ABSTRACT1. Even though beach nourishment is generally considered as an environment-friendly option for coastal protection and beach restoration, sizeable impacts on several beach ecosystem components (microphytobenthos, vascular plants, terrestrial arthropods, marine zoobenthos and avifauna) are described in the literature, as reviewed in this paper.2. Negative, ecosystem-component specific effects of beach nourishment dominate in the short to medium term, with the size of the impact being determined by (1) activities during the construction phase, (2) the quality and (3) the quantity of the nourishment sand, (4) the timing, place and size of project, and (5) the nourishment technique and strategy applied. Over the long term the speed and degree of ecological recovery largely depend on the physical characteristics of the beach habitat, mainly determined by (1) sediment quality and quantity, (2) the nourishment technique and strategy applied, (3) the place and the size of nourishment and (4) the physical environment prior to nourishment.3. The limited information available on indirect and cumulative ecological effects indicates that these effects cannot be neglected in an overall impact assessment. Hence, for ecologically good practice of beach nourishment it is advised (1) to choose nourishment sands with a sediment composition comparable to that of the natural sediment, (2) to avoid short-term compaction by ploughing immediately after construction, (3) to execute the nourishment in a period of low beach use by birds and other mobile organisms, (4) to choose a number of smaller projects rather than a single large nourishment project and (5) to select the nourishment technique with respect to the local natural values. *Correspondence to: J. Speybroeck, Ghent University, Biology Department, Marine Biology Section, Krijgslaan 281, Building S8, B-9000 Ghent, Belgium. E-mail: jeroen.speybroeck@UGent.be 4. In order to allow an objective, scientifically sound, ecological adjustment of future nourishments, research should aim at (1) taking into account the full sandy beach ecosystem, (2) avoiding strategic imperfections in experimental design and (3) elucidating the biological processes behind impact and recovery of all ecosystem components.

Spatial pa tterns of nematode community structure from two geographically spaced intermediate, microtidal beaches (i.e. Mediterranean and Baltic) were investigated. Differences in the nematode assemblages were found to be significantly different and related to the morphodynamic characteristics of the studied zones (upper beach, swash/breaker and subtidal). Highest nematode densities and species diversities were recorded on the coarse-grained, more physically controlled, Italian beach in contrast to the more chemically controlled Polish beach. This is in contrast to the worldwide pa tterns of macrofaunal communities. As demonstrated by higher taxonomic distinctness measurements, upper beaches were found to harbour species from both the marine and terrestrial ecosystem and are considered to be impo rtant ecotones between these adjacent systems. The swash/breaker zones are characterised by the loss of distinctive species caused by the high water percolation in these zones. The concept of parallel ecological communities 'isocommunities' is only supported for the upper beach zones.KEYWORDS: free-living nematodes, diversity, taxonomic relatedness, isocommunities, sandy beach morphodynamics, Mediterranean, Baltic CHAPTER III: Nematodes from wave-dominated sandy beaches 45 INTRODUCTIONSandy beaches are examples of simple ecosystems, driven principally by the interacting physical forces of waves, tides and sediment movements. Wave dominance varies from total on sandy, tide-less shores, decreasing as other processes, especially tides, increase their influence on the shore face topography.Microtidal (wave-dominated) sandy beaches represent widely fluctuating environments which have been classified into three distinctive types (reflective, intermediate and dissipative) according to the modal breaker height, modal wave period and sediment fall velocity, which are all combined in the dimensionless fall velocity or Dean's parameter (S2) (Sho rt 1999).These sandy sediments offer a considerable range and diversity of biotic habitats: horizontally, the sub-aerial (dunes and upper beach), the inte rt idal (swash zone/shoreline) and the subtidal (surfzone and near-shore) while vertically there are pelagic, benthic and interstitial environments. As the beach is the dynamic inte rface between the terrestrial and marine ecosystem several biotic and abiotic gradients characterize this interface.Due to these steep gradients (e.g. in oxygen, temperature, organic material, etc.) and the sediment heterogeneity, zones with specific physico-chemical properties can develop, harbouring, as a consequence, a different benthic fauna (Wieser el al. 1974). Most of the faunal research on sandy beaches has been concentrated mainly on macrofauna (>1 mm) (McLachlan and Jaramillo 1995 and references therein) and more recently also birds (e.g. Cornelius el al. 2001). In contrast, sandy beach meiofauna (all metazoans between 1 mm and 38 pm) have received considerably less a ttention notwithstanding their high diversity (even at taxon level) and de...

Horizontal zonation pa tterns and feeding structure of marine nematode assemblages on a macrotidal, ultra-dissipative sandy beach (De Panne, Belgium) Journal of Sea Research 52:211-226 ABSTRACTMacrobenthic zonation on sandy beaches has been studied widely, whereas meiobenthic/nematofaunal species richness and zonation pa tterns have received little a ttention. We investigated community structure, inte rt idal zonation of nematode species and feeding structure across a macrotidal, ultra-dissipative, sandy beach (De Panne, Belgium). A total of 88 free-living marine nematode species were recorded along transects. Average nematode densities increased from the upper beach (320 ± 45 Ind/10 cm') towards the low-tidal level (2784 ± 6 Ind/10 cm 2), which corresponds well to the better-known macrobenthic pa tterns on sandy beaches. While macrobenthic species richness usually increases towards the low-tidal level, nematode species richness reached highest values around the mid-tidal level (34 ± 3 sp.). This can be explained by an optimal balance between time of submergence, oxygen supply and sediment stability.Multivariate analyses indicated four different nematode assemblages that reflect the tidal zonation pa tterns: the upper beach, the strandline, the middle beach association and the lower beach association. The assemblages were significantly different from each other although similarities tended to increase down the beach, indicating a more gradual transition between the mid-tidal and low-tidal assemblages. Non-selective deposit feeders dominated all zones except in the strandline, where epistratum feeders were dominant.Percentage of very fine sand and percentage of shell fragments provided the best granulometric variables in determining these assemblages.

Tourism has long been considered as a 'clean industry' with almost no negative effects on the environment. This study demonstrated, in two different coastal systems (Mediterranean and Baltic), that tourism related activities are particularly affecting the sandy beach meio- and nematofauna in the upper beach zone, the specific ecotone in which many meiofauna species from both the marine and the terrestrial environment congregate. Tourist upper beaches are characterized by a lower % total organic matter (%TOM), lower densities, lower diversities (absence of Insecta, Harpacticoida, Oligochaeta, terrestrial nematodes and marine Ironidae nematodes) and higher community stress compared to nearby non-tourist locations. The %TOM was found to be the single most important factor for the observed differences in meiofauna assemblage structure at tourist versus non-tourist beaches in both the Mediterranean and the Baltic region. The free-living nematode assemblages from tourist upper zones depart significantly from expectations based on random selections from the regional nematode species pool. Furthermore upper zone assemblages are characterised by a low species diversity consisting of taxonomically closely related nematode species with r-strategist features. Generally, faunal differences between tourist and non-tourist beaches are decreasing towards the lower beach zones.

Horizontal and vertical distribution of meiofauna on sandy beaches of the North Sea (The Netherlands, Belgium, France) Abstract Sandy intertidal zones were analysed for the presence of meiofauna. The material was collected on six macro-tidal sandy beaches along the North Sea (The Netherlands, France, Belgium), in order to analyse the vertical and horizontal meiofaunal distribution patterns. Eleven higher meiofauna taxa (one represented by larval stage-Copepoda nauplii) were recorded. The maximum total meiofauna abundance was observed on the Dutch beach (4,295±911 ind. 10 cm À2 ) in the Westerschelde estuary, while the lowest values (361±128 ind. 10 cm À2 ) were recorded in France at the Audresselles beach. Meiofauna of the different localities consisted mainly of nematodes, harpacticoids and turbellarians. Nematodes numerically dominated all sampled stations, comprising more than 45% of the total meiofauna density. Meiofauna was mainly concentrated at the sand surface with about 70% present in the uppermost 5 cm. Meiofauna occurred across the entire intertidal zone. A clear zonation pattern in the distribution of meiofauna taxa across the beaches was observed. The present work suggests that designation of exposed sandy beaches as physically controlled (McLachlan 1988) does not explain their biological variability.