Littoral Fringe Research Articles

Modelling the spatiotemporal dynamics of land susceptibility to desertification in Algeria

Desertification is a significant environmental and socioeconomic issue that requires monitoring and early detection. In this context, holistic studies are more useful than localized ones in addressing this issue. In this study, we used the desertification sensitivity index (DSI) to pinpoint regions of Algeria that are at risk of desertification and to examine significant shifts in the sensitivity of land to desertification between 2000 and 2020, as well as the primary drivers of these shifts. Unlike the standard Mediterranean Desertification and Land Use (MEDALUS) approach, which uses equal weighting of parameters and quality indicators to construct the environmental sensitivity areas, the DSI applies statistically generated weights. Our results showed that approximately 106,000 km2 of the non-desert area was extremely susceptible to desertification in 2000, 83,200 km2 in 2010, and 98,200 km2 in 2020, with critical zones mainly located in the High Plains (steppe rangelands). Our analysis revealed that climate and vegetation quality indicators were the main drivers of the DSI, which showed a nonlinear trend during the study period. The analysis of changes in land sensitivity to desertification revealed that most of the changes were negative and occurred in the High Plains, as well as certain areas of the Tell Atlas Mountain ranges and the littoral fringe. However, some positive changes occurred due to the establishment of new forest plantations and croplands. The results provide a comprehensive overview of the risk of desertification in Algeria and its main drivers and can serve as a scientific basis for the development and implementation of necessary measures to interrupt and combat this destructive environmental phenomenon.

Cold spots and cold moments: The potential for sediment freezing to depress denitrification in wetland sediments.

Within the north-temperate zone, winters can be long and are associated with conditions of low temperature and potential for sediment freezing. There are critical gaps in our knowledge of biogeochemical cycling during winter and inadequate knowledge of how warming winters and changing snowpack might affect biogeochemistry. Here, we assessed the impacts of sediment freeze-thaw cycling and nitrate amendment on denitrification rates in the littoral fringe of four urban wetlands. We demonstrate the potential for experimental sediment freezing to suppress denitrification, although freezing effects were not observed at all sites. Multiple freeze-thaw cycles were assessed, and, although subsequent cycles may affect denitrification, the first instance of our experimental freezing seems the most critical. Although this work demonstrates potential sensitivity of wetland denitrification rates to changing winter conditions, we note nitrate availability has a larger impact upon denitrification rates. This suggests nitrification rates and changing nitrate loads may be more important determinants of nitrate retention than sediment freeze-thaw history. Although there has been great interest in hot spots and moments for biogeochemical cycling, we suggest there is similar need to understand cold spots and moments, as evidenced here. This is particularly important where cold moments may correspond with critical periods of nitrate transport, such as snowmelt.

Interference competition as a key determinant for spatial distribution of mangrove crabs

BackgroundThe spatial distribution of mangrove crabs has been commonly associated with tree zonation and abiotic factors such as ground temperature and soil granulometry. Conversely, no studies were designed to investigate the role of competition for resources and predation in shaping crab distribution in mangroves, despite these biotic factors are recognised as key determinants for spatial patterns observed in the communities colonising rocky and sandy intertidal habitats.We studied floral and faunal assemblages in two zones of a Sri Lankan mangrove, a man-made upper intertidal level and a natural eulittoral, mid-shore one. Leaf choice experiments were designed to study both feeding rate and intra and inter-specific interactions for food of sesarmid crabs in the two habitats in order to better understand crab spatial distribution.ResultsThe two intertidal belts differed in terms of floral composition and crab species abundance. The eulittoral zone was strongly dominated by Neosarmatium smithi, while within the elevated littoral fringe four sesarmids (N. smithi, N. asiaticum, N. malabaricum and Muradium tetragonum) were more evenly distributed. At both levels, all sesarmids showed to collect significantly more Bruguiera spp. and Rhizophora apiculata leaves than Excoecaria agallocha ones. There was no temporal segregation in feeding activity among the four species, resulting in a high interference competition for leaves. Regardless of the habitat, N. smithi was always successful in winning inter-specific fights.ConclusionsOur results showed that the elevated littoral fringe was more crowded with crabs, but was less favourable in terms of food availability and environmental conditions. The dominance of N. smithi in gathering mangrove leaves suggests that this species may segregate the other sesarmids into less favourable habitats. The present data strongly suggest for the first time that interference competition for food can contribute to shape mangrove crab spatial distribution.

Mediterranean dune vegetation: conservation of a threatened ecosystem in southern Spain

This paper investigates the plant diversity and current state of the vegetation of a little-known threatened dune complex located in Estepona (southern Spain). This littoral fringe has in the past 60 years experienced a continuous process of intensive occupation derived primarily from tourism and agriculture, which has led to the degradation of the fragile and dynamic coastal systems. Its diminished size and lack of legal protection make it vulnerable to a variety of anthropogenic stresses that threaten the survival of the system. Fieldwork has been the primary methodological procedure to conduct research, given the scarcity of previous studies. The results first of all provide a biogeographical and phytosociological view that elucidates the remarkable plant diversity of the area studied and the complete zonal structure of the communities that comprise the ecosystem. Secondly, a vegetal cartography was created (detail of 1: 2500) to characterize the distribution of flora. This exploration and mapping of vegetation are effective tools in forming a conservation proposal to combat anthropogenic conflicts that destabilize the system. In this sense, harmful human activities threatening the plant phytodiversity of the various strips of vegetation forming the dunes have also been identified.

The fate of Cystoseira crinita, a forest-forming Fucale (Phaeophyceae, Stramenopiles), in France (North Western Mediterranean Sea)

In the Mediterranean Sea, Fucales, and in particular the species of the genus Cystoseira C. Agardh, are habitat-forming species dominating several benthic assemblages from the littoral fringe down to 70–80 m depth in the clearest waters. They generate high primary production involved in the maintenance of diversified trophic levels, they provide shelter, food, habitat and nursery areas to many species, and they are long-lived species that constitute a good model for studying human impact on species diversity. Cystoseira crinita Duby is a Mediterranean endemic cespitose species, living in shallow waters (0–5 m depth), in places with little wave action and high solar irradiance. To reconstruct the long-term patterns of change in its distribution along the French Mediterranean coast (French Catalonia, Languedoc, Provence, French Riviera and Corsica), all the historical data (published articles, unpublished reports and herbarium vouchers) collected since the 18th century were searched and analysed. To assess the current status of the species, several field surveys were conducted between 2010 and 2016 by snorkelling and SCUBA diving. Cystoseira crinita is currently extinct in French Catalonia, near-extinct in Languedoc and western Provence, and functionally extinct on the French Riviera coast, while the eastern Provence and Corsican populations have remained stable. The main probable causes of decline are habitat destruction and overgrazing by herbivores.

Morphologic changes and sedimentary budgets along a Mediterranean coastline with a sand spit: case of the littoral fringe Sidi Ali El Mekki–Gammarth (NE Tunisia)

Morphological changes and both surface and volume budgets along the Mediterranean coastline Sidi Ali El Mekki–Gammarth which is located at the western fringe of the Gulf of Tunis (NE Tunisia) are studied, over the 1887–2010 period, by ancient minute of bathymetry and aerial photographs treated using digital photogrammetric methods and GIS tools. The accretion areas are located upstream the fishing port of Ghar El Melh which interrupts alongshore sediment transport (0.22–0.66 ± 0.21 m/year, i.e., 21,309 ± 1,113 m2/year, i.e., 106,546 ± 5,565 m3/year) and around the recent mouth of the Medjerda River because of fluvial deposits and accumulation of sediment transported by drift currents (2.35–3.35 ± 0.21 m/year, i.e., 4,956 ± 1,050 m2/year, i.e., 24,780 ± 5,250 m3/year). The erosion areas are situated downstream the fishing port of Ghar El Melh (−4.32 to 0.9 ± 0.21 m/year, i.e., −4,822 ± 1,232 m2/year, i.e., −24,114 ± 6,163 m3/year), around the ancient mouth of the Medjerda River which was abandoned and deprived from fluvial sediment supply (−15.44 to −4.55 ± 0.21 m/year, i.e., −4,499 ± 264 m2/year, i.e., −22,495 ± 1,323 m3/year). The eroded sediments are displaced to the south giving rise to the sand spit of Kalâat El Andalous. Coastline retreated also along the Raoued–Gammarth sector which lost sediments by SE–NW drift currents (−0.75 to −0.23 ± 0.21 m/year, i.e., −3,765 ± 1,113 m2/year, i.e., −18,828 ± 5,565 m3/year). The alongshore distribution of accretion/erosion patterns lead to divide the studied coastline into three littoral cells limited by natural boundaries: (a) Cap Sidi Ali El Mekki—the ancient mouth of the Medjerda River, (b) from the ancient to the recent mouth of the Medjerda river, and (c) the recent mouth of the Medjerda River–Cap Gammarth.

Infaunal zoogeography and intergeneric character blending: The case of Metaniphargus shiroi sp. nov. (Crustacea: Amphipoda: Hadziidae), from interstitial beach water on Akajima Island, the Kerama Islands, Southwestern Japan.

A survey of biogenic coralline sands in the littoral fringe of a tropical island in Japan brought a new amphipod species to light. This species represents the first record of the subterranean genus Metaniphargus from the West Pacific. The majority of the species in this genus occur in the Caribbean, but a report from Hawaii and now from Japan defies the endemic Caribbean status it kept for so long. Metaniphargus shiroi sp. nov. is described, and morphological comparisons are made with closely resembling species from Hawaii and the Cayman Islands (genus Metaniphargus), and the Great Barrier Reef and California (genus Dulzura). Involvement of non-congeners in the comparisons is necessary as character overlap is abundant. These comparisons suggest that the presence of form-related body types in the shallow marine interstitial realm is circumtropical and follows habitat suitability rather than sudden dispersal or vicariance events.

Phragmites distribution relative to progressive water level decline in Lake Koronia, Greece

ABSTRACTLake Koronia is a hypertrophic Ramsar site in northern Greece. Water level dropped progressively from approximately 6 m in the mid‐1980s to 0·8 m in 2001 associated with over extraction of groundwater for agriculture, and the open water area has decreased from 4620 to 2930 ha, respectively. The resulting annual water level loss of 0·25–0·30 m year−1 was accompanied by expansion of Phragmites australis from a littoral fringe to dominance of exposed lake bottom areas from 97 ha in 1977 to 785 ha in 2005. The aim of this work was to apply an ecohydrological approach using remote sensing and geographic information system (GIS) to examine the movement of Phragmites relative to the water level retreat and to basin morphometry. Aerial expansion of Phragmites averaged 11–32 ha year−1 during the period of progressive water level decline but increased to 38–116 ha year−1 during a brief period of water level increase (2001–2003) as the plant colonized reflooded portions of the basin. The total area of Phragmites expanded 29% per annum during 1977–2005. Landward and lakeward margins of the Phragmites area followed water level retreat, moving 55 and 129 m, respectively, during the long period of progressive water level decline. Aerial movements of Phragmites in Lake Koronia are some of the highest reported in the literature. Mean water level within the Phragmites bed varied from 0·5 to 2·0 m during the period covered by this study. Very minor changes in basin slope, however, affected plant colonization rates, as evidenced by 200–250 ha/0·5 m water level drop at 0·18% basin slope to 360–1360 ha/0·5 m water level drop at 0·029% slope. The techniques applied to Lake Koronia for reconstructing past lake levels and associated distributions of Phragmites have broad application for understanding the dynamics of Phragmites elsewhere and anticipating periods of rapid plant expansion related to subtle changes in basin morphology. This study is useful for managing Phragmites populations in areas where efforts are being made to re‐establish populations as well as where elimination of invasive populations is sought. Copyright © 2013 John Wiley & Sons, Ltd.

Impact of sewage pollution on the structure and functioning of a rocky shore benthic community

The secondary production of rocky shore macroinvertebrate assemblages impacted through sewage discharge was assessed, taking into account the trends of production among dominant species and feeding guilds. The present study was conducted on the Peniche peninsula (central-western Portuguese coast, temperate region), in three areas: one area near a sewage discharge and two undisturbed reference areas. Within each area, three intertidal zones were monitored ‐ littoral fringe, eulittoral and sublittoral fringe ‐ by taking seasonal samples during one year. The empirical model of Cusson and Bourget (2005) was used to evaluate secondary production. In the littoral fringe, no differences in the production values were found between impacted and reference areas. In the eulittoral, sewage discharge seemed to affect the natural competition between patellidae and barnacles by favouring suspension feeders (barnacles), presumably due to higher food resources near the sewage. In the sublittoral fringe, near the sewage discharge, an increase in the production values of tolerant species was observed to the detriment of the sensitive species, with higher production levels in the reference areas. Overall, secondary production was higher in the communities near the sewage affected areas, but this increase was mostly due to the production of tolerant species. The present study showed that the incorporation of secondary production in the biological assessment provided further insight into the health of the ecosystem, thus being an important tool for understanding differences in the functioning of the ecosystem.

Effects of sewage pollution on the structure of rocky shore macroinvertebrate assemblages

The urgency to find efficient indices and indicators to prevent further deterioration of coastal areas is one of the hot topics in today’s scientific publication. However, a detailed knowledge of community responses to anthropogenic impacts is essential to sustain those indices. The studies on the response of benthic community to sewage pollution on intertidal rocky shores are generally based on visual census and do not take into account the tidal levels. In order to fulfil this gap in this study: (i) the sampling was performed by destructive sampling, with all individuals identified to the species level; (ii) the sampling was done at all levels of the intertidal (sublittoral fringe, eulittoral, and littoral fringe). Sewage pollution changed the environmental variables and the abundance of macroinvertebrates, being Mytilus galloprovincialis, Melarhapheneritoides, and Chthamalus montagui the species most responsible for the dissimilarities observed. Effects were different on the three intertidal zones: community structure changed in the sublittoral fringe; suspension-feeders abundances and species richness increased in the eulittoral; no differences were detected in the littoral fringe. Moreover, the results confirm that the presence of sewage discharges tended to benefit suspension feeders, and that the sensitive species were replaced by opportunistic ones.

Thermal adaptation in the intertidal snailEchinolittorina malaccanacontradicts current theory by revealing the crucial roles of resting metabolism

Contemporary theory for thermal adaptation of ectothermic metazoans focuses on the maximization of energy gain and performance (locomotion and foraging). Little consideration is given to the selection for mechanisms that minimize resting energy loss in organisms whose energy gain is severely constrained. We tested a hypothetical framework for thermal performance of locomotor activity (a proxy for energy gain) and resting metabolism (a proxy for energy loss) in energetically compromised snails in the littoral fringe zone, comparing this with existing theory. In contrast to theory, the thermal ranges and optima for locomotor performance and metabolic performance of Echinolittorina malaccana are mismatched, and energy gain is only possible at relatively cool temperatures. To overcome thermal and temporal constraints on energy gain while experiencing high body temperatures (23-50°C), these snails depress resting metabolism between 35 and 46°C (thermally insensitive zone). The resulting bimodal relationship for metabolism against temperature contrasts with the unimodal or exponential relationships of most ectotherms. Elevation of metabolism above the breakpoint temperature for thermal insensitivity (46°C) coincides with the induction of a heat shock response, and has implications for energy expenditure and natural selection. Time-dependent mortality is initiated at this breakpoint temperature, suggesting a threshold above which the rate of energy demand exceeds the capacity for cellular energy generation (rate of ATP turnover). Mortality in a thermal range that elevates rather than limits aerobic metabolism contrasts with the hypothesis that cellular oxygen deficiency underlies temperature-related mortality. The findings of this study point to the need to incorporate aspects of resting metabolism and energy conservation into theories of thermal adaptation.

Metabolic Activity, Reproduction and Survival of the High Littoral Fringe Copepod Itunella muelleri (Harpacticoida: Canthocamptidae) at Different Combinations of Salinities and Temperatures

Survival, metabolic and reproductive activity of Itunella muelleri was tested in several combinations of temperatures (2°-30°C) and salinities (from fresh water to salinity of 34‰). Proportions of individuals alive after 18 or 22 days was high in all experimental combinations except in fresh water at 2°C and at 30°C at salinities of 4 and 16‰. Metabolic activity, as measured by the production of faecal pellets, was low in fresh water regardless of temperature. Metabolic activity was also very low at 2°C regardless of salinity. Maximum activity was found at 20°C and 22°C with little difference between salinities of 4, 8, 16, and 32‰. Production of nauplii during the first 29 days was nil in fresh water regardless of temperature, and also nil at 2°C and 30°C regardless of salinities. The maximum production was found in the combination of 22°C and salinity of 16‰. The results are discussed in relation to expected ambient conditions in the natural habitat of the species.

Impact of the swell on the stability of the littoral fringe Cape of Bizerte–Ras Ettarf (north-eastern of Tunisia)

The littoral fringe ranging between the capes of Bizerte and Ras Ettarf (north-eastern of Tunisia) represents an unstable and complex system of the Tunisian littoral. The instability of this zone is dependent, on one hand, on natural phenomena contributing to the destabilization of certain sectors to which are added the induced effects of anthropic factors on the other hand. This study was carried out from grain size analysis and a simulation of swell plans. This led the authors to highlight the increasing grain size classification from the zones of the Capes towards the sandy low coasts and to quantify the moved volumes under the effect of the dominant swells in order to simulate the fattening and erosion zones in this sector. A littoral transit of direction north–south is able to transport 45,000 m3/year of sediment which are participating in the fattening of the beach of Sidi Salem; 6,000 m3/year of sandy sediments are directed towards the beach of R'mel and 12,000 m3/year are participating in the fattening of the beaches of Chatt Mami (Ras Jebel) and Lahmmari (Raf Raf).

Benthic Community zonation in a breakwater on the north coast of the state of Rio de Janeiro, Brazil

The present study presents the vertical zonation pattern of the intertidal benthic organisms on granitic boulders in the Farol de São Tomé beach (22º02'S, 41º03'W), Rio de Janeiro State. Four sampling profiles using 20 x 20 cm quadrats through a photo quadrat technique revealed four horizontal bands: (1) Littoral Fringe characterized by empty space and Littorina; (2) Upper eulittoral mainly occupied by Chthamalus and bare rock; (3) Lower eulittoral characterized by Chthamalus, Phragmatopoma, Ulva and Centroceras; and (4) Sublittoral Fringe characterized by Ulva, Phragmatopoma and Hypnea. The high variability in the relative abundance of the dominant species among the profiles may be attributed to the high topographic irregularity, reflecting in different wave action intensity at the same height, and consequently favoring the establishment of different species. The frequent substrate alternation from granitic rock to Phragmatopoma sandy reefs might contribute to the small-scale spatial variability. The implantation of a breakwater on an area without natural rocky shores allowed the study of intertidal benthic communty zonation, and provide a baseline for the experimental studies.

Annual and spatial variation of intertidal benthic community zonation in a breakwater off the Rio de Janeiro coast, south-eastern Brazil

The present study aims to evaluate the vertical distribution of intertidal benthic organisms in different periods of the year, relating them to tide, air temperature, height and wave periodicity in breakwaters off the northern Rio de Janeiro State, and to compare the zonation at two sites (Pier and Barra) with distinct hydrodynamics, due to different wave swell. Quadrats of 400 cm2 were sampled by a photoquadrat method. The upper limit of the marine organisms was higher at the Barra site (intertidal zone of 3.8 m) than at the Pier site (intertidal zone of 2.2 m). The littoral fringe assemblage did not show significant differences between sites, but a larger range of this fringe and the upper eulittoral band at Barra was quite evident. This site was mostly characterized by species of more exposed areas such as Chaetomorpha sp. and Perna perna in the upper and lower eulittoral bands, and by C. teedii and Ulva fasciata in the sublittoral fringe. A seasonal difference was identified in the air exposure degree at the Pier site, which was higher in October 2005 and February 2006. The air temperature and wave height and periodicity differed significantly among the four studied periods. The typical seasonal species were F. clenchi (July 2005 and October 2005), Gigartina domingensis (July 2005), Grateloupia sp. (October 2005) and Porphyra acanthophora (October 2005 and February 2006). The intermediate benthic band of the intertidal zone occupied a narrow zone, changing its spatial location according to the season of the year. The hypothesis of annual variation of the benthic community zonation according to the seasonal variability of tides, air temperatures and wave's height and periodicity was accepted for the intermediate band of the intertidal zone, due to the taxonomic differences and the abundance of dominant species in the four seasons. The difference in the vertical distribution of the intertidal benthic assemblages of both breakwaters highlights a distinct wave exposure condition, and reflects the breakwaters' orientation and the wave swell at each site.

Zonação de comunidade bêntica do entremarés em molhes sob diferente hidrodinamismo na costa norte do estado do Rio de Janeiro, Brasil

O presente estudo pretende comparar a distribuição vertical da comunidade bêntica na zona entremarés em dois locais compostos por matacões graníticos caracterizados por hidrodinâmica distinta, reflexo da diferença na orientação dos molhes nas praias do Farol de São Tomé (Píer) e na Barra do Furado (Barra), norte do Estado do Rio de Janeiro. Quadrados de 400 cm² foram sobrepostos ao longo de três perfis verticais de ambos os sítios e amostrados através do método de fotoquadrats, desde o nível 0,2 m da maré até o limite superior de Littorina spp. O limite superior dos organismos marinhos foi ampliado na Barra (3,8 m) em relação ao Píer (2,2 m). Quanto à composição taxonômica, nove espécies foram comuns. Chaetomorpha sp., Chondracanthus teedii (Mertens ex Roth) Fredericq e Grateloupia sp. foram exclusivas na Barra, enquanto Tetraclita stalactifera (Lamarck, 1818), Fissurella clench, Gracilaria domingensis (Kützing) Sonder ex Dickie e Hypnea musciformis (Wulfen in Jacqu.) Lamouroux ocorreram somente no Píer. Em ambos os locais, a riqueza e a diversidade de espécies foram superiores nos quadrados intermediários. Os maiores valores foram registrados na Barra. As maiores diferenças nos agrupamentos entre faixas equivalentes de locais distintos ocorreram na faixa eulitorânea superior, seguida pela faixa eulitorânea inferior e franja sublitorânea. Apenas a orla litorânea não revelou diferença significativa entre os locais, mas uma maior extensão desta franja e da faixa eulitorânea superior era bastante evidente. As demais faixas na Barra do Furado foram caracterizadas em grande parte por espécies típicas de ambientes mais expostos como Chaetomorpha sp. na faixa eulitorânea superior e Perna perna (Linnaeus, 1758) na eulitorânea inferior, além de C. teedii e Ulva fasciata Delile, 1813 na franja sublitorânea. No Píer, as diferentes faixas apresentavam distribuição eqüitativa, refletindo um ambiente menos estressante. As diferenças observadas na distribuição vertical dos organismos bênticos, principalmente na extensão das faixas superiores, evidenciam condições de exposição a ondas variáveis.

Variability in intertidal communities along a latitudinal gradient in the Southern Ocean

Despite being one of the most intensely studied habitat types worldwide, the intertidal region around Antarctica has received little more than superficial study. Despite this, the first detailed study of a single locality on the Antarctic Peninsula reported previously unanticipated levels of species richness, biomass and diversity in cryptic intertidal habitats. The current study extends the coverage achieved from this single locality. The intertidal zone at sites in the Scotia Arc, the Falkland Islands and the Antarctic Peninsula was investigated. At all the study sites selected, a wide range of macrofauna was found inhabiting the littoral fringe. These communities, although generally cryptic and occupying predominantly the undersides of boulders and protected interstices, at some locations and sites were rich at multiple taxonomic levels. Across the study locations species richness in the intertidal zone ranged from 7 to 30 species. The highest species richness and diversity were found at high latitude localities, which experienced the highest physical disturbance due to ice scour, and appeared superficially to be denuded of life. Species assemblages varied with latitude with Adelaide Island having a high proportion of bryozoans relative to all other localities.

The biogeography of the beachflea, Orchestia gammarellus (Crustacea, Amphipoda, Talitridae), in the North Atlantic with special reference to Iceland: a morphometric and genetic study

The beachflea [Orchestia gammarellus (Pallas)] is a trans‐Atlantic amphipod inhabiting the littoral fringe. In Iceland, its distribution is temperature‐limited; it has recently colonized Iceland's relatively warm south‐western coast, and in the cooler north‐west, several small populations inhabit isolated warm springs. We address two questions: (i) Do the warm spring populations show evidence of long‐term residence in Iceland, or of recent colonization? (ii) For the new south‐western Icelandic populations, can the source population be determined? We sequenced COI for 22 populations in Iceland, Nova Scotia, the Faroe Islands, the British Isles, Norway and Sweden. Morphometric analysis of a subset of populations assessed 16 continuous and five discrete characters. Genetically, we found a star phylogeny: a common haplotype was found at all sites except two neighbouring warm spring populations, and all haplotypes were within two base pairs of this common haplotype. Morphometrically, almost all populations examined differed significantly in some characters; however, the warm spring populations differed slightly more from each other than did other populations. Although the origins of the Icelandic populations could not be well resolved, our data are consistent with a recent European origin.

The need for clear and comparable terminology in benthic ecology. Part I. Ecological concepts

Abstract This note highlights problems with the definition and use of terminology in the field of benthic ecology, and compares the French classification with the UK and EUNIS classifications. These problems stem partly from language‐related difficulties, particularly the translation from English to French and vice versa, but also from the incoherence of certain typologies used in EU classifications and Directives. The boundaries used by legislators and developers take neither ecological constraints nor environmental parameters into account. Most often, these boundaries are set using distances or depths that have no basis in the distribution of benthic species. Retaining the definition of ‘étage’ that was proposed by Pérès (1961) is recommended, and the following classification hierarchy is proposed: supralittoral, mediolittoral, infralittoral with an upper littoral fringe, circalittoral with distinct coastal circalittoral and open circalittoral zones, bathyal, abyssal and hadal. Copyright © 2007 John Wiley & Sons, Ltd.

A new genus and species of polyclad flatworm found in the mantle cavities of gastropod molluscs in the high-intertidal zone of the Pacific coast of Central America

A commensal relationship is described between the polyclad flatworm Paraprostatum echinolittorinae Faubel & Sluys gen. et sp. nov. and gastropod molluscs living on the Pacific coast of central America. Although the worms are relatively large in comparison with their hosts, the latter sustained no apparent damage. Considering the fact that the molluscs live in the upper eulittoral zone and littoral fringe of the shore, it is unlikely that the polyclads could survive for long outside the hosts. Diagnostic characters for the new genus and species are a long penial stylet joined to the proximal vesicle and absence of Lang's vesicle. It is pointed out that Aprostatum clippertoni Bock, 1913 and A. longipenis (Kato, 1943) have been incorrectly transferred to the genus Euplana Girard, 1893 and that Discoplana malagensis Doignon, Artois & Deheyn, 2003 should be transferred to the genus Ilyella Faubel, 1983.