Suitability of aquatic mosses for biomonitoring micro/meso plastics in freshwater ecosystems

Abstract Background Mesoplastics (5–25 mm) and microplastics (0.001–5 mm) are emerging pollutants of great concern. However, reliable methods of monitoring these types of plastic in river ecosystems have not yet been established. The goal of this work was to evaluate, for the first time, the suitability of Fontinalis antipyretica as a biomonitor of meso- and micro-plastics in rivers. With this aim, native samples of the moss and devitalized moss clones, held inside the bags, were compared for the uptake of fluorescent polystyrene particles under laboratory conditions, and for retention of plastic debris in the field, in sites close to wastewater treatment plants. Results In the laboratory experiment, the moss retained smaller microplastics, and a higher number of polystyrene meso and microplastics was counted in the moss bags than in the native moss. In the field study, the moss retained plastic debris chiefly in the form of fibres regardless of the capacity and flow rate of the wastewater treatment plants affecting each sampling site. The uniform morphology of moss clone seems to affect the retention of this type of pollutant. The FTIR analysis confirmed the particles entrapped by the moss bags as plastic, specifically polyethylene and polyamide type 6, among the most common plastic polymers detected in rivers. Conclusions The study findings highlighted the value of using uniform material, as the clone exhibited a greater accumulation efficiency with respect to the native moss. The mesh bags could act as selective filters and/or prevent the loss of adhering plastics. In the field, the bags favour plastic fibres retention despite the river flow. Finally, although FTIR is useful for the identification of plastic type, it is not very sensitive when small quantities of ground samples are used

TEMPORAL TRENDS OF HEAVY METAL CONCENTRATIONS IN BROWN MACROALGAE FROM COASTAL ENVIRONMENTS

Heavy metals are one of the major drivers of ecological changes in coastal ecosystems. Macroalgae are primary producers of great relevance for ecosystem structure and functioning in these environments, and play a key role in the trophic transfer of these contaminants in the food web. Here, we present the most extensive assessment until now (>3500 records) of heavy metal concentrations in brown macroalgae (Class Phaeophyceae) sampled between 1933 and 2020 worldwide. The study compiles this information from 420 peer reviewed articles to be used as a proxy of global long-term changes in metal concentrations. We report the first detailed multi-decadal time series of Cd, Co, Cr, Cu, Fe, Hg, Mn, Pb and Zn in algae using generalized additive models (GAMs), confirming a significant decrease in metal contamination in the world’s coastal environments since ca. the 1970s for Pb (84% reduction), Zn (79%), Cd (77%) and Cu (72%), since the 1980s for Mn (75%) and Hg (65%), and since the 1990s for Cr (66%), Fe (64%) and Co (60%). Important environmental consequences for the whole aquatic ecosystem, even for human health, may be expected from these changes. The present results provide a building block for the overall evaluation of the status and trends of marine metal contamination, and will help researchers and policy makers to promote new legal regulations and environmental goals against pollution

Chronological characterization of medieval villages in Northern Iberia: A multi-integrated approach

Defining the occupation sequence of medieval rural farming sites in Northern Iberia is complicated, since they feature low density of stratigraphic relationships and few finds and because of the intensive agricultural activities developed there during the last few decades. This paper presents the chronological characterization of the medieval village of Zornoztegi, located in the Basque Country, in the province of Alava. At this site, dwellings extend over an area of approximately two hectares and consist mainly of negative structures excavated in the bedrock. Radiocarbon dating measurements carried out on 32 samples, together with mortar optical microscopic analyses and other information obtained from stratigraphic relationships, changes in the settlement organization and the study of material culture, allowed structuring and characterizing the occupation sequence of the site of Zornoztegi. Furthermore, Bayesian statistics was used to reduce the range of the calibrated dates and to refine the chronology of the sequence

What dead seaweeds can tell us about metal uptake and their application to control marine pollution

The mechanisms of trace element uptake by seaweeds are still unknown, despite being key to understand the impact of pollution in coastal environments. This knowledge gap, in addition to the lack of standardization, have also hindered the use of seaweeds to monitor seawater pollution. To address these shortcomings, we tested the use of devitalization as a pre-exposure treatment for brown seaweed transplants, and we compared devitalized and fresh transplants to gain some insights into the mechanisms of element uptake. We exposed four types of Fucus vesiculosus transplants in 6 sites for 4, 8 and 20 days: fresh and devitalized (dried or boiled) algal segments held in mesh bags, and whole algal thalli imitating natural conditions. We then determined he concentrations of 11 trace elements in the algal tissues. The element concentrations were highest in the devitalized transplants, but the material lost consistency and weight throughout the exposure period, limiting their use to short periods. We proposed several factors that may contribute to the different accumulation patterns between treatments, and examined the implications for the uptake mechanisms, revealing that two of the most important are surface adsorption of sediment particles and chemical bounds to extracellular componentsThis study is part of the project PID2022–142802NB-I00 awarded by the Spanish Ministerio de Ciencia e Innovación. The authors belong to the Grupo de Referencia Competitiva GRC GI-1252/GPC2020–23 (ED431C 2020/19) which is co-funded by ERDF (EU). A. Vázquez-Arias is grateful to the Spanish Ministerio de Ciencia, Innovación y Universidades for a grant awarded within the Programa de Formacion de Profesorado Universitario (grant number FPU19/01989)S

Levels of Antioxidant Compound Glutathione in Moss from Industrial Areas

Plants possess a wide range of cellular mechanisms that help them tolerate potentially toxic substances. Several studies that were carried out under laboratory conditions have demonstrated that the antioxidant compound glutathione plays a role in enabling mosses to tolerate high levels of heavy metals without toxic effects. However, until now, the antioxidant levels have not been studied in mosses under field conditions. In this study, we aimed to clarify the antioxidant concentrations of glutathione in the terrestrial moss Pseudoscleropodium purum growing in industrial environments characterised by high atmospheric levels of Cd, Ni, and Pb, and to evaluate the potential use of the compound as a biomarker. The results indicated the existence of a glutathione threshold response, which was significantly correlated with the metal toxicity and which may be influenced by metal bioavailability. Although future studies are needed to strengthen the findings, the present study suggests that total concentration of glutathione in P. purum could therefore be used as a biomarker in air pollution biomonitoring studies, provided that metal bioavailability is taken into account

Plant-air partition coefficients for thirteen urban conifer tree species: Estimating the best gas and particulate matter associated PAH removers

Polycyclic Aromatic Hydrocarbons (PAHs) are an important class of pollutants which mostly come out from incomplete combustion of organic materials including fossil fuels. For this reason, they are often found at high concentrations in cities, contaminating air with their gas and particle phase. While European Union policies try to reduce their concentrations, huge efforts are still devoted to mitigate the pollution by PAHs. One such measure of mitigation is the use of plants in capturing PAHs and other chemicals due to the ability of leaves in filtering both gas and particle fractions. In this work thirteen conifer species among those frequently living in temperate and Mediterranean cities were selected and concentrations of 16 PAHs were measured in needles. The data for spruce were used to back-calculate air concentrations of PAHs which were later used to obtain specific equations of plant-air partition coefficient (K-PA). The results showed that the difference in total PAH uptake between the most (Pinus pinaster) and the least (Picea abies) efficient tree was close to an order of magnitude. Looking to the capability of the different species in enriching the particulate matter (PM) associated fraction of PAHs on their needles, Pinus pinaster was instead the least important (3.4% of total PAHs), while Cupressus lusitanica was the most important (34% of total PAHs). The new K-PA equations can be used to fine tune the PAH uptake of a specific amount of plant biomass on air concentration reduction

Should moss samples used as biomonitors of atmospheric contamination be washed?

When terrestrial mosses are used to monitor atmospheric contamination, the samples are usually analysed without first being washed, so that the contaminants deposited on the moss can be quantified. However, when the aim is to evaluate phyto-toxic effects and the risks associated with increased concentrations of contaminants, it is the bioconcentrated fraction that is of interest. In such cases, the samples are washed to remove deposited material adhering to the surface of the moss. In the present study, the efficacy of the washing step was evaluated, by electron microscopy and microanalysis, in samples exposed to different levels of contamination. The results obtained show that washing is not effective at removing particles deposited on the moss surface, so that an alternative cleaning method is required. Until such a method becomes available, use of the Sequential Elution Technique is recommended for precise determination of the bioconcentrated contaminants

Accumulation of polycyclic aromatic hydrocarbons in the devitalized aquatic moss Fontinalis antipyretica: From laboratory to field conditions.

AbstractThis work aims to test the feasibility of a Fontinalis antipyretica devitalized moss clone to uptake and accumulate polycyclic aromatic hydrocarbons (PAHs) from surface waters. To assess the capability of the devitalized clone to accumulate PAHs, in the laboratory, moss was placed in water and spiked with increasing concentrations of 16 PAHs, and under field conditions, the moss was transplanted to 22 sites of Galicia (Spain) rivers. In general, PAH concentrations in water samples were lower than the maximum allowable concentrations from Directive 2013/39/EU, so the sampling sites did not show water PAH contamination. The exponential accumulation kinetic in the laboratory trial highlights a good capability of the devitalized moss clone to accumulate total PAHs. In field experiments, the hydrogeological conditions and the low emission sources caused low concentrations of PAHs in the water system and, consequently, in the transplants, although an enrichment can be observed for several PAHs. Overall, the devitalized clone of F. antipyretica can uptake and accumulate PAHs in water and may be useful in bioremediation strategies

Moss bag biomonitoring: a methodological review

Although the moss bag technique has been used for active biomonitoring for the past 40 years, there is still no standardized protocol that enables application of the technique as a tool to monitor air quality. The aim of this review paper is to evaluate the degree of standardization of each of the variables that must be considered in applying the technique (i.e. the variables associated with preparation of the moss and moss bags, exposure of the bags, and post-exposure treatment). For this purpose, 112 scientific papers that report the methods used in applying the moss bag technique were consulted. Finally, on the basis of the conclusions reached, we propose a protocol that will enable each of these variables to be investigated separately, with the final aim of developing a standardized methodolog