Coastal sand dune vegetation: An extreme case of species invasion

The coastal sand-dune flora of the Gulf and Caribbean region of Mexico was analyzed to understand differences in floristic composition and richness found along the coast. Each of the 655 species reported was classified according to its ecology and distribution range by checking herbaria specimens, literature and specialists. Three groups were formed: (a) species with predominantly coastal distribution; (b) ruderal or secondary species frequently found inland, common of disturbed areas such as roadsides, abandoned fields or forming part of secondary growths; (c) inland species frequently found in other vegetation types such as tropical dry or seasonal forest and grassland. A total of 71 coastal species, 237 ruderal/secondary and 336 species from other community types were found. The distribution of these groups was analyzed along 44 sites of the Gulf and Caribbean, in the different dune habitats and for the dominant growth forms. Coastal species are more widely distributed; they predominate in habitats with sand movement and the herbaceous component prevails. Ruderal/secondary species and especially those belonging to other vegetation types frequently appear in only one or two sites occupying more protected or stabilized habitats. The two latter groups considerably increase species richness of sand dune flora, but also pose interesting problems for dune conservation.     

Atlantic storminess and historical sand drift in Western Europe: implications for future management of coastal dunes

Historical records of sand drift and dune-building along the coastline of Western Europe provide insights into the natural processes of sand dune accretion and both the impacts of, and human responses to, sand incursions. The analysis of documentary records, instrumental data and proxy records over the last 1,000 years indicates that this period, which included the Little Ice Age (AD 1570–1900), featured numerous episodes of sand drift and dune development driven by strong winds associated with Atlantic storms. It is estimated that sand drift affected over a quarter of a million hectares of coastal land in Western Europe. The widespread use of vegetation to stabilise coastal dune systems and prevent sand drift is documented across Europe from AD 1100 and by the start of the 20th century all of the larger coastal dune systems in Portugal, France, Britain and Denmark were comparatively inactive. Given that Atlantic storminess has remained more or less unchanged over the last 200 years, modern dune management strategies which consider dune devegetation, driven by an increasing focus on ‘naturalness’, may give rise to a recurrence of sand drift problems. Predictions of increased storm frequencies by the end of the 21st century, coupled with sea level rise and potential changes in sand supply will present further challenges for the more ‘dynamic’ dune management strategies.     

Vegetation dynamics on the Łeba Bar/Poland: a comparison of the vegetation in 1932 and 2006 with special regard to endangered habitats

Coastal dune ecosystems are among the most dynamic habitats with high conservation value in Europe but are also under strong anthropogenic pressure regarding coastal protection and recreation. Hence, it is of high importance to know about long-term natural and anthropogenic changes and development of protected dune habitats for nature conservation, as well as for coastal management. This paper aims to identify the vegetation dynamics on the Łeba Bar/Poland over a period of 74 years by cartometric comparison using modern Geographical Information System (GIS). To quantify the rate of vegetation dynamics two aerial photographs dating from 1932 and 2006 were digitalized and analyzed with GIS to produce digital vegetation maps. Information about decrease, increase and stability of vegetation types of this area are discussed. The results show that there has been a clear reduction in the total area of bare sand and a considerable increase of woodlands and dense grass communities. Nevertheless, the remaining extensive drift sand areas and deflation hollows on the Łeba Bar offer one of the most important habitats for pioneer vegetation on bare sand of migrating dunes and dunes at the Southern Baltic coast. The present work proved the need to observe the future development of the vegetation communities and to implement management measures to maintain the dynamic of this unique dune landscape.     

Assessment of coastal erosion susceptibility at the national scale: The Italian case

To improve the present national and local sustainable planning capability for the coastal zone a GI application for the Italian Coastal Susceptibility Assessment was planned within an institutional agreement between ENEA and the Land Defence Service of the Italian Ministry of Environment. Taking into account previous European actions a suitable methodology to assess, in a quantitative way, the susceptibility of beaches to be eroded has been set up. The methodology balances the coastline trend as evaluated for a defined time period with the present coastal areas morphology and land use, this in order to derive a value that expresses the evolutionary process in terms of probability of the loss of goods within the ‘Homogeneous Coastal Tracts’. The trend in the movement of the sea-land line has been used asgeo-indicator of a complex dynamic balance that refers both to marine and inland systems, and a vector GI application was built and locally applied in southern Italian coastal areas. The present shoreline position and some other information describing the intrinsic beach morphologies, and having significance for the coastal erosion hazard assessment, have been derived from the national 1∶10.000 ortho-images of the National Cartographic Reference System provided by the Italian Ministry of Environment. The illustrated GI application— CoSTAT—keeps the nominal scale of all data collected or produced. In this analysis the coastal dune presence is analysed as factor limiting coastal erosion susceptibility. Applying a matrix calculation a quantitative evaluation of erosion susceptibility degree was achieved and plans were made to develop new information for a suitable use of Italian coastal areas. The work describes the methodology, the conceptual frame-work and the results of a local application.     

Possible impact of sea-level rise on some habitat types at the Baltic coast of Denmark

According to estimates from the Danish Meteorological Institute global warming until 2080 may cause a relative sea-level rise in Danish waters of 33–46 cm. In the present paper the possible impact of a sea-level rise of this magnitude on coastal habitat types is discussed for three case studies, based on previous investigations of vegetation, topography and soil of localities at the Baltic coast of Denmark. The case studies include the following types of localities and habitats: (1) an off-shore barrier complex: sandy beach, sand dune, geolittoral, brackish, low-tidal meadow, reed bed; (2) a protected bay: geolittoral, brackish meadow, coastal grassland; (3) a dune area: mobile and fixed dune communities, and adjoining sea wall: coastal grassland. In the geolittoral meadow and coastal grassland habitats the sea-level rise is expected to cause a horizontal displacement of vegetation zones and a reduction in area, depending on accretion rate (sedimentation, peat formation), local topography and inland land-use. In the beach and sand dune habitats the sea-level rise is expected to cause a change in groundwater level, influencing slack vegetation, and a change in the erosion/accretion pattern, resulting in landward rebuilding of the mobile dune as well as in a more or less diffuse inland sand drift, causing destabilization of fixed dune vegetation.     

The importance of seed dispersal in the Alexandria Coastal Dunefield, South Africa

The endozoochorous dispersal of seeds by mammals and birds between distinct vegetation communities was assessed to determine the importance of these processes in coastal dune field management. Isolated pockets of thicket vegetation (bush-pockets) within a large coastal dune field provided the opportunity to study vertebrate seed dispersal and its contribution to their origin and maintenance. Mammalian and avian faeces were collected for the quantification of seeds dispersed via endozoochory. Birds and mammals showed considerable overlap, dispersing intact seeds of 17 and 29 plant species, respectively, but mammals dispersed a greater diversity and size range than birds. Extrapolation of mammalian faecal data indicates an annual input of 23 million intact seeds to the dune field. Significantly more seeds are deposited by mammals and birds in the bush-pockets than on open sand, and birds deposited greater numbers of seeds nearer the seed source. Zoochory appears to be critical for the maintenance of the bush-pocket habitats through the dispersal of climax woody plant species into the dune field. Directional dispersal by birds and mammals to the bush-pockets is considered to be responsible for the maintenance and possible origin of these bush-pockets. The high number of exotic plant propagules dispersed by both avian and mammalian zoochory highlights the importance of management of the Alexandria Coastal Dunefield (ACD) beyond the reserve boundaries. In a dynamic system such as the ACD which is within a declared nature reserve, the continued existence of the bush-pockets may depend on the maintenance, beyond the reserve boundaries, of a reservoir of not only plant material but vertebrate dispersers as well.     

Integrated shoreline management and tourism development on the cross-border World Heritage Site: A case study from the Curonian spit (Lithuania/Russia)

The varied and very dynamic landscape with a high biological diversity is a distinctive feature of the Curonian spit at the regional scale. Throughout the 20th century the main morphodynamic trend in the littoral of the Curonian spit was shoreline grading on the lagoon side, whereas on the marine side the increasing erosion at the foot of the spit, and increasing accretion at the head of the spit prevailed. The results of a discriminant analysis (Wilkes’ λ = 0.001626 and F = 29.267 when p < 0.001) show that sites with prevailing erosion, accretion and sediment input from the drifting dunes form regular inter-related spatial structures in the littoral with distinctive resulting discontinuities of the sediment drift along the lagoon coast. Dune littoral cells are characterized by Aeolian sediment input and distribution ‘down-drift’, (usually northwards) from the source. The most likely changes in the current development trends of the lagoon shore zone of the Curonian spit are related to expected climate changes and further slowing down of the dune drift. The probability of storms and ice-drift events, and their impact on coasts is expected to increase as a result of climate change. The dune advance will gradually slow down, and with it, the sand input to the coastal zone will decline. In this paper, we define integrated shoreline management as a system of long-term shoreline management measures, which is based on a littoral cell approach and aimed at harmonizing human activity in the coastal zone with the natural development of the shoreline. We propose an integrated management program for the lagoon shoreline of the Curonian spit, which is site-specific for each littoral cell as a coastal management unit. Drifting dunes and seaside beaches are the natural amenities, which are best known and best appreciated on the Curonian spit by 49% of the respondents representing the total Lithuanian population. A responsible tourism development should be considered as the key means for proper appreciation of the drifting dunes and natural coasts by society, which means to acknowledge and cherish the aesthetic and conservation values of dune and coastal landscapes of the Curonian spit as a World Heritage Site. There are at least two pre-conditions for this: (1) to provide visitors with sufficient information about diverse values and functions of the Curonian dunes and coasts within a broader regional and global heritage conservation context; (2) to enable tourists to enjoy the most impressive dune and coastal landscapes at close range. In this paper we propose to encourage active dune tourism, to reintroduce grazing into the Curonian dune areas, to restore and to preserve the most impressive landscapes of the highest white drifting dunes by bringing the blown out sand from the leeward foot of the dunes back to the crest artificially.     

Sustainability of sand dune restoration along the coast of the Tyrrhenian sea

This study reports the results of restoration management on sand dune environments along the coastal belt of the Castelporziano nature reserve (Rome, Italy) and the subsequent monitoring phases to test the sustainability of the ‘soft techniques’ applied. In the area concerned, over a length of ca. 3 km, 40 dunes were built up along with three belts located at <40 m, 40–70 m, and >70 m, respectively, from the shoreline. On each of 38 dunes 20 individuals ofAmmophila littoralis were planted; this species is one of the local autochthonous species considered particularly suitable for stabilizing sand dunes. After one year, two years and five years, respectively the changes in height and surface of each dune, the survival rates ofA. littoralis, and its changes in cover, the appearance of new shoots and the establishment of new species were observed. A progressive increase in species number, which five years after the restoration amounted to about 60% of those characterizing the natural dunes, was reported indicating a progressive trend towards populations similar to natural ones. In the colonization of new species there is a prevalence of theSporobolus-Elymetum farcti and theSalsolo Kali-Cakiletum maritimae association, while the species established successively refer to theEchinophoro spinosae-Ammophiletum arundinaceae association and theCrucianellion maritimae alliance as occurring in natural successions. This succession runs parallel to the natural dune colonization processes. In particular, the data regarding survival, cover and number of vegetative shoots indicate that the dune belt between 40 and 70 m from the sea is the one most suitable for restoration. Some changes in dune morphology was observed: the height of the artificial dunes tended to decrease considerably in the five years of observation, whereas a progressive increase in their surface area was observed. During the study period.A littoralis favoured the establishment of new species, but as yet exercises no action on increasing dune height.     

Linking marine resources to ecotonal shifts of water uptake by terrestrial dune vegetation

As evidence mounts that sea levels are rising, it becomes increasingly important to understand the role of ocean water within terrestrial ecosystem dynamics. Coastal sand dunes are ecosystems that occur on the interface of land and sea. They are classic ecotones characterized by zonal distribution of vegetation in response to strong gradients of environmental factors from the ocean to the inland. Despite the proximity of the dune ecosystem to the ocean, it is generally assumed that all vegetation utilizes only freshwater and that water sources do not change across the ecotone. Evidence of ocean water uptake by vegetation would redefine the traditional interpretation of plant-water relations in the dune ecosystem and offer new ideas for assessing maritime influences on function and spatial distribution of plants across the dune. The purpose of this study was to identify sources of water (ocean, ground, and rain) taken up by vegetation using isotopic analysis of stem water and to evaluate water uptake patterns at the community level based on the distribution and assemblage of species. Three coastal dune systems located in southern Florida, USA, and the Bahamian bank/platform system were investigated. Plant distributions across the dune were zonal for 61-94% of the 18 most abundant species at each site. Species with their highest frequency on the fore dune (nearest the ocean) indicate ocean water uptake as evidenced by delta 18O values of stem water. In contrast, species most frequent in the back dune show no evidence of ocean water uptake. Analysis of species not grouped by frequency, but instead sampled along a transect from the ocean toward the inland, indicates that individuals from the vegetation assemblage closest to the ocean had a mixed water-harvesting strategy characterized by plants that may utilize ocean, ground-, and/or rainwater. In contrast, the inland vegetation relies mostly on rainwater. Our results show evidence supporting ocean water use by dune vegetation and demonstrate an exciting relationship between seawater and ecotonal shifts in plant function of a terrestrial ecosystem.     

油松种子醇溶蛋白提取剂比较

采用乙醇、尿素、2氯乙醇、2巯基乙醇等配成的不同浓度和成分的提取剂提取了山西太岳龙门口、陕西洛南、辽宁千山和河北雾灵山4个不同油松种群的种子醇溶蛋白;用酸性聚丙烯酰胺凝胶电泳(APAGE)对蛋白提取液进行分析.条带数目反映所提取醇溶蛋白的数量,谱带颜色深浅反映不同提取剂得到的某种醇溶蛋白的量.结果表明,不同提取剂提取的醇溶蛋白图谱存在明显差异.由1%2巯基乙醇和12%尿素组成的复合提取剂提取效果最佳,其次是由20%2氯乙醇、1%2巯基乙醇和12%尿素组成的复合提取剂.提取的醇溶蛋白的电泳图谱可以用于油松种群的遗传多样性分析和系统演化的研究.图1表2参11     

Temporal and spatial changes in plant dune diversity in urban resorts

We investigated the temporal and spatial changes in the floristic composition and abundance in sand dunes along a coastal strip in the province of Buenos Aires (Argentina). Firstly, we analysed changes over a span of 70 years, comparing 41 of our own inventories carried out in 14 beach resorts in 2005–2006 with 18 inventories made in the first half of the XXth century (1930–1940) in the same study area. We grouped sampled plots into four categories for comparison, taking into account the time period (1930–1940 or 2005–2006) and location at each end of the surveyed coastal strip in the northern or southern ‘tourist’ sectors. Secondly, we analysed the effect of afforestation with exotic trees on extant sand dune vegetation for the period 2005–2006. A total of 74 plant inventories were carried out in afforested and natural dunes at the same resorts. In both comparisons we contrasted plant richness, percentage plant cover, similarity and diversity. A cluster analysis was used to classify categories taking into account plant abundance and composition. Significant differences in total diversity were observed between sampling years, suggesting an increase in diversity at the present time due to urbanization and recreation related activities. Nevertheless, no single exotic plant species was clearly dominant across the sampled sites, suggesting that these coastal areas are, up to now, resistant to alien invasion. Diversity indexes discriminated by plant groups indicating different habitat conditions and exotics were shown to be more sensitive to existing changes than to total richness and cover.     

Population biology of the annual grassTriplasis purpurea in relation to distance from shore on Staten Island, New York

Four populations of the native annual grassTriplasis purpurea were surveyed on coastal beaches along the south shore of Staten Island, NY, to determine the potential of this species to colonize shoreline habitats mostly devoid of other vegetation. If the species can establish and maintain dense populations, it may have conservation value for urban beaches disturbed by human activities. For two populations, survivorship, growth, and reproduction were monitored at different distances from shore to determine the ability of this species to maintain viable populations. At three sites,T. purpurea occurred in >75% of all quadrats and the highest density was 1195 plants/m² at 74 m from shore in one recently disturbed site. Density generally increased with increasing distances from shore at low tide (from ca. 40 – 90 m). Plants showed the greatest growth and reproduction at close distances to shore (30 – 40 m); part of this effect was due to density in one population, but when density effects were removed statistically, there still remained a decline in growth and reproduction with increasing distance from shore. Improved vigor nearest to shore may be due to continual sand deposition. Survivorship showed a Type I pattern, with low mortality throughout the growing season. By colonizing newly-deposited and continually shifting sands,T. purpurea can contribute to the earliest stages of ecological succession along disturbed beaches in eastern North America and may be valuable to the development and management of urban coastal plant communities.     

Population biology of the annual grass Triplasis purpurea in relation to distance from shore on Staten Island, New York

Four populations of the native annual grassTriplasis purpurea were surveyed on coastal beaches along the south shore of Staten Island, NY, to determine the potential of this species to colonize shoreline habitats mostly devoid of other vegetation. If the species can establish and maintain dense populations, it may have conservation value for urban beaches disturbed by human activities. For two populations, survivorship, growth, and reproduction were monitored at different distances from shore to determine the ability of this species to maintain viable populations. At three sites,T. purpurea occurred in >75% of all quadrats and the highest density was 1195 plants/m² at 74 m from shore in one recently disturbed site. Density generally increased with increasing distances from shore at low tide (from ca. 40–90 m). Plants showed the greatest growth and reproduction at close distances to shore (30–40 m); part of this effect was due to density in one population, but when density effects were removed statistically, there still remained a decline in growth and reproduction with increasing distance from shore. Improved vigor nearest to shore may be due to continual sand deposition. Survivorship showed a Type I pattern, with low mortality throughout the growing season. By colonizing newly-deposited and continually shifting sands,T. purpurea can contribute to the earliest stages of ecological succession along disturbed beaches in eastern North America and may be valuable to the development and management of urban coastal plant communities.     

The importance of coastal sand dunes for terrestrial invertebrates in Wales and the UK,with particular reference to aculeate Hymenoptera (bees,wasps &; ants)

Although most UK sand dune systems are now fossilized, with little mobility and reducing amounts of bare sand, they support important populations and assemblages of terrestrial invertebrates. Offering open conditions, warm substrates and a range of habitats and habitat structures, they have become increasingly significant as other coastal habitats have been lost. In Wales, 680 Red Data Book and Nationally Scarce species have been recorded from dunes. 109 species in the UK are restricted to dunes, and in Wales there are an additional 145 species confined to dunes and 208 species strongly associated with dunes. Of these, 172 species are dependent upon bare and sparsely-vegetated sand, in grey dunes and early-successional dune grassland, at some stage of their life cycle, rising to 292 species if those associated with the strandline, foredunes, yellow dunes and pioneer dune slacks are included, equating to 63% of the 462 dune species. Bees and wasps are particularly well represented, with 278 species (68% of the Welsh fauna) recorded on Welsh dunes, including 17 obligates and 44 species with a strong dependence, 52 of which are associated with bare and sparsely-vegetated sand. Key to maintaining invertebrate populations on UK dunes is the provision of bare sand but in Wales, bare sand accounts for only 1.7% of the total sand dune resource. As a more appropriate bare sand threshold is likely to range between 10 and 30%, radical action is required to re-mobilize at least the key sand dune systems.     

Dynamic preservation of the coastline in the Netherlands

In 1990, the Government and Parliament of the Netherlands decided on a new national policy for coastal defence. To ensure the enduring safety of the low-lying polders as well as the sustainable preservation of the coastal dunes, it was decided to maintain the coastline in its 1990 position. The main method for coastline preservation in the Netherlands is beach nourishment. Since 1991, approximately 7 million m³ of sand is added to the Dutch beaches annually. From an evaluation study of sand nourishment projects it is concluded that nourishment is an effective and efficient method to preserve the coastline. The evaluation study also proves that nourishment projects should be ‘tailor-made’, taking the local morphological and hydraulic conditions into account. The first results of an experimental shoreface nourishment are discussed. The choice for nourishment as the principal method to combat erosion is well in line with the intention to restore the natural dynamics of the dune-coast in the Netherlands. The key probably is a less strict policy with regard to the maintenance of the foredunes. Plans for the development of typical coastal features such as slufters^*, wash-overs, blow-outs and mobile dunes are currently under discussion. A slufter is a breakthrough in the first dune-ridge whereby the sea invades former dune slacks or beach plains situated behind the duneridge. In this way a tidal marsh is formed within the dune zone.     

Physical damage to coastal dunes and ecological impacts caused by vehicle tracks associated with beach camping on sandy shores: a case study from Fraser Island,Australia

As coastal populations expand, demands for recreational opportunities on beaches and coastal dunes grow correspondingly. Although dunes are known to be sensitive to direct human disturbance and provide irreplaceable ecosystem services (e.g. erosion control, critical habitat and nesting sites), dunes serve as campsites for large numbers of people (∼90,000 p.a.) on the ocean-exposed shores of Fraser Island, Australia. Campsites are located in the established dunes and can only be accessed with 4WD vehicles along tracks cut directly from the beach through the foredunes. Here we quantified the extent of physical damage to foredunes caused by this practice, and tested whether human-induced physical changes to foredunes translate into biological effects. Of the 124 km of ocean-exposed beaches, 122 km (98%) are open to vehicles driven on the beaches, and camping zones cover 28.7 km or 23% of the dunes. A total of 235 vehicle tracks are cut across the foredunes at an average density of eight tracks per km of beach. These tracks have effectively destroyed one-fifth (20.2%) of the dune front in camping zones, deeply incising the dune-beach interface. There is evidence of accelerated erosion and shoreline retreat centred around vehicle tracks, resulting in a “scalloping” of the shoreline. No dune vegetation remains in the tracks and the abundance of ghost crabs (Ocypode spp.) is significantly reduced compared with the abutting dunes. Because current levels of environmental change caused by dune camping may not be compatible with the sustainable use of coastal resources and conservation obligations for the island (listed as a World Heritage Area and gazetted as a National Park), restoration and mitigation interventions are critical. These will require spatial prioritisation of effort, and we present a multi-criteria ranking method, based on quantitative measures of environmental damage and ecological attributes, to objectively target rehabilitation and conservation measures. Ultimately, coastal management needs to develop and implement strategies that reconcile demands for human recreation, including beach camping, with conservation of coastal dune ecosystems.     

Modelling small groundwater systems: experiences from the Braunton Burrows and Ainsdale coastal dune systems,UK

Coastal dunes are delicate systems that are under threat from a variety of human and natural influences. Groundwater modelling can provide a better understanding of how these systems operate and can be a useful tool towards the effective management of a coastal dune system, e.g. by identifying strategically important locations for flora and fauna and guiding the planning of management operations through predicting impacts from climatic change, sea level rise and land use management. Most dune systems are small, typically of the size 10–100 km², compared with inland groundwater systems. Applying conventional groundwater modelling approaches to these small systems presents a number of challenges due to the local scale of the system and the fact that the system boundaries (sea, drains, ponds etc.) are close to the main body of the aquifer. In this paper, two case studies will be presented using different modelling approaches to understand the groundwater balance in two dune systems in the UK. The studies demonstrate that, although conventional hydraulic models can describe the general system behaviour, a fuller understanding of the recharge mechanisms and system boundaries is needed to represent adequately system dynamics of small groundwater systems.     

Does iodine gas released from seaweed contribute to dietary iodine intake?

Thyroid hormone levels sufficient for brain development and normal metabolism require a minimal supply of iodine, mainly dietary. Living near the sea may confer advantages for iodine intake. Iodine (I₂) gas released from seaweeds may, through respiration, supply a significant fraction of daily iodine requirements. Gaseous iodine released over seaweed beds was measured by a new gas chromatography–mass spectrometry (GC–MS)-based method and iodine intake assessed by measuring urinary iodine (UI) excretion. Urine samples were obtained from female schoolchildren living in coastal seaweed rich and low seaweed abundance and inland areas of Ireland. Median I₂ ranged 154–905 pg/L (daytime downwind), with higher values (~1,287 pg/L) on still nights, 1,145–3,132 pg/L (over seaweed). A rough estimate of daily gaseous iodine intake in coastal areas, based upon an arbitrary respiration of 10,000L, ranged from 1 to 20 μg/day. Despite this relatively low potential I₂ intake, UI in populations living near a seaweed hotspot were much higher than in lower abundance seaweed coastal or inland areas (158, 71 and 58 μg/L, respectively). Higher values >150 μg/L were observed in 45.6% of (seaweed rich), 3.6% (lower seaweed), 2.3% (inland)) supporting the hypothesis that iodine intake in coastal regions may be dependent on seaweed abundance rather than proximity to the sea. The findings do not exclude the possibility of a significant role for iodine inhalation in influencing iodine status. Despite lacking iodized salt, coastal communities in seaweed-rich areas can maintain an adequate iodine supply. This observation brings new meaning to the expression “Sea air is good for you!”     

Die verbreitung der uferwanzen (Heteroptera: Saldidae) im brackigen und marinen litoral der nordamerikanischen pazifikküste

Shore bugs (Heteroptera: Saldidae) were collected during summer 1973 along the Pacific Coast of North America between the arctic and the subtropical regions. The field studies were aimed at determining the species-specific upper and lower limits of distribution in the littoral, and the distribution range of these species in estuaries. The saldids inhabiting the littoral zones can be divided into two groups: those species which live mainly along the coast (coastal species), and those which live mainly inland (inland species). Species found in the supralittoral occur at inland localities as well, and thus can either tolerate limnetic-oligohaline conditions (Salda littoralis, S. provancheri, Saldula coxalis) or are confined to habitats along salt lakes (Pentacora signoreti). Inhabitants of the eulittoral can either occur in the supralittoral and inland localities as well and are holeuryhaline (Saldula palustris, S. pallipes), or have disconnected inland populations (S. nigrita), or they live exclusively in the intertidal zones. In the subarctic, coastal species are distributed from the intertidal zones to inland limnetic habitats. The increasing aridity of southern climatic zones may act as a limiting factor confining the distribution of coastal species to the coast. On the other hand, the distribution of inland species may be influenced by competition with the coastal forms.

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