Inferring the ecological quality status based on living benthic foraminiferal indices in transitional areas of the Guanabara bay (SE Brazil)

Comparative analysis of sedimentary metal phases and their respective roles in shaping living benthic foraminiferal communities: Implications for environmental biomonitoring

This work examines the effects of the potentially toxic element (PTEs) concentrations through total sediment digestion (TD) and sequential chemical extraction in three sedimentary phases (i.e., water, organic matter, and manganese hydroxides) on living benthic foraminifera in the Guanabara Bay (GB), one of the largest transitional ecosystems in Rio de Janeiro State (SE Brazil). It also considers the variations in the quantity and quality of organic matter, hydrodynamics and physicochemical parameters as stressors parameters for these organisms. The statistical analysis provides compelling evidence that measuring PTEs.TD through the total digestion of sediments is not the most effective method for assessing the impact of pollution on living meiofaunal organisms like benthic foraminifera. Conversely, it documents that benthic foraminifera respond to gradients of available (or soft-bound) PTE concentrations in the sediment, quantity and quality of organic matter, the level of environmental confinement, and changes in physicochemical variables. Therefore, this work supports the importance of analyzing available and/or softbound metal fractions for disentangling the response of living organisms to environmental impact. The present findings have significant implications for environmental biomonitoring studies and the development of ecological indices based on foraminifera.

Foraminifera and geomicrobiology as indicators of the environmental recovery in a mangrove affected by oil spills in the Guanabara Bay (Brazil)

Foraminifera could be used as indicators to evaluate the impacts of oil spills because the crude oil causes several disturbances on the development and reproduction of the species. However, little is known about the relationship between mangrove species and this pollutant. Foraminiferal assemblages were studied in 22 surface sediment samples collected from a mangrove in Guanabara Bay (Brazil) that was severely impacted by an oil spill six years earlier. The foraminiferal responses to the environmental stress helped to determine the most degraded areas. Elevated concentrations of aromatic compounds and potentially bioavailable heavy metals, with contamination levels up to nine times higher compared to the pre-industrial period in the Guanabara Bay. The dominance of anaerobic bacteria, and high esterase enzyme activity (ESTE) suggest that the bacterial community is metabolizing the hydrocarbons in the sediments. Despite these stressors, density and diversity of living foraminifera are comparable to values observed in less impacted Brazilian mangroves. Species distribution patterns reveal an environmental gradient across the mangrove with numerous species increasing their relative abundance towards the areas topographically lower and with higher levels of pollutants and ESTE. Specifically, Caronia exilis, Tiphotrocha comprimata, Ammobaculites exiguus, Textularia paranaguaensis, Ammotium cassis, Ammobaculites dilatatus, Polyssaccamina hipohalina, Siphotrochammina lobata, Ammonia tepida, Ammotium morenoi, Miliammina fusca, Entzia macrescens, Trochammina squamata and Paratrochammina clossi are inferred as pollution-tolerant taxa. This integrated geochemical, microbiological and ecological approach applied to assess the sediment quality in a complex ecosystem has important implications for the use of living foraminifera in recovery stage assessments and biomonitoring plans.

Application of benthic foraminiferal indices to infer the ecological quality status in the Sepetiba Bay (SE Brazil)

The Sepetiba Bay (SB, SE Brazil) is a highly anthropized and industrialized area that has experienced severe environmental degradation in recent decades. This study applies a multiproxy approach to document the response of living benthic foraminifera to environmental stress and to infer the Ecological Quality Status (EcoQS) in SB. Our methodology involved a comprehensive comparison of the density and percentage of benthic foraminiferal species with physicochemical, textural, and geochemical data, specifically the concentrations of potentially toxic elements (PTEs). We also statistically compared two geochemical indices, the pollution load index (PLI) and the potential ecological risk index (PERI), with two ecological indices, the Tolerant Species Index (TSI) and the Exp(H'bc). The TSI and the Exp(H'bc) indices are significantly correlated with the environmental stressors in Sepetiba Bay, namely the PTEs concentrations (As, Cd, Pb, and Zn). The most tolerant species to the enrichment of PTEs and organic matter are Ammonia tepida (Cushman, 1926), Elphidium excavatum (Terquem, 1875), Ammonia buzasi Hayward and Holzmann, 2021 and Ammonia rolshauseni (Cushman and Bermúdez, 1946). The Exp(H'bc) and TSI reveal that most stations located in the inner zone and near the margins of the bay have poor and bad EcoQS, which agrees with the distribution of the environmental stressors. Thus, the current environmental conditions of the inner area of Sepetiba Bay are of great concern. This work also shows that using the TSI and the Exp(H'bc) indices, it is possible to classify EcoQS in transitional coastal environments in the North and South Atlantic transitional waters. This work has relevant scientific and social implications due to its importance in biomonitoring and the management of the coastal regions.

Assessing the Ecological Quality Status in tropical Indian estuaries: testing the applicability of benthic foraminiferal indices

The ecological quality status (EcoQS) of Vellar and Uppanar estuaries (Southeast coast of India) has been monitored monthly, using a combination of foraminiferal (Foram Stress Index: FSI and exp(H'bc) indices and abiotic (Pollution Load Index: PLI, Dissolved Oxygen: DO, and Total Organic Carbon: TOC) parameters. The Uppanar Estuary shows relatively higher values of PLI and TOC and lower DO values than Vellar Estuary. The highest value of TOC and PLI are recorded during the monsoon season. These variations are well mirrored by the change in exp(H'bc) and FSI. The lowest values of exp(H'bc) are observed with the monsoon season and could be ascribed by an overall reduction of salinity, and to the highest level of TOC and PLI in response to enhanced river discharge. The FSI also exhibits great variability with significant higher values in the Vellar Estuary than in the Uppanar Estuary. The EcoQS evaluated by a combination of pollution- (i.e., PLI, TOC and DO) and foraminiferal-based [i.e., FSI and exp(H'bc)] indices are highly consistent (73.4%). The most frequent disagreement among indices is mostly associated to Uppanar Estuary and, particularly, in the inner stations. This difference might be related to a time-lag response of benthic foraminifera in terms of diversity and assemblages' compositions as well as of the pollution indicators in response to enhanced riverine input. This study further supports the application of foraminiferal-based indices in EcoQS assessment in transitional environments including tropical Indian estuaries. It also fills the gap of knowledge by providing a seasonal perspective on the variation of EcoQS based on a monthly-scale sampling.

Exploring the underwater life in transitional environments: Benthic foraminifera, ostracods, and dinoflagellate cysts - Biotic trends and EcoQS assessment in the Mar Piccolo of Taranto (Ionian sea, southern Italy)

Coastal areas have historically thrived as centers of human activities due to their resources, economic opportunities, and natural allure. The rapid growth of coastal populations has however brought forth a multitude of challenges to tackle, with pollution emerging as a significant and far-reaching issue. Our study focuses on the Mar Piccolo of Taranto (Ionian Sea, Southern Italy), a lagoon-like coastal basin (separated in two sub-basins) that, since decades, has been heavily affected by human activities and aquaculture, leading to environmental deterioration. Although past studies have looked at environmental conditions in the Mar Piccolo from a chemical perspective, the biological component (e.g., biological indicators) has been mostly neglected. In this study, we firstly aim to examine the distribution and diversity of foraminifera, ostracods, and dinoflagellate cysts in December 2016 and compare our findings with data collected in December 2011. Foraminiferal and ostracod communities exhibit similar patterns in the two sampling campaigns, while the communities of encysted dinoflagellates show differences concerning both densities and diversity. Then, we evaluate the Ecological Quality Status (EcoQS) using ecological indices. While the indices in the inner basin appear to reflect an actual ecological degradation, they yield conflicting results in the outer basin. In the outer basin, indeed, the indices overestimate the EcoQS. This study highlights the potential of these indices for characterizing the EcoQS but emphasizes the need for improvements in their reliability. This research also contributes to a more holistic understanding of environmental condition in the Mar Piccolo and underscores the importance of integrating biological quality elements into ecosystem management and remediation strategies.

Measuring ecological quality status in low-diversity Arctic intertidal foraminiferal assemblages using a diversity-based index

EcoQS assessment of the marine intertidal zone based on its fauna is challenging because the assemblages have a low diversity and consist of stress tolerant species. The new approach we propose is to pool foraminiferal diversity (effective number of species exp(H'bc)) across the whole intertidal zone including the salt marsh and tidal flat. In seven fjordheads studied in northern Fennoscandia, polycyclic aromatic hydrocarbon (PAH) concentrations indicated low levels of pollution (EcoQSPAH Excellent to Moderate). Jadammina or Balticammina dominated the salt marsh, Elphidium albiumbilicatum, Elphidium williamsoni, Elphidium clavatum, and Buccella frigida occurred in the tidal flat. Ovammina opaca thrived in both belts. While foraminiferal test abnormalities are often proposed to measure pollution impacts, we did not detect any correlation with PAHs. EcoQS based on foraminiferal diversity (EcoQSforam Excellent to Good) matched EcoQS based on PAHs suggesting that pooled foraminiferal diversity reliably measures intertidal EcoQS.

Assessment of the ecological quality status of the Sepetiba Bay (SE Brazil): When metabarcoding meets morphology on foraminifera

In recent years, the region surrounding Sepetiba Bay (SB; SE Brazil) has become a hub of intense urban expansion and economic exploitation in response to ore transport and industrial and port activities. As a result, contaminants have been introduced into the bay, leading to an overall worsening of the environmental quality. The present work applies for the first time a foraminiferal morphology-based approach (M) and eDNA-based metabarcoding sequencing (G), along with geochemical data to assess the ecological quality status (EcoQS) in the SB. Principal component analysis shows that the eDNA and morphospecies diversity as well as most of the taxa relative abundance decline in response to the environmental stress (ES) gradient related to total organic carbon (TOC) and metal pollution. Based on ecological indices, Exp(H'bc) (G), Exp(H'bc) (M), foraminifera ATZI marine biotic index (Foram-AMBI), Foram Stress Index (FSI), and geochemical indices (TOC and Potential Ecological Risk Index), the lowest values of EcoQS (i.e., bad to moderate) are inferred in the innermost part of the SB. Despite minor discrepancies among the six EcoQS indices, an agreement has been found for 63% of the stations. To improve the agreement between the ecological indices, it is necessary to fill the gap in species ecology; information on the ecology of many species is still unknown. This work reinforces the importance of molecular analysis and morphological methods in environmental impact studies and confirms the reliability of foraminiferal metabarcoding in EcoQS assessment. This is the first study evaluating the EcoQS in the South Atlantic by using combined foraminiferal eDNA metabarcoding with morphological data.