Habitat selection of wintering passerines in salt marshes of the German Wadden Sea

The salt marshes of the Wadden Sea are important wintering areas for some species of granivorous passerines, which have declined considerably since the 1960s. We investigated the habitat choice of all wintering passerines in eight study areas in German salt marshes with special consideration of human impact on these habitats. Granivorous species that almost exclusively winter in salt marshes, Shorelark (Eremophila alpestris), Snow Bunting (Plectrophenax nivalis) and Twite (Carduelis flavirostris) were concentrated in the lower salt marsh vegetation and in the driftlines, while all other species preferred the high upper salt marsh communities, although Rock Pipits (Anthus petrosus littoralis) fed in muddy areas along ditches. Shorelarks switched habitat in conditions where seeds were scarce to feed instead on arthropods in upper salt marshes. Intensively sheep-grazed upper salt marshes resemble lower salt marshes in their vegetation and were therefore mainly visited by Shorelarks, Snow Buntings and Twites. In winter, the driftline is preferred by the two former species, while in autumn and spring more birds foraged in the salt marshes. Twites prefer to feed mainly on seeds of Salicornia. Areas with S. europaea are visited mainly in late autumn and early winter, while areas with S. stricta are used throughout the winter because of a steady supply of seeds. Several years after embankment, polders are hardly used any more by the lower salt marsh species as the habitat changes into freshwater marshes. Large embankment projects since the early 1960s have included salt marshes and intertidal flats, and the resultant loss of habitat is responsible for the decline of lower salt marsh species. For other passerine species the effects of reclamation are unknown. The effects of intensified grazing on the wintering populations of Shorelark, Snow Bunting and Twite are still unresolved. Although grazing supports lower salt marsh vegetation, the seed production per plant is much lower there and some important seed producers hardly occur. Since grazing was reduced and embankment projects have been stopped, the salt marsh areas (especially lower salt marshes) have increased and so have the wintering populations of Shorelark, Snow Bunting and Twite. For the other species, the consequences of habitat changes are unknown, although it is suggested that reduced grazing will support them. Reducing the human impact on salt marshes will, in the long run, probably lead to a natural salt marsh with much variety in elevation and in its corresponding vegetation and bird communities. Meanwhile, management by grazing might be required in parts of the salt marshes.     

Short-term sedimentation in Tagus estuary,Portugal: the influence of salt marsh plants

Short-term sediment deposition was studied at four salt marsh areas in the Tagus estuary. In areas covered with Sarcocornia perennis, Sarcocornia fruticosa, Halimione portulacoides and Spartina maritima and also in the non-vegetated areas, sedimentation was measured as the monthly accumulation of sediments on nylon filters anchored on the soil surface, from August 2000 to May 2001. Our experiments were used also to determine the influence of the different plant species in vertical accretion rates. Short-term sedimentation rates (from 2.8 to 272.3 g m⁻² d⁻¹) did show significant differences when the four salt marshes studied in the Tagus estuary were compared to each others. Salt marshes closer to the sediment sources had higher sedimentation rates. Our results suggest that the salt marsh type and surface cover may provide small-scale variations in sedimentation and also that sediment deposition values do change according to the position of the different plant species within the salt marsh. Sedimentation is an essential factor in salt marsh vertical accretion studies and our investigation may provide support to help forecast the adaptative response of the Tagus estuary wetlands to future sea level rise.     

Coast of change: habitat loss and transformations in the Wadden Sea

In the southern North Sea, coastal people commenced with habitat conversions 1,000 years ago. Partly interrupted in late medieval times by large-scale inundations of marshland, progressive embankments transformed the landward half of the amphibic transition zone between a limno-terrestric and a brackish-marine ecosystem into arable land and freshwater lakes. Sea walls rigidly separated the land from the sea. Dynamic transitional habitats have vanished. Areal loss has diminished the capacity of the Wadden Sea to dissipate wave and tidal energy. A coastal ecosystem once rich in marsh plants, seagrass and diatoms on mud flats became transformed into one with less autochthonous phototroph production, dominated by sandy tidal flats, and dependent primarily on allochthonous plankton supply. The large estuaries have been dredged to serve as shipping canals, and have lost most of their former retention and filter capacity. Riverine loads are now flushed right into the North Sea. Symptoms of a syndromatic coastal habitat degradation are diagnosed, leading to a decline in natural habitat diversity. The conventional on-line coastal protection may not achieve a sustainable coastal habitat configuration. At sedimentary coasts immobilised by dikes and petrified shores, a more flexible response to sea level rise is recommended.     

Ecophysiological adaptations of coastal halophytes from foredunes and salt marshes

Ecophysiological strategies of coastal halophytes from foredunes and salt marshes are discussed. A comparison is made of the factors that limit growth in salt marshes and sand dunes. In salt marshes, zonation and succession are primarily governed by variation in soil salinity, which strongly depends on inundation with seawater. Results are described of experiments which aim at separating salinity and inundation effects on growth, osmotic and mineral relations in a comparison of salt-marsh halophytes. The growth response of plants cannot simply be correlated (and causally explained) with the concentration of Na, Cl, and K in the tissues. Also, the compatible osmotic solutes proline and methylated quaternary ammonium compounds may accumulate both in species with a positive response to increased salinity and in species with a growth reduction under seawater inundation. More likely inadequate adaptation of the plants water potential with these components is partly the cause of retarded growth. Disfunctioning of the plant in this respect may be at three levels: (a) total water potential of the plant, (b) (loss) of turgor pressure potential; (c) regulation at the cellular level. The ecological importance of some factors in seawater other than sodium chloride is considered. In coastal sand dunes airborne rather than soil salinity limits plant growth, together with the effects of abrasion, sand accretion, drought and the poor nutrient status of the dune sand. Adaptations of sand-dune species to these factors may consist of: large seeds with storage tissue germinating in the dark and seedling growth enough to emerge through the accreted sand. Aerial parts must be resistant to mechanical damage (high wind speed and abrasion), possibly by a sclerophyllous and tough structure. Efficient nutrient uptake, translocation and retranslocation seem to help survive sand-dune species in a nutrient-poor rooting medium.     

Climatic change and the Wadden Sea,The Netherlands

The predicted increase in atmospheric carbon dioxide and the effects of global warming will influence the Wadden Sea, The Netherlands, an area of exceptional ecological value. The direct effect of elevated atmospheric CO₂ on terrestrial coastal ecosystems is either marginal or unknown. The slight acidification of the sea which is predicted might have an impact on primary producers and juvenile animals. The effect of CO₂ fertilization on marine primary production remains to be elucidated. Profound changes will occur if sea level rises at the predicted rate of 60 cm per century, as sedimentation rates will be insufficient to maintain the salt marshes on the barrier islands. The marshes of the mainland coast will be impoverished, as high and low marshes are not expected to continue to coexist at the same locations. As sediment supply to the Wadden Sea is sufficient to compensate for sea level rise, the estuarine character of the Wadden Sea, with sand- and mudflats, is expected to remain largely unchanged.     

Zonation of spiders (Araneae) and carabid beetles (Coleoptera: Carabidae) in island salt marshes at the North Sea coast

The specific communities of spiders and carabid beetles of island salt marsh habitats of the East Frisian Island chain at the German North Sea coast were investigated. During the vegetation periods of 1997 and 1998 three pitfall trapping transects were installed on the islands of Borkum and Wangerooge. Within the salt marshes, transects extended from 0 m to 175 m. Elevation gradients varied between 10 cm and 232 cm above MHT (mean high tide). On Borkum, 35 traps were exposed in two transects, on Wangerooge 25 traps were placed in one transect. Three to five elevations above MHT were investigated per transect, each one with five traps. Highest species numbers were recorded in the higher elevated salt marshes. In contrast, highest activity values were noticed in the medium elevated salt marshes. Within both groups, spiders and carabids, four communities were distinguished by indirect gradient analysis. Indicator species were assigned to the different communities that were mainly assorted to different elevations of the salt marshes. Thus, the communities of both taxa corresponded well to the vegetational formations. The importance of sea level rise for structuring the communities of salt marsh arthropods is discussed. Overall, still great uncertainties exist on how arthropod communities and salt marshes themselves will develop.     

Long‐term vegetation changes in experimentally grazed and ungrazed back‐barrier marshes in the Wadden Sea

Abstract. Vegetation succession in three back‐barrier salt marshes in the Wadden Sea was studied using a data set comprising 25 years of vegetation development recorded at permanent quadrats. The effect of livestock grazing on succession was assessed by comparing quadrats where grazing was experimentally prevented or imposed. We studied changes at the species level as well as at the level of the plant community. Special attention is given to effects on plant species richness and community characteristics that are relevant for lagomorphs (hares and rabbits) and geese. Inundation frequency and grazing were most important in explaining the variation in species abundance data. The three marshes studied overlap in the occurrence of different plant communities and the observed patterns were consistent between them. Clear differences in frequency and abundance of plant species were observed related to grazing. Most plant species had a greater incidence in grazed treatments. Species richness increased with elevation, and was 1.5 to 2 × higher in the grazed salt marsh. Grazing negatively influenced Atriplex portulacoides and Elymus athericus, whereas Puccinellia maritima and Festuca rubra showed a positive response. The communities dominated by Elymus athericus, Artemisia maritima and Atriplex portulacoides were restricted to the ungrazed marsh. Communities dominated by Puccinellia maritima, Juncus gerardi and Festuca rubra predominantly occurred at grazed sites. As small vertebrate herbivores prefer these plants and communities for foraging, livestock grazing thus facilitates for them.     

Tagus estuary salt marshes feedback to sea level rise over a 40-year period: Insights from the application of geochemical indices

Sea level rise (SLR) has been evaluated using data acquired from two Tagus estuary salt marshes. Sediment accumulation rates over a 40-year study period were determined using ¹³⁷Cs along with an evaluation of several geochemical indices and ratios as proxies of the mechisms underlying these SAR variations. Correlating SLR data from 1963 to 2001 with the sediment accretion rates (SARs) an inverse pattern of interaction was observed, with lower SAR associated to periods of higher mean sea level (MSL) heights. This pointed out to an erosion effect of the salt marsh during higher tidal flooding. Although SLR apparently slows down SAR, it still presents a positive balance with SLR, similar to that identified in most mesotidal estuaries. The geochemical analysis of sediments and chemical alteration index (CAI) also suggest that the major processes inherent to the SAR vary inversely, being mostly based by physical disturbances. Geochemical ratio-based indices showed that both salt marshes presented enhanced high-energy transport driven inputs of sediments, although in Pancas salt marsh there is a slight evidence of chemical weathering of the sediments. Anthropogenic contamination of the sediments by heavy metals was identified and has been decreasing from 1963 to 2001, mostly linked to a marked reduction of industrial activities in some areas surrounding the Tagus estuary, rather than the sedimentary history of the estuary.     

The halophilous vegetation of the Orumieh lake salt marshes,NW. Iran

The halophilous vegetation of the Orumieh lake salt marshes has been studied, using the Braun-Blanquet method. Vegetation types have been defined by physiognomic-floristic system. The following six main groups of communities are recognized: (1) Semi-woody shrub and perennial halophytic communities (Class Halocnemetea strobilacei) including 6 associations and 5 subassociations, (2) Annual halophytic communities (Class Thero-Salicornietea) including 5 associations and 1 subassociation, (3) Salt marsh brushwood communities (Class Tamaricetea) including 4 associations, (4) Rush and herbaceous perennial halophytic communities (Class Juncetea maritimi) including 7 associations and 1 subassociation, (5) Rush and herbaceous perennial halotolerant communities (Class Agrostietea stoloniferae) including 5 associations, (6) Hydrophilous halotolerant communities (Class Phragmitetea) including 3 associations and 2 subassociations. The soil of these communities has been analysed and their habitats are described and discussed.     

Stratigraphy and geologic history of a southeastern salt marsh basin,North Inlet,South Carolina,USA

Forty seven vibracores and fifteen radiocarbon dates have beenobtained to outline the Holocene history of the North Inlet saltmarsh basin. Marsh deposits date from about 3500 years BP and havetransgressed over a Late Pleistocene beach-ridge terrain that waspartly eroded by Late Holocene tidal channel meandering. Marsh mudalso has prograded southward over shallow subtidal estuarine Macomamuds which date from about 4500 years BP and which are stillaccumulating in adjacent Winyah Bay. The southward migration of themarsh environment probably is due to the southward migration ofboth North Inlet and the mouth of Winyah Bay. The stratigraphy ofthe North Inlet basin offers no evidence for Late Holocene sea-level oscillations.Application of this model of marsh history to the study long-term ecosystem succession driven by slowly rising sea level isdiscussed.     

Arbuscular mycorrhizal colonization of halophytes in Central European salt marshes

 Halophytes from both coastal and inland Central European salt marshes were examined for colonization by arbuscular mycorrhizal (AM) fungi. Plants from different families were strongly colonized but the degree of colonization varied with the individual plant and apparently during the vegetation period, too. Members of the typical non-mycorrhizal families like Armeria maritima of the Plumbaginaceae and Salicornia europaea of the Chenopodiaceae were found to be colonized, particularly in the drier salt marshes. High numbers of Glomus spores were found in the saline soils, especially those of the inland locations examined. Approximately 80% of these spores were from Glomus geosporum as shown by a typical restriction fragment length polymorphism (RFLP) pattern of the amplified internal transcribed spacer regions. The present study demonstrates that RFLP analysis is useful when screening habitats for the occurrence of mycorrhizal fungi which can be identified only with difficulty by morphological criteria. Accepted: 25 August 2000     

Population dynamics of annual Salicornia species in the tidal salt marshes of the Oosterschelde,The Netherlands

1. The population dynamics of two Salicornia species from the Bergen op Zoom salt marsh (south-west Netherlands) was examined. Based on the results of several field studies three preliminary life tables were constructed, two for S. procumbens agg. populations growing respectively on the mud flats and in the salt marsh, and one for S. europaea agg. living in the upper marsh.
2. The life cycles are described and quantified in terms of eight phases and the transition probabilities between them, starting from a notional individual representative of each population.
3. The models depicting the life cycle of S. procumbens show a mean offspring number of 4.26 individuals per parent for the mud-flat population and 0.18 for the salt-marsh population. The S. europaea model gives an output of 0.44 individuals per parent. These results reflect the fluctuations in population size observed in sample plots over the years 1976–78.
4. Comparison of the transition probabilities reveals that on the mud flats most S. procumbens individuals die during pollination and seed germination, while the population in the salt marsh proper is thinned especially during the seed phase in winter time and during the growth from established seedlings to maturation. S. europaea behaves in a similar but less pronounced way to S. procumbens in the salt marsh.
5. Probabilities for one flower or one seed to produce a mature flowering plant were calculated, and were compared with those found in the literature. They are roughly of the same order of magnitude as the probabilities for other annual species, but much higher than those reported for biennial species.

     

Utilisation of Wadden Sea salt marshes by geese in relation to livestock grazing

To arctic breeding geese, the salt marshes of the International Wadden Sea are important spring staging areas. Many of these marshes have always been grazed with livestock (mainly cattle and sheep). To evaluate the influence of livestock grazing on composition and structure of salt-marsh communities and its consequences for habitat use by geese, a total of 17 pairs of grazed and ungrazed marshes were visited both in April and May 1999, and the accumulated grazing pressure by geese was estimated using dropping counts. Observed grazing pressure was related to management status and to relevant vegetation parameters.The intensity of livestock grazing influences the vegetation on the marsh. Salt marshes that are not grazed by livestock are characterised by stands with a taller canopy, a lower cover of grasses preferred by geese, and a higher cover of plants that are not preferred.Overall goose-dropping densities are significantly lower in ungrazed marshes compared to marshes grazed by livestock. Some ungrazed marshes had comparatively high goose grazing pressure, and these were all natural marshes on a sandy soil, or artificial mainland marshes with a recent history of intensive livestock grazing. Goose grazing is associated with a short canopy. The plant communities with short canopy, dominated by Agrostis stolonifera, Festuca rubra and Puccinellia maritima, together account for 85% of all goose droppings in our data.The sites that were not visited by geese differed very little from those that were visited, in the parameters we measured. This might indicate that there was no shortage of available habitat for spring staging geese in the Wadden Sea, in the study period.     

Distribution of modern salt-marsh foraminifera in the Albemarle–Pamlico estuarine system of North Carolina, USA: Implications for sea-level research

We described the distributions of foraminifera from ten physiographically distinct salt marshes in the Albemarle–Pamlico estuarine system, North Carolina using 193 surface samples. We defined elevation-dependent ecological zones at individual sites using cluster analysis and detrended correspondence analysis. Additionally, seven principal biozones of salt-marsh foraminifera were identified that have distinctive spatial distributions reflecting a pattern of salinity regimes caused by the current configuration of barrier-island inlets. High salinity sites along the southern Outer Banks are associated with sub-tidal calcareous assemblages, low marshes dominated by Miliammina fusca and high marsh environments defined by Haplophragmoides wilberti, Trochammina inflata and Arenoparrella mexicana. In contrast, lower salinity marshes have Ammobaculites spp. in sub-tidal settings, Miliammina fusca-dominated low marshes and high marsh settings characterized by Jadammina macrescens. Spatial variation of foraminiferal populations and the potential for biozones to migrate in response to changing inlet configuration and salinity, suggests that datasets of modern salt-marsh foraminifera from multiple environments would be appropriate for reconstructing Holocene relative sea level in North Carolina.     

The impact of grazing on plant communities,plant populations and soil conditions on salt marshes

Grazing an abandoned salt marsh causes retrogressive succession, since mid salt-marsh communities change into lower salt-marsh communities. Grazing and mowing are compared in detail. Both management practices enhance species diversity in an abandoned salt marsh. This can be attributed to the removal of litter. The finding that lower salt-marsh species appear more with grazing than with mowing or abandoning is not related to a higher soil salinity as compared to mowing or abandoning, but probably to locally baring of the soil by grazing animals. Only species of pioneer or unstable environments seem to have a persistent seed bank, for other species seed dispersal seems to be a limiting factor for their establishment.Nomenclature follows Heukels & van Ooststroom (1977) for species; Westhoff & den Held (1969) for syntaxa.Mrs R. Rusthoven analyzed the soil samples, Mr E. Leeuwinga drawed the figures, and Mrs J. O'Brien corrected the English text.     

Spatial and temporal distribution patterns of the macrozoobenthos assemblage in the salt marshes of Tejo estuary (Portugal)

The present study focuses on the spatial and temporal distribution of the macroinvertebrate community of the salt marsh areas of the Tejo estuary, based on surveys conducted from autumn 1998 to summer 2000. Samples were collected quarterly in five different intertidal areas along an elevation gradient in: mudflats, creek mouths, creeks, pioneer salt marsh areas and middle marsh areas. A total of 36 benthic invertebrate taxa were identified. Insect larvae were the most well represented group, with 10 taxa identified. Oligochaetes and ostracods were the most numerically abundant taxa, whereas bivalves dominated in biomass. Benthic macroinvertebrate assemblages were dominated, both in number and biomass, by deposit feeders. Three distinct macroinvertebrate assemblages were distinguished along the elevation gradient, based on species presence, density and biomass: the unvegetated muddy areas with a macrobenthic assemblage composed mostly by infauna; the salt marsh pioneer areas of Spartina maritima in which several epibenthic taxa were found, as well as endobenthic taxa characteristic of muddy sediment; and the creek margins, with epifauna taxa such as insect larvae and crustaceans and a low abundance of benthic infauna. Total biomass in the unvegetated and Spartina areas was higher during spring and summer mainly due to the increase in biomass of Scrobicularia plana and Hydrobia ulvae. No decreases in the salt marsh macroinvertebrate biomass values were observed during the highest densities of their potential nektonic predators (summer). This fact might indicate that macroinvertebrates are not a limiting resource for the nektonic species, and that the natural biomass increment of these invertebrate species could be masking the predation/disturbance caused by the nektonic species.     

Salt marshes along the coast of The Netherlands

The area of salt marshes does no longer increase. The recent erosion coincides with a rise in MHT-level in the last 25 years. Despite the decrease in area, sedimentation continues, especially in the lower salt marsh, which acts as a sink of nitrogen. Assimilation and mineralization of nitrogen are in balance in most plant communities along the gradient from lower to higher salt marshes. Mineralization of nitrogen increases towards the higher salt marsh, whereas the above-ground production and the mean nitrogen content of plants decrease. There is a positive correlation between quality of food plants in salt marshes and breeding success of Brent geese in the arctic tundra. Sedimentation on mainland salt marshes can compensate for the expected sea level rise. This is not the case for island salt marshes, if the relative sea level rise is more than 0.5–1.0 cm yr⁻¹. The natural succession on salt marshes results in an accumulation of organic material, which is related to the dominance of single plant species. It is not clear to which extent this process is enhanced by eutrophication from acid deposition and seawater. Human exploitation of unprotected salt marshes is old and heavy in the system of mound settlements. Reclamation rates by dikes in the last centuries were higher than the rate of area increase. Grazing by cattle as a management practice results in both a higher plant species-richness and community diversity than abandoning; hay-making is intermediate, but shows less structural diversity than grazing with low stocking density. The invertebrate fauna is favoured by a short period of abandoning, but eventually characteristic salt marsh invertebrates are replaced by inland species. Many bird species prefer grazed salt marshes. The final section gives some perspectives. Provided that no further embankments take place the optimal nature management option for plants and animals is a vegetation pattern, which includes areas with a low canopy (grazed) and areas with a tall canopy.     

Review of the ecosystem service implications of mangrove encroachment into salt marshes

Salt marsh and mangrove have been recognized as being among the most valuable ecosystem types globally in terms of their supply of ecosystem services and support for human livelihoods. These coastal ecosystems are also susceptible to the impacts of climate change and rising sea levels, with evidence of global shifts in the distribution of mangroves, including encroachment into salt marshes. The encroachment of woody mangrove shrubs and trees into herbaceous salt marshes may represent a substantial change in ecosystem structure, although resulting impacts on ecosystem functions and service provisions are largely unknown. In this review, we assess changes in ecosystem services associated with mangrove encroachment. While there is quantitative evidence to suggest that mangrove encroachment may enhance carbon storage and the capacity of a wetland to increase surface elevation in response to sea‐level rise, for most services there has been no direct assessment of encroachment impact. On the basis of current understanding of ecosystem structure and function, we theorize that mangrove encroachment may increase nutrient storage and improve storm protection, but cause declines in habitat availability for fauna requiring open vegetation structure (such as migratory birds and foraging bats) as well as the recreational and cultural activities associated with this fauna (e.g., birdwatching and/or hunting). Changes to provisional services such as fisheries productivity and cultural services are likely to be site specific and dependent on the species involved. We discuss the need for explicit experimental testing of the effects of encroachment on ecosystem services in order to address key knowledge gaps, and present an overview of the options available to coastal resource managers during a time of environmental change.     

Salt marsh foraminifera from the Great Marshes, Massachusetts: environmental controls

By using sites in the Great Marshes at Barnstable (Massachusetts, USA) this study examines the effects of a set of environmental parameters on the foraminiferal distribution. The studied parameters are: elevation above mean high water; salinity of the porewater; various sediment characteristics; vegetation; and food source. Relations between the environmental parameters and foraminiferal properties (frequencies, densities and diversities) are quantified with correlation coefficients. For the first time Siphotrochammina lobata and Balticammina pseudomacrescens are documented in the New England region.

The following species show a significant correlation with one or more of the studied parameters and are designated as key-species: Haplophragmoides manilaensis, Jadammina macrescens, Balticammina pseudomacrescens, Miliammina fusca and Tiphotrocha comprimata. Based on cluster analysis and the presence, absence or dominance of the key-species characteristic associations are distinguished. The distribution of three associations is indicative of specific marsh environments: the marsh fringe, the middle marsh and the marsh edge. These three marsh units are separated by their own salinity regime, flooding and sediment characteristics.

The marsh fringe is typified by the H. manilaensis Association and experiences freshwater input (seepage, surface runoff and rainwater) and only slight marine influence, resulting in low salinity values (2.5–20‰). The width of the marsh fringe is variable, dependent on the amount of seepage which in turn is controlled by the permeability of the basement and the peat. The J. macrescens Association characterizes the middle marsh where salinities are controlled by infiltration of sea- and rainwater and by evaporation. Salinity values are higher than 20‰, while temporarily salinity can reach extreme high values during periods without flooding and high evaporation rates (e.g., 44‰). The fully marine M. fusca Association occupies the daily flooded marsh edge where the salinities have the same values as Cape Cod bay water (ca. 28‰).

Unlike many other salt marshes the distribution of foraminiferal assemblages in the Great Marshes does not show a vertical zonation with respect to mean high water. This shows that a worldwide applicable model for paleoenvironmental studies in salt marshes based on foraminifera is not feasible. Each salt marsh has its own characteristics. Regional factors such as climate play an important role in the salinity regime, while the local upland characteristics determine if seepage takes place. Thus each marsh has its own foraminiferal fingerprint showing the opportunistic behaviour of the salt marsh agglutinants. A surface study is an indispensable first step in assessing the value of foraminifera as paleo-ecological indicators.