Coosen, J.

Essink, K.

Meire, P.

Ysebaert, T.J.

Open Marine Archive

\ ol\ -1">1 I 
JEEP 92: 
MAJOR BIOLOGICAL PROCESSES. IN EUROPEAN TIDAL ESTUARIES 
REPORT OF THE WORKSHOP 
HELD IN FARO 
JANUARY 27""30, 1993 
edited by 
Peter M.J . Herman and Carlo H.R. Heip 
Koninklijke Nederlandse Akademie van Wetenschappen 
NEDERLANDS INSTITUUT VOOR OECOLOGISCH ONDERZOEK 
Centrum voor Estuariene en Mariene Oecologie 
Vierstraat 28 4401 EA Yerseke - Nederland 
THE MACROFAUNA OF THE SCHELDE AND EMS ESTUARIES: 
ESTUARINE ZONATION AND COMMUNITY STRUCTURE 
T. Ysebaert1, P. Meire1, K. Essink2 & J. Coosen3 
1 Institute of Nature Conservation, Hasselt, Belgium 
2 Rijkswaterstaat. Tidal Waters Division, Haren, The Netherlands 
3 Rijkswaterstaat, Tidal Waters Division, Midde/burg, The Netherlands 
Introduction 
The principal objective of this study is to review the 
available data of the intertidal benthic macrofauna of 
the Scheide and Ems estuary. More specifically the 
study aimed to describe and compare the estuarine 
zonation and the benthic community structure in both 
estuaries, in relation to physicochemical and morpho-
logical characteristics. Only a summary of the results, 
described in detail in Ysebaert & Meire {1993), is 
presented here. 
Materials and methods 
Some general environmental aspects of 
Scheide and Ems estuary 
Scheide estuary 
The Scheide estuary measures 160 km between the 
mouth in Vlissingen (The Netherlands) and Gent 
(Belgium), where it is stemmed by a weir (Fig. 1) . 
THE NETHERLANDS 
BELGIUM 
-
Fig. 1 Map of the Scheide estuary 
The mean tidal amplitude increases from 3.82 m at 
Vlissingen to a max. of 5.2 m at Kruibeke. It dimi-
nishes more upstream to :1:: 2 m near Gent The fresh-
water input of the Scheide amounts on average 1 00 
m3/s. The mean annual chlorinity decreases from :1:: 
16.6 g cr11 near Vlissingen to :!:: 4.5 g cr11 at the 
Belgian-Dutch border, and near the tributary Rupel 
the water becomes fresh. Based on salinity, ttle 
estuary can be divided into three main zones: a mari-
ne zone (Vlissingen- Hansweert), a brackish zone 
(Hansweert-Rupel), and a freshwater zone more 
upstream. The input from inorganic and organic pollu-
tants is very high, eSpecially in the brackish and 
freshwater zone (Van Eck et al., 1991 ). The huge 
organic matter load causes oxygen depletion in the 
freshwater and brackish zone. As far as the border 
the estuary is often anoxic, especially in summer. 
Ems estuary 
The Ems estuary is situated at the border between 
The Netherlands and Germany. The total length 
between Papenburg and Eemshaven amounts 80 km 
(Fig. 2). The area between Eemshaven and the is-
land Borkum is not considered as part of the estuary. 
The mean tidal amplitude increases from 2.2 m near 
Delfzijl to 3.2 m near Emden. It diminishes more 
upstream to about 1.8 m. The 
freshwater input amounts on 
average 115 m3/s . The mean 
annual chlorinity decreases 
from = 1 6 g Cr/I near Eems-
haven to = 8 g cr11 at the 
mouth of the Dollard (marine 
zone), and near Nuttermoor the 
water becomes fresh). The 
Ems estuary suffers less from 
pollution as compared to the 
Scheide estuary. 
Available data 
This study is based on availa-
ble data from different institutes 
collected during the last ten 
years. In Ysebaert & Meire 
(1992) a detailed description is 
given of the data used in the 
study. For the Scheide and 
77 
\ 
JEEP 92 - WORKSHOP FARO JANUARY 1993 
GERIMNY 
-Flg. 2 Map of the Ems estuary 
Ems estuary resp. :::: 250 and ::t: 350 data are availa-
ble. Methodological differences exist between the 
different datasets because often different sampling 
strategies and/or laboratory analysis were used. F.i., 
some studies in the Ems estuary did not sample on 
one spot. but used a mixture of several samples 
which were collected along a transect of a few hun-
derd meters. Also in the Ems estuary, often not all 
species were detennined (e.g. Oligo-
da; the other half consists 
equally of Mollusca and 
Crustacea. Deposit feeders 
compose the major number 
of species observed. Typi-
cally for the Ems estuary is 
the occurrence of the poly-
cnaete Marenzelferia viridis. 
This North American sce-
cies is present in the Dol-
lard since 1983, and has 
established a flourishing 
population (Essink & Kleef, 
1 988, 1 992). 
Estuarine zonation 
In both estuaries a decrea-
se in the number of species 
is observed from the mouth towards the freshwater 
tidal zone; more species disappear than they are 
replaced by new species upstream (Fig. 3) . This is 
more pronounced in the Scheide estuary. In the 
oligohaline and freshwater tidal zone of the Scheide 
estuary no new species are observed, since only 
Oligochaeta (not determined at species level) are 
chaeta) or quantified (e.g. Pygospio ele-
gans, Heteromastus filiformis, Tharyx 
marioni, Hydrobia ulvae). Biomasses : 
were often detennined by trophic group, ] 
SCHELDE ESTUARY so~~~~~~~'...:.::==:.=....:::.=..:...::.:..=..:c-'--~~~~~~-, 
45 
40 
-
a. 
and not by species. For more details see i 
Ysebaert & Meire (1992) . 
35 
30 
25 
~ 
Results 
Global characteristics of the 
benthic fauna 
In the Scheide and Ems estuary, resp . 62 
and 47 macrobenthic species are obser-
ved . Additionally, in the Ems estuary 7 
species of Oligochaeta are determined , 
whereas in the Scheide estuary Oligo-
chaeta are considered as one group, 
since no detennination has been conduc-
ted. 
In general, the genera observed in both 
estuaries are similar. In both estuaries, 
half of the species observed are Anneli-
78 
~ 
" .a E 
:;J 
c 
., 
" 0 
" a. 
" 0 
~ 
.a 
E 
:;J 
c 
15 
10 
~J.,;::::::_~~~~~~~~~~--:-~~~:::==;::=~~ 
16 14 12 10 8 6 4 2 0 
chlO<inity 
EEMS ESTUARY 
35 
30 
-25 
~ 
15 
10 
5 
-0 
16 14 2 0 6 12 10 8 4 
chlO<inity 
Fig. 3 Number of species (cumulative) appearing and dis-
appearing along the estuarine gradient of Scheide and Ems 
estuary. 
YSEBAERT ET AL.: MACROFAUNA OF SCHELOE ANO EMS 
SCHELDE ESTUARY 
Macoma balthica 86 % 
Nereis diversicolor 68 % 
Heteromastus fi/iformis 82 % 
Corophium spec. 65 % 
Cerastoderma edule 38 % 
Mya arenaria 21 % 
Pygospio elegans 81 % 
EMS 
ESTUARY 
96 % 
90 % 
75 % 
86 % 
26 % 
67 % 
14 % 
Table I Occurrence (based on ttie % presence in all samples) of ttie most dominant species in Scheide and 
Ems estuary. 
density marine brackish marine brackish 
MACO BALT 733 :t: 132 498 :t: 68 302 :t: 43 176 :t: 19 
NERE DIVE 400 :t: 92 320 :t: 60 100 :t: 9 599 :t: 33 
HETE FILJ 3493 :t: 658 3295 :t: 426 1700:: 165 355 :t: 61 
COROSPEC 524 :t: 230 3786 :!: 739 2346 :t: 503 1278 :!: 189 
CERAEDUL 1154:192 139 :t: 50 63 :!: 19 0 
MYA AREN 42 :t: 33 111 :t: 42 247 .:I: 44 89 :t: 16 
PYGO ELEG 4907 :t: 1049 2597 :t: 525 ? 69 .:I: 36 
biomass marine brackish marine brackish 
MACO BALT 2.9 :t: 0 .4 1.0 :t: 0.1 2 .5 .:I: 0.2 1.4 :t: 0.1 
NEREDIVE 1.7 :t: 0.4 1.5 :t: 0 .6 1.0 :t: 0.1 2.5 :t: 0 .2 
HETE FILJ 8.0 :t: 1.4 3 .6 :t 0.7 5.2 :t 0 .6 0.5 :t: 0.1 
CORO SPEC 0.13 :t 0.07 1.0 :t 0 .2 2.0 :t 0.4 0.4 :t: 0 .1 
CERA EDUL 19.7:t5.2 0 .6 :t: 0.2 1.5 :t 0.4 0 
MYA AREN 0.2 :t: 0 .1 0.3 :t: 0 .2 29.6 :t: 5.9 1 .9 :t: 0 .2 
PYGO ELEG 0.4 :t: 0 .1 0 .3 :t: 0.2 ? ? 
Table II Mean density (N/m 2 :t: SE) and biomass (g AFDW/m 2 :t: SE) for the marine and brackish zone of the 
Scheide and Ems estuary. 
79 
JEEP 92 · WORKSHOP FARO JANUARY 1993 
I EEMS ESWARY I I SCHEWE ESTUARY I 
density N/m2 density N/m2 
:nooo ------------- :nooo ,.-------------, 
a dq>aoit r-i... I ·~­.-..-
Q dq>aoit 1-"'n 
·~""' I 
.-..-
U.000 - - · - ·· ·- - · -
10.000 --- - · · - --·- -- • 
Fig. 4 Trophic structure (in terms of density) of the benthic community in the marine and brackish zone of 
the Scheide and Ems estuary. 
found here (Ysebaert et al., 1992; 1993). Except for 
these Oligochaeta, no real freshwater organims are 
observed here (due to pollution). On the other hand, 
in the Ems estuary freshwater species like freshwater 
gastropods, gammarids and insect larvae are obser-
ved. However, no detailed observations are available. 
The taunal change is in both estuaries the most 
pronounced in the brackish zone. 
Occurrence of some key species 
The occurrence, mean density and biomass of the 
most dominant species in the marine and brackish 
zone of both estuaries is given in Table 1 and 2. 
Species like Macoma balthica, Nereis diversico/or, 
Heteromastus filiformis and Corophium spec. are very 
common species in both estuaries. However, differen-
ces in mean density and biomass exist both within 
each estuary (marine versus brackish) and between 
the estuaries (Scheide versus Ems) . For other spe-
cies like Cerastoderma edu/e and Mya arenaria the 
data show important differences between the two 
estuaries. C. edu/e is a very common species in the 
marine zone of the Scheide estuary; it contributes 
here for > 50 % to the total biomass. On the other 
hand , in the Ems estuary C. edu/e is a rare species 
which only appears in low densities and biomasses. 
M. arenaria shows the. opposite : common in the Ems 
estuary, rather rare in the Scheide estuary. In the 
80 
marine zone of the Ems estuary M. arenaria contribu-. 
tes for :: 65 % to the total biomass, in the brackish 
zone for 26 %. 
Pygospio elegans is one of the most common poly-
chaetes in the Scheide estuary and reaches very 
high densities whereas in the Ems estuary it is hardly 
found, and only in low densities. 
Benthic (trophic) community structure 
The community structure within and between the two 
estuaries shows beside similarities also some structu-
ral differences. 
The diversity is in both estuaries much higher in the 
marine zone as compared to the brackish zone. 
In both estuaries, densities in the marine zone as 
well as in the brackish zone are dominated by depo-
sit feeders (Fig . 4). Mean densities are higher in the 
Scheide estuary as compared to the Ems estuary. 
In terms of biomass, a different pattern is observed 
between the marine and brackish zone of both estua-
ries . The marine zone in both estuaries is mainly 
dominated by filter feeders (C. edule in the Scheide 
estuary and M. arenaria in the Ems estuary) (Fig . 5). 
In the brackish zone of the Scheide estuary deposit 
feeders (P. elegans, H. filiformis and Corophium 
spec.) are dominating the community . In the brackish 
zone of the Ems estuary deposit feeders , omnivors 
(N. diversico/otj and filter feeders (M. arenaria) are 
f . 
,.. 
YSEBAERT ET AL. : MACROFAUNA OF SCHELDE AND EMS 
I SCHELDE ES1VARY I 
biotna.S3 g AFDW!m2 
$0 
I EEMS ESTTJARY I 
biomass g AFDW /m2 
$0 
Fig. s Trophic structure 0n terms of biomass) of the benthic community in the marine and brackish zone of 
the Scheide and Ems estuary. 
equally present 
Conclusions 
Species composition is similar between both estua-
ries and is comparable with other european estuaries. 
It is however difficult to make good interpretations 
due to methodological differences. Therefore, stan-
dardisation of sampling and analysis procedures is 
needed in the future. 
Despite some similarities, the marine and brackish 
zone of both estuaries show structural differences, 
related not only to salinity, but probably also to food 
availability and hydrodynamics. Primary production of 
phytoplankton is relatively high in the marine zone 
and serves as food for the filter feeders {C. edule in 
the Scheide estuary and M. arenaria in the Ems 
estuary) . In the brackish zone: concentrations of 
organic matter are very high which can explain the 
dominance of deposit feeders here. Hydrodynamics 
and sediment dynamics will however in the first place 
detennine whether or not a species can settle or 
survive at a certain location. Especially in the very 
dynamic brackish zone of the Scheide estuary this 
can play an important role in determining the distribu-
tion and occurrence of benthic organisms. The role of 
these hydrodynamics is at present studied in more 
detail. 
Acknowledgements 
This study was supported by Rijkswaterstaat, Tidal 
Waters Division and is part of the PROEST-project 
{Research on processes in estuaries). 
References 
Essink, K. & H. L. Kleef. 1988. Marenzel/eria 
viridis {Verrill, 1873) {Polychaeta: Spio-
nidae) : a new record from the Ems 
estuary {The Netherlands/Federal Repu-
blic of Germany) . Zoologische Bijdragen 
{Leiden) 38: 1-13. 
Essink, K & H. L Kleef. 1992. Distribution and 
life cycle of the North American spionid 
polychaete Marenzelleria viridis {Verrill, 
1873) in the Ems estuary. Neth. J . 
Aquat. Ecol. 0n press) . 
Van Eel<, G.T.M., N. De Pauw, M. Van den 
Langenbergh & G. Verreet. 1991 . Emis-
sies, gehalten, gedrag en effekten van 
{micro)verontreinigingen in het stroom-
gebied van de Scheide en Schelde-
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het Scheide- en Eems-€stuarium. Studie 
8 1 
-~~-----------------------------------------· 
' . ' 
JEEP 92 - WORKSHOP FARO JANUARY 1993 
in opdracht van Rijkswaterstaat, Dienst 
Getijdewateren. Rapport WNE n° 29. 
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82 


The macrofauna of the Schelde and Ems estuaries: estuarine zonation and community structure

Ysebaert, Tom

Meire, Patrick

Institutional Repository Universiteit Antwerpen

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The macrofauna of the Schelde and Ems estuaries: estuarine zonation and community structure

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