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

Effects of sedimentary heavy metals on meiobenthic community in tropical estuaries along eastern Arabian Sea

The central west coast of India comprises the 720 km long coastline of Maharashtra state and houses widespread industrial zones along the eastern Arabian Sea. Sediments from seven industrial-dominated estuaries along the central west coast were studied for metal enrichment and benthic assemblages to determine sediment quality status and ecological effects in these areas. The suit of geochemical indices highlighted the contamination of sediment in the estuaries concerning heavy metals. Positive correlations of Hg with Co, Zn, Ni, Cr, and Pb indicated the source similarity and effect of anthropogenic activity. non-Metric Multidimensional Scaling (n-MDS) based on meiofaunal abundance showed a cleared separation of clusters through the gradient of heavy metal concentrations. The Canonical Correspondence Analysis (CCA) results with the Monte Carlo test signified those heavy metals influenced the meiobenthic community. Heavy metals (Cr, Ni, Zn, Cd, Pb, and Hg) were the main drivers shaping the meiofaunal community with a significant (p < 0.05) reduction in taxa richness, diversity, and evenness. Dominant meiofaunal assemblages evidence the tolerance of foraminiferans and nematodes. However, these taxa were affected by decreased abundance at impacted sites compared to other fauna. In conclusion, results demonstrated that impairment occurred in the meiofaunal community in most estuaries (except AB and KK).

Are physiological responses in foraminifera reliable environmental stress bioindicators? A systematic review

Foraminifera are considered good bioindicators of environmental stress based on morphological abnormalities, but physiological responses occur far earlier and have not been evaluated as pollution markers. The aim of this review was to collate all published articles reporting physiological changes in foraminifera after environmental and anthropogenic stressors, to evaluate their reliability as early markers of environmental stress. We reviewed 70 studies, meeting the inclusion criteria, reporting 13 physiological effects classes after exposure to 17 different stressors. Immune functions, bleaching and lifecycle disruptions, were the most reported. Amphistegina and Ammonia showed high proportion of effects with lead and mercury, with a significant relationship between these heavy metals and the number of physiological effects classes in Ammonia, and between bleaching in Amphistegina gibbosa and Amphistegina lobifera with solar light and temperature. This suggests physiological responses are potentially reliable early indicators of environmental stress. It is necessary to increase quantitative physiological measures and standard exposure protocols in order to properly evaluate these organisms as pollution bioindicators.

Conceptual methodological framework for the resilience of biogeochemical services to heavy metals stress

The idea of linking stressors, services providing units (SPUs), and ecosystem services (ES) is ubiquitous in the literature, although is currently not applied in areas contaminated with heavy metals (HMs), This integrative literature review introduces the general form of a deterministic conceptual model of the cross-scale effect of HMs on biogeochemical services by SPUs with a feedback loop, a cross-scale heuristic concept of resilience, and develops a method for applying the conceptual model. The objectives are 1) to identify the clusters of existing research about HMs effects on ES, biodiversity, and resilience to HMs stress, 2) to map the scientific fields needed for the conceptual model's implementation, identify institutional constraints for inter-disciplinary cooperation, and propose solutions to surpass them, 3) to describe how the complexity of the cause-effect chain is reflected in the research hypotheses and objectives and extract methodological consequences, and 4) to describe how the conceptual model can be implemented. A nested analysis by CiteSpace of a set of 16,176 articles extracted from the Web of Science shows that at the highest level of data aggregation there is a clear separation between the topics of functional traits, stoichiometry, and regulating services from the typical issues of the literature about HMs, biodiversity, and ES. Most of the resilience to HMs stress agenda focuses on microbial communities. General topics such as the biodiversity-ecosystem function relationship in contaminated areas are no longer dominant in the current research, as well as large-scale problems like watershed management. The number of Web of Science domains that include the analyzed articles is large (26 up to 87 domains with at least ten articles, depending on the sub-set), but thirteen domains account for 70-80% of the literature. The complexity of approaches regarding the cause-effect chain, the stressors, the biological and ecological hierarchical level and the management objectives was characterized by a detailed analysis of 60 selected reviews and 121 primary articles. Most primary articles approach short causal chains, and the number of hypotheses or objectives by article tends to be low, pointing out the need for portfolios of complementary research projects in coherent inter-disciplinary programs and innovation ecosystems to couple the ES and resilience problems in areas contaminated with HMs. One provides triggers for developing innovation ecosystems, examples of complementary research hypotheses, and an example of technology transfer. Finally one proposes operationalizing the conceptual methodological model in contaminated socio-ecological systems by a calibration, a sensitivity analysis, and a validation phase.

Biomonitoring of a Nile Delta Lake using benthic foraminifera

Lake Edku, one of the northern Nile Delta lakes, is a shallow brackish coastal lake subjected to domestic and agricultural effluents via two main drains, El-Khairy and Barsik, in addition to the discharge water of hundreds of fish farms. This study measures the responses of the benthic foraminiferal assemblage to the environmental stressors in Lake Edku. Grain size, organic carbon, and seven potentially toxic elements (Cu, Pb, Zn, Cd, Cr, Ni, and As) were determined in nine short cores (25-35 cm depth). The lake was characterized by vertical increase in mud, organic matter, and concentrations of all metals, particularly in the eastern basin at the vicinity of the drain discharges. This trend coincides with a general decrease in species diversity and increase in deformed specimens. The foraminiferal assemblage was dominated by Ammonia tepida (Cushman), a pollution-tolerant and euryhaline species. This study demonstrates that benthic foraminiferal assemblages provide a reliable pollution proxy in the brackish environments of Nile Delta that can be used in the periodical monitoring of the coastal lakes.

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.

Heavy metal incorporation in foraminiferal calcite under variable environmental and acute level seawater pollution: multi-element culture experiments for Amphisorus hemprichii

The accelerated release of heavy metals into the coastal environments due to increasing anthropogenic activities poses a severe threat to local marine ecosystems and food chains. Although some heavy metals are essential nutrients for plants and animals, higher concentrations can be toxic and hazardous. To mitigate this threat, developing quantifiable proxies for monitoring heavy metal concentrations in near-shore marine environments is essential. Here, we describe culture experiments to quantify uptake of some heavy metals using live juvenile specimens of the large benthic foraminifera (LBF) Amphisorus hemprichii collected from the subtropical waters of Rottnest Island located ~20 km offshore Perth, South West Australia. The uptake of Mn, Ni, Cd, and Pb in the newly precipitated chambers of Amphisorus hemprichii in the laboratory was characterized using the micro-analytical technique, laser ablation inductively coupled plasma mass spectrometry. We found no significant increase in Mn, Ni, Cd, and Pb incorporation in the tests of Amphisorus hemprichii with increasing temperature and light intensities. Importantly, we found that changes in the concentrations of Mn, Ni, and Cd in the A. hemprichii tests are directly proportional to those in the culture solution over a wide range of concentrations. The calculated partition coefficients for Mn, Ni, and Cd from our culture experiments are 1.3±0.2, 0.3±0.04, 2.6±0.3, respectively. These multi-element calibration studies now enable A. hemprichii to be utilized as a naturally occurring bio-archive to quantitatively monitor the anthropogenic pollution of Mn, Ni, and Cd in coastal waters.

Effects of heavy elements (Pb, Cu, Zn) on algal food uptake by Elphidium excavatum (Foraminifera)

Foraminifera are unicellular organisms and play a pivotal role in the marine material cycles. Past observations have shown that the species Elphidium excavatum is the most common foraminifera in the Baltic Sea. Feeding experiments showed that the food uptake and thus the turnover of organic matter are influenced by changes of physical parameters (e.g., temperature, salinity). Since many areas of the Baltic Sea are strongly affected by anthropogenic activity and are strongly contaminated by heavy elements from shipping in the past, this study examined the effect of heavy elements pollution on the food uptake of the most common foraminiferal species of the Baltic Sea, E. excavatum which was a subject of several previous studies. Therefore, Baltic Sea seawater was enriched with metals at various levels above normal seawater levels and the uptake of ¹³C- and ¹⁵N-labelled phytodetritus was measured by isotope ratio mass spectrometry. For each combination of metal type, concentration and time point 20 individuals of E. excavatum (three replicates) were fed with the green algae Dunaliella tertiolecta. The effect of dose parameters was measured in a two-way analysis of variance. Significant differences of food uptake were observable at different types and levels of heavy elements in sea water. Even a 557-fold increase in the Pb concentration did not affect food uptake, whereas strong negative effects were found for higher levels of Zn (144 and 1044-fold) and especially for Cu (5.6 and 24.3-fold). In summary it can be stated, that an increase in the heavy elements pollution in the Kiel Fjord will lead to a significant reduction in the turnover of organic matter by foraminifera such as E. excavatum.

Benthic foraminifera geochemistry as a monitoring tool for heavy metal and phosphorus pollution - A post fish-farm removal case study

Measuring environmental contaminants in coastal areas is critical for monitoring and managing their impacts. Commonly used techniques involve repetitive field sampling, which provides a single moment in time during each effort. In this study, we examine the potential for using foraminifera in monitoring and risk assessment as recorders of bioavailable pollutants. Geochemical analysis of benthic foraminifera (Operculina ammonoides) shells sampled annually at a previous fish farm location showed extremely high levels of copper (Cu), zinc (Zn), and phosphorus (P) during the three years following the fish cages removal, with a general reduction afterwards. Levels of Cu/Ca were still more than 4-fold higher than background levels 10 years after the removal of the fish cages. Based on our finds, it is concluded that the geochemical analysis of recent benthic foraminifera shells can serve as a powerful monitoring tool of bioavailable contaminants in seawater. Additionally, the results highlight the need for heavy metal monitoring near marine aquaculture facilities and suggest that long-term effects extend spatially and temporally far beyond the original point source. Finally, we observed variations in micro-distribution of elements within the top 1-2 μm of the shells, where Cu/Ca, Zn/Ca and P/Ca are consistently higher in the chamber wall than in the septa. This observation is relevant for studies conducting single chamber analyses.

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.

Protein Extractions from Amphistegina lobifera: Protocol Development and Optimization

Proteins are essential to life, and the evaluation of their content, identification, and modification represents a fundamental assay in biochemistry research. Different analytical techniques and protocols have been specifically designed but have rarely been compared. Here, we test and compare a variety of methodologies and treatments for the quantification of proteins in Amphistegina lessonii, a larger symbiont-bearing benthic foraminiferal species. These analyses specifically include (a) lysis buffer (homemade vs. RIPA), (b) protein assays (Lowry, BCA, and Bradford), (c) ultrasonic bath treatment, and (d) protein staining (silver staining vs. Coomassie blue). On the basis of the comparative outcome, we suggest using the homemade lysis buffer, Lowry or BCA assays, ultrasonic bath treatment, and silver stain to maximize the extraction and characterization of protein for A. lessonii. This protocol might be suitable and extended to other benthic foraminiferal species, including the smaller ones.

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.