Carlos Real

Biomonitoring Heavy Metals in Estuaries: A Field Comparison of Two Brown Algae Species Inhabiting Upper Estuarine Reaches

Biomonitoring dissolved heavy metals within estuaries,particularly at their upper reaches, frequently has to relyon several biomonitors; rarely a single species thrives allalong the salinity gradient. To properly do so, it must beestablished whether those biomonitors actually accumulateheavy metals alike. In this study, two brown seaweeds fromthe upper section of three NW Spain estuaries – the widely-known Fucus vesiculosus and the estuarine Fucusceranoides – were compared as metal biomonitors. Bothspecies were collected at five locations where they eithercoexist or live close to each other and their heavy metalcontent (Cu, Cr, Mn, Zn, Fe, Al) was measured. Analyseswere appropriately replicated for each species x locationcombination to allow a statistically reliable detection ofdifferences in bioaccumulation, with particular emphasis onthe magnitude of interspecific differences. The lack of significant differences for Cu, Mn, and Zncontents in F. ceranoides and F. vesiculosussupports the feasibility of their joint use to monitorthese metals along the estuaries. Conversely, F.ceranoides concentrated significantly higher levels of Cr,Fe, and Al than F. vesiculosus and hence combiningdata for both fucoids to monitor these elements seemsimpractical. The correlation of species differencestogether with a similar Al:Fe ratio in both weed tissue andsediment suggest that Cr, Fe, and Al tissue-burdens mightbe considerably biased by sediment retained on the surfaceof the weed. Parallel analyses of Al and/or Fe in seaweedsand sediments could serve to keep track of thisinterference and may help to combine data from both fucoidsfor monitoring elements like Cr.

Heavy-metal accumulation by Fucus ceranoides in a small estuary in north-west Spain

Abstract Concentrations of Fe, Al, Mn, Cu, Ni, Co, and Zn were measured in Fucus ceranoides and F. vesiculosus from Pontedeume, a small estuary on the northwest coast of Spain, affected by mining activities upstream and by sewage discharge to the estuary itself. Plants were collected from two intertidal levels at each of six locations, each sample eventually consisting of the homogenized tissues of ten individuals. Tips and thalli were analysed separately. By using these methods, it was found that three or four samples were sufficient to detect differences between means for different sites of 50% for all the metals considered except Cu, the high variability of which made eight samples necessary in order to detect differences of 100%. It was demonstrated that the contribution of particulate matter not removed during washing prior to analysis is significant only in the cases of Fe, Al and Cr. Mn and Co, and, to a less but still considerable extent, Ni and Zn, were found to be greatly enriched in the algae studied. Concentrations in mature tissues were higher than in apices for all the metals studied except Cu, for which there were no significant differences between the two tissues. The vertical position on shore did not affect apical metal concentrations but showed correlations with Mn, Co, Ni, Zn and Cu in mature tissues. Possible reasons for these correlations are discussed.

Heavy metal mixing behaviour in estuarine sediments in the Ria de Arousa (NW Spain). Differences between metals

Abstract We measured concentrations of total and extractable (HCl 1N) Fe, Al, Mn, Cr, Cu, Zn and Ni, and a series of related physico-chemical parameters, in sediments from the Ria de Arousa and the River Ulla estuary (Galicia, NW Spain). The results show that Ni, Cu and particularly Cr are being discharged, and allow identification of the sources of pollution. A model was developed, using Cu as the tracer, to describe the mixing of river sediments with marine sediments. Concentrations of extractable Cu, total Ni, total extratable Zn, and extractable organic matter were accurately predicted. The model did not provide an adequate description of the behaviour of Cr, and we discuss possible reasons for this.

The application of microwave heating in sequential extractions of heavy metals in estuarine sediments

Abstract Using a modification of the procedure elaborated by Tessier et al. (1979) the conditions under which microwave heat was applied to perform sequential extractions of metals in estuarine sediments were evaluated. Necessary times were determined for the complete metal extractions and substantial reductions in time were obtained in comparison with the traditional techniques, (from hours to minutes). The techniques were applied to two reference materials: MESS-1 and SEDIMENTO (a secondary standard prepared in our laboratory). The problems of methodology associated with the use of microwaves are discussed, as well as the results obtained regarding the variability of the data of each fraction and the percentages of recovery. The techniques were also applied to intertidal surface sediments of three northwestern Spanish estuaries. Percentages of recovery are discussed as well as the relationship of the results to the physical/chemical variables of the medium.

Use of macroalgae stored in an Environmental Specimen Bank for application of some European Framework Directives.

Different European Framework Directives have established a series of objectives for conservation of the coast, and monitoring tools must be made available to test compliance with these aims. In the present study the use of macroalgae deposited in an Environmental Specimen Bank was evaluated as a possible environmental tool for monitoring the coastal ecosystem. The concentrations of Al, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn in three species of the genus Fucus (Fucus spiralis, Fucus vesiculosus and Fucus ceranoides) were measured at sampling sites distributed along the coast of Galicia (NW Spain). In the period 1990-2001, the concentrations of the metals were higher in 1990 than in 2001, with the exception of: i) Mn in F. ceranoides and Fe in F. spiralis-F. vesiculosus, for which there were no differences between the sampling periods, and ii) Zn in F. vesiculosus and Fe in F. ceranoides, for which the concentrations were higher in 2001 than in 1990. In the period 2001-2007 concentrations of the metals were more stable, especially in F. ceranoides (e.g. Al, Fe, Hg, Ni and V). The concentrations were also more stable vin F. vesiculosus in 2005 (i.e. Al, Cr, Fe, Mn and Zn). The population density distributions are consistent with the results of the statistical tests. The results indicate that macroalgae of the genus Fucus may be useful for applying different European Framework Directives, given that the macroalgae are sufficiently sensitive to changes in concentrations of metals, and may be suitable for long-term monitoring and used for the detection of increased concentrations of metals (real-time monitoring).

Spatial structure of trace elements in extensive biomonitoring surveys with terrestrial mosses

The size of the area affected by contamination processes mainly depends on the type of contaminant and the way it is emitted. In regular sampling, the size of the sampling grid will therefore interact with the scale at which the contamination processes are produced, for each contaminant, so that the grid will only enable characterization of those processes that occur at scales larger than the grid, i.e. large scale processes. The present study analysed the data corresponding to tissue concentrations of Cd, Cu, Fe, Hg, Mn, Pb, Se, V and Zn in the terrestrial moss Pseudoscleropodium purum obtained in regular sampling surveys with grids of different sizes (15x15, 7.5x7.5 km) plus a series of accessory points located at 1 km from the 15x15 km sampling grid; all sampling sites were located in Galicia and were sampled in March 2004. The objective of the study was to characterize the interaction between the scale of the sampling grid and the scale at which the contamination processes are produced, for each contaminant, to enable adjustment of the size of the grids to the scale at which the contamination processes are mainly produced. For this purpose, the spatial structure of the concentration of each element was analysed by use of semivariograms created with a robust estimator of the semivariance. The results of the study verified the existence of a real interaction between the scale of the sampling grid and the scale of the contamination processes. The results also demonstrated how in the study area, the contamination processes associated with Cd, Pb and V are generally small scale processes, whereas those associated with Cu, Hg and Se are generally large scale processes.

Heavy metals in sediment cores from a NW Spain Estuary

Core samples have been used to describe the chronology of heavy metal inputs to aquatic systems. Metal concentration profiles have been investigated to detect pollution, to establish when the polluting event started, and to quantify its magnitude relative to [open quotes]precivilization[close quotes] background values. Less frequently, and mainly in studies of coastal systems, the heavy metal nonresidual fraction has been measured to estimate the portion of trace metals potentially available for the biota or remobilization processes, and to assist in identifying the origin of metal inputs. This work is part of a wider study of metal concentrations in organisms and superficial sediments from a small estuary in NW Spain. The aims of this research were to detect any potential pollutant input to the sediments of the estuary, and to establish the influence of postdepositional redistribution on the heavy metal concentrations of oxidized surface sediments. 17 refs., 1 fig.

Detection of pulses of atmospheric mercury deposition with extensive surveys and frequently sampled stations: A comparison

We present the results of the analysis of several datasets corresponding to the mercury contents of moss tissues. Some of the data were collected in regional surveys devised to study the atmospheric deposition of pollutants in Galicia (Spain). The surveys were carried out with low frequency (usually biennially) and the data obtained were compared with similar data collected with high frequency (monthly or bimonthly) at several locations in the same area. The temporal series of data demonstrated the existence of strong pulses of mercury deposition of small duration. They caused dramatic increases in the Hg contents in the samples from some localities and, sometimes, modified the Hg contents of the mosses in the complete study area. Our results demonstrate the low probability of detecting pulses in surveys separated so widely in time. This suggests that the information obtained in regional surveys should be complemented with data collected with high frequency.

The Galician-Asturian beechwoods (Saxífrago spathularidis-Fagetum sylvaticae): description, ecology and differentiation from other Cantabrian woodland types

Abstract This study presents an ecological and floristic characterization of the beechwoods of the littoral and sublittoral part of the extreme northwest of the Iberian Peninsula (the Northern Galician-Asturian Subsector), and details differences with respect to Galician-Asturian oakwoods and other beechwoods of the Cantabrian zone, as assessed using non-metric multidimensional scaling (NMDS). In view of our findings we describe a new acidophilous beechwood association, Saxifrago spathularidis-Fagetum sylvaticae nova (IIici aquifolii- Fagion sylvaticae, Querco-Fagetea), occurring under a strongly oceanic climate. This association is characterized by the presence of various taxa endemic to the northwest Iberian Peninsula as well as meso-thermophilous species.

Heavy-metal horizontal distribution in surface sediments from a small estuary (Pontedeume, Spain)

Abstract Horizontal distributions of Fe, Mn, Co, Cu, Ni, Pb, and Zn were studied after a spatially intensive sampling campaign. Special attention was devoted to the head of the estuary where metal partitioning as well as the representative nature of the sediment data were examined. Sediments showed a clear seaward decrease in all elements and variables; the Eume river appeared to be the main source of particulate metals. Heavy metal functional relationships and non-residual concentrations suggested that different mechanisms could explain the trace element gradient found in different zones of the estuary. Fluvial and marine particle mixing could account for the constant extractability observed along the gradient in the outer zone of the estuary. A change in extractability parallels the upstream metal enrichment recorded in the semi-enclosed inner zone where sediment particles seemed to be mostly of fluvial origin. The fractionation of fluvial particulate matter through settling is proposed as a way to explain the metal concentration changes registered in the inner estuary. Inner zone sediment samples were highly representative of the average situation for the surrounding area. Five samples were sufficient to detect differences between total concentration means of 20% for different sites for all metals considered except Mn. Analytical error explained most of the total variation observed, Mn being the only metal showing a remarkable field error. The higher field variability of Manganese made up 50% of the minimum detectable difference using a sample size of five.