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Exploiting beach filling as an unaffordable experiment: Benthic intertidal impacts propagating upwards to shorebirds


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Cold-season filling using much coarser sediments than the native caused dramatic suppression of beach macroinvertebrates, demonstrably degrading habitat value for foraging shorebirds. As a dual consequence of persistent steepening of the foreshore, which translated to reduction in habitat area by 14–29%, and disturbance-induced depression of invertebrate densities on filled beaches, abundances of Donax spp. and haustoriid amphipods averaged less than 10% of control levels. Donax spp. is the biomass dominant and a key prey for higher trophic levels. Haustoriids lack pelagic larvae. Recovery on filled beaches was not initiated by either taxon during the March–November sampling. Emerita talpoida, an order of magnitude less abundant than Donax spp. on control beaches, exhibited a pattern of initial depression on filled beaches but recovered by mid summer. Polychaetes, mostly the small Scolelepis squamata, experienced a warm-season bloom of equal magnitude on filled and control beaches. Summertime recruitment of predatory ghost crabs appeared inhibited on filled beaches, perhaps by persistent shell hash. Intertidal shell cover on filled beaches averaged 25–50% in mid summer as compared to 6–8% on control beaches. Largely in response to prey depression, but perhaps also to surface shell armoring and/or coarsening of sediments, shorebird (mostly sanderling) use plummeted by 70–90% on filled beaches until November. Thus, despite likely adaptations to natural sediment dynamics, the high intensity of sediment deposition, cumulative spatial scope (10.8 km), and unnaturally coarse shelly character of the Bogue Banks beach nourishment resulted in a perturbation that exceeded biotic resistance and degraded the trophic transfer function of this highly productive habitat for at least one warm season.
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Exploiting beach filling as an unaffordable experiment: Benthic
intertidal impacts propagating upwards to shorebirds
Charles H. Peterson
, Melanie J. Bishop
, Galen A. Johnson
Linda M. D'Anna
, Lisa M. Manning
University of North Carolina at Chapel Hill, Institute of Marine Sciences, Morehead City, NC 28557 USA
University of Technology Sydney, Department of Environmental Sciences, Broadway, NSW 2007 Australia
National Oceanic and Atmospheric Administration, 1315 EastWest Highway, SSMC3, Silver Spring, MD 20910 USA
Accepted 14 June 2006
Cold-season filling using much coarser sediments than the native caused dramatic suppression of beach macroinvertebrates,
demonstrably degrading habitat value for foraging shorebirds. As a dual consequence of persistent steepening of the foreshore,
which translated to reduction in habitat area by 1429%, and disturbance-induced depression of invertebrate densities on filled
beaches, abundances of Donax spp. and haustoriid amphipods averaged less than 10% of control levels. Donax spp. is the biomass
dominant and a key prey for higher trophic levels. Haustoriids lack pelagic larvae. Recovery on filled beaches was not initiated by
either taxon during the MarchNovember sampling. Emerita talpoida, an order of magnitude less abundant than Donax spp. on
control beaches, exhibited a pattern of initial depression on filled beaches but recovered by mid summer. Polychaetes, mostly the
small Scolelepis squamata, experienced a warm-season bloom of equal magnitude on filled and control beaches. Summertime
recruitment of predatory ghost crabs appeared inhibited on filled beaches, perhaps by persistent shell hash. Intertidal shell cover on
filled beaches averaged 2550% in mid summer as compared to 68% on control beaches. Largely in response to prey depression,
but perhaps also to surface shell armoring and/or coarsening of sediments, shorebird (mostly sanderling) use plummeted by 70
90% on filled beaches until November. Thus, despite likely adaptations to natural sediment dynamics, the high intensity of
sediment deposition, cumulative spatial scope (10.8 km), and unnaturally coarse shelly character of the Bogue Banks beach
nourishment resulted in a perturbation that exceeded biotic resistance and degraded the trophic transfer function of this highly
productive habitat for at least one warm season.
© 2006 Elsevier B.V. All rights reserved.
Keywords: Beach nourishment; Habitat function; Intertidal invertebrates; Sediment grain sizes; Shorebird use; Suppressed recovery
1. Introduction
The past 30 years have revealed many dramatic
changes in the focus of ecological research within aca-
demia. A generation ago, applied ecology was largely
scorned by university scientists, and untenured faculty
members at major research universities risked denial of
tenure if they pursued applied research. Over the sub-
sequent decades, new ecological sub-disciplines and
scientific journals, especially in conservation biology and
restoration ecology, have arisen and flourished, reflecting
both the societal importance of ecological applications
and their acceptance into academia (Lubchenco et al.,
Journal of Experimental Marine Biology and Ecology 338 (2006) 205 221
Corresponding author. Tel.: +1 252 726 6841; fax: +1 252 726 2426.
E-mail address: (C.H. Peterson).
0022-0981/$ - see front matter © 2006 Elsevier B.V. All rights reserved.
1991). In marine ecology, a few visionaries have con-
tributed disproportionately to this sea change in attitudes.
Tony Underwood in Australia stands tall among them,
legitimizing applied marine ecology by his influential
emphasis on experimental designs that can bring statis-
tical rigor to environmental assessment and his frequent
demonstrations of how well conceived environmental
assessment studies can provide opportunity for novel
insight into marine ecological processes of broad sig-
nificance (e.g., Underwood, 1997).
Ocean beaches represent an ecological system where
exploiting management schemes to test hypotheses
about processes at large scales is particularly important
because of the difficulty and unaffordable expense of
conducting large-scale experiments in this energetic
system. Ecological understanding of factors that dictate
composition and dynamics of sandy beach communities
has remained rudimentary because of the limited capac-
ity to conduct experimentation on appropriate scales.
Correlative approaches have been applied to establish
relationships among physical environmental variables
(especially beach slope, sedimentology, and tidal range)
and biological characteristics of populations and com-
munities of intertidal invertebrates on sandy beaches
(McLachlan, 2001; Defeo and McLachlan, 2005;
McLachlan and Dorvlo, 2005). Although such correla-
tions represent one giant step towards understanding
mechanisms that drive dynamics and produce pattern in
ecological communities, interpreting even a tight cor-
relation between a physical and biological factor can be
seriously misleading (Dayton and Oliver, 1980) because
of confounded covariates, including especially biolog-
ical intermediates (Connell, 1975). Establishing the
mechanism by which a pattern is generated requires
further insight often not attainable through correlation.
The few instances in which managerial decisions, such
as the opening and closing of fisheries (Defeo, 1998;
Brazeiro and Defeo, 1999) or the removal of wrack from
a beach (Dugan et al., 2003), have been utilized as
experiments have greatly increased our understanding of
processes that organize sandy beach systems.
Here, we take advantage of a beach fill (nourish-
ment) project and the development of rigorous statistical
approaches for inferring impacts of such planned
environmental interventions (Underwood, 1993, 1994)
to provide experimental tests of hypotheses about im-
pacts and complex recovery dynamics of sandy beach
habitat function after large-scale physical disturbance.
The overwhelming dominance of the literature by corre-
lations between physical variables and ecological char-
acteristics of sandy beach communities, in recognition of
the often intense wave and storm disturbance of the beach
substrate, has led to a common assumption that recovery
following any disturbance of the sediments should be
rapid in this community (NRC, 1995). However, the
intensity of sedimentation, the seasonal timing of distur-
bance, and the physical nature of the added sediments ina
beach fill project may not match the natural conditions to
which the sandy beach biota has adapted. Utilizing a
beach fill project, we test the hypothesis that recovery of
the intertidal-to-shallow-subtidal invertebrate community
and trophic functions of the beach habitat after massive
sediment deposition during the cold season of late fall to
early spring will occur rapidly over a period of weeks to
months within the first warm season. We also assess
whether timing of the disturbance to match the typical
winter season of storminess and biological inactivity
produces more rapid recovery than filling in early spring,
when wave climate has moderated and seasonal recruit-
ment of invertebrates has begun. By conducting synoptic
assessment of physical habitat conditions, benthic
invertebrate abundances, and predatory crab and shore-
bird abundances, we infer mechanisms that drive recov-
ery dynamics in this poorly understood system.
2. Methods
2.1. Study sites and design
We took advantage of plans for a winter 200102
beach nourishment project on Bogue Banks (North
Carolina, USA) to design an evaluation of ecological
impacts and recovery from large-scale sedimentation
during the subsequent warm season as a function of
month of filling. Our possession of previous quantitative
sampling data from 1998 (Manning, 2003) for beach
macroinvertebrates at several localities along Bogue
Banks, including areas to be filled and a control area
outside but near the fill zone, made possible a rigorous
design that could use a beyond BACI(Underwood,
1994) approach to control for natural temporal and
spatial variation. Peterson and Bishop (2005) reported
from a synthesis of the literature that only 11% of
previous monitoring studies of environmental impacts
of beach nourishment had applied any test using before
after contrasts of control and putative impact locations.
Bogue Banks is an eastwest oriented barrier island
45 km long located on the central coast of North
Carolina (Fig. 1). Mean tidal range is about 1 m and
mean wave height 1.2 m (Brooks and Brandon, 1995).
Except for five smaller beach fill projects at Fort Macon
and Atlantic Beach from 19731994 to dispose of spoils
from channel and harbor dredging (Valverde et al.,
1999) and spoil disposal in spring 1990 along two 0.5
206 C.H. Peterson et al. / Journal of Experimental Marine Biology and Ecology 338 (2006) 205221
1.0-km stretches of beach in Pine Knoll Shores
(Peterson et al., 2000), the Bogue Banks beaches had
not been modified by filling prior to the 200102 beach
nourishment. This new project dredged materials from
offshore to place 100176 m
of sediment per linear m
along 10.8 km of shoreline from the western edge of
Atlantic Beach to near the western boundary of Indian
Beach at the center of the island (Fig. 1). Filling began in
late November 2001 and moved progressively east to
west until 11 April 2002. The temporal progression
allowed us to contrast study sites that were filled in early
December, early February, and early April to test for
differences in impacts and rate of recovery as a function
of date of disturbance. By sampling at two-month
intervals, biotic samples can be compared holding date
of sampling constant or time since filling constant.
We selected six locations for documenting widths of
beach zones and sampling sediment size composition,
benthic macroinvertebrate densities, ghost crab burrow
abundances, and shorebird use after completion of the
nourishment project. Three study locations were estab-
lished on filled and three on undisturbed control beaches
(Table 1). We chose to use as many locations (three)
from our previous sampling in 1998 as possible and to
employ identical sampling methods to allow a subset of
our data to be used in beyond BACI tests of ecological
impacts (Underwood, 1994). Because filling covered a
continuous stretch of shoreline interspersion of filled
and control locations was impossible, as in virtually all
beach nourishment projects (Nelson, 1993). Neverthe-
less, sampling results indicated that, despite substantial
biological differences between filled and control beaches,
patterns did not simply follow an eastwest gradient.
Within each location, we sampled each of two study sites,
separated by 0.8 km, using three replicate vertical
transects 40 m apart. Our sampling design was
constrained to match the design used for the 1998
sampling, in which the 40 m separation between transects
was chosen to avoid sampling within individual patches
of Donax spp. or Emerita talpoida,whichcanbeob-
served during calm low tides to extend along the shore-
line for 0.514 m. The distance between sites reflects
analysis of pilot sampling data suggesting a lack of cor-
relation in macrobenthic densities at 0.51.0 km scales
on Bogue Banks, potentially allowing us to treat sites as
independent or nested within location in analyses.
Sediment sampling was conducted on three occa-
sions, in March, July, and November 2002, whereas
biological sampling (intertidalshallow subtidal macro-
invertebrates, ghost crab burrows on the high beach, and
shorebird use) took place bimonthly from March
through November 2002 (Table 1). Corresponding
sampling of sedimentology, benthic invertebrates, and
ghost crab burrows had been previously conducted in
Fig. 1. Map of the North Carolina coast showing study locations (circles) relative to the section of Bogue Banks beach filled in 200102 (boxed and
shaded). C1 = control 1 (Pierpoint), C2 = control 2 (Spinnaker's Reach), C3 = control 3 (Bear Island), F1 = beach filled in early December 2001
(Royal Pavilion), F2 = beach filled in early February 2002 (Dogwood Circle); F3 = beach filled in early April 2002 (Trinity Center).
207C.H. Peterson et al. / Journal of Experimental Marine Biology and Ecology 338 (2006) 205221
March, May, July and September 1998 (only May and
July at all three locations) at Dogwood Circle, Trinity
Center, and Pierpoint, providing information prior to the
nourishment project (Table 1). No biological sampling
took place in January because of the dramatic seasonal
depression of macrobenthic invertebrate abundances on
Bogue Banks during winter (Diaz, 1980; Leber, 1982).
All benthic sampling was stratified along vertical
transects perpendicular to the shoreline so as to integrate
across the strong environmental gradients associated with
tidal elevation, as in most previous studies of sand-beach
macroinfauna (James and Fairweather, 1996). We
identified five separate elevation zones on the beach
and conducted stratified sampling of surface sediments
and of beach macroinvertebrates, with equal effort in
each zone. Zones were defined by physical factors at low
tide, when all sampling was conducted. The supratidal
zone (1) extended from the toe of the dune to the drift line
marking the high tide mark. The high intertidal zone (2)
extended down slope from the drift line to include the
complete region where surface drying took place during
low tide. The mid-intertidal zone (3) extended across the
zone where sand remained wet throughout the low tide
and down to the upper limit of where low-tide wave run-
up extended. The low intertidal or swash zone (4) in-
cluded the complete region of low-tide wave run-up from
lowest retreat to maximum reach. And finally, the
shallow subtidal zone (5) extended from the bottom of
the swash zone to 1 m depth in the surf zone at low tide.
On every date of sampling for invertebrates, the bound-
aries of each zone were marked by surveyor's flags and
the width of each zone on each transect measured.
2.2. Sedimentology
For sediments, we created a composite sample com-
bining the contents of three 4.8-cm diameter cores taken
to 10 cm within each elevation zone. The three cores
were haphazardly located within the top, middle, and
bottom of each zone, with specific placement blind to
surface sediment appearance. In the laboratory, each
sediment sample was subdivided by coning and quar-
tering to a weight of 250 g by traditional methods
(Folk, 1974). Then this smaller subsample was repeat-
edly rinsed with de-ionized water to remove salt and the
rinse waters filtered through pre-weighed 0.7-μm filter
papers, which were then dried for 15 h at 90 °C and
reweighed to compute weight of the silt/clay fraction.
Remaining coarser sediments were also dried for 15 h at
90 °C before sieving by hand on a 2-mm (1Φ) screen
to remove and weigh the gravel-sized fraction. The
remaining sand sample was split down to a weight of
3070 g (Folk, 1974), which was passed through a
nested series of 0.5 to 3.5Φscreens at 0.5Φintervals
using a Rotap sieve shaker. Each of these samples was
weighed, allowing computation of mean sediment size
by weight by traditional methods (Folk, 1974) and thus
percentage composition of silt/clay (ΦN4.0), fine
(2.0 bΦb4.0), medium (1.0 bΦb2.0), and coarse
(1.0 bΦb1.0) sand, and gravel (Φb1.0). Because
surface shell could inhibit shorebirds and surf fish from
gaining access to infaunal invertebrates, we also con-
ducted an assessment of the percent cover of the surface
of the lowest two intertidal zones by shell of gravel size
and larger in July 2002. This sampling was achieved by
Table 1
Sampling design for tests of impact and recovery over the subsequent warm season after beach filling on Bogue Banks, NC, in 200102
Sampling location Treatment Sampling months for:
Sedimentology Benthic invertebrates
Before After Before After Before After
Royal Pavilion Filled Dec (F1) None 3,7,11 None 3,5,7,9,11 None 3,5,7,9,11
Dogwood Circle Filled Feb (F2) 3,5
3,7,11 3,5,7,9 3,5,7,9,11 None 3,5,7,9,11
Trinity Center
Filled Apr (F3) 4,5
7,11 5,7,9 5,7,9,11 None 5,7,9,11
Pierpoint Control (C1) 3,5
3,7,11 3,5,7 3,5,7,9,11 None 3,5,7,9,11
Spinnaker's Reach Control (C2) None 3,7,11 None 3,5,7,9,11 None 3,5,7,9,11
Bear Island
Control (C3) None 3,7,11 None 3,5,7,9,11 None 3,5,7,9,11
Before dates apply to 1998 and after dates to 2002. At each sampling location, there were two nested study sites separated by 0.8 km. Locations F1,
F2, and F3 are in Pine Knoll Shores, whereas C1 and C2 are in Emerald Isle. Months of sampling are indicated by numerals, with March = 3, May = 5,
Because beach filling did not occur at Trinity Center until April, there was no March aftersampling possible.
On Bear Island, shorebird counts were made on only 1 morning within each sample period, not 2 as at all other locations. All shorebird counts were
made over a 1.5-km stretch of beach, which covered both sites.
Benthic invertebrates include infauna sampled by coring and a separate data set on ghost crabs sampled by burrow counts.
Sediment data for these months lack samples for the supratidal zone and lack replication of transects.
208 C.H. Peterson et al. / Journal of Experimental Marine Biology and Ecology 338 (2006) 205221
haphazardly repeatedly placing a weighted 0.25-m
PVC quadrat 30 times in zone 3 (mid-intertidal) and 30
times in zone 4 (swash) at every site during a single low
tide and estimating percent shell cover. Such visual
estimates of percent surface cover have been shown to
be unbiased and efficient (Dethier et al., 1993). Break-
ing waves prevented analogous sampling from being
done in zone 5 (shallow subtidal), also an area of great
ecological significance.
2.3. Biota
We sampled separately for infauna and for predatory
ghost crabs along each vertical transect. Macroinfaunal
densities were estimated within each of the five vertical
zones used for sediment sampling, although only zones
35 were routinely occupied. We created a composite
sample of infauna within each zone comprised of three
core samples 82 cm
in surface area and 15 cm deep,
haphazardly located within the top, middle, and bottom
of each zone and placed blind without regard to surface
appearance. Pooling was done because densities, espe-
cially of amphipods, were so low that a surface area of 3
times that of a single core was deemed necessary to
comprise an adequate sample. Contents retained on a
1.0-mm sieve were preserved in labeled jars with 10%
formalin and stored in the lab until the benthic macro-
invertebrates could be sorted, identified, and counted.
Infaunal data are reported here for each of four dominant
taxa, the bivalve Donax spp. (mostly D. variabilis Say
1822, but also D. parvula Philippi, 1849), the mole crab
Emerita talpoida (Say 1817), amphipods almost all
haustoriids, and polychaetes mostly Scolelepis squa-
mata (Müller 1789). Ghost crab (Ocypode quadrata
Fabricius 1787) densities were estimated by counting
numbers of active burrow openings along a transect 4-m
wide beginning in the mid-intertidal zone and extending
to the top of the dune, where the crab distribution ended
on these beaches (see Wolcott, 1978 for the justification
of using active burrows as proxy for ghost crab abun-
dances). Each transect was split into two components,
one covering the relatively flat beach and the other the
steeper dune face. This separation was done because this
beach nourishment project stopped at the base of the
dunes, leaving the dune face undisturbed. One ghost crab
transect was established in association with each coring
Counts of feeding shorebirds by species were con-
ducted in 2002 on two consecutive days during each
bimonthly sampling of invertebrates. The days selected
for sampling were clear, with early morning low tides,
winds less than 25 km/h and wave heights of less than
0.5 m. Within two hours of low tide, counts of feeding
shorebirds were made at every location except Bear
Island (C3), which could not be easily accessed. Along a
1.5-km stretch of beach, which covered both study sites
at each location, feeding shorebirds were counted
through binoculars and identified. So as not to introduce
temporal bias in sampling, on each day the five sam-
pling locations were visited in random order. No bird
counts were made during the 1998 data collection, so
inferences of impacts of filling must be based upon
spatial contrasts afterwards.
2.4. Statistical analyses
Two sets of ANOVAs were employed for benthic
invertebrates, differing by time periods included. One
set contrasted all study sites in 2002 after beach filling as
the most spatially comprehensive and replicated means
of determining impacts of filling, assuming that beaches
were intrinsically similar prior to treatment. The second
set employed beyond BACI analyses to control simul-
taneously for both natural spatial and temporal variation
(Underwood, 1994). This second set was necessarily
restricted to the limited set of locations (3 of 6) and
months (2 of 5) possessing data from 1998 before the
beach filling, so the power to detect impacts was lower.
Following the recommendation by James and Fair-
weather (1996) for generic sampling of beach infauna,
the first analyses, examining only spatial patterns, were
nested. These had three factors: treatment (filled vs.
control); location (3 levels, nested within treatment);
and site (2 levels, nested within location). Because of the
large seasonal changes in the abundance of fauna, sepa-
rate analyses were conducted for each month of sam-
pling. Analyses for MayNovember included each of
the six locations sampled. Because filling at Trinity
Center (F3) was not completed until April 2002, anal-
yses for March necessarily included only two filled
locations. To balance the design we consequently omit-
ted the Bear Island control (C3) from March analyses,
resulting in two locations within treatment. Due to the
intrinsic spatial variability of infaunal populations, data
were transformed to ranks prior to analysis. Where lo-
cation proved significant ( pb0.05), hypotheses about
the effect of timing of nourishment on impact were
tested using post-hoc StudentNewmanKeuls (SNK)
The beyond BACI analyses included the spatial fac-
tors location (3 levels) and site (2 levels, nested within
location), as well as the orthogonal temporal factor, year
(two levels: pre-[1998] vs. post-[2002] nourishment),
and time (2 levels, nested within year). To enable
209C.H. Peterson et al. / Journal of Experimental Marine Biology and Ecology 338 (2006) 205221
asymmetrical tests of impact, interactions between lo-
cation and temporal terms were partitioned into sources
of spatial variability (see Underwood, 1993, 1994).
The experimental unit for post-nourishment ANO-
VAs was the transect total that weighted zone-specific
density by the width of the zone along that transect
(Brazeiro and Defeo, 1996). We deemed this to be the
most appropriate method of determining impact given
that separate analyses of beach width and faunal abun-
dance by zone indicated that impacts of nourishment
resulted from a combination of changing habitat area
and changing density of fauna. For infauna, only the
three lowest elevations (mid intertidal, swash zone, and
shallow subtidal) were included to form the sum be-
cause the two higher zones proved almost invariably
empty. Ghost crab analyses were conducted on the sum
total of active burrows for the complete transect as well
as for the separate portions on the flat beach and the
dune face. Because zone widths were not measured prior
to filling, weighting of infaunal densities by transect
width was not possible for 1998 data. Consequently,
beyond BACI analyses utilizing pre-fill densities of
invertebrates used the average densities of taxa recorded
for each transect across zones 35 as replicates. Abun-
dances per transect of infauna were sqrt (x+ 1) trans-
formed and counts of shorebirds and ghost crab burrows
ln (x+ 1) transformed prior to ANOVA. Cochran's test
was conducted on each data set following transforma-
tion to evaluate the ANOVA assumption of homogene-
ity of variances.
A single set of ANOVAs, utilizing only post-fill data,
tested for differences by month in the abundance of
feeding shorebirds between control and filled locations.
The bimonthly analyses, which had two orthogonal fac-
tors day (2levels, random) and treatment (2 levels: control
vs. filled), utilized locations as replicates. In response to
omitting Bear Island from analysis because day was not
replicated there, it was necessary to randomly exclude a
filled location (Trinity Center, F3)from analyses, resulting
in a balanced design (n= 2). Use of locations as replicates
was justified by ANOVA results indicating no effect of
timing of nourishment on other faunal components.
No geostatistical analyses like kriging were conducted
on biotic variables (as shown valuable even for density
estimation by Defeo and Rueda, 2002) because patterns
were so dramatic that the simpler approaches sufficed. We
did apply a multivariate analytic approach to the sedi-
mentology, using non-metric multidimensional scaling
(nMDS; Field et al., 1982) to generate two sets of two-
dimensional ordinations of the location averages of the
five sediment fractions (silts/clays, coarse-, medium- and
fine-grained sands and gravel). Separate nMDS ordina-
tions were done for each elevation zone and were based on
Euclidean distances, calculated from untransformed data.
One set of ordinations considered only spatial differences
in post-fill data. The second set, which used only locations
sampled in both 1998 and 2002, incorporated a temporal
factor in addition to the spatial one. Percent surface cover
by shell (arc-sine transformed) was compared between
control and filled areas using three-factor nested
Fig. 2. nMDS plots showing average (n=6) granulometry of sediments
following completion of beach nourishment in 2002, at locations inside
(F1 = filled in December 2001; F2 = filled in February 2002; F3 = filled
in April 2002) and outside (C1, C2, C3) the fill area. Zone 1 =
supratidal; zone 2 = high intertidal; zone 3 = mid intertidal; zone 4 = low
intertidal (swash zone); zone 5 = shallow subtidal. Small symbols
denote samples collected in March 2002, medium symbols, July 2002,
and large symbols, November 2002. Lines connect time series for each
location. In March, only the December and February fill treatments had
been completed.
210 C.H. Peterson et al. / Journal of Experimental Marine Biology and Ecology 338 (2006) 205221
ANOVAs, analogous to those used for the analysis of
beach infauna.
3. Results
3.1. Beach sedimentology
Despite regulatory sediment compatibilityrequire-
ments, sediment granulometry was grossly altered by
beach filling. nMDS of the five sediment fractions (silts/
clays, coarse-, medium- and fine-grained sands, and
gravel) indicated that within each of the zones not only
did filling change sediment granulometry (evidenced in
Fig. 2 by the separation of points representing control
and filled locations into distinctive and non-overlapping
groups), but it also decreased spatial and temporal
variability (spread was much less within the cluster of
points representing filled locations; Fig. 2). Tracking of
Fig. 3. nMDS plots showing average granulometry of sediments at locations on a control beach (Pierpoint, C1), a beach nourished in February 2002
(Dogwood Circle, F2) and a beach nourished in April 2002 (Trinity Center, F3), before (1998, open symbols) and after (2002, closed symbols) beach
nourishment. Sampling was done on 4 occasions in 1998 prior to and 3 in 2002 after filling. On each 1998 sampling date, 2 replicate transects were
used to calculate location averages. In 2002, 6 replicate transects were measured at each location, at each time. Dotted lines enclose data points for
filled sites following nourishment. Zones are as defined for Fig. 2.
211C.H. Peterson et al. / Journal of Experimental Marine Biology and Ecology 338 (2006) 205221
temporal trajectories of change in sediment composition
at each location across the three post-nourishment dates
of sampling did not reveal any consistent pattern of
convergence between filled and control beaches that
would indicate recovery (Fig. 2). A second set of nMDS
plots (Fig. 3) utilizing pre- and post-fill data from the
subset of locations sampled in both 1998 and 2002
confirmed that post-fill differences in the granulometry
of control and filled locations was a consequence of
nourishment, not pre-existing differences among loca-
tions. Within each of the five zones, samples collected
from nourished beaches in 2002 were generally more
similar to one another than to any of the samples col-
lected in 1998 or samples collected in 2002 from control
beaches (Fig. 3).
Multivariate changes in the sediment granulometry
of filled locations following beach nourishment appear
to be driven by increases in the percent contribution of
the two coarsest sediment fractions (Table 2). The fill
differed from the native beach in having far more gravel-
sized and coarse-sand sized particles, virtually all of
which were observed in the sieves and on the beach to
be shell hash. Within the five zones sampled, the percent
contribution of gravel to total sediment weight was up to
13 times greater and the percent contribution of coarse
sand nine times greater at filled than control locations.
The proportionate increases in the two coarsest fractions
corresponded to reductions in fine- and/or medium sand
contributions at filled beaches (varying between high
elevations 12 and low elevations 35; Table 2). Silts
and clays constituted a greater proportion of the sedi-
ment size distribution by weight at filled than at control
sites. At filled locations silts and clays accounted for
0.61.1% of the total weight of sediment samples, as
compared to 0.30.6% at control locations (Table 2).
Quantification of percent shell cover in July 2002
demonstrated enhanced shell armoring (cover of the
substrate surface by shell) within zone 4 (swash) of
filled beaches (ANOVA, F
= 45.07, p= 0.003). Within
zone 4, the percent shell cover on filled beaches (50.0 ±
[1 SE] 2.8%, n= 180) was six times greater than at
controls (8.0 ± 1.2%, n= 180). Although within zone 3
(mid-intertidal), percent shell cover was also greater on
filled (mean = 25.0 ± 2.7%, n= 180) than control beaches
(5.9 ± 0.7%, n= 180), this pattern was not statistically
significant (ANOVA F
= 3.53, p= 0.134) because of
large spatial variation at the scale of sites (F
= 7.67,
p= 0.000).
3.2. Beach macroinvertebrates
Differences in abundances of benthic macroinfauna
between nourished and control beaches in 2002 after the
beach filling were dramatic, although variable among
taxa (Fig. 4). Because of its body size and density Donax
spp. comprised the vast majority of the infaunal biomass
(unpublished data) and exhibited much lower abundances
on filled beaches, approaching convergence only by No-
vember, when abundances on control beaches had fallen
toward their winter minimum (Fig. 4). In the first three
months of sampling, ANOVA revealed that the average
abundance of Donax spp. per running m of shoreline was
Table 2
Mean (±1 S.E.) percent contribution of size fractions to total sediment weight within each of five beach zones surveyed on three dates (March, July,
November) in 2002, after completion of beach nourishment, outside (control) and inside (filled) the area of filling
Fraction Zone 1 Zone 2 Zones 12 (average)
Control Filled Control Filled Control Filled
Gravel 0.7 (0.2) 9.9 (1.3) 0.2 (0.1) 3.7 (0.7) 0.5 (0.1) 7.1 (1.1)
Coarse sand 4.1 (0.8) 19.0 (0.9) 1.4 (0.3) 13.2 (1.1) 2.8 (0.7) 16.2 (1.1)
Medium sand 36.6 (3.8) 38.6 (1.7) 33.2 (4.1) 45.5 (1.7) 36.2 (4.6) 41.5 (1.9)
Fine sand 58.0 (4.3) 31.5 (1.1) 64.7 (4.2) 36.9 (2.2) 60.0 (5.0) 34.4 (1.8)
Silt/clay 0.6 (0.1) 1.1 (0.1) 0.5 (0.1) 0.7 (0.1) 0.5 (0.1) 0.9 (0.1)
Fraction Zone 3 Zone 4 Zone 5 Zones 35 (average)
Control Filled Control Filled Control Filled Control Filled
Gravel 1.0 (0.2) 13.1 (1.3) 2.6 (0.4) 14.3 (1.1) 3.2 (0.6) 8.8 (1.1) 2.9 (0.6) 11.6 (0.9)
Coarse sand 8.9 (1.0) 22.8 (1.2) 15.4 (1.4) 23.6 (1.1) 13.1 (1.3) 19.6 (1.7) 13.4 (1.2) 21.5 (1.1)
Medium sand 43.5 (3.3) 33.7 (1.3) 42.4 (2.4) 28.9 (1.2) 38.6 (2.6) 27.8 (1.2) 41.5 (2.6) 30.6 (1.1)
Fine sand 46.3 (4.0) 30.0 (1.4) 39.2 (3.5) 32.3 (1.8) 44.7 (3.7) 43.1 (2.7) 41.9 (3.5) 35.7 (1.9)
Silt/clay 0.3 (0.1) 0.6 (0.0) 0.4 (0.1) 0.8 (0.1) 0.4 (0.0) 0.6 (0.1) 0.4 (0.0) 0.6 (0.1)
Averages were calculated across all three times and across each of the three locations within each zone, with 6 replicate transects per location and
sampling date. Zone 1 = supratidal; zone 2 = high intertidal; zone 3 = mid intertidal; zone 4 = low intertidal (swash zone); zone 5 = shallow subtidal.
Sediment fractions are defined in Section 2.1.
212 C.H. Peterson et al. / Journal of Experimental Marine Biology and Ecology 338 (2006) 205221
Fig. 4. Mean (±1 S.E.) abundances of macroinvertebrates per linear m of shoreline inside (grey) and outside (white) the fill area in 2002, after completion of beach nourishment. C1, C2, C3 = control
locations; F1 = filled in December 2001; F2 = filled in February 2002; F3 = filled in April 2002. n=6. In March, only the December and February fill treatments had been completed at F3, so NA
indicates datum unavailable. Burrow counts for ghost crabs are partitioned into those on the flat beach (patterned bars) and those on the dune face (plain bars).
213C.H. Peterson et al. / Journal of Experimental Marine Biology and Ecology 338 (2006) 205221
significantly greater on the undisturbed control beaches
(Table 3). Amphipod abundance (all haustoriids) exhib-
ited a similar pattern of lower counts on filled beaches
without a suggestion of convergence even as abundances
on control beaches progressively declined to a low in
November (Fig. 4). The differences among beaches in
amphipod abundance per running m of shoreline were
statistically significant in three of the five sampling
months and marginally significant (0.05bpb0.10) in the
other two (Tabl e 3). Abundances of both Donax spp. and
amphipods were generally greater on Bear Island (where
sedimentology also diverged: Fig. 2) than on the other
two control sites on Bogue Banks (Table 3;Fig. 4).
Recalculation of the average percent differences in abun-
dance across all sampling months between filled sites and
control sites but excluding Bear Island resulted in 85%
fewer Donax spp., as compared to 93% fewer with Bear
Island included, and 89% fewer amphipods, as opposed
to 91% with Bear Island included.
The two other taxa of benthic intertidal infauna
exhibited responses to filling that differed from those of
Donax spp. and amphipods. The mole crab, Emerita
talpoida, displayed significantly lower abundances on
filled beaches only in the first post-fill sampling month
(March: Table 3), although abundances remained great-
ly depressed on fill beaches in May (Fig. 4) and the
pattern was marginally significant (Table 3). Recovery
of the mole crab was evident from July onwards and its
abundance reached annual highs by November on both
filled and control beaches (Fig. 4). The final taxon of
numerical importance on these beaches, the polychaetes,
dominated by Scolelepis squamata,demonstrated
Table 3
Summary of P-values from three-factor nested ANOVAs and post-hoc StudentNewmanKeuls (SNK) comparisons testing for spatial variation in
the average abundance of each intertidal macroinfaunal taxon following beach nourishment of Bogue Banks
Date Tr Lo(Tr) Si(Lo(Tr)) SNK tests
Donax spp.
0.005 0.857 0.048 Tr: C NF
May 0.006 0.009
Lo(Tr): C3NC1 = C2; F1 = F2 = F3 Tr: C NF
0.017 0.176 0.098 Tr: C NF
Sep 0.147 0.003
Lo(Tr): C3NC1 = C2; F1 = F2 = F3
Nov 0.456 0.000
Lo(Tr): C3NC1 = C2; F1 = F2 NF3
0.085 0.093 0.219
May 0.002 0.062
Tr: C NF
0.009 0.008
Lo(Tr): C3NC1 = C2; F1 = F2 = F3 Tr: C NF
Sep 0.013 0.087
Tr: C NF
Nov 0.094 0.001
Lo(Tr): C3NC1 = C2; F1 = F2 NF3
Emerita talpoida
a, c
0.036 0.604 0.026 Tr: C NF
May 0.065 0.128
Jul 0.418 0.106
Sep 0.203 0.698 0.011
Nov 0.651 0.574 0.003
0.227 0.310 0.091
May 0.604 0.000 Lo(Tr): C2 NC3 NC1; F2 NF1 = F3
Jul 0.820 0.246 0.036
Sep 0.221 0.000
Lo(Tr): C3NC1 = C2; F1 = F2 = F3
Nov 0.841 0.000
Lo(Tr): C3NC1 = C2; F1 NF2 = F3
Total abundances of fauna were calculated by multiplying the width of each elevation zone times the faunal density and summing for each transect
sampled. Tr = treatment (2 levels: C = control, F = filled), Lo(Tr) = location (3 levels: C1, C2, C3 within control; F1 [filled Dec 2001], F2 [filled Feb
2002], F3 [filled Apr 2002] within filled), Si(Lo(Tr)) = site (2 levels; random). n= 3. Bold font indicates terms significant at α= 0.05. Data were
converted to ranks prior to analysis to satisfy the assumption for ANOVA of homogeneity of variances.
Because beach filling at Trinity Center (F3) was not completed until April 2002, this location was not sampled in March. To balance the
ANOVA, the control location Bear Island (B3) was also omitted from March analyses, leaving 2 locations nested within each zone.
was not significant at α= 0.25, allowing MS
to be pooled with MS
(Underwood, 1997).
Variances remained heterogeneous even after transformation. Analyses were done on untransformed data anyway because ANOVA is relatively
robust to heterogeneous variances, but because of elevated risk of Type I error, one may wish to consider results significant only at α=0.01.
214 C.H. Peterson et al. / Journal of Experimental Marine Biology and Ecology 338 (2006) 205221
almost co-incident mean abundances at control and
filled locations over the entire 2002 sampling period
(Fig. 4) and accordingly no hint of a significant effect of
filling (Table 3).
Every case of significantly lower mean abundance
of a macroinfaunal taxon on filled beaches was com-
prised of contributions from reductions in both habitat
area and organism density per unit area. In all in-
stances, however, the density reduction was the greater
contributor (26100% reduction at filled beaches for
Donax spp., 58100% for amphipods, and 8997%
for Emerita talpoida). Across all months, the combined
width of the occupied habitat area, zones 35, averaged
1429% less at filled locations than at control beaches.
In contrast to differences in intertidal macroinfaunal
abundances between control and nourished beaches,
differences among locations that were filled in different
months were small, variable, and inconsistent with the
hypothesis that filling in spring (April) would depress
biotic recovery rates (Tabl e 3 ,Fig. 4). Whereas
ANOVAs indicated a significant location effect on Do-
nax spp. at three and amphipods at two of the five
sampling dates, SNKs showed that these patterns were
primarily a consequence of differences among control
locations. Neither taxon exhibited a location effect in
May, the first sampling month after all treated locations
had been filled and thus when depressed recovery at F3
would be expected to be most serious. Although in
Table 4
Summaries of asymmetrical analyses comparing spatial variation in the density of macroinfauna and ghost crab burrows (using an unweighted
average across zones) between filled (F) and control (C) beaches
Source df Donax spp. Amphipods Emerita talpoida Polychaetes
Yr 1 316.6 926.5 2.58 37.4
Ti(Yr) 2 39.8 96.6 3.66 33.7
Lo 2 6.9 5.8 1.09 9.7
Si(Lo) 3 9.9 3.6 0.65 12.4
Yr × Lo 2 11.0 6.8 1.04 2.6
C vs. F 1 17.3 4.18 0.290 13.6 27276.40 0.004 0.55 0.36 0.655 3.7 2.44 0.363
Among F 1 4.7 0.0 1.52 1.5
Yr × Si(Lo) 3 9.0 2.9 0.19 9.0
Ti(Yr)× Lo 4 4.0 28.2 0.38 46.9
C vs. F 2 7.9 37.33 0.026 1.9 0.03 0.966 0.52 2.27 0.373 93.6 406.87 0.002
Among F 2 0.2 54.5 0.23 0.2
Ti(Yr)× Si(Lo) 6 3.7 5.1 0.20 17.7
Res 48 7.2 3.4 0.57 7.1
Cochran's test C=0.50 (Pb0.01) C= 0.23 (NS) C=0.26 (Pb0.05) C= 0.19 (NS)
Source df Ghost crabs
Yr 1 0.02
Ti(Yr) 2 0.15
Lo 2 9.03
Yr × Lo 2 6.80
C vs. F 1 1.20 0.10 0.808
Among F 1 12.41
Ti(Yr)× Lo 4 5.14
C vs. F 2 2.57 0.33 0.750
Among F 2 7.71
Res 24 0.43
Cochran's test C=0.55 (Pb0.01)
Yr = year (2 levels: 1998 [before nourishment], 2002 [after nourishment]), Ti(Yr) = time (2 levels; random), Lo = location (3 levels: C1 = control,
F2 = nourished in February 2002, F3 = nourished in April 2002), Si(Lo) = site (2 levels; random). n= 3. Bold font indicates interpretable terms
significant at α= 0.05.
Data were sqrt (x+ 1) transformed prior to analysis.
The factor Si(Lo) was omitted from analyses on ghost crabs because in 1998 this taxon was sampled at only one site per location.
215C.H. Peterson et al. / Journal of Experimental Marine Biology and Ecology 338 (2006) 205221
November Donax spp. and amphipod abundances were
lower at F3 than at F1 and F2, this pattern followed a
temporal decrease in abundance at F3 between Septem-
ber and November and not greater recovery at F1 and
F2, so is inconsistent with the hypothesis that spring-
time filling suppresses recovery. Observed differences
among locations in the abundance of polychaetes,
evident at three sampling months, were inconsistent in
direction (Table 3). Although polychaetes did exhibit a
pattern of lowest abundance among all filled locations at
F3 from May through September (Fig. 4) and may
reflect negative consequences of filling in spring, the
difference was not statistically significant in any month
(Table 3). Emerita talpoida did not display significant
location effects in any of the five months (Table 3).
Our beyond BACI contrasts, done to control simul-
taneously for both natural spatial and temporal variation,
indicated that depressed densities of amphipods on filled
beaches following the 20012002 nourishment cannot
be attributed to pre-existing differences among these
beaches (Table 4,Fig. 5). Asymmetrical analyses re-
vealed that the magnitude of change from before to after
filling varied more between control and filled treatments
than between the two filled locations that were sampled
in both years. Although a similar pattern of greater
temporal change at filled than control beaches was also
evident for Donax spp. (Fig. 5), the difference was not
significant at the scale of years because of low power
and high seasonal variability at the control location
(Table 4). Interactions between treatment and year were
similarly absent from the analysis of Emerita talpoida
and polychaete densities (Table 4). The BACI pattern of
differences in Emerita talpoida density do imply a
possible, but statistically undetected, reduction from
filling in May relative to pre-fill differences among
beaches (Fig. 5) but no similar pattern in July, which
Fig. 5. Mean (+1 S.E.) densities per transect of macroinvertebrates in 1998, before beach filling, and 2002, after beach filling, outside (C1) and inside
(F2, F3) the fill area. n=6.
216 C.H. Peterson et al. / Journal of Experimental Marine Biology and Ecology 338 (2006) 205221
matches results of our spatial analyses of 2002 data only,
which showed a marginally significant depression on
filled beaches in May but full recovery of Emerita
talpoida by July (Fig. 4,Table 3). Thus, except for the
inability to detect the larger temporal reductions in
density of Donax spp. on filled beaches than on the
control beach as an impact of filling, the beyond BACI
testing confirmed results of post-fill spatial analyses.
3.3. Predators ghost crabs and shorebirds
Our ability to detect impacts of filling varied between
the two types of predators, ghost crabs and shorebirds.
Despite the 90113% greater width on filled beaches of
the elevation zone most abundantly occupied by ghost
crab burrows, the high beach zone 1, tremendous spatial
variation at the level of both location and site within
location dominated results of our nested ANOVAs on
ghost crab burrow counts along vertical transects in
2002 (statistical results not shown). In two of five
sampling months, abundances of ghost crab burrows on
the dune face varied significantly among locations and,
on the flat beach, variability at this scale was detected in
all five months. Both control and filled locations con-
tributed to this variability, which was temporally incon-
sistent in direction (Fig. 4) and precluded any effect of
filling from being detected, even when pre-fill data were
incorporated in beyond BACI analyses (Table 4). Vari-
ation between sites was also significant or marginally
significant in nine of the fifteen nested ANOVAs done
on ghost crab burrow counts (five months of counts for
flat beach, dune face, and also total counts). Despite
greater areas of high beach habitat at filled locations,
total burrow counts on vertical transects across the flat
beach were on average up to twice as high on control
beaches, with the largest, but still non-significant,
differences in September after recruitment (evidenced
by large numbers of small-diameter burrow openings)
had increased abundances (Fig. 4).
Feeding shorebirds exhibited large and readily detect-
able reductions of use of filled beaches, with counts up to
seven times greater on control than filled beaches in 2002
(Fig. 6). The dramatic depression of abundance of feeding
shorebirds persisted from March through September, but
by November 2002, seven to twelve months after the
completion of nourishment, the difference between counts
on filled and controlled beaches was no longer statistically
significant and convergence was nearly complete (Fig. 6).
ANOVAS demonstrated no significant or marginally
significant effect of day or day× treatment interaction for
any month,so the treatment effects remained constant over
the two days of sampling within each sampling period.
Shorebird counts averaged over all months of the entire
2002 sampling were comprised of sanderling (75%),
willet (10%), ruddy turnstone (5%), red knot (5%), and
five rarer species.
4. Discussion
Because intertidal sandy beaches frequently experi-
ence erosion, transport, and deposition of the sediments
that constitute the habitat for benthic invertebrates, these
organisms are often assumed to be adapted todisturbances
that mobilize sediments (NRC, 1995). A limited literature
indeed supports this presumption of adaptation to sedi-
ment dynamics by showing little change in abundances of
sandy beach macroinfauna after intense storms (e.g.,
Saloman and Naughton, 1977). Nevertheless, experimen-
tal studies and field observations after natural sedimen-
tation events (Peterson, 1985; Peterson and Black, 1988;
Lohrer et al., 2004) demonstrate that sedimentation can
cause high mortality of infaunal invertebrates on intertidal
sand flats of coastal lagoons. Consequently, it is rea-
sonable to conclude that sandy beach invertebrates can
also suffer mass mortality from beach filling that exceeds
some threshold intensity. Such an immediate effect of
sedimentation represents a pulse disturbance(Bender et
al., 1984). Presumably magnitudes of impacts of such
pulse disturbances on sandy beach invertebrates would
depend mostly on depth of sediment burial per unit time
but also on sediment type, which is known to affect
burrowing rates (Alexander et al., 1993) and, if too fine,
cause suffocation (Peterson, 1985; Lohrer et al., 2004).
Fig. 6. Mean (± 1 S.E.) numbers of foraging shorebirds per 1.5-km
stretch of shoreline in 2002, after completion of beach nourishment, at
multiple locations inside (filled) and outside (control) the fill area.
Symbols indicate results of ANOVAs comparing the total counts of
foraging birds between stretches of filled and control beaches.
*Pb0.05 in test of fill impact. n= 2 locations, each sampled on two
dates for the control treatment. n= 3 locations, each sampled on three
dates for the filled treatment.
217C.H. Peterson et al. / Journal of Experimental Marine Biology and Ecology 338 (2006) 205221
Effects of such a pulse disturbance are evident in our study
for Donax spp., amphipods, and Emerita talpoida but not
for polychaetes because of their seasonal absence until
after March.
Recovery of the sandy beach invertebrates from this
mass mortality event is dependent upon the potential for
recolonization by reproduction and/or immigration and
probably also suitability of the sedimentary habitat.
Benthic infaunal invertebrates are known to be highly
sensitive to sediment size and associated properties (e.g.,
Gray, 1974). Consequently, even under conditions of high
potential rates of recolonization, persistently large devia-
tion away from the natural sedimentology could depress
recovery, acting as an ongoing press disturbance(Bender
et al., 1984).
Absent an experimental test of recovery as a function
of composition of fill, isolating the press disturbance
component of beach filling impacts is a challenge.
Several lines of evidence imply that it played an
important role in inhibiting full recovery of the benthic
community during the post-fill year examined in our
study. First, the coarse, shelly sediments, which were
incompatible with those naturally occurring on Bogue
Banks beaches, persisted throughout the entire study
period. Second, if a press disturbance were involved,
one would expect it to be taxon-specific as a function of
variable biotic preferences for sediment grade. In our
study, Emerita talpoida abundance recovered rapidly
within months, whereas the numerical and biomass
dominant, Donax spp., and amphipods failed even to
initiate recovery. Despite virtual convergence in abun-
dance between filled and control beaches for Donax
spp. and amphipods by November, this pattern was
driven by seasonal declines toward winter minima on
control beaches and cannot be assumed to imply
recovery on fill. Emerita talpoida is known to prefer
relatively coarse sand sediments (Bowman and Dolan,
1985), whereas the congeneric Donax serra has been
virtually eliminated by persistent coarsening of sed-
iments on a Namibian beach from deposition of
diamond mine tailings (McLachlan, 1996) and burrow-
ing rates of Donax spp. and other bivalves are slowed by
elevated coarse components of sediments, including
shell hash (Alexander et al., 1993; Manning, 2003).
Thus, the contrasting patterns of recovery of Emerita
talpoida and Donax spp. on Bogue Banks seem best
explained by the persistent displacement of fine and
medium quartz sands by shell hash in coarse sand and
gravel size classes (King, 2004).
How long the fill effects on Donax spp. and amphipods
will last is unclear from our sampling of just a single warm
season and from the literature on past responses of Donax
spp. and other infaunal invertebrates to beach nourish-
ment. Four previous studies where beach fill appears,
based on limited information, to match natural granulo-
metry and mineralogy have demonstrated limited initial
impacts on macroinvertebrate abundances and recovery
within days to weeks (Hayden and Dolan, 1974; Naqvi
and Pullen, 1982; Gorzelany and Nelson, 1987; Burlas et
al., 2001). In contrast, several other studies have shown
large depressions of macroinfaunal densities induced by
deposition of sediments in which the fine fraction com-
posed of silts and clays was unnaturally elevated (e.g.,
Reilly and Bellis, 1983; Rakocinski et al., 1996; Peterson
et al., 2000; Manning, 2003; Versar, 2003). Although
none of these studies lasted long enough to document
complete recovery of Donax spp. and other invertebrates,
sampling extended in some cases throughout the warm
season, thereby indicating effects lasting as long as on
Bogue Banks. Assuming that large modifications to sedi-
mentology represent a press disturbance that inhibits
recovery of the benthic infauna, the duration of the impact
would be expected to last as long as the sedimentological
deviation persists. Nelson (1993) concludes from his
review that enhancing the fine fraction of sediments
during beach nourishment retards recovery. McLachlan
(1996) presumes that the coarse fill on the Elizabeth Bay
beach in Namibia will last indefinitely: coarse sediments
are less readily eroded and transported off the beach than
finer materials and often become concentrated in the
swash and shore break zones (King, 2004), where benthic
invertebrate abundances should be the highest.
The biotic potential for recolonization also must
influence recovery rates after beach filling. Those studies
that have failed to demonstrate substantial and long-
lasting impacts of beach filling on the benthic inverte-
brates (Hayden and Dolan, 1974; Naqvi and Pullen,
1982; Gorzelany and Nelson, 1987; Burlas et al., 2001)
appear not only to have used more compatible sediments
but also to have been done on beaches characterized by
high rates of long-shore sediment transport. In contrast,
examples of large and long-lasting impacts (Reilly and
Bellis, 1983; Rakocinski et al., 1996; Peterson et al.,
2000; Manning, 2003; Versar, 2003)comefromsitesof
low long-shore transport. High long-shore transport not
only carries sediments and so has the capacity to dilute
and disperse any unnatural sedimentological signal but
also can enhance immigration of benthic invertebrates.
Each of these effects implies a potential to speed up biotic
recovery relative to more physically quiescent environ-
ments. A likely explanation for the failure of haustoriid
amphipods to initiate recovery during the first warm
season on Bogue Banks is their lack of pelagic larvae to
disperse propagules combined with the low long-shore
218 C.H. Peterson et al. / Journal of Experimental Marine Biology and Ecology 338 (2006) 205221
transport, which can limit immigration. This explanation
implies a serious consequence of disturbing such a long
stretch of beach, 10.8 km, in that cumulative impacts of
multiple contiguous km of disturbance would be greater
than the sum of impacts of filling multiple isolated km,
where nearby sources of colonists could initiate recovery.
Concerned by potential interference with reproduction
through burial of new recruits or through insufficient time
since filling to render the sediments biogeochemically
attractive to larvae, we designed our study to include a
test of whether the timing of the fill disturbance affects
the rapidity of recovery. A contrast of beaches filled in
early December, February, and April showed no
detectable difference in benthic macroinfaunal recovery.
This result comes as a surprise, but it may be best un-
derstood by recognition that neither of the two taxa that
experienced the largest impact of the fill disturbance
(Donax spp. and amphipods) had even initiated recovery
by the final sampling period in November, perhaps
because of the ongoing press disturbance by unnaturally
coarse substrate. Only Emerita talpoida initiated (and
completed) recovery during the year of sampling and its
recolonization occurred sometime between May and July,
after the last (early April) date of filling (consistent with
seasonality shown by Diaz, 1980). Ghost crabs recruited
through reproduction between July and September, long
after the last fill date, and so the possible late summer
depression in their recruitment on filled beaches was not
influenced by timing of filling. Polychaete worms,
largely the spionid Scolelepis squamata,exhibiteda
pattern of seasonal increase in abundance after March
with an autumn decline that did not differ between filled
and control beaches. Polychaete abundances on the beach
filled in early April did lag for several months abun-
dances on the two beaches filled in winter months,
suggesting a possible suppression of recruitment by
spring filling, but low power rendered this pattern non-
significant. Consequently, extending beach filling into
spring may slow benthic recovery rates, but our study of
responses to sedimentologically incompatible sediments
did not reveal any recovery for two most affected taxa
against which to test this hypothesis.
Ours is the first study to assess and document impacts
of beach nourishment on intertidal habitat quality pro-
pagating upwards to a higher trophic level, namely
shorebirds feeding on benthic invertebrates. The shore-
bird counts were dominated by one species, the sander-
ling, although willets and ruddy turnstones also made
meaningful contributions. Sanderlings foraged mostly by
probing the sediments, supplemented by picking up
surface items in the drift. Their greatly depressed use of
filled beaches implies reduction in habitat value after
filling, which has at least three plausible explanations.
First, the foraging area of intertidalshallow subtidal
habitat was reduced by 1429% on filled beaches.
Second, densities of the prey taxon of greatest abundance
and biomass, Donax spp., were dramatically depressed.
Infaunal prey density has frequently been shown to affect
habitat use in shorebirds (e.g., Goss-Custard et al., 1991).
Third, presence of coarse shell material armored the
substrate surface against probing bills, further reducing
foraging habitat by 33%, and probably also inhibited
manipulation of prey when encountered by a bill, as
shown experimentally to be an important factor in shore-
bird feeding by Quammen (1982). Shorebird use of filled
beaches increased by November almost matching that on
control beaches, despite unabated persistence of large
sedimentological modifications, but consistent with near
convergence of filled and control beaches in abundances
of large infaunal prey, when the seasonal crash of Donax
spp. everywhere had left a recovered Emerita talpoida as
the only abundant large infaunal prey at similar densities
on filled and control beaches. Consequently, changes in
either prey density per unit area or abundance per running
length of shoreline appears to represent the most parsimo-
nious explanation of patterns, including the fill-related
decline, in shorebird usage of beach habitat.
By extension, the degradation of habitat value pro-
bably also affected surf fishes, which use the same prey
invertebrates from the same intertidalshallow subtidal
habitat of such high productivity (McLachlan, 2001).
For example, Donax spp. is targeted not only by feeding
shorebirds, like sanderlings (Loesch, 1957) and ruddy
turnstones (Schneider, 1982), but also surf fishes, like
Florida pompano and flounders (Leber, 1982). Manning
(2003) demonstrated experimentally that feeding on
Donax spp. by Florida pompano is inhibited by shell
augmentation in surface sediments because the fish are
confused by and often ingest surface shell instead of
living clams. Amphipods and other small crustaceans
represent the sole prey for many postlarval and small
juvenile fishes, including juvenile pompano (Bellinger
and Avault, 1971), which recruit in spring to the surf
zone habitat. Based on our study of habitat function of
the sandy beach using beach filling as a large-scale
experiment, it seems clear that permitting of beach
nourishment projects should demand matching sedi-
mentology at both the fine and coarse tails of the size
spectrum to minimize habitat degradation and facilitate
recovery. However, our inference that rapid biological
recoveries appear to have occurred only under applica-
tion of compatible sediments to beaches with high long-
shore drift means that these two environmental features
seem confounded in present data and need to be isolated
219C.H. Peterson et al. / Journal of Experimental Marine Biology and Ecology 338 (2006) 205221
in subsequent tests of determinants of recovery dynam-
ics on sandy beaches.
We thank Michelle Duval, David Gaskill, Jon
Grabowski, Catherine Hoffman, Tracy Hutcherson,
Johanna Kertesz, Sarah King, Michelle Moretz, Joe
Purifoy, Taylor Riley, Glenn Safrit, Christina Tallent, Sam
Taylor, Mark Vignola, Stephanie Walters, Jake Werner,
and Brooke Willis for field and laboratory help. Funding
for this project was provided by the North Carolina Sea
Grant College Program, the North Carolina General
Assembly, the North Carolina Fisheries Resource Grants
Program, the North Carolina Division of Coastal Manage-
ment, and the Julian Price Foundation. Gee Chapman and
John Gray provided thoughtful reviews that improved the
quality of this manuscript. [SES]
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221C.H. Peterson et al. / Journal of Experimental Marine Biology and Ecology 338 (2006) 205221
... A sand nourishment can have several devastating effects on the coastal ecosystem (Speybroeck et al., 2006). The macrozoobenthic community is most directly affected, but higher trophic levels may also be influenced as a result (Peterson et al., 2006). Damage to the ecosystem is caused by the construction activities and the physical alteration of the environment. ...
... Construction activities may cause visual and audible disturbance to shorebirds and other terrestrial organisms (Peterson et al., 2006) and cause temporal murkiness of the water which could hinder visual activities of animals and hamper the feeding of filter feeding organisms (Essink, 1999). Yet, the most detrimental effect of a nourishment construction is the death of the benthic fauna by burial. ...
... As an example, during severe storms the morphology of an exposed shore can change significantly overnight. Short-term studies of post-nourishment recovery show that the nourished area is recolonized the next year by mostly juvenile benthic organisms, but full recovery of the community might take longer, as the first colonizers are mainly opportunistic species and some of the dominant species in late successional stages may require several years to reach sexual maturity (Gorzelany and Nelson, 1987;Adriaanse and Coosen, 1991;Peterson et al., 2000;Menn et al., 2003;Peterson et al., 2006;Jones et al., 2008;Fanini et al., 2009;Leewis et al., 2012). ...
Full-text available
The Sand Motor is a very large (20 million m3) nourishment constructed along the coast in The Netherlands. The huge volume of sand is redistributed along the coast by natural forces stemming from tidal currents and waves. For environmental evaluation of this large construction, the benthic subtidal fauna has been sampled prior to the construction of the Sand Motor, and at 1, 2, 4, and 6 years after construction. Although some significant differences between years were detected, overall the total density, total biomass and average number of species per sample were surprisingly constant over this time period. However, large differences were found in the species accumulation curves over samples, and in the rank-biomass and rank-abundance plots. These were related to two important trends in the communities. First, the invasive mollusk Ensis leei, the biomass dominant in the years before construction of the Sand Motor, dwindled in importance in later years. Recruitment of the species failed, but it is unclear whether, and how, this is related to the construction of the Sand Motor. Second, the correlation structure between depth, grain size, bottom shear stress due to waves and currents, which is very tight along a linear coast, was disrupted by the Sand Motor. The community composition was shown to depend strongly on these physical factors. The nature of the dependencies did not change, but the range of different combinations of factors after construction of the Sand Motor was widely larger than before. Although samples had similar number of species per sample before and after construction, the average difference between samples after construction was much larger than before. The Sand Motor is a very large construction, leading to loss of a substantial area (order 100 ha) of submarine area, which recovers at a long time scale. Total disturbance of benthos by burial, expressed as area∗(time before full recovery) was shown to be similar for the Sand Motor and for other coastal nourishment schemes when expressed per unit volume of sediment applied. However, in contrast to beach and shoreface nourishments, the Sand Motor led to a habitat diversification in the coastal zone.
... Nevertheless, high mortality rates of sand-dwelling invertebrates are expected during the construction phase and especially if grain size does not match (McLachlan 1996, Dolan 2003. This can have implications for species further up the food web (Peterson et al. 2006) and possibly be related to decreased feeding activity and wintering rates of avifauna observed following beach nourishment (Alan Grippo et al. 2007, Convertino et al. 2011. It is evident that beach nourishment has effects in the supralittoral that vary both in direction and magnitude where positive and negative consequences are not mutually exclusive but highly species-specific. ...
... These studies complement each other by assessing long and short term effects, respectively, and illustrate that any negative effects are likely to be species-specific, with less detrimental impact (or even positive effects) on opportunistic species and species with life history traits involving large dispersal abilities and longer-term pelagic recruitment strategies (Peterson et al. 2006, Speybroeck et al. 2006, Leewis et al. 2012, Wooldridge et al. 2016. Nonetheless, the lack of monitoring before beach nourishment complicates any decisive conclusions, and any indirect effects of nourishments on environmental variables (e.g. ...
... While both abundance and species richness increased at 5 m depth following beach nourishment due to the establishment of new opportunistic species, the communities in shallow water (2 m) slightly shifted towards a community more associated with finer grain sizes (Lattanzi et al. 2013). Similar effects on sediment composition have been observed elsewhere, where using too coarse sediments may have similar negative effects on recovery (Peterson et al. 2006) as using too fine-grained (Peterson et al. 2000). This highlights the importance of using similar grain sizes between the nourishment material and the recipient beach (Reilly andBellis 1983, Rakocinski et al. 1996). ...
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Coastal protection has evolved from focusing on hard solutions such as breakwaters and groynes to include soft or nature‐based solutions (NbS). NbS have been proposed as cost‐effective means to offer long‐term coastal protection and at the same time strengthen coastal resilience and biodiversity. However, projects utilizing NbS for coastal protection have often focused on a single solution and the evidence of improved biodiversity remain equivocal. In this paper, we review solutions traditionally used for disparate purposes – namely beach nourishment and the establishment of vascular plants such as seagrass and dune grass. The main incentives behind large‐scale beach nourishment projects are often the cost‐effectiveness, multifunctionality and dynamic shoreline protection whereas the focus of vegetation restoration has typically been on recreating important habitats and not specifically as a coastal protection measure. Based on previous studies and an on‐going large‐scale coastal adaptation project in southern Sweden, we investigate the feasibility of combining these seemingly dichotomous management strategies to yield a viable physical defense and at the same time strengthen coastal biodiversity and ecosystem multifunctionality. Given the urgency in combatting biodiversity loss and adapting to a changing climate, management interventions for coastal protection should explicitly incorporate ecological values into every coastal protection measure and seek innovative, integrated approaches that consider both geomorphological and ecological values and the possible complementarity between the two.
... So, beach nourishment is another possible way to mitigate the consequences of flooding. But, beach nourishment processes also have some adverse ecological consequences to mitigate (Peterson et al. 2006;Speybroeck et al. 2006). ...
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Coastlines always include a diverse range of ecosystems viz., marine ecosystem, estuarine ecosystem, freshwater ecosystem, terrestrial ecosystem, and coastline interface, providing ideal habitat for a large group of organisms. Coastline habitats are very much sensitive to various consequences due to climate change such as sea-level rise, increase in the temperature of ocean water, increasing frequency and destruction potential of storms, increasing precipitation, etc. Increasing temperature of ocean water also leads to higher absorbance of carbon dioxide into the marine water causing acidification. Changing climate also has a significant role in habitat loss of the coastal inhabitants, as well as a potential societal impact on coastline communities affecting important ecological services especially regulating services. Odisha, a state of India having a coastline of about 480 km, is frequently disturbed by various natural disasters like cyclonic storms, drought, floods, heatwaves, etc. Evidence is there proving the increasing threat of climate change on the coastline ecosystems of Odisha. Management practices exist to reduce the immediate impact of climate change on the coast, but some of them are becoming unsustainable and the reason behind the coastal squeeze is real. The introduction of more natural processes is the only solution behind the sustainable development of Odisha.KeywordsClimate changeCoastlineHabitatEcosystemOdisha
... Importantly, in these cases the beaches are artificial in their entirety and the deployment of different coastal engineering works significantly reduces the energy of the incident waves ensuring that the sediment contribution remains relatively stable. It should also be noted that it is very complicated to obtain sediment from elsewhere with similar characteristics to those of the local area that do not have a negative effect on the beach (Goldberg, 1988;Peterson et al., 2000Peterson et al., , 2006. It is also difficult to avoid the introduction of exotic invasive species, and so the sand needs to be fumigated. ...
Land uses have long modified aeolian sedimentary dynamics as has occurred in the Jandía isthmus (Fuerteventura, Canary Islands, Spain), where changes in vegetation cover, the reduction of sediment available for transport and the building of barriers to sediment transport have induced beach erosion. In the last 62 years the beach area has experienced a reduction of 800,000 m2. The aim of this paper is to analyse the current situation (in terms of sediment availability, longshore drift and the distribution of protected plant species) in order to make soft management proposals to respond to the current erosive situation. Based on a methodology that combines field work, coastline digitalization and longshore drift calculations, it is found that each year the system loses about 96,000 m3 of sediment which needs to be replaced in order to stop erosion. Four possible ways to manage the system are discussed: passive non-intervention management to allow the ecosystem to evolve and adapt to the new conditions; remobilization of the sedimentary deposits of the isthmus that feed the beaches; beach nourishment from other areas of the system or from outside the system, and; mechanical recirculation of the sands. The viability of each management system is analyzed, particularly with regard to long-term sustainability, as well as its compliance or otherwise with the protection measures that are in place. Paradoxically, the only measures that can alleviate the problem in the long term are incompatible with the current protective measures. In other words, the isthmus and the Sotavento beaches in Jandía are an example of an ecosystem in which the restrictions imposed as a result of its protected status, that do not take into account the tendences of the ecosystem, in fact constitute an obstacle to its conservation and do not allow the adoption of measures that could slow down the degradation process and, ultimately, impede its disappearance.
... Marine phytoplankton, invertebrates, and fish occur in the abutting surf zone, as either residents or transients, with some species having critical nursery habitat there (Odebrecht et al. 2014, Cahoon et al. 2017, Ortodossi et al. 2019. Studies demonstrate that beach invertebrates play critical roles as food resources for fauna that possess high social values, such as migrating and wintering birds, nesting shorebirds, and coastal fish (Peterson et al. 2006, Cohen et al. 2010, Manning et al. 2013, Nel et al. 2014. Microscopic invertebrates (meiofauna) occur in high densities (several 100 to several 1000 individuals per 100 cm 3 ) within wetted intertidal and subtidal beach sediments and play roles in organic C and N transfers in the beach (McLachlan and Brown 2006). ...
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Assessing environmental injury requires accurate, timely information of damage responses and realistic translation of that information into estimates of services lost to the public. The accuracy of both steps improves with the extent of ecological understanding of the impacted habitat; more accurate assessments produce more effective rehabilitation efforts and equitable compensation decisions. Exposed, sandy beaches are one of our most familiar and highly valued coastal areas, yet, when oiled, providing uncontested environmental assessments for beaches challenges both responsible parties and natural resource trustees. The dynamic, physical nature of exposed beaches has limited experimental inquiry preventing the development of widely accepted ecological models describing beach function. The same dynamic nature confounds sampling beaches efficiently in the aftermath of an oil spill. To constrain oiled beach impact assessments in the future and to encourage investigation of topics relevant to beach environmental assessment, we provide a summary of beach ecosystem services, re‐examine the results of the limited number of relevant oiled beach studies, define ecological criteria that would improve extrapolating injury assessments drawn from cognate literature, and identify research topics for investigation.
... Hanson et al., 2002 ;Nordstrom, 2005 ;Cooke, et al., 2012 ;Arens et al., 2010 ;De Vries et al., 2012). Cependant, cette dernière méthode a rencontré un succès variable et même si l'impact écologique de la gestion souple est généralement plus faible que celui consistant à mettre en place des ouvrages en dur, l'écosystème de la plage peut être impacté négativement (Peterson et Bishop, 2005 ;Peterson et al., 2006 ;Speybroeck et al., 2006). ...
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Les dunes littorales le long des côtes sableuses ont souvent été fixées, voire reprofilées, pour protéger des inondations et des vagues de tempêtes les biens socio-économiques situés en arrière. Mais ces méthodes de gestion ont parfois mené à la dégradation de l’écosystème des dunes et de leur résilience face aux événements extrêmes. Depuis quelques années, plusieurs études dans le monde ont porté sur la réintroduction de la dynamique naturelle dans les systèmes de dunes côtières. C’est dans ce contexte que nous avons réalisé une expérimentation pionnière en France par la mise en place de brèches dans un système dunaire du sud-ouest de la France. Après 3 ans de suivis morphologiques (photogrammétrie par drone) et écologiques (in situ), les résultats ont mis en avant que les brèches ont favorisé le transport de sable chargé en nutriments vers l’arrière dune, menant à une augmentation de la diversité des espèces. Ces travaux ont donc des implications importantes pour les stratégies de gestion des dunes côtières et le développement durable de ces systèmes, tout particulièrement dans les environnements en érosion chronique.
Our understanding of the response of macrofauna diversity patterns to the variability of sandy beaches across spatial scales is limited. Defining relationships between diversity and ecosystem productivity is key to understanding the ecological consequences of the current global rates of biodiversity loss. Here, we conducted a study across a large spatial gradient of 39 sandy beaches involving a wide range of environmental conditions and macrobenthic diversity to (1) explore macrofauna diversity patterns (2) estimate secondary production and (3) quantify how much of the variability in beach secondary production can be explained by macrofauna diversity. Beach macrofauna showed a clear increase in α-diversity across a beach geographic gradient linked to oceanographic conditions. Partitioning of β-diversity implied the replacement of some species by others between beaches (i.e. spatial turnover) instead of a process of species loss (or gain) from beach to beach (i.e. nestedness). Variance partitioning analyses revealed that environmental and oceanographic variables (i.e., sea surface temperature, beach size, slope, and exposure rate), but also macrofauna diversity (i.e., species richness and Shannon index), largely determine beach secondary production. We showed that an increase in macrofauna diversity enhances beach secondary production, promoting energy transfer across trophic levels. The positive exponential relationship between macrofauna diversity and secondary production supports the idea that macrofauna plays an essential role in maintaining beaches as productive coastal ecosystems. Consequently, macrofauna diversity loss due to the ongoing shoreline recession and coastal occupation, exacerbated by climate change might cause exponential reductions in beach secondary production, which would affect the functioning of these sea-land interface areas.
The global drive to provide the 3Ss (Sun, Sand and Sea) for the benefit of tourists has been a contributory factor in the parallel deterioration of beach-dune habitats on our coasts. In Europe, this has happened at a time when habitat conservation and integrated coastal zone management have been strongly backed to redress declining habitat condition. This paper proposes that we hijack the 3Ss slogan and use it as one tool in the continuing struggle to effect a transition to genuine sustainable coastal management. In this reappropriation of the slogan, the 3Ss stand for Sand, Space and Species. The new 3Ss would facilitate a shared focus on what are the essential components required for long-term, healthy beach-dune systems, using straight-forward language to initiate conversations between very diverse stakeholder groups.
The threatened status of sandy beaches have not stimulated their biodiversity conservation. Actually, increasing human pressure caused by overuse and unreliable management actions threats from inconspicuous invertebrates to charismatic vertebrates worldwide. Time and funding for complex assessments are often limited for mostly academic researchers, thus, efficient cost-benefit management and conservation actions are urgent demands. Conservation shortcuts are surrogates used to represent other co-occurring species or environmental aspects, being frequently applied as low-cost tools in ecological assessments targeting conservation outcomes. This chapter conceptualizes the most common conservation shortcuts and their value for optimizing management, monitoring and conservation of sandy beaches. Feasible sampling is decisive for selecting conservation shortcuts, therefore, we presented practicable tools for simple and effective ecological assessments based on focal species or assemblages. Furthermore, we depicted the potential of beach species as bioindicators, biomonitors, umbrellas, keystones and flagships. Inasmuch conservation depends on social engagement, marketing, environmental education and scientific outreach, it could rely on conservation shortcuts to raise environmental awareness and engagement of public targeting the protection of biodiversity and maintenance of ecosystem services on sandy beaches.
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In this study, we examine complex responses by macrobenthic assemblages to extensive beach restoration affecting 7 km of open shoreline at Perdido Key, Florida. Beach restoration consisted of two phases, beach nourishment and profile nourishment, each phase lasting roughly one year. We examined macrobenthic responses using an optimal impact study design incorporating ten macrobenthic surveys completed over a three-year period. This study is important because of its geographical region, its relatively large spatial scale, ito long duration, and its consideration of both nearshore assemblages from high energy sandy beaches and diverse assemblages from stable offshore habitats. The physical environment was altered by beach restoration through changes in depth profiles and sediment composition as well as through sediment dynamics. Various macrobenthic responses attributable to beach restoration included: decreased species richness and total density, enhanced fluctuations in those indices, variation in abundances of key indicator taxa, and shifts in macrobenthic assemblage structure. One long-term impact of beach nourishment at nearshore stations included the development of macrobenthic assemblages characteristic of steep depth profiles. Two long-term negative impacts of beach restoration at offshore stations included one from beach nourishment and another from profile nourishment. After beach nourishment, the macrobenthic assemblage structure changed markedly across a considerable offshore area in concert with increased silt/clay loading. Macrobenthic impacts from silt/clay loading were still evident at the end of the study, more than two years after beach nourishment. Macrobenthic populations fluctuated widely at the farthest seaward stations from apparent sediment disturbance, both during and after profile nourishment. These fluctuations involved total densities, species richness, and densities of key indicator taxa. Macrobenthic fluctuations continued through the end of the study, although profile nourishment was completed for more than one year prior to that time. Considerable macrobenthic recovery was apparent during the study, although macrobenthic recovery remained indeterminate in some places. Long-term macrobenthic impacts at several offshore stations supported the hypothesis that diverse offshore assemblages may be less resilient than contiguous nearshore sandy-beach assemblages.
The ecological impact of beach nourishment on the common mole crab, Emerita talpoioa, determined through population census surveys, was found to be a redistribution of the organisms along the beach rather than in increase in population mortality. Reductions in population densities at and immediately adjacent to the downcurrent side of the point of discharge were recorded. The population depression was restricted to a 200-ft (6.10-m) section of the beach adjacent to the point of the discharge. Population 600—1,000 ft (183—305 m) down the beach in the direction of the longshore current increased, indicating a migration of mole crabs in response to nourishment. Tidal, wave, and current motions were found to play an essential role in reducing the mortality of the mole crabs and permitting migrations associated with beach nourishment. Population numbers at the discharge site recovered within a few tidal cycles.
A winter survey of seven species of wading birds at 40 intertidal sites in six estuaries in SW England was made. Densities of the two smallest waders, dunlin Calidris alpina and redshank Tringa totanus were comparable on the twelve sites in the Severn to those in the other estuaries. Densities of the larger species, grey plover Pluvialis squatarola, bar-tailed and blacked-tailed godwits (Limosa lapponica, L. limosa), curlew Numenius arquata and oystercatcher Haematopus ostralegus were comparatively low on sites in the Severn. Bird densities generally correlated with densities of one to three widely taken prey species. When data from all estuaries were combined, bird densities correlated with the densities of one or two prey species, the polychaete Nereis diversicolor providing the best correlation in five cases. Densities of larger birds were correlated with densities of their larger-sized prey. Sediment parameters correlated additionally with the density for bar-tailed godwit and redshank. Exposure-time correlated with density of oystercatcher. Low densities of larger waders on the Severn can be explained by the low densities there of the larger-sized polychaete worms and bivalve molluscs upon which they fed. By holding back the ebbing tide, a barrage would substantially reduce the area of intertidal flats available at low water for the birds to feed, but productivity of the estuary, and thus the invertebrate density, would increase in the post-barrage environmental conditions. Wader densities would have to increase twofold to allow the same overall numbers of birds to remain post-barrage as occur on the Severn at present. Provisional estimates of the increases in prey density required to allow bird densities to increase by this amount, with the exception of the prey of dunlin, fall well within the ranges of densities found in other estuaries. An attempt was made to derive equations with which to predict post-barrage densities of invertebrates from easily measured, static environmental variables. There appears to be a special feature of the Severn, probably associated with its highly dynamic nature, whose effect was not captured by measuring static variables. This factor must be identified if the post-barrage densities of invertebrates, and thus of the birds, are to be successfully predicted. -frm Authors
Field experiments with bivalve molluscs at Mugu Lagoon, California (USA), during an intense rainstorm in February 1978 provided tests of the selectivity of mortality during catastrophic sedimentation. In a high-current sand channel, sedimentation was slight, the effects on sediment grade short-lived, and the effects on survival of two suspension-feeding bivalves, Protothaca staminea and Chione undatella, undetectable. In a lower-energy, muddy-sand environment, the storm deposited approx= 10 cm of silts and clays, which substantially increased mortality of both species. Mortality rate in muddy sand varied significantly with 1) trophic group, 2) species identity within the suspension feeders, 3) body size within the two suspension feeders, and 4) Protothaca density. A 15-day simulation of the effects of addition of 10 cm of the storm sediments to clams in laboratory aquaria tested and confirmed the species and size dependency of mortality. Catastrophic burial clearly does not produce an unbiased instantaneous snapshot of past conditions, but rather requires taphonomic considerations of trophic group, species type, size, and also density dependence prior to accurate paleoecological reconstructions. -from Author
This study documents that since 1923, approximately 350 million cubic yards of sand have been deposited on the US East Coast barrier island shoreline (from Long Island, New York to Fisher Island, Florida), by more than 573 beach nourishment episodes, at 154 locations. On East Coast barrier beaches, the use of beach nourishment to control coastal erosion has increased rapidly since the 1960's. Most of this volume (65%) has been placed by federally sponsored beach nourishment projects, either storm and erosion control projects or navigation projects with beach disposal of dredge spoil. However, the proportion of nourishment projects not involving federal funds (state/local and local/private nourishment projects) has been increasing.
(1) A winter survey of seven species of wading birds (Charadrii) at forty intertidal sites in six estuaries in south-west England was made to identify the variables that determined the variation in bird densities between the sites and to develop a method for predicting bird densities should a tidal power barrage be built on the Severn estuary. (2) The densities of the two smallest waders, the dunlin (Calidris alpina) and redshank (Tringa totanus), were comparable on the twelve sites in the Severn to those in the other estuaries. In contrast, the densities of the larger species, the grey plover (Pluvialis squatarola), bar-tailed and black-tailed godwits (Limosa lapponica and L. limosa), curlew (Numenius arquata) and oystercatcher (Haematopus ostragleus), were comparatively low on sites in the Severn. (3) Within most estuaries, bird densities correlated with the densities of one to three widely taken prey species. When data from all estuaries were combined, bird densities correlated with the densities of one or two prey species, the polychaete worm Nereis diversicolor providing the best correlation in five cases. The densities of the larger birds were correlated with the densities of their larger-sized prey. Allowing for the effects of prey density, sediment parameters correlated additionally with the density of bar-tailed godwit and redshank and exposure-time correlated with the density of oystercatcher. (4) When the effects of these variables were taken into account, bird densities on sites on the Severn were only significantly different from those on other estuaries for one or two species. Therefore, the low densities of larger wader species on the Severn can be explained by the low densities there of the larger-sized polychaete worms and bivalve molluscs upon which they feed: there was no reason to invoke a special unidentified factor in the Severn to account for the low densities of these species. It was concluded that other estuaries provide an analogue with which to predict post-barrage bird densities on the Severn from predicted densities of their prey. (5) By holding back the ebbing tide, a barrage would substantially reduce the area of intertidal flats available at low water for the birds to feed. On the other hand, the productivity of the estuary, and thus the invertebrate density, could increase in the generally more benign post-barrage environmental conditions. Wader densities would have to increase approximately twofold to allow the same overall numbers of birds to remain post-barrage as occur on the Severn at present. Provisional estimates are given of the increases in prey density required to allow bird densities to increase by this amount. With the exception of the prey of dunlin, the required values fall well within the ranges of densities found in other estuaries, and so could in principle be attained in the post-barrage Severn. (6) An attempt was made to derive equations with which to predict post-barrage densities of invertebrates from easily measured, static environmental variables whose post-barrage values could themselves be predicted. Although the densities of six of the ten important prey categories correlated with static environmental variables, such as the particle-size and organic content of the sediment, the fact that a site was in the Severn had a significant additional effect on invertebrate density in seven cases. This suggests that there is a special feature of the Severn, probably one associated with its highly dynamic nature, whose effect was not captured by measuring static variables. This factor must be identified, and the effect of a barrage upon it evaluated, if the post-barrage densities of invertebrates, and thus of the birds, are to be successfully predicted.