Bioindicator Of Metal Contamination Research Articles

Metal tolerance in enterococci isolated from seabirds in Abrolhos Archipelago, Brazil: Evaluating their role as bioindicators of marine pollution

Microbiota exposed to pollution provide insights into host physiology and ecosystem disruption. This study evaluated Enterococcus spp. tolerant to arsenic (As), copper (Cu), and mercury (Hg) from red-billed tropicbirds (Phaethon aethereus) and brown boobies (Sula leucogaster), which previously showed these metals in their blood and feathers, and their potential use as bioindicators of metal contamination. Enterococcus casseliflavus (47.9 %), E. faecalis (34.1 %), E. hirae (11.7 %), and E. faecium (5.3 %) were identified. Both seabird species had a high incidence of As-tolerant bacteria (84.0 %), with 40.4 % of these strains containing As efflux system genes (arsA_I and arsA_II). Cu efflux pump gene (tcrB) was detected in 30.9 % of strains, while Hg reductase genes (mer) were not found. As- and Cu-tolerance in enterococci observed in this study underlines their potential as bioindicators in metal-polluted marine environments. Further research may elucidate the role of these metal-tolerant enterococci in seabird gut and their adaptability to polluted environments.

Understanding the detrimental effects of heavy metal pollution in shrimp farming and treatment methods – a review

Abstract High levels of heavy metals in the environment pose a significant risk to the aquatic ecosystem and its organisms. The non-biodegradable nature and lengthy persistence of heavy metals in the environment lead to toxicity in shrimp. Using aquatic animals as bio-indicators of metal contamination provides valuable data on acute and chronic toxicity in aquatic species and environmental quality. This review aims to provide insights into the sources, impacts, diseases and mitigation strategies related to heavy metal pollution in shrimp farming and the dangers to humans. Shrimp growth and development at each stage exhibit distinct responses to toxicity, which can vary depending on the species, types of metals, their mechanisms of action, as well as the concentration of heavy metals and duration of exposure. While several heavy metals are considered essential nutrient elements that enhance shrimp growth and feed efficiency, exceeding the maximum tolerable limit threatens shrimp health, human consumers, and ecological systems’ stability. Shrimp species subjected to lethal toxic metal concentrations experience significant effects on accumulation in histopathology. Heavy metal toxicity has been linked to high mortality rates, malformation rates, oxidative stress, moulting issues, and decreased reproduction with increasing concentrations in shrimp. Various methods have been reported for removing heavy metal ions from aquatic environments, including filtration, adsorbents, removal efficacy, operating conditions, and the pros and cons of each technique. Therefore, this review provides an overview of how heavy metals can affect shrimp physiology and dangers to consumers. It aims to increase awareness about the importance of preventing and regulating their contamination in aquatic environments.

Butterflies as bioindicators of metal contamination

Anthropogenic trace metal contamination has significantly increased and has caused many hazardous consequences for the ecosystems and human health. The Terni basin valley (Central Italy) shows a heavy load of pollutants from industrial activities, while the characteristic orography structure of the valley favours air stagnation, thus limiting air pollution dispersal. The present study conducted in 2014 aimed to determine the concentration of ten metals in five species of butterflies at nine sites in the Terni valley along a 21-km-long transect, including both relatively pristine and industrial areas. At sites where soil contamination was high for a given metal, such as for chromium as in the case of site 4 (the closest to the steel plant) and for lead as in the case of site 2 (contaminated by a firing range), higher levels of contamination were observed in the tissues of butterflies. We found a correlation between soil contamination and the concentration of Cr, Al and Sr in the tissues of some species of butterflies. The sensitivity to contamination differed among the five species; in particular, Coenonympha pamphilus was generally the species that revealed the highest concentrations of all the ten trace metals at the sites closer to the industrial area. It is known that C. pamphilus is a sedentary species and that its host plants are the Poaceae, capable of accumulating high quantities of metals in their rhizosphere region, thus providing the link with soil contamination. Therefore, monitoring the metal concentration levels in butterflies might be a good indicator and a control tool of environmental quality, specifically in areas affected by high anthropogenic pollution loads linked to a specific source.

Metal bioaccumulation in stygophilous amphipod Synurella ambulans in the hyporheic zone: The influence of environmental factors

Given the increasing need to protect vulnerable freshwater ecosystems and make them more resilient to human use and climate change, biomonitoring of the hyporheic zone (HZ), which plays a critical role in pollution attenuation, is essential. The aim of the present study was to assess the potential of the amphipod species Synurella ambulans as a bioindicator of metal contamination in the HZ of the Sava River (Croatia). Amphipods were collected during the four seasons at two sampling sites (average sampling depth 55 cm) differing in type (agricultural and urban) and intensity (diffuse and point source contamination) of anthropogenic influence, one located upstream (Medsave), and the other downstream (Jarun) of the wastewater treatment plant discharge. Concentrations of Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Rb, Sn, Zn, Ca, K, Mg and Na were measured in the interstitial water, sediments and specimens of S. ambulans by HR ICP-MS. Physicochemical parameters (temperature, DO, O2 saturation, pH, conductivity, alkalinity, total water hardness, CODKMnO4, nutrients) were measured in the interstitial water, while organic carbon was measured in the interstitial water and sediments. Metal concentrations in interstitial water and sediments were below thresholds set by environmental quality standards. Metal concentrations in S. ambulans were classified as follows: higher at the Jarun site (Al, Cr, Fe, Ni, Pb, Sn), higher at the Medsave site (Cd, Cu, Rb) and mostly comparable at both sites (Co, Mn, Zn). Bioaccumulation factors were generally higher at Jarun, with average values ranging from 322 to 143,278 L kg−1. Bioaccumulation of metals in S. ambulans depended on various environmental factors, with metal exposure level and dissolved macro elements showing the strongest association with metals accumulated in S. ambulans. The findings provided the first evidence on the suitability of S. ambulans as a good bioindicator of chronic metal contamination in the HZ.

Trends and Health Risk of Trace Metals in Fishes in Liaodong Bay, China, From 2015 to 2020

Due to their toxicity, non-biodegradability, and biological amplification in the food chain, heavy metal accumulation in humans via the consumption of fishes has become a problem. In this study, we analyzed the concentrations of six trace metals (Cd, Cr, Cu, Ni, Pb, Zn) in 12 marine fish species collected from Liaodong Bay, China, from 2015 to 2020, to understand the pollution status of the bay and evaluate the impact of fish consumption on human health. In addition, 5 fish species with the potential to serve as bioindicators of metal contamination were identified. In general, the average concentrations were Zn > Pb ≈ Cr > Ni ≈ Cu > Cd. There were significant differences in the concentrations in the muscle tissues of fish with different feeding strategies. The total target hazard quotient values of some fish were greater than 1 in 2015, suggesting that people were susceptible to high health risks. The year 2017 had the lowest values, which suggests that metal pollution in Liaodong Bay may have been decreasing at that time. Monitoring of metal concentrations in marine fish from Liaodong Bay warrants more study.

Catalase Activity in Response to Metals in Freshwater Fish Catla catla

Catalase activity in response to binary metal mixture of Zn + Ni was studied in gills, hepatic, renal and cardiac tissues of Catla catla. A total of 30 fish fingerlings were kept in two glass aquaria (15 in controlled condition and 15 in metal mixture containing aquarium) for the period of two weeks. After the completion of the trial period, fish were dissected for different organ collection. The extracted organs were homogenized in phosphate buffer (50 mM; pH 7.0). The activity of catalase was determined by absorption at 240 nm by using the standard methods. The inferences showed higher catalase activity in liver (223.33 ±1 UmL-1), kidney (163.33 ± 0.7 UmL-1), gills (123.33 ±0.9 UmL-1) and cardiac (120 ±3 UmL-1) tissues of Zn + Ni treated fish in comparison to controlled fish liver (116.66 ±2 UmL-1), kidney (101.66 ±1 UmL-1), gills (96.66 ±0.66 UmL-1) and cardiac tissues (70 ±0.33 UmL-1) in this study. Statistically, significant differences at p ≤ 0.05 was observed for catalase activity between Zn + Ni stressed and control fish groups. While, in different organs of both group of fishes the catalase activity order was observed as hepatic > renal > gills > heart. Findings of this study would be helpful in monitoring aquatic ecosystems using fish antioxidant system which acts as a bio-indicator of metal contamination.

Little egret (Egretta garzetta) as a bioindicator of heavy metal contamination from three different localities in Egypt.

This work aimed at using Little Egrets (Egretta garzetta), for the first time in Egypt, as a bioindicator of heavy metal contamination from three different Egyptian land use types (Qillin within Kafr El-Sheikh (S1, agricultural), Toukh within Qalyubia (S2, semi-rural area), and Abu Rawash within Giza (S3, urban)). Concentrations of aluminum (Al), barium (Ba), cobalt (Co), cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), iron (Fe), nickel (Ni), lead (Pb), and zinc (Zn) were analyzed in liver and kidney samples of twenty-six adult Little Egrets collected from the three localities during winter 2018. Moreover, the study calculated the Metal Pollution Index (MPI) to highlight the health of the surrounding environment using birds' internal organs as a mirror. Results revealed that, throughout the three sampling sites, the total metal concentrations in liver samples exceeded that of the kidney, indicating that the liver is the target organ of metal accumulation. The Little Egret's liver was found to be the best-recommended organ to use in future biomonitoring of Cu, Zn, Fe, Mn, and Ni, whereas Al, Co, Cr, Ba, Pb, and Cd can be monitored in the kidney. Cu and Pb were higher in the Little Egret's tissues collected from the agricultural site (S1), whereas Ba, Ni, and Fe were higher in the semi-rural site (S2), followed finally by Cd in the urbanized site (S3). The concentrations of trace elements reported in Little Egrets were within the known background level for water birds. However, alarming concentrations were found for Ni levels in liver (from Qillin and Toukh), as well as Pb and Cr levels in kidney samples (from the three localities). MPI of the eleven studied metals in both liver and kidney of the studied species decreased in the order Qillin (24.36) > Abu Rawash (17.98) > Toukh (3.90). In the three investigated localities, the overall calculated MPI values were higher than one, indicating that the ecosystem is polluted. The study suggested using Little Egrets as a bioindicator of metal contamination.

Higher plants as bioindicators of metal contamination from Shangdong abandoned karst bauxite, southwestern China.

Bauxite mining on karst generates numerous ecological and environmental problems, including metal pollution, water and soil erosion and destruction of vegetation. Among these, the most important environmental problem is soil metal pollution. Higher plants have a great ability to adsorb metals and can be used as biological indicators. However, the study of bioindicators for soil contamination in karst bauxite is not clear. Plants and their soil were collected from an abandoned karst bauxite area at Shangdong, Guizhou Province, southwestern China. Plants were collected and identified as Pteris vittata, Pinus massoniana, Miscanthus floridulus, Coriaria nepalensis, Artemisia argyi and Senecio scandens. The content of metals in plant roots were in the order: P.vittata>M.floridulus>C.nepalensis, other plants roots had no consistent pattern. Concentrations of metal in plants (P.vittata and M.floridulus) and soil were: soil > root > leaf > stem. Levels of metals in soil samples easily exceeded background values, indicating that soil had been contaminated. Al and Fe were highest in soil samples of P.vittata, with a good correlation. Results show that the metal content determined in plants is relatively high, particularly in P.vittata. Data also suggest that P.vittata colonies were able to tolerate and accumulate high levels of metal elements, which evidences their suitability for use as bioindicatord of soil metal contamination caused by mining activities.

Helix aspersa as sentinel of development damage for biomonitoring purpose: A validation study.

Environmental health has always been threatened by the bioaccumulation of heavy metals in the terrestrial ecosystem, affecting its quality and safety. The aim of this review is to investigate the effects of heavy metal soil contamination, using the land snail Helix aspersa as a bioindicator. H. aspersa, a common species of land snail present in the area, has been used as a bioindicator of metal contamination and represents a promising ecological indicator. Various land snails species have become popular in microcosm studies because they accumulate high concentrations of certain trace metals. They express contamination as a whole through ingestion of polluted foods, such as live plants, microorganisms, soil, and water and also through cutaneous contact and from the polluted air they breathe. Land snails are considered appropriate sentinel species because trace metals tend to accumulate in their digestive gland to allow biomonitoring of metal pollution. Different experiments demonstrate that exposure in areas chronically polluted with metals, especially with lead, often causes changes in reproduction, with a variation in the mineral composition in the snail's eggs and also in its development, due to increased energy expenses associated with detoxification and the excretion process.

Multi-biomarkers approach to the assessment of the southeastern Mediterranean Sea health status: Preliminary study on Stramonita haemastoma used as a bioindicator for metal contamination

The present study aimed to evaluate the responses of different biochemicals parameters associated with environmental pollution in the digestive gland of the gastropod mollusc Stramonita haemastoma. Physiochemical parameters and trace metal elements (Copper (Cu), Zinc (Zn), Chromium (Cr), Cadmium (Cd) and Lead (Pb)) were measured in seawater. Spatiotemporal variations in reduced glutathione (GSH), malondialdehyde (MDA) and metallothionein (Mt) as well as the specific activities of glutathione S-transferase (GST) and catalase (CAT) were evaluated in digestive gland of this species during a one-year period in 2013–2014. Samples collection was conducted at three sites. The results obtained showed seasonal fluctuations in GST and CAT activities and in the rate of Mt content. In addition, intersite variations in GSH, MDA, Mt and CAT were recorded in individuals. Also, trace metal elements concentrations determined by season in the digestive gland revealed spatial and temporal variations for Cu and Zn but they are below the limit of detection for Cd and Pb. The highest values were generally recorded in spring for Cu and in winter for Zn. In this first regional study using in S. haemastoma as a model, the biomarkers measured were seen to be inducible parameters to evaluate the health state of the organism and the overall quality of the study sites.

Metals in Racomitrium lanuginosum from Arctic (SW Spitsbergen, Svalbard archipelago) and alpine (Karkonosze, SW Poland) tundra.

Arctic-alpine tundra habitats are very vulnerable to the input of relatively small amounts of xenobiotics, and thus their level in such areas must be carefully controlled. Therefore, we collected the terrestrial widespread moss Racomitrium lanuginosum (Hedw.) Brid. in Spitsbergen in the Arctic moss lichen tundra and, for comparison, in the Arctic-alpine tundra in the Karkonosze (SW Poland). Concentrations of the elements Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Na, Ni, Pb, V, and Zn in this species and in the parent rock material were measured. We tested the following hypothesis: R. lanuginosum from Spitsbergen contains lower metal levels than the species from the Karkonosze collected at altitudes influenced by long-range transport from former Black Triangle industry. Principal component and classification analysis (PCCA) ordination revealed that mosses of Spitsbergen were distinguished by a significantly higher Na concentration of marine spray origin and mosses of Karkonosze were distinguished by significantly higher concentrations of Cd, Cr, Cu, Fe, Hg, Li, Mn, Pb, V, and Zn probably from long-range atmospheric transport. The influence of the polar station with a waste incinerator resulted in significantly higher Co, Li, and Ni concentrations in neighbouring mosses in comparison with this species from other sites. This investigation contributes to the use of R. lanuginosum as a bioindicator for metal contamination in Arctic and alpine tundra regions characterised by severe climate habitats with a restricted number of species. This moss enables the control of pollution usually brought solely by long-range atmospheric transport in high mountains as well as in Arctic areas.

Benthic foraminiferal assemblages as bio-indicators of metals contamination in sediments, Qarun Lake as a case study, Egypt

Qarun Lake, in the Fayoum Depression of the Western Desert of Egypt, lies within the deepest area in the River Nile flood plain. The drainage water in the Qarun Lake is derived from the discharge of the natural and artificial drainage systems in the Fayoum. Mixed domestic and agricultural pollutants, including heavy metals, nitrates, phosphates, sulfates and pesticides, are discharged into Qarun Lake. Forty-six samples, collected from the undisturbed layer of sediments were used for benthic foraminiferal analysis. Concentrations of some selected trace metal elements (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, V, and Zn) were also determined. Statistical analysis of the abiotic variables (Texture distribution of sediments, Physico-chemical parameters, and metals concentrations) and of the biotic variables (distribution of benthic foraminiferal species) were also performed. The Q-mode cluster analysis of benthic foraminiferal distribution has provided evidence that the Qarun Lake can be subdivided into two cluster groups (A and B), reflecting environmental changes in the lake ecosystem. Cluster B can also be subdivided into two sub-clusters (B1 and B2). The presence of only pollution tolerant taxa with higher faunal density and lower diversity and the absence of the other foraminiferal assemblages in cluster A were attributed to the high concentration of trace metal elements and the strong environmental stress at the eastern and central parts of the Qarun Lake.

Odonata larvae as a bioindicator of metal contamination in aquatic environments: application to ecologically important wetlands in Iran

The objectives of this study were twofold: (i) assess the bioaccumulation characteristics of a suite of metals associated with several different species of Odonata and (ii) examine Odonata species richness as a reflection of ecosystem health in two ecologically important wetlands of southwestern Iran, the Shadegan and Hawr Al Azim wetlands. Levels of arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), manganese (Mn), lead (Pb), and zinc (Zn) were determined using inductively coupled plasma optical emission spectrometry (ICP-OES) in nine different Odonata larva species. Based on these data, biota-sediment accumulation factors (BSAFs) were calculated and generally, it was found that Cr, Cu, Mn, and Zn were being taken up by the Odonata (BSAFs >1). Because of its prevalence in the wetland and its observed ability to take up metals, it is suggested that Ischnura ramburii is an appropriate indicator of ecosystem health for these wetlands with respect to metal contamination. Odonata species richness across all sites was 49, while for the individual sites, the greatest species richness was 26 and the lowest species richness was 13. The species richness value across all sites is quite healthy, given the arid climate of the region.

Oxidative and cellular stress as bioindicators for metal contamination in freshwater mollusk Lamellidens marginalis.

The concentrations of 14 metals, namely, chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), selenium (Se), arsenic (As), strontium (Sr), cadmium (Cd), tin (Sn), antimony (Sb), mercury, (Hg), and lead (Pb), have been studied in freshwater mollusk Lamellidens marginalis collected from Dhimbe reservoir. In addition, also studied the cellular and antioxidative status to assess metal contamination as pollution biomarkers. The levels of all the 14 metals were elevated in different sampling sites of Dhimbe reservoir. The level of metals in the L. marginalis was followed as Mn>Zn>Ni>Sr>Cr>Cu>Hg>Se>Sn>Pb>As>Co>Cd>Sb. The oxidative biomarkers viz. catalase (CAT), superoxide dismutase (SOD), and glutathione-S-transferase (GST); glycolytic enzymes viz. lactate dehydrogenase (LDH) and malate dehydrogenase (MDH); and protein metabolic enzymes viz. aspartate amino transferase (AST), alanine amino transferase (ALT), and lipid peroxidation (LPO) were significantly (p<0.01) higher, while neurotransmitter enzymes such as acetylcholine esterase (AChE) were significantly inhibited in muscle of L. marginalis (p<0.01) collected from different sampling sites. Therefore, based on our results, we could recommend that the Dhimbe reservoir is moderately metal contaminated and investigation based on biochemical parameters such as antioxidative enzymes, cellular biomarkers, and AChE are strong indicators for metal contamination; hence, these parameters are successfully applied as reliable biomarkers for monitoring contaminated freshwater ecosystems.

Contracaecum sp. parasitizing Acestrorhynchus lacustris as a bioindicator for metal pollution in the Batalha River, southeast Brazil

Pollution in aquatic ecosystems due to negative human activities remains a problem in both freshwater and marine environments and is an ongoing subject of research. Several studies have shown that some fish parasites can be used as a tool for biomonitoring because they demonstrate higher metal accumulation capacity compared to their host tissues. However, compared to acanthocephalans, information regarding the absorption mechanisms and accumulation rates in nematodes is relatively limited. Here, we evaluated the potential of larvae Contracaecum sp. (L3) as indicators of contamination by metals by analyzing thirteen element concentrations: magnesium (Mg), aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), barium (Ba), and lead (Pb) in the parasites and host Acestrorhynchus lacustris, using inductively coupled plasma mass spectrometry. Twelve of the thirteen analyzed elements were detected in at least 2-fold higher concentrations (e.g. Ni) and were up to approximately 50-fold higher (e.g. Pb) in parasites than in host tissues, including elements known for their high toxicity (As, Cd, Pb) and those considered to be essential (Cu and Zn). Our results suggest that Contracaecum sp. larvae can be used as bioindicators of metal contamination because even in early stages of development, numerous essential and non-essential elements were accumulated, making this system a useful tool for monitoring polluted environments.

Bioaccumulation, oxidative stress and cellular damage in the intertidal gastropod Bembicium nanum exposed to a metal contamination gradient

The high concentration of population and industry in coastal areas leads to contamination. In situ biomonitors provide a reliable and cost-effective means of assessing the effects of contamination. Rigorous assessment of biomonitors is required to establish links between biomarker measurements and contamination in the environment. The aims of the present study were to assess the effects of metal contamination on the intertidal gastropod Bembicium nanum and to validate biomarkers for use in this species. B. nanum was sampled from a metal contamination gradient emanating from Port Kembla (NSW, Australia). Tissue metal concentrations were related to the condition of organisms as assessed using the biomarkers total antioxidant capacity, lipid peroxidation and lysosomal destabilisation. Total tissue metal concentrations were highest in Port Kembla organisms, with copper contributing 56% of metals measured in organisms from this site. B. nanum from Port Kembla also had significantly higher lysosomal destabilisation, being 36% higher than Kiama and 80% higher than Shellharbour over the combined sampling times. Lysosomal destabilisation was related to total tissue metal concentration and Cu tissue concentration. The results of the present study establish B. nanum as a bioindicator of metal contamination, with effects primarily relating to copper, and support previous work on the species as an effective biomonitor of bioavailable metal.

Copper uptake and copper-induced physiological changes in the marine alga Cladophora prolifera (Roth.) Kütz. (Chlorophyta, Ulvophyceae)

Green algae of the genus Cladophora have been reported as being bioindicators of metal contamination all over the world. The degree of total as well as intracellular copper (Cu) uptakes by the alga after 24-h prolonged exposure with 0 (control), 50 and 500 µM Cu doses, was compared with selected physiological markers. Increased intracellular Cu content in the Cladophora thalli was followed by decreased potassium (K) content, alteration of assimilation pigments composition, decreased integrity of chlorophyll a and its fluorescence. Increase of intracellular Cu was followed by the increases of TBARS and superoxide contents. While K content, chlorophyll a/b, chlorophyll a fluorescence and TBARS contents in C. prolifera were significantly altered as result of the lowest, 50 µM Cu dose tested, levels of chlorophyll a + b and soluble proteins did not change even after application of the 500 µM Cu dose.

Evaluation of the use of Leptodactylus ocellatus (Anura: Leptodactylidae) frog tissues as bioindicator of metal contamination in Contas River, Northeastern Brazil.

This paper presents a study on the viability of the use of tissues of the Leptodactylus ocellatus species (Anura Leptodactylidae) as a bioindicator of metal pollution. The study is based on the determination and correlation of the concentrations of manganese, chromium, zinc, nickel, copper and iron in sediments and tissues (skin, muscles and viscera) of the frog Leptodactylus ocellatus collected in the middle region of the Contas River in Bahia, Brazil. The highest levels of the metals studied were found in the viscera of this animal. In this tissue, a higher correlation of the concentration of these metals with those found in sediments was also observed. The concentrations of elements found in the skin and muscles of these amphibians have revealed no correlation with the sediment where they were collected. According to the results obtained, the viscera of the L. ocellatus species presents itself as a good bioindicator of contamination by the metals studied.

Metal accumulation and oxidative stress responses in Ulva spp. in the presence of nocturnal pulses of metals from sediment: A field transplantation experiment under eutrophic conditions

In aquatic systems under eutrophic conditions, remobilization of metals from sediment to the overlying water may occur. Consequently, adaptive responses of local organisms could result from the accumulation of metals intermittently released from the sediment. In summer 2007, a field transplantation experiment was performed in the Óbidos lagoon (Portugal) with Ulva spp. comprising three short-term exposures (between 15:30–23:30; 23:30–07:30; 07:30–15:30) during a 24-h period. In each period, Ulva spp. was collected at a reference site located in the lower lagoon (LL) and transplanted to a eutrophic site located at the Barrosa branch (BB), characterized by moderate metal contamination. For comparison purposes, macroalgae samples were simultaneously exposed at LL under the same conditions. Both sites were surveyed in short-time scales (2–4 h) for the analysis of the variability of physical–chemical parameters in the water and metal levels in suspended particulate matter. The ratios to Al of particulate Mn, Fe, Cu and Pb increased during the period of lower water oxygenation at the eutrophic site, reaching 751 × 10−4, 0.67, 12 × 10−4, 9.9 × 10−4, respectively, confirming the release of metals from the sediment to water during the night. At the reference site, dissolved oxygen oscillated around 100%, Mn/Al ratios were considerably lower (81 × 10−4–301 × 10−4) compared to BB (234 × 10−4–790 × 10−4), and no increases of metal/Al ratios were found during the night. In general, algae uptake of Mn, Cu, Fe, Pb and Cd was significantly higher at the eutrophic site compared to the reference site. The results confirmed the potential of Ulva spp. as bioindicator of metal contamination and its capability to respond within short periods. An induction of SOD, an inhibition of CAT and the increase of LPO were recorded in Ulva spp. exposed at BB (between 23:30 and 7:30) probably as a response to the higher incorporation of Mn, Fe and Pb in combination with the lack of dissolved oxygen in the water. Current findings emphasize the importance of assessing, in eutrophic systems, the relationship between the variability of chemical conditions and its repercussions on autochthonous organisms over day–night cycles.

Organ- and species-specific accumulation of metals in two land snail species (Gastropoda, Pulmonata)

In order to evaluate the usefulness of terrestrial gastropods as bioindicators there is a need for studies that simultaneously compare (1) concentrations of metals in reference and polluted plots, (2) species within the same polluted habitat, (3) metal accumulation patterns in different organs and (4) metal accumulation patterns in relation to soil physicochemical properties. This study aims to assess metal accumulation patterns in two land snail species. Instead of analyzing an organism as a whole, investigating the partitioning of metals in different organs can provide information on the actual toxicological relevant fractions. Therefore, concentrations of Ag, Cd, Cr, Cu, Ni and Zn were examined in five different organs of Cepaea nemoralis, as well as in the foot and the body of Succinea putris. Snails were sampled at four polluted dredged sediment disposal localities and three adjacent less polluted reference plots situated along waterways in Flanders, Belgium. Due to the small size and problematic dissection of S. putris only the concentrations in the foot of both species could be compared. For this reason only, C. nemoralis can be described as a better bioindicator species that allows a far more detailed analysis of organ metal accumulation. This study showed that organs other than the digestive gland may be involved in the immobilization and detoxification of metals. Furthermore, pH, soil fractionation (clay %, silt %, sand %) and organic matter, correlate with metal accumulation in organs. However, most often the soil metal concentrations did not correlate with the concentrations found in snail organs. Metal concentrations in organs of both species (1) differed among polluted plots but rarely between polluted and reference plots within a locality, (2) were organ-specific (digestive gland>foot>albumen gland=spermoviduct=ovotestis), (3) were species-specific and (4) depended on the metal type (high Cd and Cu concentrations were observed in the digestive gland and foot respectively). Our study emphasizes that background metal levels should be taken into account when using invertebrates as bioindicators of metal contamination and that bioindicators may show substantial differences in accumulation patterns even if they have a highly comparable ecology.