenyls in Oystercatchers (Haematopus ostra/egus) from the Oosterschelde (Dutch Delta area) and the Western Wadden Sea, that Died from Starvation During Severe Winter Weather*
R. H. D. Lambeck, J. Nieuwenhuize & J. M. van Liere Delta Institute for Hydrobiological Research, Vierstraat 28, 4401 EA Yerseke, The Netherlands (Received 17 July 1990; revised version received 19 October 1990; accepted 25 October 1990)
ABSTRACT Wintering oystercatchers ( H a e m a t o p u s ostralegus), charadriid shorebirds that chiefly feed on intertidal bivalves, suffered mass mortality in The Netherlands during severe frosts in 1986 and 1987. PCBs were analysed in liver and (partially) brain lipids of 96 birds to examine the influence of age (three categories), sex and wintering area (the Oosterschelde estuao' versus the westernmost Wadden Sea) on levels, and the risk of intoxication due to starvation. Victims had lost nearly 40% of their normal winter weight. PCBstructures were similar in aU age/sex categories, and in both areas. Sex did not affect total PCB-concentrations. First-winter Wadden birds had lower levels than subadults and adults, but an age-d(fference was absent in the Oosterschelde birds. Some juvenile outliers possibly originated from polluted breeding areas. Individual variation was considerable in most categories. Relevant ecological factors are discussed. A lthough a dam has considerabO' reduced the direct transport of PCBs into the Oosterschelde since 1969, contamination qf local birds was hardly lower than in Wadden winterers. Influx of riverine PCBs into the Oosterschelde from coastal water may have been underrated. Starvation increased liver concentrations by a factor of 35: factors Jbr the hrahl were 56for juveniles and approximately 120for older birds. Considering published lethal levels.for other species, it is doubtful (f PCBs contributed to this winter mortality. * Communication No. 511 of the Delta Institute for Hydrobiological Research. 1
Environ. Pollut. 0269-7491/91/$03"50 © 1991 Elsevier Science Publishers Ltd, England Printed in Great Britain
2
R . H . D . Lambeck, J. Nieuwenhuize, J. M. van Liere
INTRODUCTION Persistent chemicals, such as PCBs, are potentially toxic to animals. Many of the analytical studies of marine biota concentrate on fish and bivalves, in particular mussels, as human food (cf. Phillips, 1978; Holden, 1981; Franklin, 1987; Tanabe et al., 1987). In most estuaries and coastal bays, birds are the main predators of these two animal groups. A comparison of congener composition and total burden of PCBs in these birds on the one hand, and in their food on the other, may provide an insight into metabolism and biomagnification processes. A relatively large effort has been put into studies of fish-eating birds (Koeman et al., 1972; Parslow & Jefferies, 1973; Falandysz & Szefer, 1984; Hoffman et al., 1986; Borlakoglu et al., 1988), but little is known about PCBs in marine waders (Charadrii) that feed on macrozoobenthos along shorelines and, particularly, on tidal flats exposed during ebb tides (e.g. de Voogt et al., 1985). A problem of studies on most wader species, however, is their extensive migratory movements, with prolonged stops in many estuaries en route (Pienkowski & Evans, 1984). In contrast, the proportion of long-distance migrants among the c. 400000 oystercatchers (Haematopus ostralegus) that winter in The Netherlands is small (Hulscher, 1981; Lambeck et al., unpublished). After the breeding season adults usually return to the same feeding area in the same estuary each year. They stay there for the next 6-8 months (Lambeck et al., unpublished; see also Symonds et al., 1984). Contaminant levels in oystercatchers are, therefore, more easily attributable to specific feeding areas than is the case for most other wader species (cf. de Voogt et al., 1985). IX
Fig. 1.
WADDEN SEA ~ . . , ~
Location of the two study areas. Arrow indicates the Volkerakdam, mentioned in the text.
PCBs in starved oystercatehers
3
During harsh frost, waders can be forced to metabolize part of their fat reserves, which raises the concentrations of PCBs in vital organs, such as liver and brain. A large mortality of oystercatchers during the severe winters of 1986 and 1987 allowed us to consider: (1) the possibility of intoxication under such circumstances, (2) the impact of age category and sex on PCB burdens, and (3) the significance of local conditions by comparing victims from the Oosterschelde in the so-called Delta area (SW Netherlands) with those of the westernmost Dutch Wadden Sea. The Oosterschelde used to be one of the estuarine branches of the rivers Rhine and Meuse; a dam broke the direct connection in 1969. The impact of these rivers on the Wadden Sea, via a tributary (River IJssel and Lake IJssel) on the one hand, and via the residual northwards current along the Dutch coast on the other, remained unchanged over recent decades. Such a comparison may provide more insight into the persistence of PCBs in the estuarine environment.
MATERIAL AND METHODS
Collection of oystercatchers Corpses used in this study were collected at high-water roosts along the central and eastern Oosterschelde in February 1986 and the western Wadden Sea in January 1987 (Fig. l). At least 5100 of the 90000 Oosterschelde oystercatchers died in February 1986. This large mortality was a strictly local phenomenon, due to a combination of prolonged icy weather and a reduced tidal amplitude during the construction of a stormsurge barrier (Lambeck, 1989). To study the effects of this barrier on waders, c. 17 000 oystercatchers had been ringed between August 1984 and February 1986. Of the 288 that starved to death in our collection area, 84% were found near the place of ringing. Only a few birds left the Oosterschelde, as shown by ring recoveries and counts. Data support, therefore, the assumption that our sample of victims reflects the contamination conditions in the Oosterschelde. The cold spell in mid-January 1987 induced a large 'winter rush' out of the Wadden Sea, mainly to France (Hulscher, 1989). As shown by ring data (Swennen, C., 1989, pers. comm.), migrants died at North Sea Beaches and not at roosts near normal feeding areas where our birds were collected. So, victims from the Wadden Sea can be presumed to reflect the local contaminant conditions too. Collected birds were split into six categories based upon differences of sex (assessed by dissection) and age (three classes that can be distinguished by plumage and colour of eyes, bill and legs: (1)juveniles are first-winter birds,
4
R . H . D . Lambeck, J. Nieuwenhuize, J. M. van Liere
so about 7 months old, (2) subadults are birds in their second and third winter, and (3) adults are birds in their fourth winter or older). Eight oystercatchers of each category were analysed, giving a total of 96 birds for the two areas combined.
Analytical treatment A thawed corpse was weighed before liver and brain (only in Wadden Sea birds) were dissected with pre-cleaned stainless steel knives. Organs were freeze-dried, ground and homogenized in an agate grinder, and subsequently extracted with n-pentane in a rnicro-soxhlet. After evaporation at 50°C to constant weight, the extractable lipids were determined. After dissolution in hexane and a dual-step clean-up over A1203, a gas chromatography analysis was carried out on a United Instruments Packard 438A with ECDs, automatic injection and fused silica capillary columns CPSil 8CB of 50 m × 0.22 mm with a film of 0-12/~m. Congeners, indicated by their IUPAC number, are defined according to Ballschmiter & Zell (1980). Identification of chromatogram peaks was based on the retention time of standard congeners. Use of a conditioned room contributed to very stable retention times (variation within 0.02 rain). Recovery of a test congener, added at the start of the processing procedure of a sample, was 95-6 + SD 3.1% (N=5). The repeatability and accuracy of assessed congener concentrations were confirmed in an international intercomparison exercise. PCB concentrations are expressed in #g g- 1 pentane-extractable lipids. The efficiency of fat extraction by n-pentane and other methodological details are discussed in Duursma et al. (1986). RESULTS
Weight losses Body weights of the winter victims in the Oosterschelde (Delta) and the Wadden Sea were similar, about 310 g for the smaller-sized juveniles, 350 g for subadult and adult females and 330g for the males. Given a normal midwinter weight of approximately 570 g for adults, 530 g for subadults and 495 g for juveniles (Swennen & Duiven, 1983; Lambeck et al., in prep.), oystercatchers that starved to death lost nearly 40% of their normal weight. In none of the birds was there any visible depot fat left.
Individual congeners The average congener structure in brain and liver were similar in all Wadden categories, as illustrated for adults by Fig. 2. The patterns in livers of
PCBs in starved oystercatchers 10-
* male o female
c ~o c_
c_ 4J c oJ u c o u
5
o /
8-
or
,
4
2
0
~
.
i
i0
,
r
20 3'0 CB concentration
4'0 lzver
5'0
Fig. 2. The relation between the concentration (in/~gg- ' pentane-extractable lipid) of each of the PCB congeners in liver and brain of starved adult male and female oystercatchers (mcan values of eight birds) from the western Wadden Sea; also drawn calculated regression 3'=0'169 x-0.18 (r = 0"99). W a d d e n and Delta birds also showed a large resemblance. Two hexachlorobiphenyls (IUPAC numbers 138 and 153) were by far the most important congeners, each comprising about 20% of the total PCB concentration. Next came the penta-CB 118 and the hepta-CBs 180 and 187, each fluctuating around 10% of total PCB concentration. With the exception of the juvenile Delta males, these five congeners made up, on average, 75% (70-79%) of the PCB burden in the different oystercatcher categories (Table 1). In the Delta birds, the share of the two major congeners CB-138 and CB-153 increased from 34% in juveniles to 45% in older individuals (Mann-Whitney U-test, two-sided p < 0.01). This is the reverse of the pattern in W a d d e n birds, which had 47% in juveniles and 37"5% in subadults and adults (p < 0.01; Table 1). The contribution of the CBs 118, 180 and 187 was fairly stable in the Delta birds (c. 32%) and, moreover, was similar to that in the W a d d e n subadults and adults (Table i). In the Wadden juveniles, their level was slightly reduced (c. 28%). Mono-tetra CBs hardly occurred in the oystercatcher (Table 2). Only the tri-CB 26 had a significant contribution, about 3% o f the total PCB concentration, in the Delta juveniles. It dropped to 0-7% in older specimens, however. The overall importance of this congener was negligible in the W a d d e n birds. Distinct patterns in other congeners were absent. Considering the good resemblance in PCB-patterns between Wadden and Delta birds, total PCB values can be used as an index of the degree of contamination in the different categories.
Liver Log-transformed total PCB values (to obtain a normal distribution) for the individual birds were subjected to an analysis o f variance to assess the
0
R . H . D . Lambeck, J. Nieuwenhuize, J. M. van Liere
TABLE I
Composition of Major Congeners (in % of total PCB) in the Liver Lipids of Three Age Categories (n = 8) of Starved Oystercatchers from the Oosterschelde in the Dutch Delta Area (D) and from the Western Wadden Sea (W) IUPA C ttttmber
Age categorr Jueeniles
138 153 180 187 118
170 183 128 26 209 105 95 194 101 Total 0%
Adults
D
W
D
W
D
W
17'9 16"0 12"8 10"2 9"4 6"2 5"2 3"9 2"9 2"8 2"3 2"1 1"1 1"0
23"7 23"2 7"0 10"9 9"9 3"0 3"6 3"9 0"9 1"1 2"4 1"8 0"5 0'7
21"8 21"9 12"0 10'0 9"9 4'5 6"1 4"2 0"7 1"4 2"3 0'8 0'7 0"4
19"7 18"6 9"9 11"6
22"4 24"6 10"4 10-0 8-2 4-3 5-6 3"6 0"5 2"0 2'0 0"9 1'2 0"5
18"6 18"4 11-4 11"8
93.8
600
-
92.6
96'7
12"2
5"3 5"5 4-9 0'4 1'8 2"7 1"2 0"9 0'5 95.2
96.2
11 "7
4'8 5'2 5"0 0"4 1"8 2"8 1"3 1-0 0-5 94-7
L i vet o
50O
"7
Subadults
o •
40O o
@
•
JUV
F SUB
M
o o
20oD,_ l-4
loo OdUV
M
SUB
AD
AO F
Fig. 3. Mean total PCB liver concentrations in six age/sex categories (M =male, F - female, Juv=juvenile, Sub=subadult, A d = a d u l t ) of starved oystercatchers from the Oosterschelde (hatched column) and the western Wadden Sea (open column); vertical bar = SE. Concentrations for individual birds indicated (A Wadden; O Oosterschelde).
PCBs in starved oystercatchers
7
TABLE 2
Percentage Contribution of Congener Categories to the total PCB Burden in the Liver Lipids of Three Age Categories of Starved Oystercatchers from the Oosterschelde, and in Body Lipids of Local Mussel (Mytilus edulis) in August and Winter (Average of November and January) and Tellin (Macoma balthica) from November. Mollusc Data after Hummel et al. (1990 and unpubl.) Trichloro
Tetrachloro
Oystercatcher juvenile subadult adult
3.2 0"8 0.7
1.3 0.4 0-5
15-2 13-6 11.6
39.7 48.6 51 "3
34.4 32"6 30-3
6'2 3.9 5.5
Mytilus August Winter
6.2 3'5
15-7 11.1
20.5 21.8
45.2 52.3
12.4 11.1
0 0"3
13.4
16-8
24.9
37-1
7.9
Macoma November
Pentachloro Hexachloro Heptachloro
Octadecachloro
0
impact of area, age class and sex. The average total PCB concentration in the livers amounted to ~ 250/~g g-1 pentane-extractable lipids (PEL). There were no overall differences between sexes, and between the Delta and Wadden birds (Fig. 3); significant differences (p < 0.05) were found between age classes, but interpretation is hampered because of interactions (p < 0-05) between sex and area, as well as age class and area. Two factors are involved. First, juveniles from the Wadden Sea had a lower total PCB level than older birds. No such difference was found with oystercatchers from the Delta, where juvenile females contained similar residues to older birds (Fig. 3). Mean values for juvenile males were strongly influenced by two Delta and one Wadden outlier: their concentrations of 470-600/~g g- 1 PEL were the highest found in this study (Fig. 3). Excluding these outliers, mean levels for the Delta juvenile males and the Wadden juvenile males and females were nearly identical at about 135/~g g - i . Secondly, subadult and adult Delta males showed relatively low levels without much variation (mean 209g, range 145-275/lg g-1 PEL). The majority (10 out of 16) of Wadden (sub)adult males had higher concentrations, resulting in a mean of 295/~g g-1 PEL. In contrast, both mean (261 and 247/~g respectively) and range were quite similar for Delta and Wadden (sub)adult females (Fig. 3). Brain
Total PCB levels in the brain lipids of the Wadden Sea oystercatchers were about one sixth of those in the liver lipids (Fig. 4). With an average of
8
R . H . D . Lambeck, J. Nieuwenhuize, J. M. van Liere Brain I00
-3 BO "7
60
--
40
•
t
.
20-
JUV M JUV F SUB M SUB F
AD M
AD F
Fig. 4. Mean (column) and individual total PCB brain concentrations (in #g g- Lpentaneextractable lipids) in six age/sex categories of starved oystercatchers from the western Wadden Sea. See further Fig. 3.
24 llg g- l PEL, juvenile concentrations were lower (Mann-Whitney U-test, p < 0.05) than the 44/tgg -1 in subadults and adults. There were no differences between sexes: the somewhat higher average for juvenile males compared to juvenile females can be completely ascribed to one outlier (Fig. 4). In all categories, a good correlation (r = 0"79; p < 0-001) existed between total PCB values in liver and brain of a single bird (Fig. 5). Data suggest a proportional partitioning between liver and brain over the entire concentration range in juveniles (Fig. 5a). In older birds, the brain held a higher proportion of the body burden at low concentrations (Fig. 5b). laY .
t00 "n '
male • female 0
male female
sub. • []
ad. • A
80
[] A
z[
c
•~
60
o 40
•
m 20
zx
13.. r.-4
o
3Go 4Go ZPCB l i v e r (a)
( ~ g g-i PEL)
6Go
3 o,4o 5Go ZPCB l i v e r
(~g
6OO
g-i PEL)
(b)
Fig. 5. The relation between the total PCB concentration (in pg g-1 pentane-extractable lipid) in the brain and in the liver of (a) starved juvenile O' = 0.139 x + 1.1; r = 0"94) and (b) starved subadult and adult oystercatchers (y=0-096 x + 17"4; r=0"76) from the western Wadden Sea.
PCBs in starvedoystercatchers
9
DISCUSSION The analysis of whole bodies, as carried out in a study of some small wader species (Schick et al., 1987), is not practicable in a large bird such as the oystercatcher. Our results suggest that congener composition and total PCB level in one organ may provide a reliable index of the contamination of the entire individual. This confirms findings of de Voogt et al. (1985) for two small waders, dunlin (Calidris alpina) and knot (C. canutus), and Larsson & Lindegren (1987) for a duck, the red-breasted merganser (Mergus serrator). Congener patterns in bivalves more or less reflect those in the ambient water (Boon et al., 1989). A crude comparison between patterns in oystercatchers and two bivalve prey species (see below) from the Oosterschelde study area shows a distinct shift towards higher chlorinated CBs in the birds (Table2). The major CBs in oystercatcher (Table 1) are persistent, they are characterized by a lack of unsubstituted adjacent metapara H-atoms in the biphenyl skeleton. Details on metabolic aspects are provided by Borlakoglu et al. (1988) and Boon et al. (1989). Individual variation in PCB concentrations
In most categories, PCB concentrations varied considerably between individuals. This is also reported for other bird species (e.g. Borlakoglu et al., 1988). Variation may originate from the breeding area, the wintering area, and the staging areas used en route. Dutch breeders (90000 pairs: nearly 60% of the European mainland population (Piersma, 1986)) and their offspring comprise the majority of the wintering birds in our study areas; the rest originate from an area ranging from Belgium to northern Norway and the White Sea (Hulscher, 1981). Remote northern areas will, in general, be less contaminated than industrialized western Europe. PCB levels in juvenile dunlin and knot, hatched in boreal and arctic habitats indeed rapidly increase during the first months in the Wadden Sea (de Voogt et al., 1985). Our oystercatcher data show an increase in burden between the first and second winter for most individuals. This also results from uptake via marine zoobenthos, because the birds spend their second year entirely in tidal habitats. Apparently, inland prey, predominantly earthworms (Lumbricidae) and insects, are mostly a less important source of contamination. In contrast to inland birds, coastal breeders and their chicks depend partly or entirely on estuarine food. Consequently, besides latitude, the breeding biotope will also contribute to individual variation. The proportion of juveniles hatched in contaminated habitats, such as industrialized port areas and the water-meadows of the River Rhine, is much higher in the Delta than in the Wadden Sea (Lambeck et al., unpublished). If
10
R. H. D. Lambeek, J. Nieuwenhuize, J. M. van Liere
all our Delta juvenile females originated, by chance, from such areas, the higher burdens in this category might be explained. Local pollution of a breeding area is, in fact, the only plausible explanation for the extremely high burdens found in some juveniles (see also Becker, 1989). In a wintering area, there are two potential sources for variation in PCBsuptake: (1) differences in prey choice by individual oystercatchers (cf GossCustard & Durell, 1983) and (2) variability in contamination between individuals of the same prey in different sectors of a feeding area. The mussel M y t i l u s edulis, the cockle Cerastoderma edule and the tellin M a e o m a balthiea are the main food species in our study areas. Locally or temporarily, other molluscs, polychaetes and crustaceans may also be important. Prey species indeed differ in PCB-structure and total burden (Goerke et al., t979; Duinker et al., 1983; de Voogt et al., 1985; Boon et al., 1989; see also Duursma et al., 1986), due to species-dependent differences in the amount of body lipids (Phillips, 1978) or a different potential to metabolize PCBs (Langston, 1978; Boon et al., 1989). When uptake of PCBs by a benthic invertebrate results from equilibrium partitioning between body lipids and the ambient water (Schneider, 1982; Duursma et al., 1986), intraspecific spatial variation may be mediated via a pollution gradient or via systematic differences in feeding conditions and hence lipid contents between subareas, because of, for example, differences in length of the immersion period or in population densities. These aspects deserve more attention. Differences between Oosterschelde and western Wadden Sea
The large resemblance in congener patterns reconfirms the common origin of PCBs in the two study areas, the rivers Rhine and Meuse. About 20% of their discharge, on average 450 m 3 s- 1, enters the Wadden Sea (Duinker et al., 1984). The resultant PCB contamination has deleterious effects, for example on seal reproduction (Reijnders, 1986). Conditions in the Oosterschelde have improved since the construction of the Volkerakdam (Fig. 1) in 1969. The former average Rhine-Meuse discharge of 50m 3 swas reduced by 20% (Anon., 1986) and, of more importance, the transport of suspended matter has largely ended. Adsorbed PCBs constitute 75% of the riverine input (cf Duinker et al,, 1984). This has not resulted in distinctly lower burdens in oystercatchers as compared to the Wadden Sea. There are three possible explanations: (1) (bio)degradation in the sediment pool is very slow, (2) decreasing PCB loads in the rivers during the 1980s (Kerkhoff et al., 1986) have overruled a developing difference between the two areas, and (3) coastal water was, and is, the principal source of contaminants for the Oosterschelde. Rhine-Meuse water constitutes, on average, 10% of the tidal volume in its mouth (Anon.,
PCBs in starved oystercatchers
11
1986); mussels from that sector have indeed higher burdens than mussels elsewhere in the Oosterschelde (Hummel et al., 1990). This aspect warrants further study. Differences between sexes and loss rate
As in our oystercatcher data, a sex difference in PCB-burden is also absent in herring gull (Larus argentatus) (Lemmetyinen et al., 1982) and Adelie penguin (Subramanian et al., 1986). In other species, for example red-breasted merganser (Larsson & Lindegren, 1987; Duursma et al., 1989), arctic tern (Sterna paradisea) (Lemmetyinen et al., 1982) and sparrowhawk (Accipiter nisus) (Newton et al., 1981), adult females have lower levels than males. Although a difference in migration between sexes should be considered too, release via eggs is the obvious explanation for lower female levels. The total clutch weight in relation to body weight is of relevance, but Lemmetyinen et al. (1982) showed, besides, considerable interspecific differences in the efficiency of transferring PCBs into eggs. The amount of PCBs in oystercatcher eggs (e.g. Becker, 1989) is apparently insignificant in the annual budget of this species. Water birds can also excrete PCBs, mainly lower chlorinated congeners, via the lipids of the uropygeal gland (Subramanian et al., 1987; Larsson & Lindegren, 1987). Metabolism and elimination via faeces is the principal mechanism of loss. Loss rates have mainly been studied in experiments based on a short-term administration of a high dosage of a commercial PCB mixture (e.g. Stickel et al., 1984). Conditions are hence unnatural and results will depend also on the composition of the mixture. Little is known about natural loss rates. An estimate for Adelie penguins, that are characterized by low burdens, arrived at 0-26% day -a, implying a half-life of 270 days (Subramanian et al., 1987). From our oystercatcher data a rough estimate of the natural loss rate can be derived when some simplifying assumptions are made: (1) contamination of juveniles starts as soon as they arrive in the estuaries (an average date is taken as 1 August), (2) daily uptake is constant over the year, and (3) a constant fraction of the total body burden is excreted per day. We then have, in general: Ca = C~(1 - e/'la- 60~) where, C~ is the asymptotic total PCB concentration in/tg g- 1 PEL; 2 is the daily loss rate (day- 1); a is the age (days); and 60 is the average age of(Dutch) juveniles at 1 August (Beintema, A. J., 1990, pers. comm.). The average age of subadults at the assumed day of death (1 Feb.) was estimated as 2 years. For adults an approximation must be used; with an annual mortality of 10% (cf Goss-Custard et al., 1982) and a maximal life
12
R. H. D. Lambeck, J. Nieuwenhuize, J. M. van Liere
span of 30years, the average age of an adult in a stable population is 11 years. By applying a non-linear regression (Wilkinson, 1988) to the set of individual Wadden liver data, the daily loss rate was estimated as 0"50% day-x (a half-life of 139 days). For the brain data 0.45% day-1 (153 days) was found. Because the total PCB levels in most of the Delta juveniles were as high as in older birds, which is a violation of our assumptions, no reasonable estimate could be obtained for the Delta birds. Starvation effects
A weight loss of nearly 40% has also been found in other oystercatcher winter mortalities (Swennen & Duiven, 1983). It results from depletion of fat and, partly, protein reserves (Davidson, 1981). In the oystercatcher (Heidmann et al., 1987) as well as in other species (Parslow & Jefferies, 1973; Newton et al., 1981; Fossi et al., 1986; Subramanian et aL, 1986), the bulk of the PCBs in a healthy bird is deposited in the subcutaneous fat. Subramanian et al. (1986) demonstrated a redistribution of PCBs from this adipose tissue to some organs in fasting Adelie penguins. In guillemots (Uria aalge), depletion of reserves hardly changed the total body burden, but the share in the liver increased from a normal 0"9 to 22-5% (Parslow & Jefferies, 1973). A similar twentyfold increase was found in the brain of emaciated loons (Gavia immer) (Frank et al., 1983). In March 1984, a few hundred oystercatchers drowned in the western Wadden Sea. Victims were in good condition; per age/sex category, 4-5 were analyzed. Total PCB levels in the liver were, on average, 4-5 #g g- ~ PEL in juveniles and 8 #g g- 1 in subadults and adults (Everaarts et al., 1991, original data). Figures for our starved Wadden birds were thus 35 times higher in each of the six categories. Levels in the brain of the drowned birds were, on average, 0.42#gg-~ PEL in juveniles and 0.36#g in older individuals, implying concentration factors of 56, 134 and 113, respectively, for juveniles, subadults and adults. Lipids constitute an important structural component in the nervous system. Starvation did indeed not affect the proportion of lipids in the brain of our oystercatchers, while a decrease of 70% was found in the liver (see also Parslow & Jefferies, 1973). Such a difference will contribute to the higher concentration factors found in the brain compared to the liver. Data for healthy birds agree with the different relationship between brain and liver levels found in starved juveniles and (sub)adults (Fig. 5). It is plausible that in juveniles proportionally more of the total body burden goes to the brain, because they have considerably lower fat reserves than older birds. High concentration factors for the latter show that this difference in allocation is partially counterbalanced during starvation.
PCBsinstarved oystercatchers
13
Heidmann et al. (1987) suggest that PCBs contributed to the large winter mortality of oystercatchers in the German Wadden Sea in 1987. Since neither concentrations in extractable lipids and in fresh adipose tissue, nor weight loss and loss of fat, are simple equivalents, they probably overestimated body burdens by at least a factor of two, however. A comparison between our data and burdens found in victims of winter mortalities, in which PCBs were claimed to have played a part (Koeman et al., 1972; Parslow & Jefferies, 1973), and those in experimentally poisoned birds (e.g. Stickel et al., 1984), is difficult, due to methodological differences (see also Phillips, 1978; Duinker et al., 1983). Because of differences in toxicity between individual congeners (Safe, 1984), the PCB-structure is also important. Bird species may furthermore differ in sensitivity (Koeman et al., 1972; Stickel et al., 1984). Healthy wintering grebes (Podiceps cristatus) and mergansers from the Dutch Delta area, with a PCB-structure resembling that of oystercatchers, had about six times higher burdens in the liver than healthy Wadden oystercatchers (Duursma, E. K. & Nieuwenhuize, J., unpublished). Levels of around 500 ppm fresh weight in poisoned passerine birds (Stickel et al., 1984) correspond with at least a few thousand #g g- 1 PEL, an order of magnitude higher than in our starved oystercatchers. It is therefore doubtful that PCBs contributed to the oystercatcher winter mortality. ACKNOWLEDGEMENTS We would like to thank our colleagues from The Netherlands Institute for Sea Research, Texel, for collecting and dissecting the Wadden Sea oystercatchers. A team composed of collaborators from the Delta Institute and the former 'Deltadienst of Rijkswaterstaat', plus some volunteers, collected the frost victims in the Oosterschelde. We especially like to mention E. B. M. Brummelhuis who dissected the selected birds. E. G. J. Wessel was of great help during part of the data processing; he also made the computer graphs. Dr P. M. J. Herman gave statistical advice; special thanks are due for his loss rate calculations. Dr J. P. Boon, Dr J. M. Everaarts and two referees made useful comments on an earlier draft of the manuscript. Dr P. G. Harrison corrected the English. REFERENCES Anon. (1986). De waterkwaliteit van de Oosterschelde. Driemaand. Berichten Deltawerken, 116, 263-71. Ballschmitter, K. & Zell, M. (1980). Analysis of polychlorinated biphenyis (PCBs) by glass capillary gas chromatography. Composition of technical Aroclor- and Clophen-PCB mixtures. Fresen. Z. Anal Chem., 302, 20-31.
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