Marine Ecology. ISSN 0173-9565
ORIGINAL ARTICLE
Pilot assessment of depth related distribution of
macrofauna in surf zone along Dutch coast and its
implications for coastal management
Gerard Janssen, Hans Kleef, Saskia Mulder & Peter Tydeman
Centre for Water Management, Directorate-General of Public Works and Watermanagement, The Netherlands
Abstract
Keywords
Coastal management; depth distribution;
macrofauna; nourishment; surf zone
sampling; zonation.
Correspondence
Gerard M. Janssen, RWS Centre for Water
Management, PO Box 17, 8200 AA Lelystad,
The Netherlands.
E-mail: [email protected]
Conflict of interest
The authors declare no conflict of interests.
Surf zones are highly dynamic, physically stressful parts of sandy beach ecosystems. The high wave energy of surf zones has in the past severely hampered
ecological surveys of these systems. Here we used a novel technique to collect
fauna from this environment along the Dutch coast. A large vehicle in the form
a tripod that drives along the sandy seafloor and supports a sampling platform
11 m above the water line can collect both infaunal (grabs) samples and pull
beam trawls for epibenthos. The distribution and diversity of macrofauna were
studied at different depths in the surf zone along the Dutch coast. Species
diversity and abundance increased with increasing depth of the water column.
This increase was especially noticeable on the seaward side of the outer breaker
bar. Within the surf zone, in the trough between the two breaker bars, there
were spots of high diversity and abundance of macrobenthic infauna. Moreover, the area is also important for epibenthic and fish species, like the commercially important flatfish sole. Spatial patterns of species richness and
abundance across an onshore-offshore gradient from the beach to seawards of
the breakers suggest the presence of faunal zonation in this environment. The
high abundance recorded in troughs was primarily caused by patches of juvenile Sand mason Lanice conchilega. The management implications of these
results are that we suggest to protect the surf zone, including the trough
between the two breaker bars, as a potential area of high diversity and abundance and to reconsider the objectives of the EU-Habitat Directive and the
Water Framework Directive for the coastal area.
Problem
Dunes, beaches and surf zones have always protected the
land against flooding by the sea. However, a sandy coast
is more than just a pile of sand providing a natural
defence against the sea. The protection of the Dutch
coastal environment is laid down in (inter)national legislation and regulations, such as the EU Water Framework
Directive (WFD), the EU Bird and Habitat Directive, and
in international treaties and recommendations. Moreover,
in 2006, the European Commission adopted the Marine
Strategy Directive to protect the marine environment; it
186
states that management of coasts should be based on an
ecosystem approach (http://ec.europa.eu). To protect the
coastal environment, one has to know what to protect
and (i) what are its characteristics (ii) which organisms
inhabit it and (iii) which functions does it fulfil? The surf
zone of beaches is, however, rarely accessible for faunal
sampling because of harsh and dynamic wave climate.
On the Dutch coast, we assume that the main shortterm threats are sand nourishment to counter erosion,
the mechanical cleaning of beaches, and disturbance by
vehicles and tourists – all consequences of increasing recreational pressures, pollution and fisheries. Important
Marine Ecology 29 (Suppl. 1) (2008) 186–194 ª 2008 No claim to Original Government ª 2008 Blackwell Publishing Ltd
Janssen, Kleef, Mulder & Tydeman
long-term threats include climate change and its consequences such as sea-level rise and increasing storminess,
and the increase in social and economic use of the land
on or immediately behind the dunes. Threats originating
simultaneously from the sea and from the land lead to
‘coastal squeeze’. In this situation, beaches and surf zones
become trapped between these pressures.
In this article, we describe the distribution of macrobenthic infauna and epifauna of the surf zone along the
coast of the Netherlands. Benthic invertebrates and fish
are important components of coastal waters (Guidance
Document No 5. 2003). On the basis of sparse information available for surf zone macrofaunal abundance and
diversity, Brown & McLachlan (1990) presented a conceptual model of the distribution of macrobenthic species
diversity across the beach – surf zone system. It predicts
that benthic fauna is sparse in the high-energy surf zones,
and increases in diversity towards the beach and is the
highest beyond the breaker point (Brown & McLachlan
1990). Janssen & Mulder (2005) have shown that this distribution pattern describes the situation in the Dutch surf
zone rather well, although they did not find an increase
in diversity from the breaker point towards the beach.
Management of the Dutch coastal zone that incorporates the surf zone and beach as part of the nearshore area
is based on sparse ecological information for surf zones.
In the absence of data, the nearshore zone abutting the
beach – from the low water line on the beach to one nautical mile offshore – is considered to be homogeneous
with respect to the distribution of macrofauna. Samples
taken in nearshore waters as part of a regular biological
monitoring program that samples sites located approximately 4 km seawards of the beach are considered to be
representative of the entire coastal area, including the tidal
beach and surf zone. This assumption may have important
consequences to meet ecological objectives and to assess
accurately human impacts on the ecological status of the
coastal zone. Moreover, from a management perspective,
beach and foreshore nourishment are increasingly important activities to combat erosion of sandy shores. Therefore, if the assumption of ecological homogeneity across
the nearshore zone is not correct, it may have implications
for coastal management. Consequently, in this article, we
present spatial and bathymetric distribution data of benthos and epibenthos in the surf zone and nearshore benthos and discuss their management implications.
Pilot assessment macrofauna in surf zone
of the North Sea and extends from Cap Blanc Nez in
France as far as Northern Jutland in Denmark. The Dutch
coast can be divided into three physically different sectors: the Wadden Sea islands in the north, the Schelde
delta in the south, and the central coast, a sand barrier
system fronted by beach and surf zones containing two or
three bars. The beaches and surf zones are the products
of waves generated by the wind, interacting with the
medium to fine sands of the beach face, in a mesotidal
environment (Short 1992). Tidal forces at the study
site (mean tidal range ± 1.6 m) contribute little to beach
morphology. Breaker height ranges from 1.0 m (summer
mean) to 1.7 m (winter mean) along this part of the
Dutch coast.
Sampling
Transects in the surf zone were sampled in June 2002 in
the central coastal area at two sites, Castricum and
Egmond (Fig. 1), using a large tripod on wheels (Fig. 2).
The height of the platform of this amphibious motorized
vehicle is 11 m. The platform measures 6 · 2.5 m. The
base is an equilateral triangle (9.9 · 9.9 · 9.9 m) with a
distance of 11 m between the wheels. The tripod travels
at 10 kmÆh)1 on the beach and at 5 kmÆh)1 in the water.
A Davit crane, capable of hoisting up to 1000 kg, fitted
with a hydraulic winch is mounted at the rear of the
platform. The design is based on the Coastal Research
Amphibious Buggy used by the US Army Corps of
Material and Methods
Study site
Sandy shores make up 82% of the 432 km long Dutch
coast. This coast forms part of the sandy coastal ecosystem
Fig. 1. Location of the sampling transects at the two sites Egmond
and Castricum at the Dutch coast.
Marine Ecology 29 (Suppl. 1) (2008) 186–194 ª 2008 No claim to Original Government ª 2008 Blackwell Publishing Ltd
187
Pilot assessment macrofauna in surf zone
Janssen, Kleef, Mulder & Tydeman
used to classify samples taken with van Veen grabs that
collected infauna (A: 1–3 m, B: 3–6 m, C: 6–7 m) differ
slightly from those taken with a 2-m beam trawl for epifauna (A: 1–3 m, B: 3–5 m, C: 5-7 m). We therefore present the data as ‘pilot assessments’ rather than definitive
statements on the distribution and diversity of surf zone
benthos.
Results
Infauna
Fig. 2. Tripod, a large multi-purpose vehicle constructed for coastal
research. It can operate from the beach and drive into the sea up to
water depths of 7 m.
Engineers. The surf zone was sampled to a maximum
water depth of 7 m.
The geographical position and the depth were determined with satellite navigation equipment. Water depth
is presented relative to the mean tidal level. Infauna was
collected with a 2000 cm2 van Veen grab to a depth of
approximately 0.25 m into the sediment. Epibenthos was
sampled with a 2-m wide beam trawl (mesh size:
5 · 5 mm) pulled by the tripod (Kuipers et al. 1992).
The hauls were on average 131 ± 22 m long at a driving
speed of approximately 35 mÆmin)1; hauls were made in
an along-shore direction.
On the basis of pilot sampling with the tripod, we used
a stratified random design along two across-shore transects. However, because of foul weather and the composition of the sediments, not all scheduled samples could be
taken. Therefore, the samples were classified afterwards
into three depth zones (A, B, C) to achieve an optimal
distribution of samples among depth bands. Depth zones
188
A total of 41 species were recorded, 27 at Egmond and
33 at Castricum (Table 1). Faunal differences between
the two sites were mainly because of a higher richness of
bivalve species. Polychaetes followed by crustaceans were
the most speciose groups. Based on frequency of occurrence, seven species that were found in more than half
of all samples could be regarded as common (i.e. Ensis
sp., Scolelepis squamata, Nephtys cirrosa, Nephtys hombergii, Lanice conchilega, Spiophanus bombyx and Spio
martinensis). In the part of the surf zone closest to the
beach, ‘typical’ beach species such as S. squamata,
Haustorius arenarius and Bathyporeia pilosa occurred. A
number of species such as the Sand mason L. conchilega
were characteristic of the through approximately 300 m
from the beach. The highest numbers of species occurred
on the seaward side of the outer bar, where S. bombyx
was the most abundant species. Depth zone 3 showed
the highest number of species (Fig. 3). Species richness
increased gradually in an offshore direction from 450 m
seawards (Fig. 4). Species richness was generally low in
the surf zone, except for a sample taken from the trough
between the two breaker bars. We recorded 41 species
from 39 samples taken over an across-shore gradient up
to 800 m from the beach. In comparison, the annual
Dutch biological monitoring programme tallied 60 species in coastal and 90 species in offshore areas (Daan &
Mulder 2006).
With the exception of N. hombergii and S. martinensis,
there appears to be no difference in abundance between
the two sites. The most frequently recorded species
occurred in deeper zones, except for S. squamata (Fig. 5).
The general distribution pattern of the abundance of the
macrobenthos is a strong indication of interspecific zonation in the surf zone along the Dutch coast. The exceptional high abundance of L. conchilega in depth zone 2 is
the result of sampling a dense field of young Sand mason.
These peak densities of Sand mason were found at both
sites but in one sample only, taken from the trough
between the two breaker bars; localized high abundance
and richness in the trough suggest the possibility of special environmental conditions in this area.
Marine Ecology 29 (Suppl. 1) (2008) 186–194 ª 2008 No claim to Original Government ª 2008 Blackwell Publishing Ltd
Janssen, Kleef, Mulder & Tydeman
Table 1. Frequency of occurrence (expressed
as the percentage of samples in which the
species occurs) of macrofauna (macrobenthos
and epifauna) sampled at two transects across
the surf zone.
Pilot assessment macrofauna in surf zone
sampling gear
van Veen grab
location
number of samples
Egmond
n = 27 (%)
Bivalvia
Angulus tenuis
Spisula subtruncata
Macoma balthica
Donax vittatis
Fabula fabula
Montacuta ferruginosa
Mytilus edulis
Ensis sp.
Nemertini Polychaeta
Scolelepis squamata
Scolelepis foliosa
Microphthalmus sp.
Nephtys cirrosa
Nephtys hombergii
Lanice conchilega
Spiophanus bombyx
Spio martinensis
Capitella capitata
Phyllodoce maculata
Phyllodoce mucosa
Eumida sp.
Nereis sp.
Eteone longa
Magelone mirabilis
Sigalionidae
Scoloplos armiger
Lagis koreni
Crustacaea
Corophium sp.
Haustorius arenarius
Pontocrates altamarinus
Bathyporeia elegans
Bathyporeia pelagica
Bathyporeia guilliamsoniana
Megaluropis agilis
Gammarus locusta
Gammarus crinicornis
Perioculodes longimanus
Atylus falcatus
Urothoë poseidonis
Cumopsis longipes
Anomura (two species)
Carcinus maenas
Liocarcinus holsatus
Portumnus latipes
Pinnotheres pisum
Crangon crangon
Pontophilus trispinosus
Mysidacea
Echinoidae
Echinocardium cordata
Asterias rubens
19
11
59
15
11
56
15
44
33
26
4
7
4
15
4
11
4
2-m beam trawl
Castricum
n = 12 (%)
25
8
8
8
17
8
8
50
33
33
Egmond
n = 14 (%)
Castricum
n = 13 (%)
14
17
42
50
67
67
67
17
33
8
25
25
17
8
8
8
44
37
22
26
7
7
11
4
15
15
33
8
8
17
33
33
17
79
7
86
86
7
93
71
+
85
69
85
100
15
+
17
Marine Ecology 29 (Suppl. 1) (2008) 186–194 ª 2008 No claim to Original Government ª 2008 Blackwell Publishing Ltd
7
189
Pilot assessment macrofauna in surf zone
sampling gear
van Veen grab
location
number of samples
Egmond
n = 27 (%)
Pisces
Ammodytes tobianus
Hyperoplus lanceolatus
Trisopterus luscus
Agonus cataphractus
Pomatoschistus sp.
Aphia minuta
Clupea harengus
Sprattus sprattus
Pleuronectes platessa
Solea solea
Scophthalmus rhombus
Limanda limanda
Syngnathus rostellatus
Gadus morhua
Ciliata mustela
Merlangius merlangus
Trachinus vipera
Trigla lucerna
Cephalopoda
Loligo vulgaris
Species numbers
(incl. 2 spec. Anomura):
Total species numbers in
all samples:
Janssen, Kleef, Mulder & Tydeman
Table 1. (Continued)
2-m beam trawl
Castricum
n = 12 (%)
Egmond
n = 14 (%)
Castricum
n = 13 (%)
86
7
7
43
50
14
86
62
23
46
31
46
100
15
69
77
15
15
31
8
15
15
79
36
36
36
7
14
7
7
27
33
macrobenthos: 41
8
22
25
epifauna: 29
Fig. 3. Diversity (number of species per sample, mean + SE) of macrobenthic infauna and epifauna in three depth zones; number of grab
samples in depth zone 1, 2 and 3 respectively 10, 15 and 8; number
of beam-trawl samples respectively 6, 10 and 9.
swimming crab (Portumnus latipes), brown shrimp (Crangon crangon), sandeel (Ammodytes tobianus), Atlantic herring (Clupea harengus), plaice (Pleuronectes platessa) and
sole (Solea solea)]. Epibenthic species richness increased
in an offshore direction (Fig. 3), with differences between
depth zones mainly attributable to several fish species,
hermit crabs and the flying crab in zones 2 and 3. Species
richness was high in the trough and seawards of the surf
zone (Fig. 4).
Abundance of several species (Anomura, C. crangon,
L. holsatus) was lower in the shallowest parts closest to
the beach, but spatial patterns in abundance of A. tobianus were unusual in that they decreased at greater depth
(Fig. 6). As was the case for the infauna, the general distribution pattern of the epibenthos strongly suggests the
presence of interspecific zonation across the surf zone of
the Dutch Coast.
Epifauna
A total of 30 epifauna species were found in the surf
zone: 26 at the Egmond site and 23 at Castricum
(Table 1). Most abundant were fishes, followed by crustaceans. Eight species can be considered common, occurring in more than half of all trawls [i.e. hermit crabs
(Anomura), flying crab (Liocarcinus holsatus), Pennant’s
190
Discussion
The pattern of increasing macrobenthic species richness
seaward from the outer breaker bar found in this study
concurs broadly with the model proposed by Brown &
McLachlan (1990). It is, however, unknown at what water
depth or distance from the shore this increase in species
Marine Ecology 29 (Suppl. 1) (2008) 186–194 ª 2008 No claim to Original Government ª 2008 Blackwell Publishing Ltd
Janssen, Kleef, Mulder & Tydeman
Pilot assessment macrofauna in surf zone
Fig. 4. Diversity (number of species per sample) and abundance (ln ind.Æm)2) of macrobenthic infauna and epifauna along a across shore transect
(x-axis: distance offshore from the beach).
richness will peak, because the spatial layout of other
monitoring sites (Daan & Mulder 2006) did not follow
an onshore-offshore gradient. On the Belgian continental
shelf, species richness and abundance also increase in an
offshore direction, reaching a maximum at 5500 m from
the shore (Hoey van et al. 2004).
Within the surf zone, however, the diversity in the
Dutch surf zone is not decreasing from the low water
level towards the breaker point, which is in contrast to
the generalized scheme of zonation across sandy shores
(Brown & McLachlan 1990), Moreover, within the surf
zone, we found indications of spots of high diversity and
abundance in the trough between bars. As increased sediment stability is a plausible explanation for the increasing diversity towards the outer turbulent zone, the
relative stability of the sediment in the trough may also
contribute to higher diversity and abundance. The high
abundance is mainly caused by high numbers of Lanice
conchilega, whose fields of tubes may act as a special
microhabitat attracting other species, providing them
with food and shelter. Zühlke et al. (1998) also found a
positive effect of both natural and artificial tubes on
numbers of macrofaunal species and abundance. As our
results of high abundance and diversity are based on
only a few samples, we strongly suggest studying the
trough within the surf zone in this as well as in other
coastal areas.
The surf zone is used as nursery area for many fish
species (McLachlan & Brown 2006). The very high local
abundance of juvenile sole found just outside the surf zone
in the nearshore area corroborates this for Dutch beaches.
The abundance of juvenile (0-group) sole found in the near
shore area of 35 ind.Æ1000 m)2 was high compared to
densities found in well known nursery area for flatfish
(Zijlstra 1972) like the Ems-Dollard estuary [<5
ind.Æ1000 m)2; Jager et al. (1995)] and the Balgzand
Wadden Sea area [peak densities up to 35 ind.Æ1000 m)2;
Veer et al. (2001)]. These results indicate that the coastal
area might be as important as or even more so than the
estuary and the tidal flat systems of the Dutch Wadden Sea.
The geographical distribution of macrofauna across
the onshore-offshore gradient is of utmost importance
from the perspective of national and international
legislation (Hoey van et al. 2004) and has consequences
for management. The species specific distribution in the
area studied from the low water line to 800 m offshore,
including the surf zone, and the difference in diversity
between this area and the data for the coastal area
from literature, showed that the area protected by the
EU-Water Framework Directive (1 nautical mile) could
not be considered homogeneous. The present biological
monitoring program is therefore not suited to monitor
quality of the coastal area, needed for the WFDobjectives. There is a need for reconciliation of the
Marine Ecology 29 (Suppl. 1) (2008) 186–194 ª 2008 No claim to Original Government ª 2008 Blackwell Publishing Ltd
191
Pilot assessment macrofauna in surf zone
Janssen, Kleef, Mulder & Tydeman
Fig. 5. Number of individuals
ln-transformedÆm)2, mean and SE of the most
abundant macrobenthic infauna species in
three depth zones; number of grab samples
in depth zone 1, 2 and 3 respectively 10, 15
and 8.
objectives and monitoring programme in coastal management.
Another important issue in coastal management is sand
nourishment. Although widely accepted as best method
to counter coastal erosion, nourishment has detrimental
environmental effects that should be mitigated. One of
the adverse effects of foreshore nourishment is the death
of benthic animals, which are buried under the sand. This
effect will be the least in areas of low diversity and abundance. As there are indications of hotspots of high diversity and abundance in the trough between the breaker
bars, the area with the least effect on diversity and abundance will be on the seaward side of the outer breaker
bar. This area, however, is important as a nursery for
192
juvenile sole. The impact of sand nourishment on this
group of organisms should be studied in more detail.
The distribution of benthic fauna in this study follows the model of Brown & McLachlan (1990). We can
therefore assume that sand particle size, beach face
slope and tidal range will also be controlling factors for
faunal assemblages in the Dutch sandy coastal environment. Climate change is likely to result in a higher
number of storms and a rise in sea level. In combination with the policy to fix the Dutch coastline at its
present position, the coastal development will probably
mean that the beaches and foreshores will have steeper
slope in the future. Using coarser sand compared with
the original particle size of the sand on the beach and
Marine Ecology 29 (Suppl. 1) (2008) 186–194 ª 2008 No claim to Original Government ª 2008 Blackwell Publishing Ltd
Janssen, Kleef, Mulder & Tydeman
Pilot assessment macrofauna in surf zone
Fig. 6. Number of individuals
ln-transformedÆ1000 m)2, mean and SE of
the most abundant epifauna species in three
depth zones; number of beam-trawl samples
respectively 6, 10 and 9.
in the surf zone – a common practice in nourishment
– may also have adverse effects on the fauna. We therefore recommend that sand nourishment should best be
performed with sand that closely matches the original
material and is placed on the seaward side of the outer
breaker bar.
With the newly gained understanding, made possible
by using the new tripod sampling technique in the surf
zone, that our sandy coast is more than just sand, it
becomes possible to combine the protection of the land
and the protection of the marine environment into
‘coastal protection’ in the true sense of the word. An
important step forward can thus be made in attempts of
‘integrated coastal zone management’, in which human
activities, such as nourishment of sand, are based on an
ecosystem approach.
Acknowledgements
The data were collected under the Dutch Stuurboord project, sponsored by the Ministry of Transport, Public
Works and Water Management.
References
Brown A.C., McLachlan A. (1990) Ecology of Sandy Shores.
Elsevier, Amsterdam: 328 pp ISBN0-444-88661-3.
Daan R., Mulder M. (2006) The macrobenthic fauna in the
Dutch sector of the North Sea in 2005 and a comparison
with previous data. Netherlands Institute for Sea Research
Report 2006-3. ISSN 0923-3210.
Guidance Document No 5. (2003) Common Implementation
Strategy for the Water Framework Directive (2000 ⁄ 60 ⁄ EC)
Marine Ecology 29 (Suppl. 1) (2008) 186–194 ª 2008 No claim to Original Government ª 2008 Blackwell Publishing Ltd
193
Pilot assessment macrofauna in surf zone
Transitional and Coastal Waters – Typology, Reference Conditions and Classification Systems ISBN. 92-894-5125-4.
Hoey van G., Degraer S., Vincx M. (2004) Macrobenthic community structure of soft-bottom sediments at the Belgian
Continental Shelf. Estuarine, Coastal and Shelf Science, 59,
599–613.
Jager Z., Kleef H.L., Tydeman P. (1995) Mortality and growth
of o-group flatfish in the brackish Dollard (Ems estuary,
Wadden Sea). Netherland Journal of Sea Research, 34(1–3),
119–129.
Janssen G.M., Mulder S. (2005) Zonation of macrofauna
across sandy beaches and surf zones along the Dutch coast.
Oceanologia, 47(2), 265–282.
Kuipers B.L., Maccurrin B., Miller J.M., Veer H.W., van der
Witte J.iJ. (1992) Small trawls in juvenile flatfish research:
their development and efficiency. Netherlands Journal of Sea
Research, 29(1–3), 109–117.
194
Janssen, Kleef, Mulder & Tydeman
McLachlan A., Brown A.C. (2006) The Ecology of Sandy Shores.
Elsevier, Amsterdam: 373 pp ISBN 13: 978-0-12-372569-1.
Short A.D. (1992) Beach systems of the central Netherlands
coast: processes, morphology and structural impacts in a
storm driven multi-bar system. Marine Geology, 107, 103–137.
Veer H.W., van der Dapper R., Witte J.I.J. (2001) The nursery
function of the intertidal areas in the western Wadden Sea
for o-group sole Solea solea (L.). Journal of Sea Reasearch,
45, 271–279.
Zijlstra J.J. (1972) On the importance of the Wadden Sea as a
nursery area in relation to the conservation of the southern
North Sea fishery resources. Symposium of Zoological Society
London, 29, 233–258.
Zühlke R., Blome D., Bernem K.H., van Dittmann S. (1998)
Effects of tube-building polychaete Lanice conchilega (Pallas)
on benthic macrofauna and nematodes in an intertidal
sandflat. Senckenbergiana maritime, 29(1 ⁄ 6), 131–138.
Marine Ecology 29 (Suppl. 1) (2008) 186–194 ª 2008 No claim to Original Government ª 2008 Blackwell Publishing Ltd