Modelling the extra and intracellular uptake and discharge of heavy metals in Fontinalis antipyretica transplanted along a heavy metal and pH contamination gradient

Looking at moss through the bioeconomy lens: biomonitoring, bioaccumulation, and bioenergy potential

The field of bioeconomy has been experiencing a surge in interest in recent years as society increasingly recognizes the potential of utilizing renewable biological resources to create sustainable solutions for economic growth, resource management, and environmental protection. Despite its potential, there is a notable lack of studies exploring the utilization of moss as a viable resource within the bioeconomy framework. Aligned with this objective, this paper conducts a keyword analysis using the VOSviewer application to explore the applicability of mosses as a bioeconomy resource. While biomonitoring using mosses has been studied extensively, this paper shifts its focus to discuss advancements in this area. Moreover, it evaluates the viability of moss utilization for bioenergy production and concisely summarizes their application in microbial fuel cells. The review also highlights challenges pertinent to moss utilization and presents future prospects. The overarching goal of this review paper is to assess the potential and utilization prospects of mosses within the realms of bioaccumulation, air purification, and bioenergy. By offering a comprehensive summary of moss applications, performance, and viability across diverse sectors, this paper endeavors to promote the versatile application of mosses in various contexts. It repositions the discussion on mosses, accentuating their utilization potential prior to exploring conclusions and future prospects.

The significance of heterophasic ion exchange in active biomonitoring of heavy metal pollution of surface waters

We have carried out studies to examine the possibility of using biosorbents: the epigeic mosses Pleurozium schreberi (Willd. ex Brid.) Mitt., and the epiphytic lichens Hypogymnia physodes (L.) Nyl. in active biomonitoring of heavy metal pollution of surface waters. The dried sea algae Palmaria palmata (L.) Weber & Mohr were used as the third biosorbent. The studies were conducted in the waters of the Turawa Reservoir, a dam reservoir with a significant level of eutrophication in south-western Poland. Incremental concentrations of Mn, Ni, Zn, Cu, Cd, and Pb were determined in the exposed samples. It was shown that a 2-h exposure period increases the concentration of some metals in the exposed samples, even by as much as several hundred percent. High increments of nickel concentrations in the algae Palmaria palmata (mean: 0.0040 mg/g, with the initial concentration of c0 < 0.0016 in the algae) were noted, with negligible increments in concentrations of this metal in mosses and lichens. In contrast, mosses and lichens accumulated relatively high amounts of Cd (mean: 0.0033 mg/g, c0 = 0.00043 mg/g) and Pb (mean: 0.0243 mg/g, c0 = 0.0103 mg/g), respectively.

Lamina Cell Shape and Cell Wall Thickness Are Useful Indicators for Metal Tolerance-An Example in Bryophytes

Bryophytes are widely used to monitor air quality. Due to the lack of a cuticle, their cells can be compared to the roots of crop plants. This study aimed to test a hypothetical relation between metal tolerance and cell shape in biomonitoring mosses (Hypnum cupressiforme, Pleurozium schreberi, Pseudoscleropodium purum) and metal sensitive species (Physcomitrium patens, Plagiomnium affine). The tolerance experiments were conducted on leafy gametophytes exposed to solutions of ZnSO4, ZnCl₂, and FeSO₄ in graded concentrations of 1 M to 10⁻⁸ M. Plasmolysis in D-mannitol (0.8 M) was used as a viability measure. The selected species differed significantly in lamina cell shape, cell wall thickness, and metal tolerance. In those tested mosses, the lamina cell shape correlated significantly with the heavy metal tolerance, and we found differences for ZnSO4 and ZnCl₂. Biomonitoring species with long and thin cells proved more tolerant than species with isodiametric cells. For the latter, “death zones” at intermediate metal concentrations were found upon exposure to ZnSO4. Species with a greater tolerance towards FeSO₄ and ZnSO₄ had thicker cell walls than less tolerant species. Hence, cell shape as a protoplast-to-wall ratio, in combination with cell wall thickness, could be a good marker for metal tolerance.

Combined use of native and transplanted moss for post-mining characterization of metal(loid) river contamination

Abandoned mine sites are a cause of great environmental concern, being potential sources of toxic elements for adjacent aquatic ecosystems with intrinsic difficulties for their management (i.e. episodic nature of pollution, technical difficulties and high costs of monitoring, remoteness). Aquatic macrophytes can find effective application in these situations, providing cost-effective data for instream water quality assessment. In this study, native and transplanted specimens of the aquatic moss Platyhypnidium riparioides were used to evaluate metal(loid) contamination in a river receiving multiple acidic and metalliferous drainages from sulphide mineralized areas and derelict mines. Analysis of native P. riparioides thalli was used to identify, in the upland course of the river, the pattern of contamination (As, Cd, Cu, Pb and Zn) which was related to the geo-environmental features of the watershed and the nearby historical mining areas. Attenuation of metal(loid) availability in the lowland river, apparently due to eco-hydrological and physic-chemical processes, was also highlighted by spatial trends of concentrations data of native and transplanted moss. The latter, deployed for 21 days at specific stretches of the river and in a tributary hydrologically connected with a dismissed mine, supported the identification of point sources (i.e. mine effluents, metallurgical waste piles amassed on the banks of the river) and the reckoning of their quantitative impact on different segments of the watercourse. By exploring multi-elemental and native-to-transplant relationships, differences in metal(loid) accumulative capacities were recognized between sampled thalli and exposed moss bags in relation to the severity of the contamination. The observed discrepancy in the accumulation of As, Fe, Ni and Pb in highly contaminated areas between native and transplanted moss of P. riparioides raises questions on the possible competing mechanisms of element uptake and retention. These findings prompt studies to discern possible limitations of the transplanting moss technique under extreme stream-quality conditions.

Methodological advances to biomonitor water quality with transplanted aquatic mosses

The active biomonitoring technique has been demonstrated to be an excellent tool for monitoring water quality; however, further improvement of the protocol is urgently needed. The present study was carried out to determine the best options for various methodological aspects of monitoring some metals and metalloids (i.e. Al, As, Cd, Co, Cu, Fe, Hg, Ni, Zn and Pb): i) the type of transplant, ii) pre-exposure washing (with or without cellular extractants), iii) the ratio between moss weight and bag surface area, and iv) the depth at which the bags are exposed. The importance of the different methodological aspects in the outcome of biomonitoring studies was also assessed by considering the results of the present and other previously published studies. Regarding the type of transplant, the traditionally used net bags were the best option for enclosing the moss; in addition, washing the moss with extracellular extractants (i.e. EDTA) prior to exposure increased the sensitivity of the technique and reduced the required exposure time (i.e. one week). For the amount of moss packed in each bag, a ratio of 12.5 mg cm^-2 was the best choice. Finally, the depth at which the transplants were exposed did not affect pollutant accumulation (in shallow rivers, reservoirs or dams). Pollutant concentrations were also not affected by the existence of thermocline in deep waters during warmer months. Different methodological aspects involved in applying this technique determine the final concentrations of metals in moss. Although the influence of those was variable, for most elements (i.e. As, Cd, Co, Cu, Hg, Pb, Zn) 80% of the total variance was explained by 3-4 aspects, being species selection, devitalization treatment, duration of exposure, and number of transplants exposed the most important.

Perspective of mitigating atmospheric heavy metal pollution: using mosses as biomonitoring and indicator organism

Mosses were proved as an ideal and reliable biomonitor as well as an indicator of atmospheric trace metal pollution. They are used as model indicator species of air pollution since long back due to their simple structure, genetic diversity, totipotency, rapid colony-forming ability, and high metal resistance behavior. Bryomonitoring technique is gradually being popularized as an economically viable procedure for estimating the degrees of environmental health and evaluating the toxic pollutants in biosphere. Thus, in the present scenario, many parts of the world use these organisms for monitoring the air pollution. This article describes an overview of the relationship of terrestrial mosses with trace metals with respect to their uptake, accumulation, and toxification as well as detoxification and tolerance mechanisms. The review article explicitly expresses the caliber of the cryptogamic mosses in establishing the pristine environment around the world. It also highlights the underpinning mechanisms and potential for future research directions. We have referred more than 250 articles, which deals with the assessment and impact of different heavy metals on 52 numbers of different moss species belongs to different climatic zones. The present review covers the research work in this area carried out worldwide since 1965.

Zinc Uptake, Photosynthetic Efficiency and Oxidative Stress in the Seagrass Cymodocea nodosa Exposed to ZnO Nanoparticles

We characterized zinc oxide nanoparticles (ZnO NPs) by dynamic light scattering (DLS) measurements, and transmission electron microscopy (TEM), while we evaluated photosystem II (PSII) responses, Zn uptake kinetics, and hydrogen peroxide (H₂O₂) accumulation, in C. nodosa exposed to 5 mg L⁻¹ and 10 mg L⁻¹ ZnO NPs for 4 h, 12 h, 24 h, 48 h and 72 h. Four h after exposure to 10 mg L⁻¹ ZnO NPs, we noticed a disturbance of PSII functioning that became more severe after 12 h. However, after a 24 h exposure to 10 mg L⁻¹ ZnO NPs, we observed a hormetic response, with both time and dose as the basal stress levels needed for induction of the adaptive response. This was achieved through the reduced plastoquinone (PQ) pool, at a 12 h exposure, which mediated the generation of chloroplastic H₂O₂; acting as a fast acclimation signaling molecule. Nevertheless, longer treatment (48 h and 72 h) resulted in decreasing the photoprotective mechanism to dissipate excess energy as heat (NPQ) and increasing the quantum yield of non-regulated energy loss (Φ_NO). This increased the formation of singlet oxygen (¹O₂), and decreased the fraction of open reaction centers, mostly after a 72-h exposure at 10 mg L⁻¹ ZnO NPs due to increased Zn uptake compared to 5 mg L⁻¹.

Functional and structural biomarkers to monitor heavy metal pollution of one of the most contaminated freshwater sites in Southern Europe

This study evaluated the biological effects of highly polluted freshwater environment (Regi Lagni channels, S Italy) on the aquatic moss Leptodictyum riparium, exposed in bags at three sites representative of different environmental conditions and characterized by different heavy metal burdens. Bioaccumulation, ultrastructural alterations, Reactive Oxygen Species (ROS) production, antioxidant enzymes activity and DNA damage were assessed. To better evaluate the biological response of the moss species to heavy metals, the same biological parameters were assessed also in L. riparium samples cultured in vitro using metal mixtures at the same concentrations as measured at the 3 field exposure sites. Heavy metals were accumulated into the moss tissues causing severe ultra-structural damages at higher concentration case studies, and the ROS production as well as the activity of the enzyme followed a concentration-dependent increase. However, the DNA damage trend suggested a threshold effect that changed between field and in vitro experiment. The enrichment factor suggests that the concentration in the most polluted site is close to the upper limit of L. riparium to accumulate metals. Overall, combining measures of the morpho-functional traits at different level contribute to improving the knowledge about the tolerance of L. riparium to heavy metal stress, suggesting that this moss could be suitable for biomonitoring activity in field conditions.

Cadmium uptake kinetics in parts of the seagrass Cymodocea nodosa at high exposure concentrations

Background

Seagrass species have been recommended as biomonitors of environmental condition and as tools for phytoremediation, due to their ability to concentrate anthropogenic chemicals. This study aims to provide novel information on metal accumulation in seagrasses under laboratory conditions to support their use as a tool in the evaluation and abatement of contamination in the field. We investigated the kinetics of cadmium uptake into adult leaf blades, leaf sheaths, rhizomes and roots of Cymodocea nodosa in exposure concentrations within the range of cadmium levels in industrial wastewater (0.5–40 mg L⁻¹).

Results

A Michaelis–Menten-type equation satisfactorily described cadmium accumulation kinetics in seagrass parts, particularly at 0.5–5 or 10 mg L⁻¹. However, an S equation best described the uptake kinetics in rhizomes at 5 mg L⁻¹ and roots at 10 and 20 mg L⁻¹. Equilibrium concentration and uptake rate tended to increase with the exposure concentration, indicating that seagrass displays a remarkable accumulation capacity of cadmium and reflect high cadmium levels in the surrounding medium. Concerning leaf blades and rhizomes, the bioconcentration factor at equilibrium (range 73.3–404.3 and 14.3–86.3, respectively) was generally lower at higher exposure concentrations, indicating a gradual reduction of available binding sites. Leaf blades and roots accumulated more cadmium with higher rate than sheaths and rhizomes. Uptake kinetics in leaf blades displayed a better fit to the Michaelis–Menten-type equation than those in the remaining plant parts, particularly at 0.5–10 mg L⁻¹. A marked variation in tissue concentrations mainly after the steady state was observed at 20 and 40 mg L⁻¹, indicative of the stress induced on seagrass cells. The maximum concentrations observed in seagrass parts at 5 and 10 mg L⁻¹ were comparatively higher than those previously reported for other seagrasses incubated to similar exposure concentrations.

Conclusions

Cymodocea nodosa displays a remarkable cadmium accumulation capacity and reflects high cadmium levels in the surrounding medium. Kinetic models satisfactorily describe cadmium uptake in seagrass parts, primarily in adult leaf blades, at high exposure concentrations, permitting to predict cadmium accumulation in field situations. Cymodocea nodosa appeared to be a valuable tool in the evaluation and abatement of cadmium contamination in coastal areas.

Historical legacies of river pollution reconstructed from fish scales

Many rivers have been impacted by heavy metal pollution in the past but the long-term legacies on biodiversity are difficult to estimate. The River Ulla (NW Spain) was impacted by tailings from a copper mine during the 1970-1980s but absence of baseline values and lack of subsequent monitoring have prevented a full impact assessment. We used archived fish scales of Atlantic salmon to reconstruct levels of historical copper pollution and its effects on salmon fitness. Copper bioaccumulation significantly increased over baseline values during the operation of the mine, reaching sublethal levels for salmon survival. Juvenile growth and relative population abundance decreased during mining, but no such effects were observed in a neighbouring river unaffected by mining. Our results indicate that historical copper exposure has probably compromised the fitness of this Atlantic salmon population to the present day, and that fish scales are suitable biomarkers of past river pollution.

Historical record of trace elements (1983-2007) in scales from Atlantic salmon (Salmo salar): Study of past metal contamination from a copper mine (Ulla River, NW Iberian Peninsula)

The chemical composition of fish scales has been reported to reflect the composition of the waters in which fish have been resident, therefore having the potential for the assessment of temporal trends in watershed water quality. Here we studied the historical (1983-2007) metal contamination in the Ulla river (NW Iberian Peninsula) watershed - impacted by a Cu mine that was in operation from 1973 until 1988 - by means of the analysis of major and trace elements in salmon scales. Results indicate the presence of a significant contamination for several metals (especially Cu, Au, Ag, Sb, Zn) during the 1980's. Concentrations of Cu in salmon scales during the influence of the mine (1983-1990) were 20 ± 5 μg/g, exceeding the values for the recent years (1995-2007): 1.8 ± 0.4 μg/g. Concentrations for Au in these two periods were 31 ± 12 and 2.1 ± 1.2 ng/g; for Ag: 21 ± 4 and 4 ± 2 ng/g; for Sb: 48 ± 21 and 15 ± 4 ng/g; and for Zn: 133 ± 16 and 93 ± 10 μg/g. The estimated concentrations of dissolved copper during the operation of the mine indicate a scenario of toxic effects due to sensory impairments in the salmon, and a reduction in scales calcification. The results presented here demonstrate that the analysis of trace elements in archived fish scales is a suitable tool for the reconstruction of the past contamination in aquatic systems, and it can be also used as a non-lethal approach for biomonitoring purposes.

Copper bioaccumulation, photosystem II functioning, and oxidative stress in the seagrass Cymodocea nodosa exposed to copper oxide nanoparticles

Photosynthetic activity, oxidative stress, and Cu bioaccumulation in the seagrass Cymodocea nodosa were assessed 4, 12, 24, 48, and 72 h after exposure to two copper oxide nanoparticle (CuO NP) concentrations (5 and 10 mg L^-1). CuO NPs were characterized by scanning electron microscopy (SEM) and dynamic light scattering measurements (DLS). Chlorophyll fluorescence analysis was applied to detect photosystem II (PSII) functionality, while the Cu accumulation kinetics into the leaf blades was fitted to the Michaelis-Menten equation. The uptake kinetics was rapid during the first 4 h of exposure and reached an equilibrium state after 10 h exposure to 10 mg L^-1 and after 27 h to 5 mg L^-1 CuO NPs. As a result, 4-h treatment with 5 mg L^-1 CuO NPs, decreased the quantum yield of PS II photochemistry (Φ _PSΙΙ ) with a parallel increase in the regulated non-photochemical energy loss in PSII (Φ _NPQ ). However, the photoprotective dissipation of excess absorbed light energy as heat, through the process of non-photochemical quenching (NPQ), did not maintain the same fraction of open reaction centers (q _p ) as in control plants. This reduced number of open reaction centers resulted in a significant increase of H₂O₂ production in the leaf veins serving possibly as an antioxidant defense signal. Twenty-four-hour treatment had no significant effect on Φ _PSΙΙ and q _p compared to controls. However, 24 h exposure to 5 mg L^-1 CuO NPs increased the quantum yield of non-regulated energy loss in PSII (Φ _NO ), and thus the formation of singlet oxygen (¹O₂) via the triplet state of chlorophyll, possible because the uptake kinetics had not yet reached the equilibrium state as did 10 mg L^-1. Longer-duration treatment (48 and 72 h) had less effect on the allocation of absorbed light energy at PSII and the fraction of open reaction centers, compared to 4-h treatment, suggesting the function of a stress defense mechanism. The response of C. nodosa leaves to CuO NPs fits the "Threshold for Tolerance Model" with a threshold time (more than 4 h) required for induction of a stress defense mechanism, through H₂O₂ production.

The artificial and natural isotopes distribution in sedge (Carex L.) biomass from the Yenisei River flood-plain: Adaptation of the sequential elution technique

The study of migration pathways of artificial isotopes in the flood-plain biogeocoenoses, impacted by the nuclear fuel cycle plants, requires determination of isotope speciations in the biomass of higher terrestrial plants. The optimal method for their determination is the sequential elution technique (SET). The technique was originally developed to study atmospheric pollution by metals and has been applied to lichens, terrestrial and aquatic bryophytes. Due to morphological and physiological differences, it was necessary to adapt SET for new objects: coastal macrophytes growing on the banks of the Yenisei flood-plain islands in the near impact zone of Krasnoyarsk Mining and Chemical Combine (KMCC). In the first version of SET, 20 mM Na₂EDTA was used as a reagent at the first stage; in the second version of SET, it was 1 M CH₃COONH₄. Four fractions were extracted. Fraction I included elements from the intercellular space and those connected with the outer side of the cell wall. Fraction II contained intracellular elements; fraction III contained elements firmly bound in the cell wall and associated structures; fraction IV contained insoluble residue. Adaptation of SET has shown that the first stage should be performed immediately after sampling. Separation of fractions III and IV can be neglected, since the output of isotopes into the IV fraction is at the level of error detection. The most adequate version of SET for terrestrial vascular plants is the version using 20 mM Na₂EDTA at the first stage. Isotope ⁹⁰Sr is most sensitive to the technique changes. Its distribution depends strongly on both the extractant used at stage 1 and duration of the first stage. Distribution of artificial radionuclides in the biomass of terrestrial vascular plants can vary from year to year and depends significantly on the age of the plant.

Trace elements in the Fontinalis antipyretica from rivers receiving sewage of lignite and glass sand mining industry

Intensive lignite and glass sand mining and industrial processing release waste which may contain elements hazardous to the aquatic ecosystem and constitute a potential risk to human health. Therefore, their levels must be carefully controlled. As a result, we examined the effects of sewage on the aquatic Fontinalis antipyretica moss in the Nysa Łużycka (lignite industry) and the Kwisa Rivers (glass sand industry). The Nysa Łużycka and the Kwisa Rivers appeared to be heavily polluted with As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn, which were reflected in the extremely high concentration of these elements in F. antipyretica along the studied watercourses. In the Nysa Łużycka, trace element composition in the moss species is affected by lignite industry with accumulation in its tissues of the highest concentrations of Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn, while samples from the Kwisa sites influenced by glass sand industry revealed the highest concentrations of As, V and Fe. The principal component and classification analysis classifies the concentration of elements in the aquatic F. antipyretica moss, thus enabling the differentiation of sources of water pollution in areas affected by mining industry.

Development of a standard protocol for monitoring trace elements in continental waters with moss bags: inter- and intraspecific differences

This paper is a contribution for validating a standard method for trace element monitoring based on transplants and analysis of aquatic bryophytes, in the framework of the EC Directive 2000/60. It presents the results of an experiment carried out to assess significant differences in the amount and variability of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in three moss species (Cinclidotus aquaticus, Fontinalis antipyretica, Platyhypnidium riparioides) and two different parts of the moss (whole plant vs apical tips). Mosses were caged in bags made of a plastic net and transplanted for 2 weeks to an irrigation canal impacted by a waste water treatment plant. Trace element concentrations were measured by inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) before and after exposure to the experimental and control sites in five samples. Enrichment factors >>2 were found for Cu, Ni, Mn, Pb and Zn in all moss species, lower in C. aquaticus, intermediate in F. antipyretica and higher in P. riparioides (the species we recommend to use). The analysis of apical tips after exposure instead of the whole plant led to (I) lower concentrations of As, Co, Cr, Fe and Zn in C. aquaticus (-7 to -30%) and of Fe and Pb (-13, -18%) in P. riparioides, (II) higher concentrations of Cu, Ni and Zn (+14 to +18%) in P. riparioides, while (III) no significant difference (p > 0.05) in F. antipyretica. Data variability after exposure was generally lower in apical tips, especially in C. aquaticus and in F. antipyretica, less in P. riparioides. In the aim of standardizing the moss-bag technique, the analysis of apical tips is recommended.

Effects of lead uptake on microtubule cytoskeleton organization and cell viability in the seagrass Cymodocea nodosa

The effects of lead uptake on microtubule integrity and cell viability in intermediate-juvenile leaf blades of the seagrass Cymodocea nodosa were investigated under laboratory conditions in increasing exposure concentrations (0.1, 0.25, 0.5, 5, 10, 20 and 40mg/L). Uptake kinetics was generally fitted well to the Michaelis-Menten equation. The equilibrium concentration and the velocity of lead uptake tended to increase as the exposure concentration increased up to 5-10mg/L; equilibrium concentration values at most of the treatments were comparable to reported lead concentrations in seagrass leaves. Lead caused a drastic change in the microtubule organization; microtubule depolymerization was observed after 3-7 days of exposure, depending on metal dosage. This observation indicates that microtubule integrity could be utilized as an early biomarker of emerging lead contamination. Cell death starting to occur at later time than microtubule disturbance was also observed at all of the treatments. Microtubule depolymerization expressed as percentage of fluorescence intensity reduction and cell mortality expressed as percentage of dead cells (blue stained) increased with time. Toxic effects were first detected during or at the beginning of the steady state-phase of lead uptake. The lowest experimental tissue lead concentrations associated with the onset of toxic effects (18.33-20.24μg/g dry wt, 0.1-0.25mg/L treatments, 7th day) were comparable to or lower than lead concentrations measured in leaves of C. nodosa and other seagrass species from various geographical areas, probably implying that lead may play a important role in the worldwide decline of seagrass meadows. These lowest tissue concentrations were exceeded up to the 3rd day of incubation at higher exposure concentrations, but microtubule depolymerization at 0.5mg/L and cell death at 0.5-20mg/L were first detected at later time. The time period required for the onset of microtubule depolymerization tended to decrease as lead uptake velocity increased; in particular, a significant negative correlation was found between these variables. These results suggest that the onset of toxicity appears to be related to lead uptake rate rather than to the total tissue lead concentration. Thereby, tissue residues should be interpreted in relation to the time frame of the exposure, while the estimation of metal uptake rate could be utilized for predicting toxic effects. The data presented provide insight on metal uptake kinetics, toxicological effects and their linkage in seagrasses, contribute to a better understanding of metal toxicity on aquatic organisms and could be utilized in biomonitoring programmes for the identification of ecotoxicologically significant metal accumulation in coastal environments.

Moss bags as sentinels for human safety in mercury-polluted groundwaters

An equation to estimate Hg concentrations of <4 μg/L in groundwaters of a polluted area in NE Italy was set out by using transplants of the aquatic moss Rhynchostegium riparioides as trace element bioaccumulators. The equation is derived from a previous mathematical model which was implemented under laboratory conditions. The work aimed at (1) checking the compliance of the uptake kinetics with the model, (2) improving/adapting the model for groundwater monitoring, (3) comparing the performances of two populations of moss collected from different sites, and (4) assessing the environmental impact of Hg contamination on a small river. The main factors affecting Hg uptake in the field were-as expected-water concentration and time of exposure, even though the uptake kinetics in the field were slightly different from those which were previously observed in the lab, since the redox environmental conditions influence the solubility of cationic Fe, which is a negative competitor of Hg(2+). The equation was improved by including the variable 'dissolved oxygen concentration'. A numerical parameter depending on the moss collection site was also provided, since the differences in uptake efficiency were observed between the two populations tested. Predicted Hg concentrations well fitted the values measured in situ (approximately ±50%), while a notable underestimation was observed when the equation was used to predict Hg concentration in a neighbouring river (-96%), probably due to the organic pollution which hampers metal uptake by mosses.

Kinetics of cadmium accumulation and its effects on microtubule integrity and cell viability in the seagrass Cymodocea nodosa

The kinetics of cadmium accumulation and its effects on microtubule cytoskeleton and cell viability in leaf blades of the seagrass Cymodocea nodosa were investigated under laboratory conditions in exposure concentrations ranging from 0.5 to 40 mg L(-1). An initial rapid accumulation of cadmium was followed by a steady state. The Michaelis-Menten model adequately described metal accumulation; equilibrium concentration and uptake velocity tended to increase, whereas bioconcentration factor at equilibrium to decrease, as the exposure concentration increased. Cadmium depolymerized microtubules after 3-9 d of exposure, depending on trace metal concentration, indicating that microtubules could be used as an early biomarker of cadmium stress; cell death, occurring at later time than microtubule disturbance, was also observed. Microtubule depolymerization expressed as percentage of reduction of fluorescence intensity and cell mortality expressed as percentage of live cells increased with time. The lowest experimental tissue concentration associated with the onset of microtubule depolymerization and cell death (98.5-128.9μgg(-1)drywt, 0.5 mg L(-1) treatment, 7th and 9th d) was within the wide range of reported cadmium concentrations in leaves of seagrass species from various geographical areas. This lowest tissue concentration was exceeded up to the 3rd d at higher exposure concentrations, but toxic effects were generally detected at later time. The time periods required for the onset of depolymerization and for 10 and 50% of cells to die tended to decrease as the uptake velocity increased; in particular, significant negative correlations were found between these variables. These results suggest that toxicity appears to be a function of cadmium uptake rate rather than of the total tissue metal concentration. Hence, tissue residues should be interpreted in relation to the time frame of the exposure, while the estimation of metal uptake velocity could be utilized for predicting toxic effects. The data presented provide insight on the relationship between metal bioaccumulation and toxic effects in seagrasses and, overall, contribute to a better understanding of the impact of metals on aquatic organisms.

DGT as surrogate of biomonitors for predicting the bioavailability of copper in freshwaters: an ex situ validation study

The present report is the companion study of our previous study in which we investigated the impact of the dissolved organic matter, water cationic composition and pH on the bioavailability and the bioaccumulation of copper (Cu) in aquatic mosses (Fontinalis antipyretica). The impact had been assessed under laboratory controlled conditions and modelled using a two-compartment model calibrated under a wide range of water compositions (Ferreira et al., 2008, 2009). Herein are reported the validation stage of the abovementioned approach for contrasted geochemical field conditions. Experiments were performed with aquatic mosses that were exposed for 7d to two nominal Cu concentrations (5 and 15μgL(-1)) in a flow-through field microcosm supplied with four contrasting natural waters. At the end of the exposure period, a 6-fold difference in the bioaccumulated Cu contamination levels was found among the four deployment sites, suggesting a significant control of the water quality on the metal bioaccumulation by aquatic mosses. In parallel, the so-called 'labile' Cu concentration for the same four field conditions was determined using a DGT device (Diffusive Gradient in Thin film). By coupling these DGT measurements and a cation competition model involving Ca(2+), Mg(2+), Na(+) and H(+), the time-dependent Cu concentrations in aquatic mosses were predicted; these simulation results were compared to the actual bioaccumulation of Cu in mosses. We found that any bioaccumulation model that ignores water characteristics is not suitable to predict the Cu accumulation by aquatic mosses under various water quality conditions. Instead, we found that our approach integrating DGT measurements and cationic composition was able to reproduce the Cu bioaccumulation kinetics by aquatic mosses for a wide range of water quality conditions. In conclusion, the DGT approach was demonstrated to be a dynamic in situ measuring technique that can be used as a surrogate of bioindicators if the cationic correction is taken into account.

Cellular location of K, Na, Cd and Zn in the moss Pseudoscleropodium purum in an extensive survey

The aim of the present study was to determine if use of the Sequential Elution Technique (SET) improves interpretation of data on the total concentrations of elements in the moss Pseudoscleropodium purum, obtained in a regional network, by providing information about the cellular location, bioavailability and temporal representativeness of different elements. In total, 147 sites located at the vertices of a 15×15 km network were sampled. The total, extra- and intracellular concentrations of K, Na, Cd and Zn were determined and the spatial structure was analysed by use of robust variograms. The percentage of intracellular K was high (85%) compared with that of the extracellular K (15%), whereas those of the extra and intracellular Na and Cd were similar, both close to 50%. Zinc comprised a higher percentage of extracellular metal (61%). Spatial structure was clearly observed in both the total and intracellular concentrations of Na and in the total and extracellular concentrations of Zn. These results demonstrated that use of the SET improves interpretation of the total concentrations of elements, with differences between the elements that are metabolically regulated and those that possibly are not. Despite problems regarding particles deposited on the moss surface, the extracellular concentration of elements may provide information about the potential risks associated with possible solubilization of these particles and their posterior absorption. However, the intracellular concentration, which is not influenced by the presence of particles on the moss surface, provides more realistic toxicological information, as it may be related to metabolic processes in the moss. We therefore recommend prioritizing the use of the intracellular fraction when using mosses in environmental monitoring networks.

S.TR.E.A.M., system for trace element assessment with mosses. An equation to estimate mercury concentration in freshwaters

Hundred experiments of Hg bioaccumulation with the aquatic moss Rhynchostegium riparioides (Hedw.) C.E.O. Jensen transplanted under laboratory conditions were carried out with the aim of (1) measuring the metal uptake at increasing water concentrations (0.25-128 microg Hg(2+)L(-1)) and increasing exposure time (24-189 h), (2) studying the influence of pH (6.3-8.5) and water concentration of Na (3-114 mg L(-1)), Ca (62-125 mg L(-1)) and Mg (13-54 mg L(-1)) on the metal uptake, (3) achieving a database for mathematical and statistical elaborations, and, (4) producing an equation modelling the uptake. A linear uptake was observed for water concentrations <or=4 microg Hg(2+)L(-1), while a saturation curve was observed at higher concentrations. Uptake followed a 3-stage trend for increasing exposure times: a phase of rapid accumulation (4-5d), followed by an equilibrium plateau (2-3d) and then by a second accumulation phase. The factor influence study revealed that variations in pH or water concentration of alkaline metals, within the range of typical values in freshwaters of NE Italy, did not produce significant differences (p>0.05) in the Hg uptake ratio (0.496x10(5)<or= Bio Accumulation Factor <or= 1.73x10(5)). From a database of 28 Hg concentrations in mosses exposed to 0.25-4 microg Hg(2+)L(-1) for 24-114 h, a mathematical equation was produced, to assess Hg micro-contamination in water. The difference between predicted and real concentration was generally included in the range+/-50%.

Induction of oxidative stress biomarkers associated with heavy metal stress in Fontinalis antipyretica Hedw

The aquatic bryophyte Fontinalis antipyretica Hedw. was exposed to different heavy metals (Cd, Cu, Pb, Zn) at 0, 0.1, 1, 10, 100 and 1000muM concentrations. Lipid peroxidation and anti-oxidative responses in apices were evaluated after 2 and 7 days of exposure. Most treated plants showed increased levels of lipid peroxidation and enzyme activities (superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GRD), ascorbate (APX) and guaiacol (GPX) peroxidases, compared to control (untreated) plants. Most of our results suggest that plants possess antioxidant enzymes which operates either unspecifically (SOD and APX) or depending on the nature of the contamination (CAT, GPX, GRD). However, for the highest metal concentration tested, these cellular defence systems seemed overwhelmed since MDA levels increased significantly. These results confirm the important role of antioxidant defences in the mechanisms of plant-resistance to heavy metal stress. Moreover, two types of concentration-response trends were identified: clear monotonous relationships were often found for SOD and MDA while bell-shaped trends were usually observed for APX, GPX and GRD. These tendencies are discussed with emphasis on possible use of these responses as plant biomarkers for freshwater biomonitoring surveys.

Modelling exchange kinetics of copper at the water-aquatic moss (Fontinalis antipyretica) interface: influence of water cationic composition (Ca, Mg, Na and pH)

The present study investigated the effect of water cationic composition (Ca, Mg, Na, pH) on the bioaccumulation and elimination rates of copper by an aquatic moss (Fontinalis antipyretica), under laboratory conditions. For this purpose, mosses were exposed to copper at an environmentally relevant and usually non-toxic concentration (5 microg L(-1)) in natural waters where cationic composition and concentrations were varied. To describe copper bioaccumulation by aquatic mosses, a two-compartment model was the first-order kinetics, was developed and calibrated under a wide range of water cationic composition. Bioaccumulation rates of Cu in mosses were significantly reduced as the concentrations of competitive cations in solution increased. Hence, in hard-water, Ca and Mg cations play a protective role as they compete with Cu2+ ions for the absorption on transport sites at the organism-water interface. Based on the relationships between each major cation concentration and the exchange kinetics on mosses, the binding constants (K(Ci)(BL)) of each competing cations to the biological surfaces were derived. Using the present cationic-dependent kinetic model, it is now feasible to incorporate water cationic composition in the (re)interpretation of bryophytes contamination levels and in the (re)definition of Water Quality Criteria (WQC) as illustrated through two selected examples of biomonitoring programmes. In the framework of future national water quality guidelines revisions, a such flexible and mechanistic biomonitoring tool (integrating the protective effects of competing cations) may greatly improve the ability of regulators to derive site-specific Cu (metal) guidelines for protecting aquatic biota, while limiting the use of conservative assumptions.

A factor influence study of trace element bioaccumulation in moss bags

Moss bags of Rhynchostegium riparioides were exposed to different water concentrations of 11 trace elements under laboratory conditions, according to a saturated fractional factorial design (67 treated combinations), with the aim of measuring (1) element uptake and (2) the main effects and first-order interactions of influent factors. Bioaccumulation was directly proportional to water concentration, but the uptake ratio (ranging from 10(2) to 10(5)) also depended on the concentration of other metals. The highest uptake ratios were observed for Al, Cu, Cr, Hg, and Pb. The multiple regression model showed that interactions among elements exist and induce both antagonism (Fe is the most frequent competitor) and synergism (Cr exerts a great influence on Pb and Zn uptake). Interactions might be relatively strong (as for As, Cr, and Pb) or weak (Cd and Hg). This evidence should be taken into consideration in biomonitoring surveys of industrial sites, where effluents release more than one contaminant.

Hydroxycinnamic acid derivatives in an aquatic liverwort as possible bioindicators of enhanced UV radiation

We examined, under laboratory conditions, the physiological responses of the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia to artificially enhanced ultraviolet (UV) radiation for 82 days, especially considering the responses of five hydroxycinnamic acid derivatives. This species lives in mountain streams, where it is exposed to low temperatures and high UV levels, and this combination is believed to increase the adverse effects of UV. Enhanced UV radiation hardly caused any change in several physiological variables indicative of vitality, such as Fv/Fm and chlorophylls/phaeopigments ratio (OD430/OD410). Thus, this liverwort seemed to be tolerant to UV radiation, probably due to the accumulation of three UV-absorbing hydroxycinnamic acid derivatives: p-coumaroylmalic acid, 5''-(7'',8''-dihydroxycoumaroyl)-2-caffeoylmalic acid, and 5''-(7'',8''-dihydroxy-7-O-beta-glucosyl-coumaroyl)-2-caffeoylmalic acid. These compounds might serve as bioindicators of enhanced UV radiation.

Biomonitoring: an appealing tool for assessment of metal pollution in the aquatic ecosystem

Wide occurrence of aquatic metal pollution has caused much attention. Biomonitoring offers an appealing tool for the assessment of metal pollution in aquatic ecosystem. The bioindicators including algae, macrophyte, zooplankton, insect, bivalve mollusks, gastropod, fish, amphibian and others are enumerated and compared for their advantages and disadvantages in practical biomonitoring of aquatic metal pollution. The common biomonitoring techniques classified as bioaccumulation, biochemical alterations, morphological and behavior observation, population- and community-level approaches and modeling are discussed. The potential applications of biomonitoring are proposed to mainly include evaluation of actual aquatic metal pollution, bioremediation, toxicology prediction and researches on toxicological mechanism. Further perspectives are made for the biomonitoring of metal pollution in aquatic ecosystem.

Testing the use of juvenile Salmo trutta L. as biomonitors of heavy metal pollution in freshwater

Individual specimens of Salmo trutta were captured, from four sampling sites in Galician rivers (NW Spain) affected by different types of contamination: diffuse urban waste, run-off from an unrestored dump at a copper mine and waste from a fish farm. The ages of the captured trouts were established and only those belonging to the 1+ age class were selected for study. The liver and kidney were removed from each fish and analysed to determine the tissue concentrations of Cu, Fe and Zn. The results obtained showed that: (i) the use of 1+ individuals allowed differentiation of contamination scenarios on the basis of the tissue concentrations of metal; (ii) the use of 1+ individuals allowed standardization of the time of exposure, which was sufficiently long for differential uptake to have taken place; (iii) liver tissue provided the best results as, less effort was required than for processing kidney tissue, and significant differences between sampling sites were detected because the intrapopulational variability in metal levels was lower than for kidney, and (iv) the levels of elements detected were not affected by basal tissue concentrations or residual concentrations due to past contamination, which older trouts may have been exposed to. In addition, the use of 1+ trout may provide better results in annual environmental sampling surveys.

Sulphate toxicity to the aquatic moss, Fontinalis antipyretica

The aquatic moss, Fontinalis antipyretica was exposed to elevated sulphate concentrations for 21-days. Gametophores were sectioned to 2 cm lengths and exposed to sulphate concentrations up to 1500 mg/l, in waters of different water hardness. Significant reductions in shoot length, dry weight, and chlorophyll a and b concentrations (per gram dry weight) were observed in soft water (19 mg/l as CaCO3); however, effects were significantly reduced in waters of increasing hardness (up to 105 mg/l as CaCO3). The substantial reduction of sulphate toxicity in waters of increasing hardness suggests water chemistry plays a significant role in affecting sulphate toxicity and should be considered when setting sulphate discharge limits.