Effects of pollution on the
morphology and condition of
Littorina littorea along the
Scheldt estuary
Heidi Van den Broeck(1), Hans De Wolf(1) , Thierry Backeljau(2) and Ronny Blust(1)
(1) University
of Antwerp – Campus Groenenborger, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
Belgian Institute of Natural Sciences, Vautierstraat 29, B-1000 Brussels, Belgium
mailto: Heidi.VandenBroeck@ua.ac.be, Tel: +32 (0)3 265 37 79, Fax: +32 (0)3 265 34 97
(2) Royal
Introduction
The Scheldt estuary (The Netherlands) consists of 2 tributaries, of which the western part is heavily polluted and the
eastern is relatively clean. The Western Scheldt estuary has been ranked among the most heavily polluted in the world with
reference to metal concentrations. A metal pollution gradient, which increases upstream, has been reported in the sentinel
species Littorina littorea [1]. Furthermore, effects of tributyltin (TBT) pollution, namely intersex (i.e. masculinized phenotype)
in Littorina littorea, have been detected in the Western Scheldt estuary [2,3]. Besides these anthropogenic stress gradients
(i.e. metal and TBT pollution), the Western Scheldt estuary is also subjected to natural stressors (i.e. salinity, O2, organic
material).
??? Question ???
Can we detect differences in shell morphology, reproductive anatomy and condition that are stress related, in the Scheldt
estuary using the periwinkle Littorina littorea?
Materials & Methods
• L. littorea sampling: 6 sites along the Western Scheldt, 4 sites along the Eastern Scheldt
(n = 395) (Figure 1).
• Shell morphology: shell height, shell width, aperture height, aperture width, top height,
total weight and body weight were measured.
• Reproductive anatomy: sex was based on presence/absence of vesicula seminalis.
Males: checked for penis shedding.
Females: assessment of intersex and sterility.
• Condition: 1) Lipid concentration was determined using the method of Bligh and Dyer [4]
2) Dry:wet weight ratio was assessed.
Figure 1. Overview of the
Scheldt estuary and the
different sampling sites of Littorina littorea.
W1 Hansweert, W2 Hoedekenskerke, W3
Ellewoutsdijk, W4 Borssele, W5 Vlissingen, W6
Westkapelle, E1 Krabbendijke, E2 Yerseke, E3
Wemeldinge, E4 Kattendijke.
Results & Discussion
Within Western Scheldt
Within Eastern Scheldt
Between Western and Eastern Scheldt
• Significant differences for shell
morphology (Figure 2).
• Significant differences for the
distribution of intersex (i.e. ISI index)
and sterility in females.
Site W4 has the highest ISI index and
sterility (Figure 3), which is probably
caused by its close proximity to the
harbour of Vlissingen.
• Significant differences for condition
(i.e. lipid concentration and dry:wet
weight ratio).
Both parameters increased
downstream (Figure 4), thus opposing
the known metal pollution gradient.
• Significant differences only for shell
morphology (Figure 2).
• Significant differences for shell
morphology (Figure 2).
• Significant differences for the
distribution of intersex (i.e. ISI index)
and sterility in females.
The Western Scheldt has a higher ISI
index and sterility percentage than
the Eastern Scheldt (Figure 3).
TW
BW
HS
WS
HA
WA
HT
4
3
3
2
2
1
1
0
Weight (g)
Shell measurement (cm)
4
0
W1
W2
W3
W4
W5
W6
E1
E2
E3
E4
Sites
• Canonical Discriminant Analysis
(CDA): the main difference between
Western and Eastern Scheldt is
caused by the vectors total weight
and body weight which are
oppositely orientated (Figure 5).
Males with shedded penis
Normal females
0,8
0,8
0,6
0,4
ISI index
Percentage
1,0
0,6
Lipid
0,21
1,2
Sterile females
ISI index
16
dw:ww ratio
1,4
0,4
Dry/wet tissue weight ratio
Normal males
0,2
14
0,20
12
0,19
10
0,18
8
0,17
6
0,2
0,0
0,0
W1
W2
W3
W4
W5
W6
E1
E2
E3
W1
E4
W3
W4
W5
W6
E1
E2
E3
E1
BW
E4
1
W2
E2
HS
0
Figure 4. Mean dry:wet weight ratio (dw:ww), lipid
concentration and standard errors for Littorina littorea
collected along the Scheldt estuary.
WA
E3 HA
W5
WS
HT
W3
W4
dw:ww Lipid
-1
W1
-2
W6
E4
Sites
Sites
Figure 3. Distribution of female (normal and sterile) and
male (normal and penis shedded) Littorina littorea along
the entire Scheldt estuary. Intersex index (ISI) of females
is also given.
W2
2
CV2 (32,52%)
0,22
1,0
Lipid concentration (mg lipid/g wet tissue weight)
Figure 2. Mean shell height (HS), shell width (WS),
aperture height (HA), aperture width (WA), shell top
height (HT), total weight (TW), body weight (BW) and
standard errors for Littorina littorea collected along the
entire Scheldt estuary.
TW
-3
-3
-2
-1
0
1
Figure 5. Graphical representation of the first two
canonical variables, representing all sampling sites
collected along the Scheldt estuary.
Conclusions
Intersex and sterility, which are known indicators for TBT pollution, show a difference in distribution between the Western
and Eastern Scheldt estuary
The pattern of the condition parameters opposes that of the known pollution gradient
References
[1] De Wolf et al. (2005) Marine Pollution Bulletin 50: 479-484.
[2] De Wolf et al. (2001) Marine Environmental Research 52: 249-255.
[3] De Wolf et al. (2004) Marine Pollution Bulletin 48, 592-596.
[4] Bligh & Dyer (1959) Canadian Journal of Biochemistry and Physiology 37: 911-917.
2
CV1 (38,57%)