Dead Assemblages Research Articles

Anthropogenic effect recorded in the live-dead compositional fidelity of land snail assemblages from San Salvador Island, Bahamas

Terrestrial malacofaunas that inhabit islands are vulnerable to human activities. Habitat destruction, introduction of exotic species, predators, etc. are distorting the composition and distribution of indigenous snail communities. Specifically, the taxonomic discordance between live and dead assemblages may be the consequence of anthropogenic disturbances rather than natural post-mortem processes. Live-dead fidelity may hence reflect the degree of human alteration in a given locality. This approach was used to study the relative abundance of live and dead land snails from pristine and urbanized localities around San Salvador Island (Bahamas). Thirteen species were encountered from 64 samples containing 5,343 specimens. Taxonomic composition was significantly different between areas of negligible anthropogenic disturbance and those impacted by humans. Although which species of land snails are endemic to San Salvador is unknown, all identified species are native to the Caribbean region and invasive species were not encountered. However, some synanthropic species, found exclusively in urban-developed areas, have not been recovered from the local fossil record, pointing to their relatively recent introduction possibly from nearby islands. Non-metric MDS, Jaccard-Chao index, and Spearman correlation analyses indicated that dead assemblages displayed a good compositional correspondence to live communities at pristine sites, whereas considerable disparity was sometimes observed at human-modified areas. Urbanized areas probably favored the proliferation of synanthropic species whereas dead assemblages may contain anthropophobic taxa that lived there prior to recent human modification. These findings are consistent with previous live-dead fidelity studies of marine molluscan and terrestrial small-mammal assemblages, and suggest that the taxonomic discordance between live and dead assemblages of land snails may be indicative of recent anthropogenic alteration.

COMPOSITIONAL FIDELITY OF SUBFOSSIL MOLLUSK ASSEMBLAGES IN STREAMS AND LAKES OF THE SOUTHEASTERN PAMPAS, ARGENTINA

The compositional fidelity of dead assemblages—the extent to which subfossil remains reflect the composition, structure, and scale of the original living community—is an indispensable component of studies assessing the quality of the fossil record and the effects of taphonomic biases on species composition and diversity. The aim of the present study is to evaluate (1) how faithfully abundances of subfossil freshwater mollusk shells deposited in dead assemblages correspond to their abundances in the local living assemblages, (2) how reliably diversity of living assemblages is captured by dead assemblages, (3) whether spatial variation in species composition in living assemblages is captured by dead assemblages in the southeastern Pampas, Argentina. Twenty sites corresponding to five lotic and five lentic sites from two geographic areas were analyzed in terms of taxonomic composition and diversity, and homogeneity of multivariate dispersions. We find that (1) living and dead assemblages occupy similar portions of multivariate space and do not significantly differ in composition within an area, (2) living and dead assemblages show similar richness and evenness, and (3) between-environment differences in among-site variation in composition (beta diversity) captured by living assemblages are preserved by dead assemblages. Thus, the results highlight the potential these environments have to enhance the preservation of mollusks and result in fossil assemblages that are suitable for paleoecological and paleoenvironmental studies of freshwater ecosystems.

The FOBIMO (FOraminiferal BIo-MOnitoring) initiative—Towards a standardised protocol for soft-bottom benthic foraminiferal monitoring studies

The European Community Marine Strategy Framework Directive (MSFD) was established to provide guidelines for monitoring the quality of marine ecosystems. Monitoring the status of marine environments is traditionally based on macrofauna surveys, for which standardised methods have been established. Benthic foraminifera are also good indicators of environmental status because of their fast turnover rates, high degree of specialisation, and the preservation of dead assemblages in the fossil record. In spite of the growing interest in foraminiferal bio-monitoring during the last decades, no standardised methodology has been proposed until today. The aim of the FOraminiferal BIo-MOnitoring (FOBIMO) expert workshop, held in June 2011 at Fribourg, Switzerland, which assembled 37 scientists from 24 research groups and 13 countries, was to develop a suite of standard methods. This paper presents the main outcome of the workshop, a list of motivated recommendations with respect to sampling devices, sample storage, treatment, faunal analysis and documentation. Our recommendations fulfil the criteria imposed both by scientific rigour and by the practical limitations of routine studies. Hence, our aim is to standardise methodologies used in bio-monitoring only and not to limit the use of different methods in pure scientific studies. Unless otherwise stated, all recommendations concern living (stained) benthic foraminiferal assemblages. We have chosen to propose two types of recommendations. Mandatory recommendations have to be followed if a study wants to qualify as sound and compatible to the norms. The most important of these recommendations are the interval from 0 to 1 cm below the sediment surface has to be sampled, and an interface corer or box corer that keeps the sediment surface intact is to be used for offshore surveys. A grab sampler must not be deployed in soft sediments. Three replicate samples are to be taken and analysed separately. Samples are to be washed on a 63-μm screen, and the living benthic foraminiferal fauna of the > 125 μm fraction is to be analysed. Splits are to be picked and counted entirely, and all counted foraminifera from at least one replicate per station have to be stored in micropalaeontological slides. Census data, supplementary laboratory data and microslides have to be archived. Advisory recommendations are to sample in autumn, to have a sample size of 50 cm 2 or a tube of 8 cm inner diameter, to use > 70% ethanol as a preservative, rose Bengal at a concentration of 2 grams per litre for staining, and a staining time of at least 14 days. The split size should be defined by a target value of 300 specimens, heavy liquid separation should be avoided, and the 63–125 μm fraction or deeper sediment levels may be considered in some environments. We are convinced that the application of this protocol by a large number of scientists is a necessary first step to a general acceptance of benthic foraminifera as a reliable tool in bio-monitoring studies. ► Benthic foraminifera are proposed for monitoring the quality of marine ecosystems. ► No standardised methodology has been proposed until today. ► The FOBIMO initiative developed a suite of standard methods. ► They concern sampling devices, storage, treatment, faunal analysis and documentation. ► The application will help to establish foraminifera as a tool in bio-monitoring.

Live and dead benthic foraminiferal faunas from Whittard Canyon (NE Atlantic): Focus on taphonomic processes and paleo-environmental applications

Abstract Dead benthic foraminiferal assemblages were studied in the > 150 μm fraction of 4–5 cm deep sediment levels at 18 stations in the Whittard Canyon area in June 2007. This sediment layer is composed of fairly recent sediment ( In both canyon branches, the population dynamics, such as seasonal response to phytodetritus deposition, certainly contribute to differences between live and dead faunas. For instance, Bulimina marginata , which is usually considered as an opportunistic species is over-represented in the dead assemblage. The fragility of the tests of some species can explain their total absence in the thanatocoenoses. This concerns many organic cemented arenaceous tests, miliolid tests sensitive to dissolution and perforate taxa with thin tests. Furthermore, transport (e.g. sediment gravity flows), active in both canyon branches, leads to an increasing relative contribution of allochthonous individuals, originating from outer shelf and upper canyon sites, towards the deeper canyon stations. Consequently the dead faunas do no reflect local environmental conditions. The high abundance of transported dead foraminifera in both canyon branches leads to important biases in the foraminiferal assemblage composition, but may also significantly bias the interpretation of δ 13 C, δ 18 O, trace-elements and 14 C concentration in foraminiferal shells. It may therefore strongly complicate the reconstruction of environmental parameters such as bottom water temperature or exported paleoproductivity, and radiocarbon dating of the foraminiferal assemblages. Therefore, in both canyon axes, the use of dead foraminiferal faunas to reconstruct paleoenvironmental in situ conditions is precluded. However, the study of dead assemblages in the canyon branches, in particular the quantity of allochthonous foraminifera, can give important clues about the downslope sedimentary dynamics. On both open slopes, despite taphonomic (test destruction) and biological processes (population dynamics), the distribution and the composition of the live fauna resemble those of the dead assemblage. In these areas, dead foraminiferal faunas include much less material derived from downslope transport. Consequently, on the open slope, dead assemblages appear to better reflect local conditions. Therefore, the ecological information obtained from fossil open slope samples can be more reliably used to reconstruct paleoenvironmental conditions.

SHELL TAPHONOMY AND FIDELITY OF LIVING, DEAD, HOLOCENE, AND PLEISTOCENE LAND SNAIL ASSEMBLAGES

Variations in the taxonomic composition of ancient land snail assemblages can potentially reflect changes in past ecosystems. The use of fossil associations as a paleoenvironmental-paleoecological proxy assumes that the original biological signature is retained, but postmortem processes can distort it. In this study, the fidelity of land snail assemblages was tested by comparing taphonomic and ecological variables recorded by live and dead, middle Holocene and Upper Pleistocene land snail shelly assemblages from San Salvador Island (Bahamas). Shells of living organisms were practically unaltered whereas dead and fossil shells were primarily affected by fragmentation, ornament loss, color loss, and carbonate coating. Taphonomic features fluctuated across space and time likely due to variable environmental conditions and/or time of exposure prior to shell burial. Live assemblages showed good taxonomic agreement with dead assemblages, although the later exhibited a higher number of taxa and individuals than the former. Assemblages that were moderately (dead and Holocene) and strongly (Pleistocene) taphonomically altered did not differ in species abundances, suggesting that the original biological signal was preserved. In contrast, unaltered (live and some dead) assemblages differed taxonomically from moderately and strongly damaged assemblages, likely as a consequence of different scales of time-averaging rather than variable shell-specific destruction rates. Taxonomic richness and simple dominance of time-averaged land snail assemblages were similar at various interglacial time periods (∼125 ka, ∼5–6 ka, and today). Such apparently equivalent snail richness may suggest that the climatic-environmental and/or ecological conditions at those times were comparable to the present.

The environmental setting and microfauna of the oligohaline Timsah pond, Israel: The last remnant of the Kabara swamps

Abstract Enot Timsah is a spring-fed wetland ecosystem at the foot of the Carmel Mountain, a relict of the much larger Holocene Kabara swamps, at the northern outlet of the Yarqon-Tanninim mountain aquifer. This groundwater-surface water interaction zone supports a unique living foraminiferal and ostracod fauna. Sampling of water and sediment was carried out approximately monthly in 2002/3 as part of a study of the species richness and history of this distinctive ecosystem. Enot Timsah is nearly isothermal (23.98 ± 0.4 °C) and oligohaline with total dissolved solids (TDS) of 3,213 ± 118.5 mg/l. The water column is transparent and highly oligotrophic, with very low phosphate concentration. Living ostracods and Rose Bengal stained benthic foraminifera occur in low numbers. A monospecific population of the ostracod Cyprideis torosa lives at the surface, with a reproductive peak in April, 2002. Foraminifera occur throughout the topmost 0–4 cm. Extreme oligotrophy of this ecosystem means that there is a low flux of phytoplankton, limiting abundance of surface-dwelling ostracods and foraminifera. Microbial decomposition of vascular plant debris was the food source for infaunal foraminifera. The low salinity means that living conditions are marginal explaining low numerical abundance of foraminifera. However, foraminiferal diversity is exceptionally high at Enot Timsah compared with other oligohaline environments, with 15 living benthic taxa and three additional species found in the dead assemblage. The living assemblage is composed of cosmopolitan agglutinants known to live in brackish environments, together with some calcareous hyaline and miliolid taxa. The exceptional foraminiferal diversity is attributed to four factors: the very stable conditions of salinity and temperature; the high Ca2+ and HCO3− concentrations derived from the karstic aquifer (promoting mineralization of calcareous tests), the maturity of the Kabara ecosystem dating from the early Holocene; and the repetitive reintroduction of cosmopolitan brackish foraminifera by avian transport. Increased numbers of living foraminifera with abnormal morphologies testify to stress conditions. Dead foraminifera are more abundant than living ones, with agglutinated foraminifera dominating the living assemblage, and calcareous forms dominating the dead assemblage. This taphonomic reversal is attributed to microbial decomposition of organic cement of the agglutinants, while the calcareous forms are resistant to dissolution because of the high Ca2+ and HCO3− of the aquifer-derived spring waters. The Holocene fossil record of the predecessors of the Kabara swamps therefore represents an estimated 10–40% of the information found in the living foraminiferal assemblage at Timsah.

Formation processes of shell concentrations in the Lower Cretaceous estuarine sediments of the Okurodani Formation, Tetori Group, Gifu Prefecture, central Japan

The formation processes of shell concentrations in estuarine environments are complicated by the interplay between the original biogenic and overprinting sedimentary processes. In order to better understand this interplay, the formation processes of shell concentrations composed exclusively of monospecific Myrene tetoriensis (“corbiculoid” bivalve) occurring in the Lower Cretaceous estuarine deposits of the Okurodani Formation of the Tetori Group in central Japan were considered within in the context of their mode of life. In addition, the size–frequency distribution of shells was discussed in relation to the formation processes of shell concentrations. As a result, the autochthonous occurrence of M. tetoriensis clarified a gregarious mode of life in the muddy sediments of a central estuary. In contrast, the post-mortem exhumation, accumulation, and degree of transport of dead shells by hydrodynamic processes were reflected in various occurrence modes of allochthonous shell concentrations. The size distribution patterns of these shell concentrations suggested that the primary size composition of autochthonous living and dead assemblages could have been retained in the absence of sufficient overprinting, even through reworking and transport. This was probably possible because of the high production of dead shells as compared to the relative effect of sedimentary processes.

INFLUENCE OF PATCHINESS ON MODERN SALT-MARSH FORAMINIFERA USED IN SEA-LEVEL STUDIES (NORTH CAROLINA, USA)

We collected replicate samples at stations placed systematically along a transect at Oregon Inlet (North Carolina, USA) to investigate spatial homogeneity of dead assemblages of salt-marsh foraminifera. Analysis of variance (ANOVA) was used to investigate the differences in mean proportions for six species ( Miliammina fusca, Trochammina inflata, Arenoparrella mexicana, Tiphotrocha comprimata, Haplophragmoides wilberti and Jadammina macrescens ) selected because of their importance in distinguishing assemblages across salt marshes in the study region. As expected, ANOVA’s on all species indicated significant differences among low-, middle-, and high-marsh zones defined by their flora. No significant differences were found between stations in the low- and high-marsh indicating homogeneity in these zones. In contrast, for all six species in the middle-marsh zone, significant outcomes for ANOVA, cluster analysis and post-hoc comparisons suggested that the middle-marsh should be divided into two zones. In addition, two species exhibited a patchy (inhomogeneous) distribution among all stations in the middle marsh. If confirmed by additional studies, our results indicate that sampling of modern salt-marshes to document the distribution of foraminifera for use in sea-level reconstructions should recognize the spatial variability associated with the middle-marsh floral zone.

COMPARATIVE ANALYSIS OF EPIPHYTIC FORAMINIFERA IN SEDIMENTS COLONIZED BY SEAGRASS POSIDONIA OCEANICA AND INVASIVE MACROALGAE CAULERPA SPP.

Mediterranean shallow-water soft bottoms are characterized by extensive meadows of the endemic seagrass Posidonia oceanica (L.) Delile that support abundant benthic biota including numerous epiphytic foraminiferal taxa. The biomass of the epiphytic communities varies with the P. oceanica cycle, especially influencing those taxa with higher abundances in summer, when the foliar surface is maximum. During the past decades exotic macrophyte species have invaded habitats formerly dominated by P. oceanica . Two of these taxa are the green algae Caulerpa taxifolia (Vahl) Agardh, 1817 and C. racemosa (Forsskal) Agardh, 1873, that, along with the non-invasive C. prolifera (Forsskal) Lamouroux, 1809, produce defensive, secondary metabolites such as caulerpenyne that affects turnover rates of P. oceanica leaves. As a consequence of different architectural features of the algal substrate, replacement of P. oceanica by Caulerpa spp. results in the change from a complex three-dimensional, long duration substrate into a simpler, two-dimensional one with a shorter life span. Epiphytic foraminifers can be clustered into functional groups according to their shape, structure, behavior and life span. The foraminiferal dead assemblage includes a total of 110 species, that included 43 species in sediments colonized by P. oceanica , 82 species in sediments with C. prolifera , 78 in sediments invaded by C. taxifolia , and 55 in sediments invaded by C. racemosa . Taxonomic composition of all assemblages is similar, though differences occur in the relative abundance of each taxon. Sediments in P. oceanica meadows are characterized by flat, encrusting, long life-span species (e.g., Planorbulina mediterranensis d’Orbigny, 1826), whereas in Caulerpa spp. habitat, temporarily motile, shorter life-span taxa (e.g., Lobatula lobatula (Walker and Jacob, 1798) and Rosalina bradyi Cushman, 1915) tend to dominate. Multivariate analysis shows that only the thanathocoenosis of P. oceanica sediments is representative of the P. oceanica epiphytic foraminiferal assemblage ( Planorbulinatum medi-terranensae Colom, 1942). Hence, differences among the foraminiferal assemblages in sediments colonized by different phytal substrates occur prior to taphonomic and dissolution processes and may be applicable to paleoecological interpretations.

Distribution of recent benthic foraminifera in shelf carbonate environments of the Western Mediterranean Sea

The distribution of recent shallow-water benthic foraminifera in surface sediment samples from cool-water carbonate environments of the Oran Bight, Alboran Platform and Mallorca Shelf in the Western Mediterranean Sea was studied. Multivariate statistical analyses resulted in the identification of species assemblages, representing different environmental settings. In all three regions the assemblages show a distinct bathymetric zonation that is mainly attributed to the distribution of rhodoliths and related substrates, but also to water turbulence and the availability of food at the sea floor. The live assemblages (Rose Bengal stained individuals) are characterised by rather low diversity and low standing stocks, likely reflecting seasonal population dynamics. In the Oran Bight, elevated standing stocks of “high food”-taxa suggest the impact of anthropogenic eutrophication on the near-coastal benthic ecosystems of this area. The diversity of the dead assemblages is higher than in siliclastic shelf ecosystems of the Mediterranean Sea but lower when compared to carbonate environments of the Levantine Sea. This regional difference is mainly attributed to lower sea surface temperatures and the lack of Lessepsian invaders in the western Mediterranean Sea. In all study areas, a distinct faunal change occurs between approximately 80–90 m water depth. This change coincides with the lower distribution limit of living rhodoliths at the shelf of Mallorca, providing coarse-grained substrates that are dominated by attached taxa. Below this depth interval, the fauna shows regional differences depending on the grain-size and related accumulation of organic material. Fine-grained substrates with infaunal niches are restricted to low-energy environments on the deeper shelf southwest off Mallorca.

COLONIZATION OF COASTAL ENVIRONMENTS BY FORAMINIFERA: INSIGHT FROM SHRIMP PONDS IN NEW CALEDONIA (SW PACIFIC)

The objectives of this study were to observe foraminiferal colonization patterns and behavior in shrimp ponds in New Caledonia during a shrimp-growing (farming) cycle. Weekly collecting at 10 stations in 8 shrimp ponds yielded a total of 170 samples accompanied by environmental data. Seawater pumped from the nearby ocean filled the ponds at the beginning of the growth cycle and its daily renewal maintained salinity at 32–39, and supplied the ponds with influxes of smaller, mostly juvenile, foraminifera. A few days after initial filling, the pioneering species Ammonia tepida and Quinqueloculina seminula appeared, with A. tepida dominant. Their high reproduction rates increased both living and dead assemblage densities during the first 10 weeks. Populations of these two species then stabilized with higher oxygen demand (drop of redox) and consumption of living foraminifera by shrimp. Only a few colonizers subsequently appeared, which was attributed to the isolation of the pond, despite the high rate of water renewal. Only one pond had notably higher species richness, but it could not be distinguished from the others by its physicochemical parameters. The species that appeared in ponds initially barren of foraminifera also survived where there was water seepage between growing cycles, suggesting that the assemblages had already reached equilibrium with the environment. Despite the number of environmental parameters measured, only oxygen and reactive organic matter correlated with the microfauna on a weekly timescale. We assume that other parameters do not significantly affect foraminifera until they reach critical threshold. Consistent with previous studies, A. tepida was the species most tolerant of organic influx, but its relative abundance dropped once the organic matter flocculated and settled, leading to disoxic conditions in the sediment. Conversely, Q. seminula was able to climb through the floc and reach the oxygenated layer, where its relative abundance increased.

Taphonomic signatures and patterns of test degradation on tropical, intertidal benthic foraminifera

The preservational condition of benthic foraminifera from tropical intertidal sediments in Cleveland Bay, north Queensland, Australia was examined in order to provide systematic descriptions of taphonomic signatures and semi-quantitative estimates of test degradation. The primary aim was to improve understanding of the processes of test degradation experienced by intertidal foraminifera during early burial. Eight common tropical, intertidal foraminiferal species were examined: Arenoparrella mexicana, Miliammina fusca, Miliammina obliqua and Trochammina inflata from two upper mangrove stations, and Ammonia aoteana, Elphidium excavatum clavatum, Pararotalia venusta and Parrellina hispidula from two mudflat stations. Taphonomic alteration was broadly divided into surface/textural features and larger-scale, structural losses to tests. Surface alteration of calcareous tests was dominated by the etching and roughening associated with dissolution processes, with limited evidence for bioerosion and abrasion. Both surficial etching and larger-scale structural damage were closely related to test architecture, with degradation most intense on porous chamber walls, as opposed to non-porous-areas, interlocular walls and chamber tips. Furthermore, all calcareous species exhibited consistent pathways of degradation whereby the most recently formed chambers were the most vulnerable to degradation. The correspondence between larger-scale test loss and these patterns of surface textural alteration, suggests calcareous test degradation is primarily driven by dissolution. Degradation of agglutinated tests contrasts in a number of ways. Pristine tests of all four species examined exhibited a smooth, outer organic coating, which may be missing from other specimens. The extent to which this initial loss effects further test breakdown is uncertain, but appears to differ between species. M. obliqua and some specimens of A. mexicana exhibited structural damage which corresponded to clear cement losses and agglutinant disaggregation. More generally, agglutinated species displayed fracturing and test breakages which bore no conspicuous relation to cement loss. Furthermore, neither surface alteration nor structural loss affected any part of agglutinated tests preferentially, and therefore pathways of degradation were inconsistent across specimens. The fact that agglutinated tests degrade in a more arbitrary manner, compared with calcareous tests, is taken as evidence that their degradation is (1) not entirely controlled by test architecture, and (2) at least partially driven by physical/mechanical processes. We suggest that, if agglutinated tests are not already inherently weaker than their calcareous counterparts, the loss of organic cements may sufficiently weaken agglutinated tests so as to increase susceptibility to physical damage. Tests were also graded according to the extent to which they were structurally degraded. Average taphonomic grades and taphonomic variability (i.e. standard deviation) for all species at Cocoa Creek were statistically invariant with depth, contrary to expectations based on the concept of progressive burial through a taphonomically-active zone. This indicates that shallow sub-surface sediments are significantly homogenised, and that sediment mixing and infaunal test production imparts a considerable effect on the development of surface and sub-surface dead assemblages at the study site.

POSTMORTEM PROCESSES AFFECTING BENTHIC FORAMINIFERAL ASSEMBLAGES IN THE RIA DE VIGO, SPAIN: IMPLICATIONS FOR PALEOENVIRONMENTAL STUDIES

This study evaluates the postmortem processes acting during the transition from live to dead assemblages in the Ria de Vigo, Spain. The thanatocoenosis component of benthic foraminifera has been studied along the muddy central axis of the ria and compared with previously published data on living taxa. There are some general differences between live and dead assemblages; biological processes might have caused some of the dissimilarities, but transport of allochthonous foraminifera from nearby areas and the destruction of tests likely have caused the remainder. Assemblages located in the inner parts of the ria and those near shallow, coarse-grained substrates include proportions of allochthonous foraminifera introduced by high-energy bottom currents (e.g., Ammonia heccarii and Haynesina germanica in inner settings and Elphidium crispum , Rosalina anomala ,and Cihicides spp. in areas close to coarse sediments). Thin-shelled calcareous tests (e.g., Hopkinsina atlantica and the upwelling-related species Bolivinellina translucens , Leptohalysis scottii , Nonionella stella , and Nonionella turgida ) are destroyed soon after the death of individuals. The agglutinated tests of Eggerelloides scaher within the first centimeters of substrate might be prone to disaggregation, possibly as the result of organic membrane decomposition by bacterial activities. The hydrodynamics and microenviromental conditions in the Ria de Vigo are likely to cause displacement or destruction of tests. As a result, microfossil assemblages recovered for analysis are unlikely to reflect the in situ living assemblage at the time of deposition. Recognition of allochthonous taxa is therefore an important part of such studies.

Bone Assemblages Track Animal Community Structure over 40 Years in an African Savanna Ecosystem

Reconstructing ancient communities depends on how accurately fossil assemblages retain information about living populations. We report a high level of fidelity between modern bone assemblages and living populations based on a 40-year study of the Amboseli ecosystem in southern Kenya. Relative abundance of 15 herbivorous species recorded in the bone assemblage accurately tracks the living populations through major changes in community composition and habitat over intervals as short as 5 years. The aggregated bone sample provides an accurate record of community structure time-averaged over four decades. These results lay the groundwork for integrating paleobiological and contemporary ecological studies across evolutionary and ecological time scales. Bone surveys also provide a useful method of assessing population changes and community structure for modern vertebrates.

Foraminiferal biofacies across mangrove-mudflat environments at Cocoa Creek, north Queensland, Australia

Contemporary and relict (subsurface) intertidal foraminiferal dead assemblages were collected from a site near to Cocoa Creek, north Queensland, Australia, and analysed for the purpose of understanding fossil assemblage development and preservation. A marked dichotomy was identified between dead foraminiferal assemblages within mangrove sediments and those within adjacent mudflat sediments. Mangrove assemblages were almost exclusively represented by agglutinated species (mainly Arenoparrella mexicana, Haplophragmoides wilberti, Milliammina fusca, M. obliqua, Trochammina inflata) while calcareous species dominated the mudflat (mainly Ammonia aoteana, Pararotalia venusta, Parrellina hispidula). Surface and subsurface test abundances were also an order of magnitude greater within mudflat sediments (1000–3000 tests per cm 3) than in the sediments beneath the mangroves (100–300 tests per cm 3). Statistically significant differences in the abundance of calcareous and agglutinated tests between wet and dry seasons within the mangrove suggest that tests are systematically lost from this part of the system on an annual basis. A model of assemblage formation under shoreface progradation is presented which makes a direct link between surface assemblages, post-depositional processes and the composition and environmental resolution of the fossil assemblages entering the stratigraphic record. Assemblages within the mangrove undergo rapid taphonomic loss and are then overprinted during burial by the deep infaunal communities associated with the prograding higher-elevation environments. As such, much of the eventual mangrove sequence is represented entirely by assemblages produced relatively recently within an upper mangrove environment, and therefore cannot be differentiated according to elevation at the time of deposition. In addition, organic enrichment of upper mudflat deposits by mangrove roots, which occurs during progradation, results in the dissolution of calcareous tests from an ~ 40 cm thick stratigraphic interval. It is argued that in order to reliably recognise the changes to foraminiferal assemblages which occur during burial, assemblages must be compared with respect to stratigraphy, rather than reflexively downcore.

Environmental constraints of foraminiferal assemblages distribution across a brackish tidal marsh (Caminha, NW Portugal)

Foraminiferal living assemblages from a brackish tidal marsh were studied across three sampling transects, under Spring and Autumn conditions. Foraminiferal analysis was also extended to the dead assemblages of Spring samples. Altimetric control of each sampling point was acquired through the connection to the national datum by GPS differential positioning combined with a regional geoid model. The influence of the geochemical characteristics on the assemblages including chemical composition of the estuarine and marsh surface sediments, in addition to salinity, pH and calcite saturation of estuarine and marsh interstitial waters was evaluated. A high affinity was found between Spring and Autumn living assemblages, probably related to the low number of representative species. The affinity also found between living and dead assemblage was seen as a consequence of low pH and calcite undersaturation that prevent the accumulation effect of several generations of foraminifera. Salinity appears as a clear constraint to the foraminiferal assemblages composition that is enhanced by calcite undersaturation in brackish marshes interstitial waters and sediments. Generally abundant marsh species like Trochammina inflata, Jadammina macrescens and the calcareous foraminifera are limited to an episodic presence. Foraminiferal assemblages distribution across brackish tidal marsh can be assumed as an elevation proxy. The high marsh IB sub-zone is dominated by Haplophragmoides sp. and Haplophragmoides manilaensis. Low marsh zone II is characterised by the dominance of Miliammina fusca but can be subdivided in an IIA upper part, where is followed by Pseudothurammina limnetis, and in a IIB lower part defined by a subsidiary presence of Psammosphaera sp. Haplophragmoides manilaensis dominance between 1.55 m and 1.67 m, at living as well as dead assemblages, suggests this species as a potential sea-level indicator for the brackish tidal marshes.

The spatial and vertical distribution of living (stained) benthic foraminifera from a tropical, intertidal environment, north Queensland, Australia

We investigated the distribution of living (stained) benthic foraminifera across a tropical, intertidal shoreline adjacent to Cocoa Creek, Queensland, Australia for the purpose of better understanding the nature of test production and ultimately fossil assemblage development within such environments. Short cores (up to 1 m) were collected during the wet and dry season, along an elevational gradient comprising non-vegetated intertidal mudflat and higher-intertidal mangrove forest environments. The distribution of stained specimens can be broadly delineated into assemblages characterising ‘upper mangrove’ (2.64–2.91 m above Lowest Astronomical Tide (LAT)) and ‘low mangrove-mudflat’ (1.62–2.18 m above LAT) environments. Agglutinated species were generally limited to upper mangrove stations. Calcareous species occurred within all of the intertidal environments examined but differ in their composition between upper and lower intertidal settings. Upper mangrove faunas were characterised by the agglutinated species Arenoparrella mexicana, Haplophragmoides wilberti, Miliammina fusca, Miliammina obliqua and Trochammina inflata and the calcareous species Helenina anderseni. Live (stained) assemblages at lower intertidal elevations were dominated by the calcareous species Ammonia aoteana, as well as Rosalina spp., Elphidium oceanicum, Triloculina oblonga, Ammonia pustulosa and Shackoinella globosa. Absolute densities of stained specimens were lowest within the low mangrove sediments (6–8 specimens per cm 2) but higher within the upper mangrove (25–249 specimens per cm 2) and mudflat (8–77 specimens per cm 2). Abundances within mudflat sediments varied seasonally (being significantly larger in the wet season) whereas those within mangrove zone sediments changed little through the year. Stained foraminifera were found to a maximum depth of 50 cm at Cocoa Creek, extending to the greatest depth at the upper mangrove stations, and were generally shallowest beneath the lower mangroves. All stations had over 50% of their foraminiferal standing crop below the upper 1 cm, although at most stations < 10% of living specimens occurred within this layer. Comparison of this data with dead assemblages suggests that: (1) abundances of stained specimens, averaged over two sampling events, reasonably approximate aggregate in situ test production; and (2) a clear enrichment of infaunal species occurs within the mangrove. The latter effect was less conspicuous on the mudflat due to high rates of mixing and assemblage time-averaging, which obscure the signal of test production within the dead assemblages. In both cases, the validity and stratigraphic resolution of surface assemblages for sea-level and other palaeoenvironmental reconstructions is questionable.

J. Murray 2006. Ecology and Applications of Benthic Foraminifera. xi + 426 pp. Cambridge, New York, Melbourne: Cambridge University Press. Price £80.00, US $150.00 (hard covers). ISBN 9780 521 82839 0.

In this book, John Murray sets out to discuss benthic foraminiferal ecology and its applications on the basis of observations of living assemblages on a global scale. This strict approach is different from previous efforts, which often considered dead assemblages as well. It results in a very clear observational framework about the actual conditions that support the assemblages found. The book is very clearly laid out, supported by an enormous web-based resource, with tables of all the data presented in the book. The book starts with brief summaries on methods and biological/ecological aspects. Next, it launches into the discussion of benthic foraminiferal distributions. Here, the …

LIVE AND DEAD FORAMINIFERAL FAUNAS FROM SAINT-TROPEZ CANYON (BAY OF FREJUS): OBSERVATIONS BASED ON IN SITU AND INCUBATED CORES

The impact of sedimentary processes on the live (rose- Bengal-stained) foraminiferal faunas and on the composition of dead assemblages was investigated at a 373-m-deep station in Saint-Tropez Canyon (Bay of Frejus, France). For the .150-mm fraction, biocoenoses and thanatocoenoses were investigated in two 10-cm-long cores collected with a classical Barnett multi-corer. In the 63- to 150-mm size fraction, living faunas were investigated in the first centimeter of the sediment. The first core was fixed with ethanol and rose- Bengal at the time of the sampling (the in situ core) whereas the second core was stored in a culture room during a 2.5- year-long incubation before its fauna was investigated. Both cores present similar thanatocoenoses (.150-mm size fraction) that are substantially contaminated by neritic foraminifera presumably transported from adjacent shelves. The sedimentological analysis of a third core reveals neither graded sediments nor erosional surfaces. Abundant organic remains are detected downcore in the muddy silt sediment. All these observations preclude the idea of deposition by a recent turbidite. Therefore, our canyon environment seems to behave at present as a depocenter for a rather continuous flux of fine sediment and resuspended organic matter originating from shallower areas.

The distribution of molluscan assemblages and their postmortem fate on coral reefs in the Gulf of Aqaba (northern Red Sea)

Molluscan assemblages were studied on fringing reefs (reef flats, Millepora-fringing reefs, fringing reefs with massive corals) and fore-reef hard substrata (coral patches, coral carpets and small patch reefs) in the Gulf of Aqaba at water depths ranging from the intertidal to 26 m. A total of 1,665 molluscan individuals from 51 taxa was counted on 44 transects, which covered 220 m² at eight diving sites. The most important molluscs in the assemblage were the parasitic gastropod Coralliophila neritoidea, the encrusting gastropod Dendropoma maxima and the coral-associated bivalve Pedum spondyloideum. The dead assemblage, in contrast, was dominated by encrusting bivalves (Ostreoidea, Chamoidea, Spondylidae) and the coral-predating gastropod Drupella cornus. Distinct molluscan assemblages inhabit each of the three fringing reef-habitats and most of the important depth-related community changes occurred within the uppermost 5 m. In contrast, the three deeper fore-reef habitats are characterized by a more uniform molluscan composition. Molluscan assemblages were more dependent on substrata and their coral associations than on water depth. Comparisons with other published studies indicate that reefoidal hard substrata in the northern Red Sea are largely characterized by similar species-abundance patterns. The minor differences to other Red Sea studies probably reflect the northern, isolated position of the Gulf of Aqaba, the lack of certain molluscan habitats, and the differential impact of anthropogenic influences. Strong differences between living and dead assemblages in Aqaba are similar to those observed in other regions and are due to distinct biases in the dead assemblage. Molluscs closely associated with living corals (mostly bivalves and Dendropoma) can easily be overgrown after death and are thus undetectable in visual censuses. Some gastropod taxa are preferentially transported into surrounding soft-substrata postmortem or redistributed by hermit crabs. Such complex relationships between ecology and taphonomy are crucial in evaluating the quality of the molluscan fossil record in coral reef environments. The comparison of our results with literature data documents an increase in coral predators during the last two decades in the northern Red Sea. Due to the greater mollusc biodiversity in the shallower Aqaba reef habitats, damage to this coral reef zone would have the greatest impact on the overall mollusc community.