Grazing of intertidal benthic foraminifera on bacteria: Assessment using pulse-chase radiotracing

Although foraminifera are a dominant component of many marine benthic communities, quantification of their predation on prokaryotes remains an experimental challenge. We have developed an approach that allows us to study grazing by adult specimens of the calcareous species Haynesina germanica and Ammonia beccarii, and the single-chambered agglutinated species Psammophaga sp., on bacteria (Halomonas sp.), pulse-chase-labelled with ³H- and ¹⁴C-Leucine. The bacterivorous ciliate Uronema sp. and flagellate Pteridomonas sp. were used as positive controls. The rate of release of ³H when protozoa were incubated with the labelled bacteria indicated the predator's grazing rate; the proportion of ¹⁴C found in the foraminiferal biomass and shell indicated the prey assimilation rate. All three foraminiferal species grazed bacteria at a rate of 3.2-5.7 ng C ind⁻¹ h⁻¹ depending on bacterial concentrations. About 23% of the biomass of the ¹⁴C-labelled prey was most likely assimilated into foraminiferal pseudopodia, 12% was expelled in dissolved waste material, about 62% was respired and only 0.1% was incorporated into the carbonate shell. Extracellular digestion associated with pseudopodia could explain the very low proportion of the labelled food assimilated in the cell body and the significant proportion located in pseudopodial networks. These experiments also suggest that very little of the carbon ingested by adult calcareous foraminifera is incorporated into the shell. However, we cannot conclude that diet has no influence on the stable isotope composition of the shell since none of our calcareous specimens grew new chambers during the experiments.     

Diversity and geographic distribution of benthic foraminifera: a molecular perspective

The diversity and distribution of modern benthic foraminifera has been extensively studied in order to aid the paleoecological interpretation of their fossil record. Traditionally, foraminiferal species are identified based on morphological characters of their organic, agglutinated or calcareous tests. Recently, however, new molecular techniques based on analysis of DNA sequences have been introduced to study the genetic variation in foraminifera. Although the number of species for which DNA sequence data exist is still very limited, it appears that morphology-based studies largely underestimated foraminiferal diversity. Here, we present two examples of the use of DNA sequences to examine the diversity of benthic foraminifera. The first case deals with molecular and morphological variations in the well-known and common calcareous genus Ammonia. The second case presents molecular diversity in the poorly documented group of monothalamous (single-chambered) foraminifera. Both examples perfectly illustrate high cryptic diversity revealed in almost all molecular studies. Molecular results also confirm that the majority of foraminiferal species have a restricted geographic distribution and that globally distributed species are rare. This is in opposition to the theory that biogeography has no impact on the diversity of small-sized eukaryotes. At least in the case of foraminifera, size does not seem to have a main impact on dispersal capacities. However, the factors responsible for the dispersal of foraminiferal species and the extension of their geographic ranges remain largely unknown. Special Issue: Protist diversity and geographic distribution. Guest editor: W. Foissner.     

Denitrification, nitrate turnover, and aerobic respiration by benthic foraminiferans in the oxygen minimum zone off Chile

Population density, nitrate turnover, and oxygen respiration of benthic foraminiferans were investigated in the oxygen minimum zone (OMZ) off the Chilean coast. Live foraminiferans were found predominantly in the upper 3 mm of the sediment, and the nitrate accumulating species Nonionella cf. stella and Stainforthia sp. dominated with a combined standing stock of 2.0 × 10⁶ Rose Bengal stained specimens m^− 2. The rate of denitrification in cells of N. cf. stella analyzed with nitrous oxide microsensors during acetylene inhibition was 84 ± 33 pmol C individual^− 1 d^− 1. Multiplied with the standing stock of N. cf. stella and Stainforthia sp. this yielded a minimum benthic denitrification rate of 173 µmol N m^− 2 d^− 1 by foraminiferans. Foraminiferal denitrification, which seemed to account for almost all benthic denitrification at the investigated site will be overlooked by most conventional methods measuring benthic denitrification. Compared to the denitrification rates, the potential rates of nitrate accumulation and oxygen respiration by N. cf. stella were an order of magnitude higher (864 pmol N individual^− 1 d^− 1 and 760 ± 87 pmol C individual^− 1 d^− 1, respectively), which seems an adaptation to the infrequent availability of nitrate and oxygen in the sediment surface.     

Biomass-specific respiration rates of benthic meiofauna: Demonstrating a novel oxygen micro-respiration system

Meiofauna (small-sized Metazoa and Foraminifera) may constitute a significant part of seafloor biomass and potentially play an important role in benthic metabolism. However, respiration measurements are limited and the methods used are diverse together complicating comparison or upscaling. Here we describe a novel glass micro-respiration chamber used to perform non-invasive measurements (built-in oxygen-sensitive fluorogenic membrane and stirrer) and together with direct organic carbon measurements report initial biomass-specific respiration rates of common intertidal meiofauna. Results indicate large differences between respiration rates of different taxa (biomass 0.7-5.2 µg C per individual) but very similar organic carbon biomass-specific respiration rates (1.6-2.5 µl O₂ h^− 1 mgC^− 1 or on average 2.0 ± 0.3 µl O₂ h^− 1 mgC^− 1). This new, rapid and accurate method allows the study of metabolic allometry of the different small-sized taxa and determining their functional role in benthic metabolism.     

Cluster analysis of recent benthic foraminifera from the northwestern Mediterranean coast of Egypt

A suite of 74 surface sediment samples, collected from two areas along the Egyptian Mediterranean coast (the Western Harbor of Alexandria and its environs, and the area comprising the Gulf of Kanayis and the Abu Hashafa Bay), have been examined for their benthic foraminiferal faunas. A total of 82 species were identified. Census data were obtained for different species in each sample and the statistically significant fractional abundances values (≥5%) were analyzed using a Q-mode cluster analysis. Samples were segregated into four clusters, each having its peculiar benthic faunal assemblage (biotope), reflecting particular environmental conditions. These clusters are: (1) the Ammonia beccarii forma tepida Biotope, found in samples located in areas with waters of low energy, characterizing semi-closed basin conditions, with muddy or sandy mud bottom sediments (Harbor Proper); (2) the Quinqueloculina spp. Biotope, found in samples collected from depths bathed by turbid inner shelf conditions with some fresh water inflow and sandy bottom sediments (Harbor’s environs); (3) the Peneroplis-Amphistegina Biotope, found in samples collected from depths characterizing marine shelf environments with calcareous algae, and medium to very coarse calcareous sands (the Gulf of Kanayis and the Abu Hashafa Bay); (4) the Triloculina trigonula-Adelosina laevigata Biotope was represented by only one sample (at the far eastern part of the Gulf of Kanayis), collected from a site exhibiting very restricted environmental conditions. The study suggests that nutrients, turbidity, light intensity, type of substrate, and salinity are the main ecological factors controllingthe distribution of benthic foraminifera.     

Biogeographic distribution of rudists and benthic foraminifera: An approach to Campanian-Maastrichtian palaeobiogeography of Turkey

Transgressive sequences of Campanian-Maastrichtian Stages in Turkey generally begin with medium- to coarse-grained clastics and continue with shallow marine limestones, reefal limestones and then open marine rhythmic fine-grained clastics. These mixed siliciclastic-carbonate sequences are observed on three main platforms known as Rhodope-Pontide (RPP), Anatolide-Tauride (ATP) and Arabian (AP). New species of the rudist genera Gorjanovicia, Radiolites, Sauvagesia, Durania and Sabinia are observed on the RPP. Yvaniella and Ugarella are only found on this platform. Orbitoides gruenbachensis Papp is the most abundant species of benthic foraminifera on the RPP. Cideina soezerii (Sirel), Dizerina anatolica Meriç, Helicorbitoides boluensis Sirel, Ilgazina unilateralis Erdo?an, Nummofallotia kastamonica Özgen-Erdem, Selimina spinalis ?nan, Sirelina orduensis Meriç and ?nan, Smoutina cruysi Drooger are also observed on this platform. Rudist and benthic foraminifera on the ATP have both high diversity and abundance in comparison with RPP and AP faunas. Genus and species diversity of the rudist fauna is quite high: 17 genera and 36 species are described. New rudist genera such as Darendeella, Kurtinia and Balabania and many new species of Radiolitidae and Hippuritidae may be restricted to this platform. Characteristic larger benthic foraminifera contain 18 genera and 37 species. Among benthic foraminifera Loftusia ketini Meriç, L. turcica Meriç and Av?ar, Postomphalocyclus merici ?nan and Pseudoedomia hekimhanensis Görmü? are also likely restricted to this platform. Rudist diversity on the AP is poor. Four endemic genera (Vautrinia, Dictyoptychus, Paracaprinula and Hatayia) and two species (Hippurites syriaca Vautrin, Pironaea syriaca Vautrin) characterize the fauna on this platform. Loftusia diversity and abundance among the benthic foraminifera is quite high. Arnaudella grossouvreii Douvillé, Discyclina schlumbergeri Munier-Chalmas, Loftusia harrisoni Cox, L. elongata Cox, L. matsumaruii Meriç and Görmü? and Pseudorbitolina marthae Douvillé are only documented from southeastern Anatolia. Biogeographic distributions of rudist and benthic foraminifera show different faunal associations on the three main platforms (RPP, ATP and AP). Our data from both rudist and benthic foraminifera indicate that different faunal associations and existence of restricted genera and species may be associated with a deep marine barrier to circulation during the Campanian-Maastrichtian. Southern and northern branches of the Neotethyan Ocean are considered to be barriers in preventing migration of the species.     

Calcite crystal orientation patterns in the bilayers of laminated shells of benthic rotaliid foraminifera

Shells of calcifying foraminifera play a major role in marine biogeochemical cycles; fossil shells form important archives for paleoenvironment reconstruction. Despite their importance in many Earth science disciplines, there is still little consensus on foraminiferal shell mineralization. Geochemical, biochemical, and physiological studies showed that foraminiferal shell formation might take place through various and diverse mineralization mechanisms.In this study, we contribute to benthic foraminiferal shell calcification through deciphering crystallite organization within the shells. We base our conclusions on results gained from electron backscattered diffraction (EBSD) measurements and describe microstructure/texture characteristics within the laminated shell walls of the benthic, symbiontic foraminifera: Ammonia tepida, Amphistegina lobifera, Amphistegina lessonii. We highlight crystallite assembly patterns obtained on differently oriented cuts and discuss crystallite sizes, morphologies, interlinkages, orientations, and co-orientation strengths.We show that: (i) crystals within benthic foraminiferal shells are mesocrystals, (ii) have dendritic-fractal morphologies and (iii) interdigitate strongly. Based on crystal size, we (iv) differentiate between the two layers that comprise the shells and demonstrate that (v) crystals in the septa have different assemblies relative to those in the shell walls. We highlight that (vi) at junctions of different shell elements the axis of crystal orientation jumps abruptly such that their assembly in EBSD maps has a bimodal distribution. We prove (vii) extensive twin-formation within foraminiferal calcite; we demonstrate (viii) the presence of two twin modes: 60°/[0 0 1] and 77°/~[6 –6 1] and visualize their distributions within the shells.In a broader perspective, we draw conclusions on processes that lead to the observed microstructure/texture patterns.     

Abyssal NE Atlantic benthic foraminifera during the last 15 kyr: Relation to variations in seasonality of productivity

Benthic foraminiferal faunas (> 63 μm) and stable isotopes from the last 15 kyr were studied in BENGAL programme (high-resolution temporal and spatial study of the BENthic biology and Geochemistry of a north-eastern Atlantic abyssal Locality) kasten core 13078#16 from the Porcupine Abyssal Plain, NE Atlantic (48°49.91 N, 16°29.94 W, water depth 4844 m). Changes occurred in the accumulation rates, species composition, diversity, and stable isotopes during the last 15 kyr. Today, the area is strongly influenced by seasonal inputs of phytodetritus following the spring blooms in surface water primary productivity. Variations in the relative abundance of the two most abundant species, Epistominella exigua and Alabaminella weddellensis, which today show significant increases in abundance with the presence of phytodetritus on the sea-floor, are interpreted as resulting from changes in the seasonality of productivity. Seasonal productivity was higher during the Holocene than during the last deglaciation and Younger Dryas, probably coinciding with the retreat of the polar front to higher latitudes. This hypothesis is consistent with simultaneous decreases in the percentage of the polar planktic foraminifera Neogloboquadrina pachyderma (s), and increases in the percentage of Globigerina bulloides, a warmer water planktic foraminifera indicative of phytoplankton blooms and enhanced productivity. The relative abundance of the ‘phytodetritus species’ (E. exigua and A. weddellensis) covary between 14.7 and 8.1 kyr, but not between 7.8 and 1.2 kyr. Major decreases in the numbers per gram and accumulation rates of planktic and benthic foraminifera occurred at ∼ 12–8.5 kyr and at ∼ 4 kyr which correspond to decreases in the % sediment coarse fraction and published data on inorganic carbon contents suggesting that dissolution may have increased at these times. Relationships between benthic foraminiferal faunas and benthic stable isotope records suggest no simple relationship between faunal abundances and test isotope chemistry. For example, the abundances of phytodetritus species do not show strong correlations with either the δ¹³C values of E. exigua or the Δδ¹³C _{E. exigua − P. wuellerstorfi} record, which have previously been suggested as indicative of seasonality of productivity.     

Benthic foraminifera as bioindicators of pollution: A review of Italian research over the last three decades

Since the 1950s, numerous studies have demonstrated the value of benthic foraminifera in detecting ecosystem contamination. The interest in benthic foraminifera has partly been driven by government policies and programs aimed at developing suitable, non-invasive bioindicators of marine environmental quality. This paper accomplishes two things: it reveals that Italian experience has significantly contributed to the advancement of our understanding of this topic and summarizes the most important results that have served to greatly improve our knowledge in this field. Although many issues are still a matter of debate, since it is difficult to separate natural vs human-induced pollution and a foraminiferal protocol has not yet been produced, foraminifera have been proven to be successful candidates as part of an integrated monitoring program.     

Spatial distribution of live benthic foraminifera in the Rhône prodelta: Faunal response to a continental–marine organic matter gradient

Benthic foraminifera were collected in the Rhône prodelta (Gulf of Lions, Mediterranean Sea), an enriched zone with high organic matter content. In June 2005, sediment cores were sampled at depths ranging from 20 to 100 m. Four distinct foraminiferal assemblages were determined in the study area, reflecting the geographical distribution of the impact of river supply. The living foraminiferal faunas present a typical picture, with strongly impoverished faunas composed exclusively of stress-tolerant taxa (Fursenkoina fusiformis, Bulimina aculeata, Leptohyalis scottii, and Adelosina longirostra) in the immediate vicinity of the river mouth. This assemblage is well adapted to a high input of continental organic matter and a minimum oxygen penetration depth into the sediment. To the southwest, under the main corridor followed by the river plume, high organic input with a dominantly terrestrial signature (more refractory) may be stressful for many taxa which need organic matter of a more labile quality. In this area, Nonion scaphum, Nonionella turgida and Rectuvigerina phlegeri are present in low densities. On the edge of this area, these taxa show much higher densities. A greater proportion of marine organic carbon could explain their increasing abundances in this area. Towards the east and towards the deepest stations, in the outer part of the enriched zone, biodiversity increases. Faunas at these stations have intermediate densities and contain a number of taxa (Cassidulina carinata, Epistominella vitrea, Valvulineria bradyana, Nonionella iridea/bradyi) at the deepest stations; Bolivina dilatata/spathulata and Textularia porrecta at the eastern stations) that seem to benefit from more marine organic matter. The comparison of geochemical measurements and foraminiferal data strongly suggests that the spatial distribution of foraminifera in the Rhône prodelta is mainly governed by the quality and the quantity of organic matter reaching the sediment–water interface. Since bottom waters are well oxygenated (215–260 µmol/L), and oxygen penetration into the sediment is less than 1 cm at all stations, benthic ecosystem oxygenation appears to have only a minor impact on regional differences in faunal distribution.     

The Foram Stress Index: A new tool for environmental assessment of soft-bottom environments using benthic foraminifera. A case study from the Saronikos Gulf,Greece, Eastern Mediterranean

Saronikos Gulf, including the industrial zone of Elefsis Bay and the Port of Piraeus, is one of the most anthropogenically impacted coastal regions of Greece. Distinct assemblages of benthic foraminifers in sediment samples, collected from this gulf in February 2012, defined three zones that reflect abiotic parameters of the sediments (e.g., organic carbon, metal content). A low-diversity assemblage, dominated by stress-tolerant Ammonia tepida and Bulimina spp., was characteristic of samples from Elefsis Bay. Samples from the western and central part of Saronikos Gulf were the most variable with respect to both abiotic parameters and the foraminiferal assemblage, characterized by a mix of stress-tolerant and more sensitive taxa, especially Bolivina spp. and Nonion fabum. Samples from the coast of Salamis and at the eastern sector of the gulf were characterized by a diverse assemblage that included Peneroplis pertusus, miliolids, and a variety of small, epiphytic rotaliid taxa. A new biotic index, the Foram Stress Index (FSI), is based on the relative percentages of two ecological groups of benthic foraminiferal species, grouped according to their tolerance/sensitivity to organic matter enrichment and weighted proportionately to obtain a formula to define five ecological-status classes. The FSI produced three rankings for these samples (Poor, Moderate and Good), that strongly correlate with the macroinvertebrate-classification tool known as the BENTIX Index. The FSI provides a new tool to assess sediment or substrata quality based upon the benthic foraminiferal assemblages, which are a significant component of living meiobenthic communities that are generally not considered in most biotic benthic indices.     

The oxygen isotope composition of planktonic foraminifera from the Cariaco Basin,Venezuela: Seasonal and interannual variations

Material collected during a three-year sediment trapping experiment in the Cariaco Basin, Venezuela (January 1997 to December 1999) is used to examine both temporal and inter-species variability in the oxygen isotope composition of planktonic foraminifera. Specifically, this study compares the oxygen isotope composition of six species of planktonic foraminifera (Globigerinoides ruber (pink), Globigerina bulloides, Neogloboquadrina dutertrei, Orbulina universa, Globorotalia menardii and Globorotalia crassaformis) with the climatology and hydrography of the region, and evaluates the application of each species for use in paleoceanographic reconstructions. The isotope results are consistent with known depth habitats for all six species. The lowest δ¹⁸O values (− 1 to − 2‰) were measured on G. ruber (pink) and G. bulloides, two species that live in the surface mixed layer. Values for deeper-dwelling species such as N. dutertrei, G. menardii and G. crassaformis are higher, predominantly ranging from 0 to − 0.5‰. Temperature estimates derived using species-specific paleotemperature equations indicate that G. ruber (pink) accurately estimates sea surface temperatures (SSTs) throughout the year, while G. bulloides temperature estimates are similar to measured surface temperatures only during the upwelling season (January–April). For the remainder of the year, the δ¹⁸O-derived temperatures for G. bulloides typically are lower than the measured SST. Although the maximum flux of all species occurs during upwelling, the flux-weighted annual mean isotopic composition of the six species indicates that only G. bulloides is biased towards this season. Therefore, we conclude that the sediment δ¹⁸O record of G. ruber (pink) is most suitable for estimating past values of mean annual SST, while G. bulloides provides information on conditions during spring upwelling. The depth of calcification of N. dutertrei varies seasonally in response to changes in the depths of the thermocline and chlorophyll maximum. As a result, the δ¹⁸O difference between G. ruber (pink) and N. dutertrei provides an estimate of the annual surface to thermocline temperature gradient in the basin.     

The surface ocean productivity response of deeper water benthic foraminifera in the Atlantic Ocean

We test the relationship of deep sea benthic foraminiferal assemblage composition to the surface ocean productivity gradient in the low latitude Atlantic Ocean using 81 surface sediment samples from a water depth range between 2800 and 3500 m. The samples are selected so that the surface ocean productivity gradient, controlling the flux of organic carbon to the seabed, will be the most important environmental variable. The first two principal components of the assemblage data account for 73% of data variance and are clearly linked to the productivity gradient across the Atlantic. These components show that under higher productivity the assemblages contain a higher abundance of Uvigerina peregrina, Melonis barleeanum, Globobulimina spp. and other taxa with probable infaunal microhabitats. Alabaminella weddellensis, a species linked to episodic phytoplankton debris falls, is also important in these assemblages. As productivity decreases there is a regular shift in assemblage composition so that low productivity assemblages are dominated by Globocassidulina subglobosa and several Cassidulina species along with Epistominella exigua. We hypothesize that these taxa are epifaunal to very shallow infaunal since nearly all organic carbon oxidation occurs near the sediment-water interface in low productivity settings. Discriminant function analysis of the foraminiferal assemblages, with groups selected on the basis of surface ocean productivity, shows clear separation among five productivity levels we used. This analysis demonstrates that productivity variations have a strong influence on assemblage composition. Finally, we used two groups of samples from the Rio-Grande Rise representing water depths from 2007 to 2340 m and 2739 to 3454 m to test for effects produced by changing water depth. All these samples are from a low productivity region and represent nearly identical environmental conditions. Although the low productivity nature of all the Rio-Grande Rise samples is obvious, there are assemblage differences between our depth groups. We cannot account for the assemblage differences with changes in organic carbon flux, dissolution effects or other physical/chemical properties of the ocean. Thus there are as yet unidentified factors related to water depth which cause some assemblage variation in the low productivity setting we investigated.     

Use of oxygen microsensors to measure the respiration rates of five dominant copepods and Euphausia crystallorophias furcilia from the Amundsen Sea,West Antarctica

The individual respiration rates of five biomass-dominant copepods (Calanoides acutus, Rhincalanus gigas, Metridia gerlachei, Calanus propinquus and Paraeuchaeta antarctica), and Euphausia crystallorophias furcilia, from the Amundsen Sea, West Antarctica, were determined using a Clark-type oxygen microsensor affording high temporal resolution. Measurements were conducted on specimens collected from waters exhibiting a very narrow temperature range (?1.68 to ?1.32 °C), at sites located between 71 and 75°S, during the summer (31 January–20 March 2012). A short incubation time (3 h) was sufficient to reveal significant declines in dissolved oxygen concentrations by 12–45%. The respiration rates of the copepods and E. crystallorophias furcilia were within the ranges of previously reported values. The respiration rates of relatively large-bodied species were rather low, whereas the smaller species generally exhibited higher respiration rates. The data show that this simple microsensor technique is a useful high-resolution non-invasive means of investigating the metabolism of zooplankton in the Southern Ocean. The method could be used in other situations when such information is required.     

Suitable sediment fraction for paleoenvironmental reconstruction and assessment of contaminated coastal areas based on benthic foraminifera: A case study from Augusta Harbour (Eastern Sicily,Italy)

Since the 1990s several studies noticed that, along coastal marine areas, the mean size of benthic foraminifera may be reduced due to heavy metal pollution, even if no biometric studies were carried out to quantify this aspect. The Augusta harbour (Sicily, Italy), is characterized by a strong contamination due to several anthropogenic activities, the most important of which are a petrochemical pole and an important industrial harbour. Taking into account the previous studies carried out in the area, which recorded small-sized foraminifera, the present study compared assemblage composition and faunal parameters in the >125 μm and >63 μm fractions of a sediment core collected in the most polluted sector of Augusta harbour. The aim was to understand if the two fractions have comparable environmental significance providing reliable information on the environmental status. In order to quantify the amount of smaller foraminifera in a community and to determine species loss between size fractions, two new indices are used: the Foraminiferal Size Index (FSI) and the Lost Species Index (LSI). Species richness, diversity and composition of the two assemblages were determined to characterize their structure. The results highlighted great depletion and different composition of the >125 μm assemblage with respect to the >63 μm one, showing a selective loss of particular ecological groups (stress-tolerant infaunal taxa). Also the better correlation of Foraminiferal Number (FN) and H’ index of >63 μm fraction with Polychlorobiphenyls (PCBs), Polycyclic Aromatic Hydrocarbons (PAHs), Barium (Ba) and Mercury (Hg), demonstrated the higher reliability of this size fraction for environmental assessment purposes.     

Factors influencing the distribution of Subantarctic deep-sea benthic foraminifera,Campbell and Bounty Plateaux,New Zealand

We investigate the combination of environmental factors that influence the distribution patterns of benthic foraminiferal tests (> 63 μm) in a topographically varied region crossed by both the Subtropical and Subantarctic Fronts, south-east of New Zealand. Seafloor sample sites, extending from outer shelf (50 m) to abyssal (5000 m) depths, are bathed by five different water masses, and receive phytodetritus from Subtropical, Subantarctic and Circumpolar surface water masses. Eight mappable associations are recognised by Q-mode cluster analysis of the benthic foraminiferal census data. Similar associations are identified using cluster analysis based solely on the presence or absence of species. Canonical correspondence analysis and a correlation coefficient matrix were used to relate the faunal data to a set of environmental proxies. These show that factors related to water depth (especially decreasing food supply with increasing depth) are the most significant in determining the overall foraminiferal distribution. Other contributing factors include surface water productivity and its seasonality; bottom water ventilation; energetic state of the benthic boundary layer and resulting substrate texture; and bottom water carbonate corrosiveness. Three shallow-water associations (50–700 m), dominated by Cassidulina carinata, Trifarina angulosa, Globocassidulina canalisuturata, Gavelinopsis praegeri, and Bolivina robusta, occur in coarse substrates on the continental shelf, and on the crests and upper slopes of four seamounts under well-oxygenated, high energy regimes, and high food input. Three mid bathyal to upper abyssal associations (500–3300 m), dominated by Alabaminella weddellensis, C. carinata, and Epistominella exigua, occur in biopelagic sandy mud, beneath a region of strongly seasonal food supply, with their composition influenced by total food flux, ventilation (Oxygen Minimum Zone), and bottom current strength. An unusual lower bathyal association (1200–2100 m), dominated by T. angulosa and Ehrenbergina glabra, occurs in a belt of coarser sandy substrate that runs along the crest of the submarine plateaux slopes beneath the strongly-flowing Subantarctic Front-related currents. A deep abyssal association (3500–5000 m), dominated by Nuttallides umbonifer and Globocassidulina subglobosa, occurs on the abyssal plain beneath oligotrophic lower Circumpolar Water south-east of the Subantarctic Front and is strongly influenced by the cold, carbonate-corrosive conditions.     

Influence of temperature,oxygen and food availability on the migrational activity of bathyal benthic foraminifera: evidence by microcosm experiments

Foraminifera are a dominant group of amoeboid protists in the deep-sea and play possibly a significant role in decomposition processes of incoming organic matter. In order to study the poorly known ecology of these protozoans, microcosm experiments with living bathyal benthic foraminifera have been conducted. Foraminifera from 2880 m and shallower water depths were successfully maintained and their movement patterns investigated. By video documentation, high mean migration speed of 20,02 (N = 22) and 24,48 m min^-1 (N = 10) at 4 °C were found for species such as Hoeglundina elegans and Quinqueloculina seminula from 1847 m and 1921 m water depth, respectively. The results demonstrate that some bathyal foraminifera have migration speeds comparable to those of shallow water species. Environmental factors such as temperature, food concentration and oxygen content showed a marked influence on the migration of some species. An increase in temperature from 10 °C to 15 °C resulted in an increase of 35% in the migration speed of Allogromia spp. However, other species reacted differently. Higher food concentration resulted in a decrease in speed of some species. While in Quinqueloculina lamarckiana speed was not greatly affected by a low oxygen content in the sediment, other foraminifera responded to oxygen depletion by migration to the surface layers. Observations of benthic foraminifera in the laboratory microcosms are discussed in relation to microhabitats and the fate of organic matter on the sea floor and in the sediment.     

Distribution of live benthic foraminifera in the Ría de Vigo (NW Spain)

The spatial and vertical distributions of live benthic foraminifera from the muddy central axis of the Ría de Vigo were examined under downwelling and upwelling conditions. The spatial distribution of the main benthic foraminiferal species is controlled by salinity variations (San Simón Assemblage), food availability (Outer Ría Assemblage) and oxygen concentrations and/or reducing microenvironmental conditions in the sediment (Inner Ría Assemblage).The microhabitat distribution of benthic foraminifera is mainly dependant on the oxygenation/redox conditions in the sediment and the vertical segregation of food. In the inner areas of the ría, low oxygen and/or reducing microenvironmental conditions prevent the vertical segregation of microhabitats. In outer areas oxygen penetration is deep but microhabitat partitioning only occurs in the presence of additional food resources (mainly fresh organic carbon from phytoplankton blooms) which triggers the colonisation of the surface layer by new species and the migration upwards and reproduction of opportunistic species.     

Supratidal foraminifera as ecological indicators in anthropically modified wetlands (Lagoon of Venice, Italy)

In transitional environments, the intertidal zones represent a peculiar case characterized by halophile vegetation and by a low diversity benthic community. On these areas just a few particular foraminiferal species, a class of Protoctista secreting a shell called test, can survive for a certain time out of water. They are distributed in well-defined vertical zonations with respect to mean sea level and they correspond to analogous marsh floral zonations. In particular, the Trochammina macrescens Brady + Trochammina inflata (Montagu) association characterizes the salt marsh zone above mean high water level. The potential of these taxa as bioindicators is tested, since their presence-absence-dominance differentiates the subtidal/supratidal environments. Over the last few centuries, various engineering works generated major physical changes in the Venetian Lagoon. These changes affected the natural evolution of the intertidal morphologies, the surface of which is decreasing. In an attempt to reverse this tendency, numerous artificial salt marshes have been constructed and more are under construction. In this study, the Mazzorbo artificial salt marsh, built during the second half of 1999, is considered. On its surface, 16 samples were collected along a transect line in May 2008 to verify the ecological role of this salting within the lagoon ecosystem. The sediment grain size distribution of the salt marsh reflects the dissipative role of the tide and the effect of sediment transport due to the wave and tidal action. However, the presence of only a few Trochammina individuals shows that the foraminiferal fauna did not recognise this morphology as a salt marsh. The lack of Trochammina colonisation can be related to the excessive elevation of the salt marsh surface. This hypothesis is confirmed by the lack of the salt-tolerant plant Spartina. The unsuccessful colonisation by the foraminifera seems to indicate that this artificial salting does not have the natural dynamism of the intertidal morphologies and it may only be classified as land recovery. The supratidal foraminiferal taxa can act as an ecological indicator: through their observation it is possible to verify whether an artificial salt marsh accomplishes its task of functioning as an ecological unit with the community of organisms.