Foraminifers as indicators of marine pollution: a culture experiment with Rosalina leei

Impacts of Desalination Brine Discharge on Benthic Ecosystems

Seawater reverse osmosis (SWRO) desalination facilities produce freshwater and, at the same time, discharge hypersaline brine that often includes various chemical additives such as antiscalants and coagulants. This dense brine can sink to the sea bottom and creep over the seabed, reaching up to 5 km from the discharge point. Previous reviews have discussed the effects of SWRO desalination brine on various marine ecosystems, yet little attention has been paid to the impacts on benthic habitats. This review comprehensibly discusses the effects of SWRO brine discharge on marine benthic fauna and flora. We review previous studies that indicated a suite of impacts by SWRO brine on benthic organisms, including bacteria, seagrasses, polychaetes, and corals. The effects within the discharge mixing zones range from impaired activities and morphological deformations to changes in the community composition. Recent modeling work demonstrated that brine could spread over the seabed, beyond the mixing zone, for up to several tens of kilometers and impair nutrient fluxes from the sediment to the water column. We also provide a possible perspective on brine's impact on the biogeochemical process within the mixing zone subsurface. Desalination brine can infiltrate into the sandy bottom around the discharge area due to gravity currents. Accumulation of brine and associated chemical additives, such as polyphosphonate-based antiscalants and ferric-based coagulants in the porewater, may change the redox zones and, hence, impact biogeochemical processes in sediments. With the demand for drinking water escalating worldwide, the volumes of brine discharge are predicted to triple during the current century. Future efforts should focus on the development and operation of viable technologies to minimize the volumes of brine discharged into marine environments, along with a change to environmentally friendly additives. However, the application of these technologies should be partly subsidized by governmental stakeholders to safeguard coastal ecosystems around desalination facilities.

Mercury-Induced Oxidative Stress Response in Benthic Foraminifera: An In Vivo Experiment on Amphistegina lessonii

The evaluation of the effects of pollution (e.g., Hg pollution) is a difficult task and relies mostly on biomonitoring based on bioindicators. The application of biomarkers may represent a complementary or alternative approach in environmental biomonitoring. Mercury is known to pose a significant health hazard due to its ability to cross cellular membranes, bioaccumulate, and biomagnify. In the present research, the effects of short-term (i.e., 24 h) Hg exposure in the symbiont-bearing benthic foraminiferal species Amphistegina lessonii are evaluated using several biomarkers (i.e., proteins and enzymes). Mercury leads to significant changes in the biochemistry of cells. Its effects are mainly associated with oxidative stress (i.e., production of reactive oxygen species: ROS), depletion of glutathione (GSH), and alteration of protein synthesis. Specifically, our findings reveal that exposure to Hg leads to the consumption of GSH by GPx and GST for the scavenging of ROS and the activation of antioxidant-related enzymes, including SOD and GSH-enzymes (GST, GSR, GPx, and Se-GPx), that are directly related to a defense mechanism against ROS. The Hg exposure also activates the MAPK (e.g., p-p38) and HSP (e.g., HSP 70) pathways. The observed biochemical alterations associated with Hg exposure may represent effective and reliable proxies (i.e., biomarkers) for the evaluation of stress in A. lessonii and lead to a possible application for the detection of early warning signs of environmental stress in biomonitoring.

Benthic Foraminifera as Bio-indicators of Coastal Marine Environmental Contamination in the Red Sea-Gulf of Aqaba, Saudi Arabia

To assess heavy metals contamination in shallow marine environments using benthic foraminifera as bio-indicators. Forty-six species of foraminifera were found in 33 benthic samples from the Saudi Arabian coast of the Red Sea-Gulf of Aqaba. Forty-six species belonging to 27 genera and 10 families under the Textularina, Rotalina, and Miliolina suborders were recorded in the study area. The most common genera of the recorded fauna were Peneroplis (37.2%), Coscinospira (15.06%), Sorites (10.36%), and Quinqueloculina (7.76%). The influx of clastic sediments would dilute the abundance of foraminifera species, and It may be the main reason for the decrease in abundance Concentrations of Fe, Mn, Cu, Ni, Zn, Pb, Cr, Co, and Cd were measured in the four common species of benthic foraminifera (Sorites orbiculus, Peneroplis planatus, Peneroplis pertusus, and Coscinospira hemprichii) using inductively coupled plasma mass spectrometry. The average values of heavy metals in the study area show that Iron was the most abundant metal (3367 μg/g), followed by Mn (142 μg/g), Cu (30 μg/g), Zn (24 μg/g), Cr (21 μg/g), Ni (14 μg/g), Pb (7 μg/g), Co (4.6 μg/g), and Cd (0.82 μg/g). Iron concentrations recorded in the foraminiferal tests in the study area were lower than those from the Jeddah area of Saudi Arabia. Other metals were found at higher concentrations than those recorded off the Red Sea coast of Saudi Arabia and Egypt. The heavy metals concentrations in the study area may be attributable to terrestrial influx or anthropogenic activities. The increase of abundance of epiphytic foraminifers and the absence of opportunistic foraminifers show normal the environment in the study area.

Geochemistry of large benthic foraminifera Amphisorus hemprichii as a high-resolution proxy for lead pollution in coastal environments

Anthropogenic lead (Pb) contamination resulting from the rapid growth of industrialization in coastal environments poses significant challenges. In this study, we report a novel approach utilising the large benthic foraminifera Amphisorus hemprichii as a biogeochemical archive for monitoring Pb pollution in tropical to warm-temperate coastal waters. Live juvenile specimens of A. hemprichii were cultured in the laboratory for 16 weeks with a range of seawater Pb concentrations. Lead uptake in both newly grown and pre-existing chambers of individual specimens was characterised using the microanalytical technique, Laser ablation-ICP mass spectrometry. We found that Pb concentration in the tests of cultured foraminifera in the laboratory is proportional to seawater [Pb] with the lead partition coefficient (K_D^Pb) of 8.37 ± 0.3. This calibration together with a new biomineralisation model now enables A. hemprichii to be utilised as a naturally occurring bio-archive to quantitatively monitor anthropogenic Pb pollution in coastal waters.

Epiphytic benthic foraminiferal preferences for macroalgal habitats: Implications for coastal warming

Considering the thermal limits of coastal macroalgae habitats in the South-Eastern Mediterranean, it is important to study the response of the associated meiofauna to better understand the expected feedback of ecosystems to future warming. In this study, we compared benthic foraminiferal assemblages from two common macroalgal habitats, Turf and Coralline algae, based on ecological monitoring of a thermally polluted station representing near future warming, and an undisturbed environment. None of the common local species is confined to a specific algal habitat. This implies that their existence is not threatened by the disappearance of the Coralline algae. However, most likely their community structure will be impacted with coastal warming. Species that are more affiliated with Coralline algae are highly thermally tolerant, thus their proliferation might be reduced with warming. Specifically, the negative response of Coralline algae to warming may limit the contribution of invasive species such as Pararotalia calcariformata.

Vertical variability of benthic foraminifera and trace elements in a tropical coastal lagoon in the Gulf of California

Population growth around water bodies is deteriorating environmental quality. The benthic foraminiferal and trace element concentration in a pair of short sediment cores were used to establish the quality of the sedimentary environment in a tropical coastal lagoon in the southwestern Gulf of California. From 25 cm depth towards the surface of the sediment core, Ammonia beccarii was dominant over nontolerant species and the concentrations of V, Ni, Co, Zn, Cu, Hg and Pb in the sediments increased compared with the lower depth intervals. This finding suggests a deterioration in the environmental quality of the lagoon since 1980, associated with an increase in the sizes of the population and vehicle fleet in the city of La Paz, Baja California Sur, and with the operation of three fossil fuel-based thermoelectric plants since 1985.

Shell Growth of Large Benthic Foraminifera under Heavy Metals Pollution: Implications for Geochemical Monitoring of Coastal Environments

This study was promoted by the recent efforts using larger benthic foraminiferal (LBF) shells geochemistry for the monitoring of heavy metals (HMs) pollution in the marine environment. The shell itself acts as a recorder of the ambient water chemistry in low to extreme HMs-polluted environments, allowing the monitoring of recent-past pollution events. This concept, known as sclerochronology, requires the addition of new parts (i.e., new shell) even in extreme pollution events. We evaluated the physiological resilience of three LBF species with different shell types and symbionts to enriched concentrations of Cd, Cu, and Pb at levels several folds higher than the ecological criteria maximum concentration (CMC) (165-166, 33-43, 1001-1206 µg L^-1, respectively), which is derived from aquatic organisms' toxicity tests. The physiological response of the holobiont was expressed by growth rates quantified by the addition of new chambers (new shell parts), and by the chlorophyll a of the algal symbionts. The growth rate decrease varied between 0% and 30% compared to the unamended control for all HMs tested, whereas the algal symbionts exhibited a general non-fatal but significant response to Pb and Cu. Our results highlight that shell growth inhibition of LBF is predicted in extreme concentrations of 57 × CMC of Cu and 523 × CMC of Cd, providing a proof of concept for shell geochemistry monitoring, which is currently not used in the regulatory sectors.

Assessing the Cadmium Effects on the Benthic Foraminifer Ammonia cf. parkinsoniana: An Acute Toxicity Test

Heavy metals are one of the most hazardous pollutants in marine environments because of their bioaccumulation and biomagnification capabilities. Among them, cadmium (Cd) has been considered as one of the most dangerous for marine organisms. Here we incubated Ammonia cf. parkinsoniana specimens, a benthic foraminiferal taxon used in previous experiments, for up to 48 h in natural seawater with different concentrations of Cd to unravel the physiological change. We document a reduced pseudopodial activity of the Cd-treated specimens at concentrations >10–100 ppb in comparison with the control specimens. Moreover, confocal images of Cd-treated specimens using Nile Red as a fluorescent probe reveal an enhanced intracellular neutral lipid accumulation in the form of lipid droplets at 6 h and 12 h. This bioassay experiment allows for the direct evaluation of Cd-dose to A. cf. parkinsoniana-response relationships under laboratory controlled conditions and provides complementary information to field observations as well as to water quality guidelines and thresholds.

The effect of long-term brine discharge from desalination plants on benthic foraminifera

Desalination plants along the Mediterranean Israeli coastline currently provide ~587 million m³ drinking water/year, and their production is planned to increase gradually. Production of drinking water is accompanied by a nearly equivalent volume of brine discharge with a salinity of ~80 that is twice the normal, which can potentially impact marine ecosystems. The goal of this study was to examine whether benthic foraminifera, a known sensitive marine bio-indicator, are affected by this brine-discharge. For that, we investigated the seasonal and cumulative effect of brine discharges of three operating desalination facilities along the Israeli coast. Those facilities are located in Ashkelon, Hadera, and Sorek. The brine-discharge in the first two desalination plants is associated with thermal pollution, while the Sorek facility entails increased salinity but no thermal pollution. In four seasonal cruises during one year, we collected surface sediment samples in triplicates by grabs from the outfall (near the discharge site), and from a non-impacted control station adjacent to each study site. Our results highlight that the most robust responses were observed at two out of three desalination shallow sites (Ashkelon and Hadera), where the brine was discharged directly from a coastal outfall and was accompanied with thermal pollution from the nearby power plants. The total foraminiferal abundance and diversity were, generally, lower near the outfalls, and increased towards the control stations. Moreover, changes in the relative abundances of selected species indicate their sensitivity to the brine discharge. The most noticeable response to exclusively elevated salinity was detected at Sorek discharge site, where we observed a sharp decline in organic-cemented agglutinated benthic foraminifera, suggesting that these are particularly sensitive to elevated salinity. The herein study contribute new insights into the effect of brine discharge from desalination plants, on benthic foraminifera, and propose a scientifically-based ecological monitoring tool that can help stakeholders.

Assessing the effect of mercury pollution on cultured benthic foraminifera community using morphological and eDNA metabarcoding approaches

Mercury (Hg) is a highly toxic element for living organisms and is known to bioaccumulate and biomagnify. Here, we analyze the response of benthic foraminifera communities cultured in mesocosm and exposed to different concentrations of Hg. Standard morphological analyses and environmental DNA metabarcoding show evidence that Hg pollution has detrimental effects on benthic foraminifera. The molecular analysis provides a more complete view of foraminiferal communities including the soft-walled single-chambered monothalamiids and small-sized hard-shelled rotaliids and textulariids than the morphological one. Among these taxa that are typically overlooked in morphological studies we found potential bioindicators of Hg pollution. The mesocosm approach proves to be an effective method to study benthic foraminiferal responses to various types and concentrations of pollutants over time. This study further supports foraminiferal metabarcoding as a complementary and/or alternative method to standard biomonitoring program based on the morphological identification of species communities.

Mercury-Pollution Induction of Intracellular Lipid Accumulation and Lysosomal Compartment Amplification in the Benthic Foraminifer Ammonia parkinsoniana

Heavy metals such as mercury (Hg) pose a significant health hazard through bioaccumulation and biomagnification. By penetrating cell membranes, heavy metal ions may lead to pathological conditions. Here we examined the responses of Ammonia parkinsoniana, a benthic foraminiferan, to different concentrations of Hg in the artificial sea water. Confocal images of untreated and treated specimens using fluorescent probes (Nile Red and Acridine Orange) provided an opportunity for visualizing the intracellular lipid accumulation and acidic compartment regulation. With increased Hg over time, we observed an increased number of lipid droplets, which may have acted as a detoxifying organelle where Hg is sequestered and biologically inactivated. Further, Hg seems to promote the proliferation of lysosomes both in terms of number and dimension that, at the highest level of Hg, resulted in cell death. We report, for the first time, the presence of Hg within the foraminiferal cell: at the basal part of pores, in the organic linings of the foramen/septa, and as cytoplasmic accumulations.

Selective responses of benthic foraminifera to thermal pollution

Persistent thermohaline pollution at a site along the northern coast of Israel, due to power and desalination plants, is used as a natural laboratory to evaluate the effects of rising temperature and salinity levels on benthic foraminifera living in shallow hard-bottom habitats. Biomonitoring of the disturbed area and a control station shows that elevated temperature is a more significant stressor compared to salinity, thus causing a decrease in abundance and richness. Critical temperature thresholds were observed at 30 and 35°C, the latter representing the most thermally tolerant species in the studied area Pararotalia calcariformata, which is the only symbiont-bearing species observed within the core of the heated area. Common species of the shallow hard-bottom habitats including several Lessepsian invaders are almost absent in the most exposed site indicating that excess warming will likely impede the survival of these species that currently benefit from the ongoing warming of the Eastern Mediterranean.

Effects of lead pollution on Ammonia parkinsoniana (foraminifera): ultrastructural and microanalytical approaches

The responses of Ammonia parkinsoniana (Foraminifera) exposed to different concentrations of lead (Pb) were evaluated at the cytological level. Foraminifera-bearing sediments were placed in mesocosms that were housed in aquaria each with seawater of a different lead concentration. On the basis of transmission electron microscopy and environmental scanning electron microscopy coupled with energy dispersive spectrometer analyses, it was possible to recognize numerous morphological differences between untreated (i.e., control) and treated (i.e., lead enrichment) specimens. In particular, higher concentrations of this pollutant led to numerical increase of lipid droplets characterized by a more electron-dense core, proliferation of residual bodies, a thickening of the organic lining, mitochondrial degeneration, autophagosome proliferation and the development of inorganic aggregates. All these cytological modifications might be related to the pollutant-induced stress and some of them such as the thickening of organic lining might suggest a potential mechanism of protection adopted by foraminifera.

Distribution of trace metals and the benthic foraminiferal assemblage as a characterization of the environment in the north Minjiang River Estuary (Fujian, China)

A study of the total benthic foraminifera was carried out in 173 surficial sediment samples collected from the north Minjiang River Estuary and two bays. Foraminiferal assemblages are dominated by Ammonia tepida and subordinately by Elphidium advenum. Trace metal analyses reveal that the study area is unpolluted to moderately polluted with As, Cr, Cu, Ni, Pb, and Zn. The metal distribution has an affinity with fine-grained sediment. Five metal groups are recognized based on their distribution patterns: (1) As, Cr, Cu, Ga, Ni, V, and Zn, (2) Hg, Pb, and Sb, (3) Ba and Zr, (4) Rb and Y, and (5) Sr. The species-environment relationship showed that the species composition is adversely influenced by Cr, Cu, Ga, Pb, Rb, Zn, and Zr, whereas sand may exert a positive influence on Quinqueloculina. This study supports the adaptability of using benthic foraminifera as bio-monitors of trace metal pollution in marginal marine environments.

Benthic foraminiferal response to trace element pollution-the case study of the Gulf of Milazzo, NE Sicily (Central Mediterranean Sea)

The response of benthic foraminiferal assemblages to trace element pollution in the marine sediments of the Gulf of Milazzo (north-eastern Sicily) was investigated. Since the 1960s, this coastal area has been a preferred site for the development of two small marinas and a commercial harbour as well as for heavy industry. Forty samples collected in the uppermost 3-4 cm of an undisturbed layer of sediment in the littoral environment were used for this benthic foraminiferal analysis. The enrichment factors (EFs) of selected trace elements (As, Co, Cr, Cu, Mn, Ni, Pb and Zn) were also calculated. Changes both in benthic foraminiferal assemblages and in some trace elements concentrations have provided evidence that the gulf's littoral zone can be subdivided into three sectors characterised by environmental changes in the marine ecosystem. In the sector unpolluted, close to the Milazzo Cape, foraminiferal assemblages exhibit high values of species richness and foraminiferal density while trace element concentrations and their EFs are very low. Here, the highest densities of Miliolids and epiphytic species are present. On the contrary, in the sector polluted, from the marinas to the crude oil refinery, foraminiferal density and species diversity are low, and assemblages are dominated, albeit with very low densities, by species that tolerate stressed environmental conditions, such as LOFAs, agglutinants and Ammonia spp. Here, the highest trace elements concentrations of Pb, Zn and Cu and related EFs were detected. Eastwards, in the sector moderately polluted, foraminiferal populations are quite poor. They are characterised by low values of species richness and foraminiferal densities, nevertheless trace element concentrations become lower than in the other sectors and their EFs are often below 1. Deformed foraminifera, with percentages up to 7.14 %, were found in all three of the sectors. Differences in benthic foraminiferal assemblages, coupled with results from statistical analysis, indicate that anthropogenic trace element pollution could be considered as one of the most important causes of the modifications of foraminiferal assemblages in the study area.

A note on the laboratory culture of the benthic foraminifer Cornuloculina balkwilli (MacFadyen)

Background

Genetic studies of the Foraminifera provide valuable insights into marine speciation and biogeography, yet the discovery of vitally needed new genetic markers for this important group is being severely limited by an extreme lack of genetic data. The establishment of a laboratory culture from a single, asexually reproducing foraminifer, will be essential to provide enough pooled genetic material from these unicellular organisms, to facilitate full genome sequencing and genetic marker discovery, using next-generation sequencing techniques.

Findings

The aim of this study was to develop a simple and inexpensive method of culturing benthic foraminifera, via asexual reproduction, in a controlled laboratory environment. Individual specimens of the benthic foraminfer Cornuloculina balkwilli (MacFadyen) were placed in 7 cm plastic beakers, containing 50 ml natural seawater, filtered to 0.2 μm, and kept at 23°C, with a 12-hour light/dark cycle, and fed weekly on a mixed algal diet of Dunaliella tertiolecta and Phaeodactylum tricornutum. Asexually derived cultures were successfully established from 4 specimens of Cornuloculina balkwilli, originally added to the culture vessels as immature specimens. Many thousands of individuals were present after 6 months.

Conclusions

The method presented here demonstrates that only basic laboratory equipment is required to establish and maintain a thriving culture of the benthic foraminfer, C. balkwilli, from a single asexually reproducing specimen, providing an excellent source of genetic material for use in next generation sequencing. The method is easily reproducible and will greatly aid in the discovery of critically needed new genetic markers in the Foraminifera. It also highlights C. balkwilli as a good candidate species for use in the field of environmental micropaleontology.

Sediment characterization of the highly impacted Augusta harbour (Sicily, Italy): modern benthic foraminifera in relation to grain-size and sediment geochemistry

The Augusta harbour is affected by high anthropogenic impact due to intense harbour activity and a large chemical and petrochemical pole. Thirty-seven sediment samples were collected during an environmental characterization project and analyzed for grain size, chemical parameters (Al, As, Cd, Cr, Cu, Fe, Hg, Ni, Pb, Zn and V) and foraminifera, the last one generally being used as ecological indicators of environmental quality. Anthropogenic enrichment was recognized for As, Cu, Hg, Pb and Zn and, among these, Hg showed very high concentrations (up to 191 mg kg(-1) d.w.) often associated in the southern sector of the study area to very high PCB levels (up to 0.83 mg kg(-1)). In this area, an assemblage dominated by Rosalina bradyi and Quinqueloculina lata was recognized. This assemblage shows a clear decrease of foraminiferal density and diversity and, at the same time, increased dominance with respect to the assemblage characterizing the central and northern less polluted sectors, in which Miliolinella subrotunda prevails. Quinqueloculina lata was demonstrated to be a stress-tolerant species because it was not influenced by sediment texture, but positively correlated with the concentration of Hg, PCBs and PAHs. The environmental stress shown by the high-dominance of the Ammonia tepida assemblage was attributed mainly to the influence of stream mouths, which determine environmental instability. Foraminiferal assemblages showed a clear response to environmental degradation in the most polluted area but, at the same time, they demonstrated a high adaptation to pollution.

Benthic foraminifera as proxies of pollution: The case of Guanabara Bay (Brazil)

Due to economic importance of Guanabara Bay, a multidisciplinary approach was adopted to investigate 88 surficial sediment samples in order to use the benthic foraminifera as indicators for the characterization of environmental variations. Grain-size analyses indicate that bottom sediments of the inner part of the bay are mainly muddy while those close to the entrance of the bay are sandy. Geochemical data show high concentration of heavy metals mainly in the northern region of the bay. Micropalaeontological analyses indicate the boundaries of the areas with the highest concentration of heavy metals. The dominant benthic foraminifera in the bay are Ammonia beccarii and Buliminella elegantissima, taxa capable of differentiating the presence of pollutants of different sources. B. elegantissima, in particular, has shown to be an indicator of anthropogenic pollution. The study highlights the worsening of environmental conditions since 2000 and those areas of the bay in need of a priority recovery.

The effect of thermal pollution on benthic foraminiferal assemblages in the Mediterranean shoreface adjacent to Hadera power plant (Israel)

The thermal pollution patch of Hadera power plant was used as a natural laboratory to evaluate the potential long-term effects of rise in Eastern Mediterranean SST on living benthic foraminifera. Their sensitivity to environmental changes makes foraminifera ideal for this study. Ten monthly sampling campaigns were performed in four stations located along a temperature gradient up to 10 °C from the discharge site of heated seawater to a control station. The SST along this transect varied between 25/18 °C in winter and 36/31 °C in summer. A significant negative correlation was found between SST in all stations and benthic foraminiferal abundance, species richness and diversity. The total foraminiferal abundance and species richness was particularly low at the thermally polluted stations especially during summer when SST exceeded 30 °C, but also throughout the entire year. This indicates that thermal pollution has a detrimental effect on benthic foraminifera, irrelevant to the natural seasonal changes in SST.

Comparison of benthic foraminifera and macrofaunal indicators of the impact of oil-based drill mud disposal

We compare foraminifera and macrofauna as bio-indicators of oil-based drill mud disposal site off Congo. The most polluted sites are characterized by poor faunas, dominated by some very tolerant taxa. Slightly further from the disposal site, there is an area with strongly increased densities, heavily dominated by opportunistic taxa. Still further, macrofauna appears to be similar to that at the reference area, but the foraminiferal meiofauna still suggests a slight environmental perturbation. The foraminiferal FIEI index, based on the species distribution in the study area, appears to be more discriminative than the macrofaunal ITI index, based on a priori definitions of the trophic guilds of the various taxa. Our comparative approach allows us to point out the benefits of (1) the use of macrofauna and foraminifera together and (2) the definition of the species groups used in biotic indices on the basis of observations made directly in the study area.

Benthic foraminiferal assemblages and trace element contents from the lagoons of Orbetello and Lesina

The Italian marginal areas of Orbetello and Lesina lagoons have been investigated in order to assess the response of benthic foraminifera to the trace element contents in the sediments. The investigated lagoons are deeply affected by high values of trace elements. The lagoon of Orbetello shows the highest values of Cd, Cu, Ni, Pb, Zn, and Hg, whereas the lagoon of Lesina exhibits the highest values of As. On the basis of the trace element contents, both lagoons can be considered from moderately to strongly polluted. Biotic and abiotic factors have been investigated with multivariate technique of statistical analysis. On the basis of the trace element content, the cluster analysis reveals the occurrence of three main clusters. These natural groupings are also confirmed by the principal component analysis. The comparison of trace element concentration patterns with the Foraminiferal Abnormality Index shows a possible influence of these pollutants on the benthic foraminiferal assemblages. Generally, the highest concentrations of trace elements in the investigated areas are remarkably mirrored by the highest percentages of deformed specimens.

Effects of sudden stress due to heavy metal mercury on benthic foraminifer Rosalina leei: laboratory culture experiment

Laboratory culture experiments were carried out to understand the response of benthic foraminifer Rosalina leei to gradual as well as sudden addition of heavy metal mercury into the media. When mercury was added suddenly, specimens did not show any change in morphology during the initial 40 days. However, later on, out of all the specimens subjected to mercury concentrations up to 150 ng/l, 75% developed deformities, whereas all the specimens subjected to 150-275 ng/l Hg concentrations, had deformed chambers. All specimens kept at 300 ng/l Hg concentration died within 20 days. In addition to this, irregularities were also observed in the rate of reproduction, number of juveniles produced and the survival rate of the juveniles. Where as in an earlier experiment where Hg concentration was increased gradually, irregularities in the newly added chambers were noticed only in case of specimens subjected to very high (180 ng/l) Hg concentration. However, during this experiment, growth was found to be inversely proportional to the mercury concentration.

The impact of easily oxidized material (EOM) on the meiobenthos: foraminifera abnormalities in shrimp ponds of New Caledonia; implications for environment and paleoenvironment survey

This study was carried out in shrimp ponds from New Caledonia, in order to determine the cause of the exceptional proportion of abnormal tests (FAI) (often >50%, sometimes >80%). FAI was positively correlated to the quantity of easily oxidized material (EOM) deposited on the bottom of the ponds and to the sediment oxygen demand, and negatively correlated to redox. These results suggest that a very high FAI is a potential indicator for great accumulations of native organic matter, leading to a high sediment oxygen demand. When studying ancient sediments in core samples, exceptional abundances of abnormal tests may indicate periods of high accumulation of EOM, and therefore of oxygen depletion. This finding should help in better management of aquaculture ponds, but should also allow new insight into the interpretation of sedimentary records, providing a useful proxy for paleoenvironmental reconstructions.

Benthic foraminifera and trace element distribution: a case-study from the heavily polluted lagoon of Venice (Italy)

Living benthic foraminiferal assemblages were studied in surface samples collected from the lagoon of Venice (Italy) in order to investigate the relationship between these sensitive microorganisms and trace element pollution. Geochemical analysis of sediments shows that the lagoon is affected by trace element pollution (Cd, Cu, Ni, Pb, Zn and Hg) with the highest concentrations in its inner part, which corresponds to the Porto Marghera industrial area. The biocenosis are largely dominated by Ammonia tepida, Haynesina germanica and Cribroelphidium oceanensis and, subordinately, by Aubignyna perlucida, Ammonia parkinsoniana and Bolivina striatula. Biotic and abiotic factors were statistically analyzed with multivariate technique of cluster analysis and principal component analysis. The statistical analysis reveals a strong relationship between trace elements (in particular Mn, Pb and Hg) and the occurrence of abnormalities in foraminiferal tests. Remarkably, greater proportions of abnormal specimens are usually found at stations located close to the heaviest polluted industrial zone of Porto Marghera. This paper shows that benthic foraminifera can be used as useful and relatively speedy and inexpensive bio-indicators in monitoring the health quality of the lagoon of Venice. It also provides a basis for future investigations aimed at unraveling the benthic foraminiferal response to human-induced pollution in marine and transitional marine environments.

Benthic foraminifera as bio-indicators of trace element pollution in the heavily contaminated Santa Gilla lagoon (Cagliari, Italy)

In order to assess the response of benthic foraminifera to trace element pollution, a study of benthic foraminiferal assemblages was carried out into sediment samples collected from the Santa Gilla lagoon (Sardinia, Italy). The lagoon has been contaminated by industrial waste, mainly trace elements, as well as by agricultural and domestic effluent. The analysis of surficial sediment shows enrichment in trace elements, including Cr, Cu, Hg, Ni, Pb and Zn. Biotic and abiotic data, analyzed with multivariate techniques of statistical analysis, reveal a distinct separation of both the highly polluted and less polluted sampling sites. The innermost part of the lagoon, comprising the industrial complex at Macchiareddu, is exposed to a high load of trace elements which are probably enhanced by their accumulation in the finer sediment fraction. This area reveals lower diversity and higher percentages of abnormalities when compared to the outermost part of the lagoon.

Application of foraminifers in ecotoxicology: retrospect, perspect and prospect

In view of the extensive use of foraminifers for the pollution monitoring especially their unmatched utility in deciphering the temporal variation in the type and concentration of pollutants at a given location, the literature dealing with the application of foraminifers for pollution studies has been reviewed. The pollution monitoring through foraminifers started with attribution of peculiar foraminiferal features at any location to the circumstantial presence of pollutants at that site. These peculiar features of the foraminifers in polluted areas included, variation in the abundance of total, calcareous and agglutinated foraminifers, species diversity, abnormal tests, etc. The abnormalities of tests included stunted growth, abraded margins, dissolved ornamentations, etc. Initially, much attention was paid to the effects of sewage pollution on the foraminifers but later on all kinds of human induced as well as natural pollutants came under the preview of foraminiferologists working on pollution aspects. The advantage of application of foraminifers, over other chemical and biological techniques, for pollution monitoring lies in their potentiality to decipher temporal variation in type and concentration of pollutants at any site even in the absence of pre-pollution studies, based on the recovery of foraminifers from the sediment core samples. Realizing the potential application of characteristic foraminiferal features from the polluted areas to decipher the variation in introduction and concentration of pollutants at any given location with time, efforts were made to characterize the specific types of foraminiferal features to the specific pollutants. It was at this point that the need of culture studies was widely felt which resulted in numerous lab and field culture studies where foraminifers were subjected to specific pollutants in order to document their response to these pollutants and to develop effective foraminiferal proxies for pollution monitoring through time. Such studies are still going on and it is felt that culture studies need to be supplemented with advanced crystallographic and molecular studies in order to find the mechanism through which foraminifers respond to the pollutants.