Overview of trace metal contamination in the Scheldt estuary and effect of regulatory measures

Seasonally, dissolved and particulate metal concentrations in the Scheldt estuary were assessed over a period of 4 years (1995–1998). High quality data were obtained following stringent analytical protocols for each step: sampling, sample treatment, sample storage and analysis. Of the 5 trace metals, Ni showed the most conservative behaviour, while Cd and Cu were clearly transferred from the particulate to the dissolved phase in the middle estuary. A substantial part of the particulate metals entering the estuarine system are lost through sedimentation. General seasonal patterns are the following: lower concentrations in spring and higher ones in winter (sometimes late fall/early winter) for dissolved metals, while in summer a pronounced rise of the longitudinal concentration profile is observed for the particulate metals. A comparison of the trace metal concentrations (dissolved and particulate) at the mouth of the estuary in 1995–1998 with those from 1981 to 1983, reveal reductions between 30 and 58%. Reductions based on direct emission measurements for almost the same period suggest reductions (dissolved + particulate) between 42 and 64%. Biomagnification (BMF) is the accumulation of a compound through the food-chain. It is in our case expressed as the ratio of the metal concentration in the organism (g g^–1, d.w.)/the metal concentration in total suspended matter (g g^–1, d.w.). Almost all BMF-values of Periwinkle, Nereis diversicolor and Macoma balthica (3 bottom organisms in the Scheldt estuary) are negative meaning that these organisms contain less heavy metals than the particulate suspended matter. For all organisms log BMFs for Pb, respectively Ni, are around –1.8, respectively –0.7. For Cd, Periwinkle shows slight enrichment (0.05) and for Cu even more (0.45), while negative values were observed for Nereis diversicolour and Macoma balthica. The latter organisms are more enriched in Zn (–0.09) than Periwinkle (–0.43).     

Use ofEnteromorpha intestinalis (Chlorophyceae) for active biomonitoring of heavy metals in the weser estuary

The present study was planned to assess the validity ofEnteromorpha intestinalis for an active biomonitoring of heavy metals in the Weser estuary. Exposure of cultured algae (active biomonitoring) was carried out in 1987 and 1988, simultaneouslyEnteromorpha spp. was collected from the banks (passive monitoring) in the estuary. Cd, Pb, Ni, Zn and Cu contents of exposed algae were higher than the metal content of collected algae. Metal contents of both collected and field algae varied significantly over space and time. Bioconcentration factors and results of linear regression analysis indicate, that the bioavailability of Cu and Ni varies with regard to the sampling location but cannot be calculated from heavy metal concentration in the water. Due to the different metal and species specific bioavailability, we want to stress the need to monitor contamination of organisms directly. An active biomonitoring usingE. intestinalis will establish a rationale to compare contamination of different estuaries.     

Temporal and spatial trends in heavy metal concentrations in the marine mussel Mytilus edulis from the Western Scheldt estuary (The Netherlands)

Since the first North Sea Conference (1984, Bremen), all countries bordering the North Sea made commitments to reduce discharge of hazardous substances into the North Sea. From Belgium and The Netherlands, large reductions (upto 90) in heavy metal emissions from land-based sources have been reported between 1985 and 2000. Recently, some studies in the Western Scheldt estuary (WS) have shown that total metal concentration in the water, sediments and suspended particles have decreased compared to levels in the 70s. However, data on aquatic organisms is still very limited and it is therefore difficult to confirm whether the reductions in pollution input and generally improving water quality in the WS have a corresponding impact on the levels of heavy metals in aquatic organisms. The current study measured metal concentrations in the soft tissues of mussels, Mytilus edulis (known to be good indicators of environmental metal pollution) during the period 1996–2002. Spatial (salinity and pollution gradients), temporal and seasonal variations were also studied. Results showed a down-stream decreasing trend for the metals studied (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) during all sampling campaigns. There was also a significant seasonal effect on tissue metal concentrations, with a peak observed around spring in both WS and the nearby less polluted Eastern Scheldt (ES). On temporal trends, a clear drop of metals in mussels was observed in the early 80s coinciding with the start of the efforts to reduce chemical pollution input into the North Sea. Since those early reductions, metal concentrations in mussels generally remained unchanged upto mid 90s. However, in recent times metal concentration in mussels have increased significantly, for example Cd in 2002 was almost 10 times the values in 1983 and similar to levels seen during the peak in the 70s. Other metals also increased in the 90s also reaching levels seen in the 70s. As there is no indication of recent increase in metal input into the estuary, we suggest that increased metal concentrations observed in mussels in recent years especially in the upper estuary are most likely a result of changes in physical and chemical speciation and metal bioavailability. Such changes may be caused by changes in some water quality parameters in the estuary (i.e. increased dissolved oxygen, concentration of organic matter), resulting in conditions that favour releases of sediment-bound metals into the water column. The relationship between metal content and season showed very similar annual profiles in the polluted WS and less polluted ES. Thus, seasonal variations in metal concentrations appear to be largely controlled by biological processes, while total body burdens are dependent on environmental levels and bioavailability.     

胶州湾海水、海洋生物体中重金属含量的研究

研究了胶州湾海水、海洋生物体中重金属含量.结果表明,沿岸河口地区海水中重金属污染主要受沿岸工业排放废水的影响;海洋生物体内重金属含量不仅受海水中的重金属含量大小的支配,温度对其也有一定的影响.海洋生物体中重金属含量为底栖生物大于鱼类,以沉积物为主要饵料的杂食性底栖动物内重金属含量大于鱼类;海洋生物对于Cu比其它重金属具有较强的富集能力.     

胶州湾海水,海洋生物体中重金属含量的研究

研究了胶州湾海水、海洋生物体中重金属含量 .结果表明 ,沿岸河口地区海水中重金属污染主要受沿岸工业排放废水的影响 ;海洋生物体内重金属含量不仅受海水中的重金属含量大小的支配 ,温度对其也有一定的影响 .海洋生物体中重金属含量为底栖生物大于鱼类 ,以沉积物为主要饵料的杂食性底栖动物内重金属含量大于鱼类 ;海洋生物对于Cu比其它重金属具有较强的富集能力 .     

Subcellular distribution of accumulated heavy metals in Saccharomyces cerevisiae and Kluyveromyces marxianus

Summary Kluyveromyces spp. have been found to be more efficient than a CUP1^R strain of S. cerevisiae in heavy metal resistance and accumulation. The present study describes the subcellular distribution of the accumulated metals (Ag, Cd, Cu) in S. cerevisiae and K. marxianus. Absorption by insoluble cellular material of the metals appears as the main mechanism of metal accumulation in both organisms.     

Algal bioassays to determine toxicity of metal mixtures

The shortcomings of many established toxicity criteria for metals have resulted from a simplification of bioassays performed with single metals. A more comprehensive approach was needed to diagnose the effects of metal mixtures on aquatic organisms. Using Chlorella, Ankistrodesmus and Scenedesmus as test organisms, we experimented on a number of factors which affected metal toxicity bioassays. These included metal interactions, algal competitions, species sensitivities, the ratio of an excess metal to other metals and nutrient levels. An alternative technique was finally established which involved an evaluation of individual assays of Chlorella and Ankistrodesmus in separate media and a tissue-metal analysis on Chlorella. Chlorella fusca, commonly found in lakes with high metal concentrations, showed high tolerance to mixed-metal solutions, while Ankistrodesmus proved to be very sensitive. By determining the maximum yield ratio between Ankistrodesmus and Chlorella (i.e. the A/Ch ratio) it was possible to compare the toxic strength of harmful metals according to an established standard curve of A/Ch ratio versus mixed-metal concentrations. The levels of tissue-metal analysed in Chlorella also gave some indication as to which metals were responsible for the toxicity.     

Mobility of metals in salt marsh sediments colonised by <Emphasis Type="Italic">Spartina maritima</Emphasis> (Tagus estuary,Portugal)

Chemical associations of Zn, Pb, Cu, Co and Cd were determined using a sequential extraction procedure in sediments colonised by S. maritima in three salt marshes within the Tagus estuary: Rosário, Corroios and Pancas. Concentrations of these metals were also analysed in above- and belowground parts of Spartina maritima, as well as in sediments colonised by the plant. The highest metal concentrations in sediments were found in the marshes near the industrial and urban areas, whereas metal concentrations in plants were not significantly different among sites. This was thought to be a consequence of differences observed in metal bioavailability: Metals in Pancas, the least polluted location, were largely associated to easily accessible fractions for plant uptake, probably as a result of low organic matter content and high sandy fraction in sediments. S. maritima was able to induce the concentration of metals between its roots in the three salt marshes. The results obtained in this study indicate that S. maritima could be useful to induce phytostabilisation of metals in sediments, although the effectiveness to modify chemical associations is highly dependent on existing sediment parameters, and thus different results could be obtained depending on site characteristics. Guest editors: J. Davenport, G. Burnell, T. Cross, M. Emmerson, R. McAllen, R. Ramsay & E. Rogan Challenges to Marine Ecosystems     

Biomonitoring of trace metal contamination in mangrove-lined Brazilian coastal systems using the oyster Crassostrea rhizophorae: comparative study of regions affected by oil, salt pond and shrimp farming activities

The oyster Crassostrea rhizophorae has been used as a biomonitor of trace metal contamination in two Brazilian coastal systems. C. rhizophorae were collected in January 1998 from 15 stations (from 4 coastal inlets (including 1 estuary) and 1 coastal beach) near Macau, Rio Grande do Norte (RN), Brazil, a region affected by the activities of the oil industry and salt manufacture in coastal salt ponds; oysters were also collected in September 1999 from 8 stations in the Curimatau estuary (RN), an estuary becoming increasingly affected by shrimp farming activities. C. rhizophorae is a net accumulator of trace metals and can be used as a biomonitor, the accumulated soft tissue concentrations representing integrated records of bioavailable metal over the life of the oyster. At Macau, significant differences in oyster accumulated concentrations (and hence bioavailabilities to the oyster) of Fe, Zn, Cu, and Mn were found between stations; raised zinc availabilities at the coastal site are in close proximity to oil industry activities but the very high availabilities of Fe, Cu and Mn in the Rio dos Cavalos estuary originate from an unknown source. In the Curimatau estuary, bioavailabilities of Mn, Pb and Cd, but particularly of Cu and Zn, to the oysters are raised at the two most downstream sites, the only sites below the effluent of a large shrimp farming enterprise. The oysters also act as a local food source, and concentrations of Zn, Cu and Pb of some of the oysters are above typical public health recommended limits.     

Metals contents in two fishes of different feeding behaviour in the Lower Paraná River and Río de la Plata Estuary

Cd, Cr, Cu and Pb concentrations were measured in the water and these plus Zn were measured in the diet, muscle and liver of the detritivorous fish Prochilodus lineatus and the omnivorous fish Pterodoras granulosus at two sites (Lower Paraná River and Río de la Plata right margin) located upstream and downstream, respectively, from Buenos Aires, an important source of xenobiotics. Cu and Cr concentrations in water were higher in the Río de la Plata coastal waters, while Cd and Pb were below detection limits. The stomach contents of P. lineatus showed a higher metal content at the estuary, attaining concentrations within the range reported for contaminated sediments. However, metals in fish tissue were not higher at the estuary and, except for Cd in liver, were lower than in the organic fraction of the stomach content. Thus, only Cd was accumulated. The P. granulosus diet was composed mainly of river vegetation debris and clams, Corbicula fluminea, at the estuary. Cd, Cu and Pb in liver were higher at the estuary while only Cu was higher in the diet at this site. The different nature of the diet seems associated with a differential bioavailability of its metal content. P. granulosus accumulates Cu at both sites and Cd at the estuary. Both fishes showed higher metal content in liver than in muscle. Cr in liver was below detection limits. No relation was found between metal content and fish size. Overall, metal content in fish tissues were low, except for Cu in P. granulosus and Cd in P. lineatus, similar to those of uncontaminated sites, suggesting that homeostatic mechanisms prevent metal accumulation.     

Mercury in benthic invertebrates of the Elbe estuary

Hg concentrations in benthic invertebrates of the Elbe estuary were analyzed by atomic absorption spectrophotometry and instrumental neutron activation analysis. In general Hg levels in organisms decreased from the limnic region to the marine environment. Highest Hg levels were found inAsellus aquaticus andRadix balthica taken from the Elbe upstream of Hamburg (0.35 and 0.34 ppm wet weight). The concentrations in gammarid species decreased from 0.20 ppm (limnic region) to 0.02–0.05 ppm (brackish and marine environment). Hg levels in organisms from the brackish region proved to be 0.08–0.16 ppm(Littorina littorea), 0.04–0.09(Crangon crangon) 0.05–0.10(Corophium volutator) and 0.04–0.08 ppm (wet weight)(Nereis diversicolor). Some factors which may influence the heavy metal concentrations in aquatic organisms are discussed, such as: food chain, weight of organisms, and elimination via moulting products in the case of crustaceans.     

调水调沙工程黄河口近岸沉积物重金属和砷含量的空间分布及其生态风险评估

为了明确调水调沙工程长期影响下黄河口近岸沉积物中重金属含量的分布特征及其生态风险,基于2012年黄河口近岸27个站位的表层沉积物样品,通过ICP-MS测定重金属(Zn、Cr、Ni、Pb、Cu、Cd)和砷(As)含量,并运用潜在生态风险指数法(RI)对其进行生态风险评估。结果表明:近岸沉积物中重金属和As的平均含量表现为AsZnCrNiPbCuCd。Cr、Ni、Cu和Pb四种元素的分布规律较为一致,整体呈现出近岸和近黄河口高而远离河口和岸线低的空间分异特征。Ni、Cu、Pb、Zn与粘土均呈极显著或显著正相关(P0.01或P0.05),而Cd、Cr和As与其相关性均未达到显著水平(P0.05)。近岸沉积物中6种重金属和As的平均单项潜在生态风险指数大小顺序整体表现为CdAsNiPbCuCrZn。就潜在生态风险(RI)而言,研究区域18.52%的站位属轻微生态危害,70.07%的站位属中等生态危害,7.41%的站位属强生态危害,Cd和As是造成危害的两种主要元素。近岸沉积物中重金属和As的来源复杂且多样,主要是由于农业化肥使用、海上石油开采和泄漏、化石燃料燃烧以及河口污染物输入所致。对比研究发现,随着调水调沙工程的长期实施,除Cd和As外沉积物中其他重金属含量均呈下降趋势,说明二者的生态风险将会随调水调沙的长期实施呈增加趋势,而其他重金属的生态风险将呈降低趋势,故未来应重点关注近岸沉积物中Cd和As的生态毒理风险。     

Comparing the responses of diatoms and macro- invertebrates to metals in upland streams of Wales and Cornwall

SUMMARY 1. Surprisingly few data compare the apparent responses of diatoms and macroinvertebrates to metals in streams. We examined variation in metals, diatoms and macroinvertebrates between 51 streams in metal‐mining areas of Wales and Cornwall, U.K., using a survey design with multiple reference and polluted sites. 2. To quantify variations in metals between sites, we calculated cumulative criterion unit (CCU) scores, a recently defined measure of total stream metal concentration and toxicity, to account for additive effects of each metal relative to putative toxic thresholds. We compared assemblage responses among epilithic diatoms and macroinvertebrates to CCU scores or individual metal concentrations using correlation and detrended correspondence analysis (DCA). 3. Macroinvertebrate diversity, richness and total abundance declined and evenness increased with increasing copper concentrations. Trends with CCU scores were significant but less pronounced. Some individual macroinvertebrate taxa varied significantly in abundance with CCU scores, copper or zinc, but overall assemblage composition correlated only with manganese, pH and nitrate. 4. Among diatoms, pH and conductivity explained the major variations in assemblage composition, and neither diversity, richness nor evenness varied with metal concentration. Nevertheless, the single strongest predictor of diatom assemblages on ordination axis 2 was the CCU score. The abundances of some macroinvertebrate taxa, particularly grazers, also explained significant variations in diatom assemblages that were linked to both metals and acid–base status. 5. Diatom species apparently tolerant of high metal concentrations included Psammothidium helveticum, Eunotia subarcuatoides, Pinnularia subcapitata and Sellaphora seminulum. Of these, P. helveticum, E. subarcuatoides and P. subcapitata were abundant at lower pH than S.seminulum and might indicate metal enrichment over different pH ranges. Sensitive species included Fragilaria capucina var. rumpens, Achnanthes oblongella and Tabellaria flocculosa. 6. We conclude that macroinvertebrates at these sites reflected metal pollution most strongly through variations in diversity while effects on diatoms were best reflected by changes in assemblage composition. We suggest that, with further refinement, CCU scores might be useful in evaluating the possible effects of metal pollution on benthic organisms in European rivers.     

The Lusitanian toadfish as bioindicator of estuarine sediment metal burden: The influence of gender and reproductive metabolism

Early diagenetic processes and anthropogenic activities are responsible for metal enrichment in estuarine sediments. The Tagus estuary (Portugal) is no exception, and as a result of past and present pressures, surface sediment contamination is still an issue in some areas. Since such metal loads may be incorporated by benthic organisms, this study analyzed the accumulation of trace metals in the Lusitanian toadfish (Halobatrachus didactylus) in the Tagus estuary. In order to determine the role played by the seasonal reproductive cycle of the Lusitanian toadfish in the bioaccumulation process of trace metals in its tissues, the concentrations of Cd, Co, Cr, Cu, Ni, Pb and Zn were determined in the liver of male and female specimens captured during reproductive and non-reproductive periods. The results showed that metal accumulation in the liver was related simultaneously with gender and season, with females having higher levels of Cd, Cu and Zn during the reproductive period. The metabolic roles of Cu and Zn in embryonic development may explain such results, as both metals accumulated in the female liver to be transported to the gonads later on. Cd, on the other hand, does not have a metabolic role, and the higher concentrations of this metal found in spawning females could be related to the high affinity of Cd to vitellogenin, which is produced in the liver. To assess the species’ potential as an indicator of metal contamination, the concentrations of the seven elements were compared in the muscle tissue of adult, type I males (age ≥5), from two areas with distinct sediment metal loads. Non-essential metals in the muscle reflected the same differences between areas that were found in the sediment samples, evidencing H. didactylus as a potential indicator of those elements bioavailability from the sediment. The results showed that the muscle tissue of adult specimens of a relatively sedentary species such as H. didactylus is a useful indicator of long term accumulation of trace metals. On the contrary, liver concentrations of trace metals showed variation according to the reproductive status, which could lead to overestimate of the environmental status concerning trace metals bioavailability. Spawning season and liver tissue should thus be avoided in biomonitoring studies targeting this benthic fish.     

Etude du transfert de quelques oligo-éléments dans les chaînes trophiques néritiques et estuariennes: Accumulation biologique chez les poissons omnivores et super-carnivores

Five species of fishes(Dicentrarchus labrax, Gobius microps, Stizostedion lucioperca, Gadus luscus, Merlangius merlangus) and their major prey organisms were collected monthly from two stations in the Loire estuary (France). The levels of several trace elements (Cd, Pb, Cu, Zn) in their tissues were determined by means of atomic absorption spectrophotometry. The concentrations of Cd, Pb and Cu were shown to decrease in the highest trophic levels: the relatively highest metal levels were determined in annelids, followed by crustaceans, the lowest levels being encountered in fishes. However, a preferential uptake of Cu was observed in crustaceans. There is no biomagnification for these three metals, the concentrations in preys being generally lower than in predators. For Zn, the highest concentrations were measured in worms and copepods but preys such as shrimps and mysids exhibit values of the same order of magnitude compared to predator fishes.

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Avec la collaboration technique de R. Ferre.     

Identification of a copper-responsive promoter and development of a copper biosensor in the soil bacterium <Emphasis Type="Italic">Achromobacter</Emphasis> sp. AO22

A number of human activities result in environmental contamination with copper compounds that can cause severe detrimental effects on the ecosystem as well as human health. The physico-chemical methods of metal detection have limitations such as inability to distinguish between total versus bio-available metals and differences in metal uptake in different organisms. The heavy metal resistance-encoding genetic systems of certain bacteria provide critical tools for development of biosensors for these purposes. This study reports a copper biosensor utilizing the cop operon of the heavy metal resistant bacterial isolate, Achromobacter sp. AO22, isolated from a contaminated site in Australia. A section located between the divergently transcribed putative response regulator gene copR and multicopper oxidase gene copA that included a palindromic cop box was identified as a copper-responsive promoter using a lacZ reporter construct, pCOPRP, in E. coli. The expression was found to be enhanced by inclusion of copR. Another engineered strain, AO22(pCOPRP), showed stronger induction, and the lacZ expression in both backgrounds was enhanced significantly (250–400 fold) by copper but minimally by other metals. The construct in Achromobacter sp. AO22 thus has a high potential as biosensor for detecting copper bioavailability (hence potential toxicity) in a soil bacterial background, while the construct in E. coli is ideal for laboratory-based testing.     

Analysis of in situ manganese(II) oxidation in the Columbia River and offshore plume: linking Aurantimonas and the associated microbial community to an active biogeochemical cycle

The Columbia River is a major source of dissolved nutrients and trace metals for the west coast of North America. A large proportion of these nutrients are sourced from the Columbia River Estuary, where coastal and terrestrial waters mix and resuspend particulate matter within the water column. As estuarine water is discharged off the coast, it transports the particulate matter, dissolved nutrients and microorganisms forming nutrient‐rich and metabolically dynamic plumes. In this study, bacterial manganese oxidation within the plume and estuary was investigated during spring and neap tides. The microbial community proteome was fractionated and assayed for Mn oxidation activity. Proteins from the outer membrane and the loosely bound outer membrane fractions were separated using size exclusion chromatography and Mn(II)‐oxidizing eluates were analysed with tandem mass spectrometry to identify potential Mn oxidase protein targets. Multi‐copper oxidase (MCO) and haem‐peroxidase enzymes were identified in active fractions. T‐RFLP profiles and cluster analysis indicates that organisms and bacterial communities capable of oxidizing Mn(II) can be sourced from the Columbia River estuary and nearshore coastal ocean. These organisms are producing up to 10 fM MnO₂ cell^?1 day^?1. Evidence for the presence of Mn(II)‐oxidizing bacterial isolates from the genera Aurantimonas, Rhodobacter, Bacillus and Shewanella was found in T‐RFLP profiles. Specific Q‐PCR probes were designed to target potential homologues of the Aurantimonas manganese oxidizing peroxidase (Mop). By comparing total Mop homologues, Aurantimonas SSU rRNA and total bacterial SSU rRNA gene copies, it appears that Aurantimonas can only account for ～1.7% of the peroxidase genes quantified. Under the broad assumption that at least some of the peroxidase homologues quantified are involved in manganese oxidation, it is possible that other organisms oxidize manganese via peroxidases.     

Mechanisms of heavy-metal sequestration and detoxification in crustaceans: a review

This review is an update of information recently obtained about the physiological, cellular, and molecular mechanisms used by crustacean organ systems to regulate and detoxify environmental heavy metals. It uses the American lobster, Homarus americanus, and other decapod crustaceans as model organisms whose cellular detoxification processes may be widespread among both invertebrates and vertebrates alike. The focus of this review is the decapod hepatopancreas and its complement of metallothioneins, membrane metal transport proteins, and vacuolar sequestration mechanisms, although comparative remarks about potential detoxifying roles of gills, integument, and kidneys are included. Information is presented about the individual roles of hepatopancreatic mitochondria, lysosomes, and endoplasmic reticula in metal sequestration and detoxification. Current working models for the involvement of mitochondrial and endoplasmic reticulum calcium-transport proteins in metal removal from the cytoplasm and the inhibitory interactions between the metals and calcium are included. In addition, copper transport proteins and V-ATPases associated with lysosomal membranes are suggested as possible sequestration processes in these organelles. Together with several possible cytoplasmic divalent and trivalent anions such as sulfate, oxalate, or phosphate, accumulations of metals in lysosomes and their complexation into detoxifying precipitation granules may be regulated by variations in lysosomal pH brought about by bafilomycin-sensitive proton ATPases. Efflux processes for metal transport from hepatopancreatic epithelial cells to the hemolymph are described, as are the possible roles of hemocytes as metal sinks. While some of the cellular processes for isolating heavy metals from general circulation occur in the hepatopancreas and are beginning to be understood, very little is currently known about the roles of the gills, integument, and kidneys in metal regulation. Therefore, much remains to be clarified about the organs and mechanisms involved in metal homeostasis in decapod crustaceans.Abbreviations ER endoplasmic reticulum - SERCA sarco/endoplasmic reticulum calcium ATPase - V-ATPase vacuolar ATPase - PMCA plasma membrane calcium ATPaseCommunicated by I.D. Hume     

Late Holocene pollution in the Gernika estuary (southern Bay of Biscay) evidenced by the study of Foraminifera and Ostracoda

The Arketas pier in the Gernika estuary (southern Bay of Biscay) has during summer periods waters with strong hypoxia (1 ml l^–1) but curiously bears the richest assemblages of foraminifers and ostracods in the whole estuary. The most abundant species in Arketas are: Ammonia beccarii, Cribroephidium williamsoni, Haynesina germanica and Lobatula lobatula (foraminifers) Loxoconcha elliptica and Leptocythere castanea (ostracods). The benthic foraminifer sub-species A. beccarii tepida exhibits in this estuary three different morphotypes, whose distributions are controlled by changes in the salinity, dissolved oxygen and nutrient content of the waters, and thus could be used as a good indicator of environmental alteration caused by those parameters. To determine whether this environmental alteration is due to natural causes or is anthropogenic, micropalaeontologic and sedimentologic contents of a sediment core 140 cm thick have been analysed. The study of Foraminifera and Ostracoda assemblages, species diversity, and A. beccarii tepida morphotypes allows us to reconstruct the evolution of this part of the estuary over the last 3800 years. To examine anthropogenic effects at this site, we compared the occurrence of heavy metals Pb, As, with the record of A. beccarii tepida morph C in Arketas. The maximum concentration of heavy metals coincides with the maximum occurrence of A. b. tepida morph C, in the 1970s (date calculated according to the estimated rate of sedimentation in this area). This indicates that distribution of A. b. tepida morph C is, at least partially, caused by heavy metal pollution. Nevertheless, the fact that we have found no deformed tests of this taxa in Arketas induces us to think that another factor, such as dysaerobia caused by eutrophization of nutrient inputs in several areas of this estuary, might have been responsible for at least of part of the anomalous shift of A. b. tepida morph C at that time. In recent times, an increase in this anthropogenic activity was evident, reaching its maximum in the 1970s and decreasing from the 1980s. During the late Holocene period (up to 3500 years BP), this site was a middle-outer estuarine settlement, euryhaline with low to moderate salinity. This episode ends with a marine transgressive pulsation. After depositional hiatus of unknown duration, recent sediments suggest a modern palaeogeographic position of Arketas located in a lower estuary environment. The study of A. beccarii through the Holocene sediments of Arketas indicates that dysaerobic/pollution conditions were not a singular event. At the same time, the increase of A. b. tepida morph C were particularly strong over several years of the 20th Century, at precisely the time that a noticeable decrease of richness and diversity of calcareous microfauna is detected in the estuary.     

Phytoremediation of Cd,Ni, Pb and Zn by Salvinia minima

Most metals disperse easily in environments and can be bioconcentrated in tissues of many organisms causing risks to the health and stability of aquatic ecosystems even at low concentrations. The use of plants to phytoremediation has been evaluated to mitigate the environmental contamination by metals since they have large capacity to adsorb or accumulate these elements. In this study we evaluate Salvinia minima growth and its ability to accumulate metals. The plants were cultivated for about 60 days in different concentrations of Cd, Ni, Pb and Zn (tested alone) in controlled environmental conditions and availability of nutrients. The results indicated that S. minima was able to grow in low concentrations of selected metals (0.03 mg L^?1 Cd, 0.40 mg L^?1 Ni, 1.00 mg L^?1 Pb and 1.00 mg L^?1 Zn) and still able to adsorb or accumulate metals in their tissues when cultivated in higher concentrations of selected metals without necessarily grow. The maximum values of removal metal rates (mg m² day^?1) for each metal (Cd = 0.0045, Ni = 0.0595, Pb = 0.1423 e Zn = 0.4046) are listed. We concluded that S. minima may be used as an additional tool for metals removal from effluent.