Scolelepis Squamata Research Articles

Potential long-term disturbance associated with beach nourishment - insights and observations from Pea Island National Wildlife Refuge, Outer Banks, North Carolina

The longer-term ecosystem impacts associated with a beach nourishment project conducted in 2014 were studied on an ocean beach on the Pea Island National Wildlife Refuge on North Carolina's Outer Banks. The unique nature of the project is tied to the study's duration, which spans nine years, and the venue, a national wildlife refuge where human-sourced confounding effects are minimal. Populations for five invertebrates: Emerita talpoida (the Atlantic Mole Crab), Donax variabilis (the Coquina Clam), Scolelepis squamata, Ocypode quadrata (the Atlantic Ghost Crab), and indigenous Amphipods were monitored seasonally over nine-years that asymmetrically straddled the 2014 nourishment event. Beach sediments were also monitored in concert with the biodata. Results show that the 2014 nourishment fill sands were finer than those native to the study area beach, however, reworking quickly brought the fill sands on the nourished beach into size parity with native sediments observed on a predefined control site.Findings from this investigation fail to present evidence to suggest that any type of ephemeral species die-off occurred in association with the 2014 nourishment event. While die-offs are commonplace reported, such outcomes are not inevitable. Other investigators have documented ecosystem resilience against significant disturbances such as beach nourishment—this study appears to corroborate such findings, both at the system and species levels. Many argue that nourishment fill sand characteristics: their fit to the native sediment in terms of size and composition, and their application during construction, are the principal determinants driving the disturbance response and subsequent post-nourishment recovery. This study corroborates this fill-sand/recovery relationship but provides evidence to support a causation argument only circumstantially.

Assessing the benthic quality status of three fine sand tropical beaches from the Andaman Islands through the application of marine biotic indices.

The rapid coastal development in the Andaman Islands has resulted in littoral habitat degradation. Understanding the performances of marine biotic indices and the interpretation and translation of those results into coastal health assessment could become an integral tool in future monitoring and management policies. In this line of efforts, the ecological quality status of three sandy beaches, two urban and one nonurban, was evaluated by using three marine biotic indices. The faunal community belonged to moderately well-sorted fine sand biocenosis. The relatively high species richness (15.9 ± 0.80 taxa sample-1) and moderate abundance (563 ± 38.8 ind.m-2) were features of the benthic fauna. The urban beaches (Aberdeen Bay and Carbyn's Cove) corresponded to tolerant benthic communities. Malacoceros indicus, Grandidierella megnae and Scolelepis squamata (tolerant species), and Ampelisca diadema (indifferent species) were the major constituents of urban beaches, while Scoloplos capensis, Urothoe grimaldii, and Urothoe platydactyla (sensitive species) were important at the nonurban beach (Wandoor). The high-good quality status prevailed across the spatial and temporal scales except for Carbyn's cove beach, where good-poor status was noticed. The M-AMBI appeared to be the most robust measure in distinguishing the impact between the urban and nonurban beaches. The constrained ordinations revealed a gradient of disturbance across the beaches. The distinct patterns of sample segregation were the result of the ecological response. This attempt should be considered a comprehensive measure of quality assessment of beaches under human pressure and draw a parallel line of evidence to global studies on sandy beaches.

Effects of vehicle traffic and trampling on the macrobenthic community of Amazonian macrotidal sandy beaches

AbstractWe report for the first time the effects of vehicle traffic and beachgoer trampling on macrobenthic communities of Amazonian sandy beaches. Sampling was performed during four consecutive months with different beach use intensity in 2017 (before, during vacation, and two months after the vacation period) on three contrasting beaches with regard to disturbance (Urban: Atalaia; Intermediate: Farol-Velho; and Protected: Corvinas) in the intertidal zone along two equidistant transects at seven equidistant sampling stations from the high-tide water mark to the swash zone. At each sampling station, four biological and sediment samples were randomly collected. Also, in each station, the sediment compaction was determined using a manual penetrometer. Physical sediment variables remained constant over time in all beaches, whereas differences were found in sediment compaction over the months. Macrobenthic community differences in density and richness among months were observed at Atalaia and Farol-Velho beaches. In contrast, Corvinas beach remained constant throughout the study period. Furthermore, the vulnerability of the polychaetesThoracophellia papillata,Scolelepis squamataandParaonissp. indicates that they might be potential indicators of recreational activity impact.

Nonadditive effects of consumption in an intertidal macroinvertebrate community are independent of food availability but driven by complementarity effects.

Suboptimal environmental conditions are ubiquitous in nature and commonly drive the outcome of biological interactions in community processes. Despite the importance of biological interactions for community processes, knowledge on how species interactions are affected by a limiting resource, for example, low food availability, remains limited. Here, we tested whether variation in food supply causes nonadditive consumption patterns, using the macroinvertebrate community of intertidal sandy beaches as a model system. We quantified isotopically labeled diatom consumption by three macroinvertebrate species (Bathyporeia pilosa, Haustorius arenarius, and Scolelepis squamata) kept in mesocosms in either monoculture or a three‐species community at a range of diatom densities. Our results show that B. pilosa was the most successful competitor in terms of consumption at both high and low diatom density, while H. arenarius and especially S. squamata consumed less in a community than in their respective monocultures. Nonadditive effects on consumption in this macroinvertebrate community were present and larger than mere additive effects, and similar across diatom densities. The underlying species interactions, however, did change with diatom density. Complementarity effects related to niche‐partitioning were the main driver of the net diversity effect on consumption, with a slightly increasing contribution of selection effects related to competition with decreasing diatom density. For the first time, we showed that nonadditive effects of consumption are independent of food availability in a macroinvertebrate community. This suggests that, in communities with functionally different, and thus complementary, species, nonadditive effects can arise even when food availability is low. Hence, at a range of environmental conditions, species interactions hold important potential to alter ecosystem functioning.

Archigregarines of the English Channel revisited: New molecular data on Selenidium species including early described and new species and the uncertainties of phylogenetic relationships.

BackgroundGregarines represent an important transition step from free-living predatory (colpodellids s.l.) and/or photosynthetic (Chromera and Vitrella) apicomplexan lineages to the most important pathogens, obligate intracellular parasites of humans and domestic animals such as coccidians and haemosporidians (Plasmodium, Toxoplasma, Eimeria, Babesia, etc.). While dozens of genomes of other apicomplexan groups are available, gregarines are barely entering the molecular age. Among the gregarines, archigregarines possess a unique mixture of ancestral (myzocytosis) and derived (lack of apicoplast, presence of subpellicular microtubules) features.Methodology/Principal findingsIn this study we revisited five of the early-described species of the genus Selenidium including the type species Selenidium pendula, with special focus on surface ultrastructure and molecular data. We were also able to describe three new species within this genus. All species were characterized at morphological (light and scanning electron microscopy data) and molecular (SSU rDNA sequence data) levels. Gregarine specimens were isolated from polychaete hosts collected from the English Channel near the Station Biologique de Roscoff, France: Selenidium pendula from Scolelepis squamata, S. hollandei and S. sabellariae from Sabellaria alveolata, S. sabellae from Sabella pavonina, Selenidium fallax from Cirriformia tentaculata, S. spiralis sp. n. and S. antevariabilis sp. n. from Amphitritides gracilis, and S. opheliae sp. n. from Ophelia roscoffensis. Molecular phylogenetic analyses of these data showed archigregarines clustering into five separate clades and support previous doubts about their monophyly.Conclusions/SignificanceOur phylogenies using the extended gregarine sampling show that the archigregarines are indeed not monophyletic with one strongly supported clade of Selenidium sequences around the type species S. pendula. We suggest the revision of the whole archigregarine taxonomy with only the species within this clade remaining in the genus Selenidium, while the other species should be moved into newly erected genera. However, the SSU rDNA phylogenies show very clearly that the tree topology and therefore the inferred relationships within and in between clades are unstable and such revision would be problematic without additional sequence data.

Sandy beaches in a coastline vulnerable to erosion in Atlantic Canada: Macrobenthic community structure in relation to backshore and physical features

Most literature suggests that sandy beach macrobenthic communities are structured by physical factors. However, an aspect that has not been studied in detail is whether those physical factors change with erosion or the association of beaches to backshore features like sand dunes, till bluffs, and sandstone cliffs. We addressed this question by sampling 14 sandy beaches on the north shore of Prince Edward Island, Atlantic Canada. Two null hypotheses were tested: first, there is no relationship between physical factors and community descriptors across sandy beaches, and second, there is no difference among beaches associated with distinct backshore features both in terms of physical factors and community descriptors. In order to test these hypotheses, samples of macrobenthic organisms and measurements of grain size, slope, beach deposit index and erosion rates were obtained. Our surveys collected a total of 14 taxa numerically dominated by the spionid polychaete Scolelepis squamata. With regards to the first hypothesis, regression analyses showed that community descriptors were all positively related to erosion rates while unrelated to the variation in grain size, slope and beach deposit index. As for the second hypothesis, erosion rates were significantly different among beaches associated to till bluffs (highest), dunes and sandstone cliffs (lowest). Meanwhile, the other physical factors did not significantly differ among backshore features. Species richness was highest in beaches associated to till bluffs and lowest in those associated to sandstone cliffs. Abundance values were also lowest in beaches associated to sandstone cliffs, and their community composition was significantly different to those associated to dunes and till bluffs. We suggest that the relationship between erosion rates and community descriptors is complex and may be mediated by the availability of nutrients: higher erosion levels might account for higher concentrations of nutrients for suspension feeders, the numerically dominant organisms in this system. We call for further attention to the relationship between erosion and suspended nutrients.

Variability of macrofauna distribution along a dissipative log-spiral sandy beach in Rio de Janeiro, Southeastern Brazil

Log-spiral beaches display defined physical gradients alongshore. However, the majority of studies focus on the variability of a single population of macrofauna species. We aimed to investigate the variation in species distribution and in community structure along ten transects on a log-spiral beach. Principal component analysis indicated a clear physical gradient alongshore. Redundancy analysis showed that the sheltered end was related to smaller particle sizes, higher organic matter content and high densities of polychaetes. The exposed end was characterized by coarser sand, lower organic matter content and a high presence of crustaceans. Model selection indicated that the “best fit” to explain the variability in the number of individuals included grain size and beach slope. Variability of the polychaete Scolelepis squamata was best explained by grain size, slope and sediment sorting. The best model for the cirolanid Excirolana armata only included sediment sorting. The physical gradient in sediment texture and the beach slope explained more than one-third of the variability in community structure. The physical variables were also correlated with the distribution of the individual species. We showed that the physical gradient on log-spiral coasts may be an important driver of macrofauna variability, even at mesoscales and in dissipative conditions.

Breadth and composition of polychaete diets and the importance of diatoms to species and trophic guilds

Polychaetes are important components of trophic webs in sandy beaches, mainly due to their abundance and diversity of feeding modes, acting as detritivores or primary/secondary consumers. We characterized diets of several polychaete species from intertidal sandy beaches by gut content evaluation. Diet breadth (Levins Index) was calculated for each species to evaluate the influence of different feeding strategies on this metric. Diatom composition was also assessed to verify the relevance of microphtyobenthic primary production to macrobenthic feeding on sandy beaches and its relationship with feeding strategies. A total of 2583 guts from 17 species were evaluated. Diet information is compared with literature, and added to taxa with previously unknown feeding habit. Diet breadths were generally low, but surface deposit feeders had the highest values. Scolelepis squamata guts were dominated by foraminfera, which may either be an specialization or local conditions. Subsurface deposit feeders usually had few items and lower breadths, highlighting the importance of organic matter to this guild. Diatoms were frequently found, and benthic were more frequently consumed than planktonic ones. The high numbers of benthic diatoms found for some species highlight the importance local food sources to sandy beach food webs.

On the taxonomic status of the European Scolelepis (Scolelepis) squamata(Polychaeta: Spionidae), with description of a new species from southern Europe On the taxonomic status of the European Scolelepis (Scolelepis) squamata (Polychaeta: Spionidae), with description of a new species from southern Europe

In order to clarify taxonomic problems relating to the identity of Scolelepis (Scolelepis) specimens from the Black Sea, the identified material was compared with specimens of Scolelepis cirratulus (Delle Chiaje, 1829) from the Mediterranean, of S. squamata (Abildgaard, in O.F. Müller, 1806) from the North Sea and the Atlantic coast of Spain, and with the syntypes of S. mesnili (Bellan & Lagardère, 1971) from the Atlantic coast of France. The examination of a large number of specimens (both juveniles and adults) reveals that the currently accepted morphological differences distinguishing all species show size-related patterns, suggesting that they all belong to one species. Therefore, this study supports the view that Scolelepis cirratulus and Scolelepis mesnili are junior synonyms of Scolelepis (Scolelepis) squamata. As a result of the re-assessment of the species limits of Scolelepis (Scolelepis) squamata, a new species, Scolelepis (Scolelepis) neglecta sp. nov., is distinguished and described from the Cantabrian coast of Spain. It inhabits shallow sublittoral fine sands and was earlier misidentified and reported from the Atlantic coast of Europe and the Mediterranean Sea as Scolelepis squamata, Scolelepis mesnili, Scolelepis cantabra (Rioja, 1918), or Dispio uncinata Hartman, 1951. The new species is characterized by having a trilobate prostomium with an acuminate medial portion, a short peristomium with well-developed dorso-lateral wings, short palps with two longitudinal bands of elevated lobes, neuropodial postchaetal lamellae notched from chaetigers 14-41, and strongly curved bidentate neuropodial hooded hooks with a slight constriction on the shaft starting from chaetigers 19-49. The morphology, diagnostic characters and ecology of both Scolelepis (Scolelepis) squamata and Scolelepis (Scolelepis) neglecta sp. nov. are discussed.

Prey type and foraging ecology of Sanderlings Calidris alba in different climate zones: are tropical areas more favourable than temperate sites?

Sanderlings (Calidris alba) are long-distance migratory shorebirds with a non-breeding range that spans temperate and tropical coastal habitats. Breeding in the High Arctic combined with non-breeding seasons in the tropics necessitate long migrations, which are energetically demanding. On an annual basis, the higher energy expenditures during migration might pay off if food availability in the tropics is higher than at temperate latitudes. We compared foraging behaviour of birds at a north temperate and a tropical non-breeding site in the Netherlands and Ghana, respectively. In both cases the birds used similar habitats (open beaches), and experienced similar periods of daylight, which enabled us to compare food abundance and availability, and behavioural time budgets and food intake. During the non-breeding season, Sanderlings in the Netherlands spent 79% of their day foraging; in Ghana birds spent only 38% of the daytime period foraging and the largest proportion of their time resting (58%). The main prey item in the Netherlands was the soft-bodied polychaete Scolelepis squamata, while Sanderlings in Ghana fed almost exclusively on the bivalve Donax pulchellus, which they swallowed whole and crushed internally. Average availability of polychaete worms in the Netherlands was 7.4 g ash free dry mass (AFDM) m−2, which was one tenth of the 77.1 g AFDM m−2 estimated for the beach in Ghana. In the tropical environment of Ghana the Sanderlings combined relatively low energy requirements with high prey intake rates (1.64 mg opposed to 0.13 mg AFDM s−1 for Ghana and the Netherlands respectively). Although this may suggest that the Ghana beaches are the most favourable environment, processing the hard-shelled bivalve (D. pulchellus) which is the staple food could be costly. The large amount of daytime spent resting in Ghana may be indicative of the time needed to process the shell fragments, rather than indicate rest.

Dominant macrobenthic populations experience sustained impacts from annual disposal of fine sediments on sandy beaches

Despite increasing use of dredged mate- rials as beach fill to protect coastal property and public beaches from storm damage, knowledge of how this practice affects sandy beach ecosystems re- mains poor. We coupled field monitoring of 2 succes- sive beach disposal events with mesocosm experi- ments to assess mechanisms of ecological effects of fine sediment disposal. Macrobenthic sampling on Topsail Island, North Carolina, revealed that disposal of dredge spoils transformed beach grain sizes from medium to fine sand. Water sampling documented substantially elevated surf-zone turbidity during and occasionally after sediment deposition. When disposal occurred before spring invertebrate recruitment to the beach, it negatively influenced recruitment of the mole crab Emerita talpoida and the amphipod Para- haustorius longimerus. When disposal followed re- cruitment, it affected abundances of the bean clam Donax variabilis and 3 species of haustoriid am- phipods negatively, and abundance of the spionid polychaete Scolelepis squamata positively. Effects lasted for the full warm season, and suppressions of invertebrate abundances were repeated across suc- cessive annual disposal events. In mesocosms, turbid- ity matching that induced in the field slowed growth of clams and modified habitat choices by predatory fishes. Hence, annual disposal of fine-grained dredge spoils on these sandy beaches maintained depressed abundances of 5 of 6 macroinvertebrate prey of shore- bird and surf fish, without sustaining elevated volumes of beach sediments as long as a year. Implementation of disposal projects before the beginning of the sea- sonal recruitment of benthos resulted in fewer nega- tive impacts on abundance than disposal projects con- ducted after the recruitment season, probably reflecting a more universal risk from burial and suffocation.

Polychaete diversity in the estuarine habitats of Términos Lagoon, southern Gulf of Mexico

Hernandez-Alcantara, P., Cortes-Solano, J.D., Medina-Cantu, N.M., Aviles-Diaz, A.L. and Solis-Weiss, V. 2014. Polychaete diversity in the estuarine habitats of Terminos Lagoon, Southern Gulf of Mexico. Memoirs of Museum Victoria 71: 97–107. In order to establish the status of the biodiversity of the polychaete fauna inhabiting the soft bottoms in the largest lagoon-estuarine system from the southern end of the Gulf of Mexico, Terminos Lagoon, we collected and identified 3,398 specimens belonging to 119 species and 33 families of polychaetes. The soft bottom fauna was then compared with records of polychaetes collected in other habitats in the lagoon such as seagrass beds and mangroves. In all, 190 species from 34 families of polychaetes previously recorded there were taken into account. The families Nereididae (20 spp.), Spionidae (15 spp.) and Syllidae (14 spp.) were the most diverse. The soft bottom habitat has by far the largest number of species (119) followed by the seagrass beds and mangroves with 75 and 42 species respectively. Large spatial heterogeneity in polychaete composition was observed, as only 5% of the species (Melinna maculata, Capitella sp., Mediomastus californiensis, Schistomeringos rudolphii, Marphysa sanguinea, Alitta succinea, Diopatra cuprea, Scoloplos treadwelli, Prionospio heterobranchia and Scolelepis squamata) were widely distributed in the lagoon. The polychaete fauna living in the mangroves is quite similar to that from seagrasses and soft bottoms (R(ANOSIM) = 0.247 and 0.3 respectively), but the polychaetes in the seagrasses and soft bottoms are clearly different from each other (R(ANOSIM) = 0.622). The 119 polychaete species identified in this study represent a significant increase in the records of biodiversity recorded so far in Terminos Lagoon, while the total of 190 species recorded for the whole lagoon represents a larger number than any other recorded for an American tropical estuary.

Is nematode colonisation in the presence of Scolelepis in tropical sandy-beach sediment similar to the colonisation process in temperate sandy beaches?

The role of a dominant macrobenthic polychaete, Scolelepis squamata, in the colonisation of defaunated tropical sediments by sandy-beach nematodes was investigated and compared with a previous colonisation experiment carried out on a temperate sandy beach. Experimental cylinders, equipped with lateral windows allowing infaunal colonisation, were filled with defaunated sediment containing two treatments, with and without S. squamata. These cylinders were inserted into microcosms containing sediment with indigenous meiofauna collected from the field. The treatments were incubated in the laboratory at ambient temperature and salinity for 7, 14 and 21 days. The nematode assemblages in both treatments did not differ in composition between treatments and from the natural assemblages, suggesting that all the species were equally able to colonise the experimental cores. The presence of the polychaete did not affect the development of the nematode community composition, in contrast to the results from a previous temperate-beach experiment. However, our results did not indicate whether the difference in results was caused by the different behaviour of the polychaete specimens, or by the different composition and response of the present nematode community.

Does beach nourishment have long-term effects on intertidal macroinvertebrate species abundance?

Coastal squeeze is the largest threat for sandy coastal areas. To mitigate seaward threats, erosion and sea level rise, sand nourishment is commonly applied. However, its long-term consequences for macroinvertebrate fauna, critical to most ecosystem services of sandy coasts, are still unknown. Seventeen sandy beaches – nourished and controls – were sampled along a chronosequence to investigate the abundance of four dominant macrofauna species and their relations with nourishment year and relevant coastal environmental variables. Dean's parameter and latitude significantly explained the abundance of the spionid polychaete Scolelepis squamata, Beach Index (BI), sand skewness, beach slope and latitude explained the abundance of the amphipod Haustorius arenarius and Relative Tide Range (RTR), recreation and sand sorting explained the abundance of Bathyporeia sarsi. For Eurydice pulchra, no environmental variable explained its abundance. For H. arenarius, E. pulchra and B. sarsi, there was no relation with nourishment year, indicating that recovery took place within a year after nourishment. Scolelepis squamata initially profited from the nourishment with “over-recolonisation”. This confirms its role as an opportunistic species, thereby altering the initial community structure on a beach after nourishment. We conclude that the responses of the four dominant invertebrates studied in the years following beach nourishment are species specific. This shows the importance of knowing the autecology of the sandy beach macroinvertebrate fauna in order to be able to mitigate the effects of beach nourishment and other environmental impacts.

Growth rates of arctic juvenile Scolelepis squamata (Polychaeta: Spionidae) isolated from Chukchi Sea fast ice

In spring, Arctic coastal fast ice is inhabited by high densities of sea ice algae and, among other fauna, juveniles of benthic polychaetes. This paper investigates the hypothesis that growth rates of juveniles of the common sympagic polychaete, Scolelepis squamata (Polychaeta: Spionidae), are significantly faster at sea ice algal bloom concentrations compared to concurrent phytoplankton concentrations. Juvenile S. squamata from fast ice off Barrow, Alaska, were fed with different algal concentrations at 0 and 5 °C, simulating ambient high sea ice algal concentrations, concurrent low phytoplankton concentrations, and an intermediate concentration. Growth rates, calculated using a simple linear regression equation, were significantly higher (up to 115 times) at the highest algal concentration compared to the lowest. At the highest algal concentration, juveniles grew faster at 5 °C compared to those feeding at 0 °C with a Q10 of 2.0. We conclude that highly concentrated sea ice algae can sustain faster growth rates of polychaete juveniles compared to the less dense spring phytoplankton concentrations. The earlier melt of Arctic sea ice predicted with climate change might cause a mismatch between occurrence of polychaete juveniles and food availability in the near future. Our data indicate that this reduction in food availability might counteract any faster growth of a pelagic juvenile stage based on forecasted increased water temperatures.

The effect of the dominant polychaete Scolelepis squamata on nematode colonisation in sandy beach sediments: An experimental approach

The effect of an abundant sandy beach polychaete, Scolelepis squamata, on the colonisation of defaunated sediments by marine nematodes indicates that sandy beach fauna can be partially controlled by biological interactions within and across size groups. Experimental cores, equipped with windows allowing infaunal colonisation, were filled with defaunated sandy beach sediment containing two different treatments with and without S. squamata. These cores were inserted into microcosms filled with sediment with indigenous meiofauna collected from the field. The treatments were incubated in the laboratory at ambient temperature and salinity for 2, 7, 14 and 21 days, in order to follow the colonisation process of the defaunated sediments by the indigenous nematode fauna over time. Nematodes initially colonised both treatments, with abundances of up to 10% of the densities in the control; after 2 weeks, nematode densities in the cores without S. squamata surpassed the control densities. Nematode assemblages in both treatments were not species rich, and also differed in composition from the natural assemblages. The most successful colonising species, Enoplolaimus litoralis, was rare in the surrounding sediment, suggesting that colonisation was determined by species-specific characteristics such as body size, motility and feeding strategy. Initially the presence of macrofauna did not affect the nematode community composition, but after 2 weeks of the experiment, the presence of the polychaete seemed to facilitate the earlier establishment of non-opportunistic species.

Polychaetes of commercial interest from the Mediterranean East Coast of Algeria

Three species of polychaetous annelids are commercially collected, as baits, from natural populations along the coast of Algeria. They are collected by semi-professional bait harvesters supplying a variety of local outlets and are used as bait by local fishermen. Bait harvesters commonly use bleaching liquid (10% in sea water) or a KMnO4 (0.5 to 1% in sea water) solution to force Perinereis cultrifera (Nereididae) individuals out of their algal mat. Hediste diversicolor (Nereididae) and Scolelepis squamata(Spionidae) are dug from intertidal mudflats and sandy beaches. Commercial prices and ways of utilization are given for each species. The necessity for the legislative establishment of a regulatory management plan for worm angling is demonstrated.

The Belgian sandy beach ecosystem: a review

AbstractThis paper reviews the available knowledge on sedimentology, hydrodynamics and five major ecosystem components (microphytobenthos, vascular plants, terrestrial arthropods, zoobenthos, and avifauna) of Belgian sandy beaches. It covers the area from the foredunes to the lower foreshore, takes an ecosystem approach to beaches of this specific geographic area. Morphodynamically, Belgian beaches are (ultra‐)dissipative, macrotidal, and wide. Characteristic grain sizes are 160–380 μm. The sand becomes coarser, beach slopes steeper and tidal range smaller towards the south‐west, where beaches have also been frequently reshaped by human interference such as nourishment. Beach organisms are highly adapted to this unique environment and can reach high numbers. We show that even on a heavily populated coastline subjected to intense recreational and development pressure, beaches provide critical, yet threatened, habitats. Vascular plants growing near the drift line, on the dry beach and in the embryonic dunes are mostly short‐lived and thalassochorous; the most common species include sea rocket (Cakile maritima), prickly saltwort (Salsola kali subsp. kali), and sea sandwort (Honckenya peploides). These zones are habitat to a highly diverse suite of terrestrial arthropods of halobiontic, halophilous and haloxene species; prominent members are sandhoppers (Talitrus saltator) and dipterans (flies). Microphytobenthos, mainly diatoms, is an important primary producer on Belgian beaches but is not well known. The meio‐ and macrobenthos of Belgian beaches contains specific assemblages such as the Scolelepis squamata–Eurydice pulchra community of the upper intertidal zone. Birds no longer nest on the beaches itself, but Belgian sandy shores continue to function as important resting and foraging areas for birds such as the sanderling Calidris alba. We identify several human pressures on the beach ecosystems arising from recreation, beach management and fisheries.

Understanding the life of a sandy beach polychaete of functional importance – Scolelepis squamata (Polychaeta: Spionidae) on Belgian sandy beaches (northeastern Atlantic, North Sea)

The cosmopolitan sandy beach polychaete Scolelepis squamata constitutes an important food resource for juvenile flatfish and wading birds in the northeastern Atlantic, thus playing an important role in sandy beach ecosystem functioning. However, its population dynamics and life history in this part of the world have gone widely uninvestigated. Eight beach transects on Belgian sandy beaches were sampled monthly from October 2003 until October 2004, in order to investigate seasonal trends in the species' abundance, biomass, secondary production, and patterns in reproduction and zonation. Average density, modal density and modal biomass (ash-free dry weight) (mean average density = 169 ± 9 SE ind/m 2; mean modal density = 505 ± 38 SE ind/m 2; mean modal biomass = 0.25 ± 0.02 SE g/m 2) did not exhibit major seasonal changes, whereas average biomass (0.081 ± 0.005 SE g/m 2) and individuals and biomass per strip transect (IST = 16286 ± 1330 SE ind/m; BMST = 7.8 + 0.7 SE g/m) did, peaking in May 2004. Production was calculated at 1.9 g/(m 2*year) (size-frequency method, SFM) and 0.88 g/(m 2*year) (mass specific growth rate method, MSGR) and mean annual biomass was 0.797 g/m 2; resulting in a P/B ratio of 2.40/year (SFM) and 1.11/year (MSGR), which is intermediate to moderately low compared to other polychaete species. Gravid individuals were found from February until August and a single recruitment period was observed from July until September. An average sex ratio of 1.41 ± 0.08 SE was calculated, with a female predominance. Highest densities (>200 ind/m 2) were mostly found above 3 m above MLLWS and at a median grain size from 190 to 320 μm. Average modal or peak density along each transect was situated from 3.95 m up to 4.40 m above MLLWS, in contrast to some other studies where the species was restricted to mid-tidal levels. Significant differences in elevation of peak density were found between non-gravid (411 ± 4 SE cm) and gravid (402 ± 5 SE cm) animals, but none between gravid males and females. The portion of the tidal range that was occupied by the species in the vertical dimension, just failed to differ significantly between non-gravid and gravid individuals, while gravid males (48.2 ± 5.6 SE cm) occupied a significantly wider range than gravid females (36.8 ± 4.7 SE cm), corresponding with a horizontal range difference of 6–9 m cross-shore. The observed zonation pattern, together with a trend in the difference of peak abundance elevation between males and females, are hypothesised to be a result of a strategy of gravid animals to ensure co-occurrence in a narrower zone during reproduction. Observed differences between Brazilian, Moroccan and Belgian populations (e.g. density, biomass, productivity, P/B, life span, body width, period of presence of gravid individuals and recruitment) do not seem to concur with differences in morphodynamics and might be attributed to latitude-associated gradients like climate. Furthermore, the fact that Scolelepis squamata, as defined today, might be a superspecies, cannot be ruled out.

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

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.