Multi-element Signatures Research Articles

Pre-alpine mire sediments as a mirror of erosion, soil formation and landscape evolution during the last 45 ka

Peat and lake sediments as well as a nearby soil catena were sampled to reconstruct the environmental history of a small infilled lake basin (mire) in the central alpine foreland of Switzerland. Soil evolution is best regarded as discontinuous over time and conceptualised by ‘progressive’ or ‘regressive’ process phases. We analysed the surrounding soils and used corresponding pedosignatures in the mire sediments to characterise notable phases of erosion and deposition. We assumed that the mire sediments would reflect these phases, that elemental composition (major and minor compounds) and rare earth elements (REEs) would allow us to differentiate past processes and that progressive and regressive phases of soil development can be discerned. Although radiocarbon ages are equivocal, it appears from pollen analyses that a lake was present here by c. 45kaBP. After the retreat of the glacier from this area following the LGM, continuous sedimentation occurred until a mire developed during Pleistocene–Holocene transition. This transition period was accompanied by more intense erosion, as characterised by chemical signatures. A stable phase developed between c. 10–5kaBP giving rise to progressive soil evolution. Between 5 and 4kaBP, evidence appears for several erosional phases, predominantly detectable at the margin of the mire. These erosion phases, coupled with accumulation in the mire, are even more evident after 4ka BP and especially after 2.1ka BP. Based on soil investigations, elemental fluxes are detected along the slopes with distinct accumulations at the footslope. Evidence for anthropogenic influences and subsequent regressive soil formation phases appear in this pre-alpine landscape about 5kaBP (Neolithic/Early Bronze Age), which appears to intensify after 2.1kaBP (Roman period to present). Multi-elemental signatures enabled us to identify the important geochemical processes that have occurred here. Together with radiocarbon and pollen analyses, we placed these processes in a logical temporal context. The use of lacustrine (lake or mire) sediments has great potential to decipher and detail the surrounding landscape history and soil evolution of this region of Switzerland.

Uranium in Larval Shells As a Barometer of Molluscan Ocean Acidification Exposure

As the ocean undergoes acidification, marine organisms will become increasingly exposed to reduced pH, yet variability in many coastal settings complicates our ability to accurately estimate pH exposure for those organisms that are difficult to track. Here we present shell-based geochemical proxies that reflect pH exposure from laboratory and field settings in larvae of the mussels Mytilus californianus and M. galloprovincialis. Laboratory-based proxies were generated from shells precipitated at pH 7.51 to 8.04. U/Ca, Sr/Ca, and multielemental signatures represented as principal components varied with pH for both species. Of these, U/Ca was the best predictor of pH and did not vary with larval size, with semidiurnal pH fluctuations, or with oxygen concentration. Field applications of U/Ca were tested with mussel larvae reared in situ at both known and unknown pH conditions. Larval shells precipitated in a region of greater upwelling had higher U/Ca, and these U/Ca values corresponded well with the laboratory-derived U/Ca-pH proxy. Retention of the larval shell after settlement in molluscs allows use of this geochemical proxy to assess ocean acidification effects on marine populations.

Low interbasin connectivity in a facultatively diadromous fish: evidence from genetics and otolith chemistry

Southern smelts (Retropinna spp.) in coastal rivers of Australia are facultatively diadromous, with populations potentially containing individuals with diadromous or wholly freshwater life histories. The presence of diadromous individuals is expected to reduce genetic structuring between river basins due to larval dispersal via the sea. We use otolith chemistry to distinguish between diadromous and nondiadromous life histories and population genetics to examine interbasin connectivity resulting from diadromy. Otolith strontium isotope ((87) Sr:(86) Sr) transects identified three main life history patterns: amphidromy, freshwater residency and estuarine/marine residency. Despite the potential for interbasin connectivity via larval mixing in the marine environment, we found unprecedented levels of genetic structure for an amphidromous species. Strong hierarchical structure along putative taxonomic boundaries was detected, along with highly structured populations within groups using microsatellites (FST =0.046-0.181), and mtDNA (ΦST =0.498-0.816). The presence of strong genetic subdivision, despite the fact that many individuals reside in saline water during their early life history, appears incongruous. However, analysis of multielemental signatures in the otolith cores of diadromous fish revealed strong discrimination between river basins, suggesting that diadromous fish spend their early lives within chemically distinct estuaries rather than the more homogenous marine environment, thus avoiding dispersal and maintaining genetic structure.

Recruitment sources and dispersal of an invasive fish in a large river system as revealed by otolith chemistry analysis

The contributions of nursery habitats to recruitment of non-native common carp (Cyprinus carpio) were estimated via analysis of water and otolith 87Sr/86Sr and otolith trace element concentrations (Mg:Ca, Mn:Ca, Sr:Ca, Ba:Ca) over 3 years in the Lachlan River, Australia. Water samples and otoliths of postlarval carp were analyzed to characterize 87Sr/86Sr and multi-elemental signatures of nursery habitats. Considerable temporal variation occurred in both water 87Sr/86Sr and otolith multi-elemental signatures, which limited our ability to directly match water and otolith 87Sr/86Sr in nurseries of the lower catchment. However, spatial variation in multi-elemental signatures was sufficient to allow accurate classification of nurseries within years. Assignment analysis of young-of-year fish suggested that several wetland and floodplain systems made significant contributions to young-of-year recruitment in the lower catchment. These contributions were strongly influenced by river flows and water management. Nurseries contributed fewer recruits to the main channel as distance from the nursery increased. Fish from the upper catchment originated from local sources, and there was no evidence of mixing of recruits between the upper and lower catchments. We conclude that identification of recruitment “hotspots” via otolith chemical analysis can assist in developing strategies to control invasive fishes in large river networks.

Does the trace element composition of brown troutSalmo truttaeggs remain unchanged in spawning redds?

The temporal stability of trace element concentrations in fertilized, artificially incubated anadromous brown trout Salmo trutta eggs and newly hatched fry was investigated. The anadromous status of the parental fish was confirmed using strontium isotopic analysis of otoliths. Whilst manganese concentrations in eggs varied over time, concentrations of aluminium, potassium, magnesium, strontium, barium and calcium were all unchanged 1 week and 6 weeks post-fertilization as well as in recently hatched larvae. The results clearly suggest that the distinctive trace element signature present in the eggs and newly hatched larvae of anadromous S. trutta (typically characterized by high strontium, low barium) is stable over time. Therefore analysis of the trace element composition of eggs is concluded to be a cost-effective and reliable method for determining the spatial and temporal extent of upstream spawning migration by anadromous salmonids. The temporal variability of at least one element in this study suggests the stability of untested multi-element signatures cannot automatically be assumed.

Otolith microchemistry inSicydium punctatum: indices of environmental condition changes after recruitment

The amphidromous life cycle and morphological characteristics of Sicydiinae species allow them to colonise tropical freshwater habitats from the river mouth to the upper reaches of the river basin. Otolith microchemistry of 62 Sicydium punctatum from the Perou River, Guadeloupe (French West Indies) was investigated with a femtosecond laser ablation-inductively coupled plasma mass spectrometer (fs-LA-ICP-MS) in order to reconstruct individual life history and follow the possible movements of Sicydium punctatum after the recruitment. Sr:Ca fingerprint confirmed the amphidromous cycle of this species. Variations of Ba:Ca in some individuals indicated changes in environmental conditions after the recruitment in the river. Even if results did not allow concluding to the specific origin of these variations, the hydrological regime and the biofilm composition may have a non negligible influence on the Ba availability. Results supported the use of multi-elemental signatures in otoliths and highlight the need for a large geographical and temporal sampling of Ba and Sr in freshwater systems for a better understanding of amphidromous fish species. © 2011 EDP Sciences, IFREMER, IRD.

Comment on: ‘Multi-element signatures of stream sediments and sources under moderate to low flow conditions’ by M.I. Stutter, S.J. Langan, D.G. Lumsdon, L.M. Clark

In a recent paper on ‘Multi-element signatures of stream sediments and sources under moderate to low flow conditions’, Stutter et al., 2009 M.I. Stutter, S.J. Langan, D.G. Lumsdon and L.M. Clark, Multi-element signatures of stream sediments and sources under moderate to low flow conditions, Appl. Geochem. 24 (2009), pp. 800–809. Article | PDF (392 K) | View Record in Scopus | Cited By in Scopus (2)Stutter et al. (2009) presented results of a simple sediment source tracing method based on major and trace elements for a small agricultural catchment in NE Scotland. The authors reported statistically significant, larger concentrations of four trace elements (Ce, Nd, Th and Y) in bank subsoils (n = 5) and stream bed sediments (n = 3) compared to topsoils from both pasture (n = 5) and arable (n = 5) land. They used these differences to aid discrimination between topsoil and subsoil (stream bank erosion) contributions to bed sediment. These elements may be more depleted in topsoil compared to subsoil because the former have been subject to more intense weathering over a longer period. If these naturally occurring trace elements could be used to understand the relative proportions of topsoil and subsoil contributions to headwater bed sediments this approach might be applied more widely to elucidate transport pathways for the transfer of agricultural contaminants such as particulate phosphorus to streams (Walling et al., 2008). This approach warrants further investigation across a range of catchments at different scales with contrasting land use and bedrock types. This can be undertaken using data from regional-scale geochemical surveys (Johnson et al., 2005) which include analyses of both stream bed sediments and subsoil samples. Previous studies have shown that much of lowland central England is at risk of topsoil transfer to watercourses via land drains (Chapman et al., 2003). A geochemical survey across part of central England covering 15 400 km2 was recently undertaken and these data are well-suited to testing whether three of the four trace elements identified by Stutter et al. (2009) might be used to discriminate between topsoil and subsoil in sediments more widely. Specifically, if the concentrations of these elements are significantly smaller in stream bed sediments than in the subsoil, this may be due to mixing with topsoils which have lower concentrations of these elements. Below the regional-scale survey, the methods the author used to compare the geochemical data in subsoil and bed sediments described, and the findings and their implications discussed.

Reply to comment on: ‘Multi-element signatures of stream sediments and sources under moderate to low flow conditions’ by Barry Rawlins

Reply to comment on: ‘Multi-element signatures of stream sediments and sources under moderate to low flow conditions’ by Barry Rawlins

Connectivity clues from short-term variability in settlement and geochemical tags of mytilid mussels

The use of geochemical tags in calcified structures of fish and invertebrates is an exciting tool for investigating larval population connectivity. Tag evaluation over relatively short intervals (weeks) may detect environmental and ecological variability at a temporal scale highly relevant to larval transport and settlement. We collected newly settled mussels ( Mytilus californianus and M. galloprovincialis) weekly during winter/spring of 2002 along the coast of San Diego, CA, USA, at sites on the exposed coast (SIO) and in a protected coastal bay (HI), to investigate temporal patterns of geochemical tags in mussel shells. Analyses of post-settlement shell via LA-ICP-MS revealed statistically significant temporal variability for all elements we examined (Mg, Mn, Cu, Sr, Cd, Ba, Pb and U). Despite this, our ability to distinguish multielemental signatures between sites was largely conserved. Throughout our 13-week study, SIO and HI mussels could be chemically distinguished from one another in 78–87% of all cases. Settlement varied between 2 and 27 settlers gram-byssus −1 week −1 at SIO and HI, and both sites were characterized by 2–3 weeks with “high” settlement. Geochemical tags recorded in early larval shell of newly settled mussels differed between “high” and “low” settlement weeks at both sites (MANOVA), driven by Mg and Sr at SIO (p = 0.013) and Sr, Cd, Ba and Pb at HI (p < 0.001). These data imply that shifts in larval sources or transport corridors were responsible for observed settlement variation, rather than increased larval production. In particular, increased settlement at HI was observed concurrent with the appearance of geochemical tags (e.g., elevated Cd), suggesting that those larvae were retained in upwelled water near the mouth of the bay. Such shifts may reflect short-term changes in connectivity among sites due to altered transport corridors, and influence the demography of local populations.

Role of mangroves as nurseries for French grunt Haemulon flavolineatum and schoolmaster Lutjanus apodus assessed by otolith elemental fingerprints

Juvenile French grunt Haemulon flavolineatum and schoolmaster Lutjanus apodus were captured in mangrove and seagrass stations in St. Croix, and Puerto Rico in 2006 and 2007 to deter- mine whether areas for juvenile fish can be discriminated by means of otolith chemistry. Concentra- tions of 16 elements were determined in 0-group fish otoliths using laser ablation-inductively coupled plasma mass spectrometry. Two stable isotopes, δ 18 O and δ 13 C, in French grunt and schoolmaster otoliths were also analyzed. Multi-elemental signatures for both species differed significantly (p < 0.001) among mangrove and seagrass stations within both islands. Furthermore, concentrations of 6 el- ements (Sr, Ba, Cu, Mg, Co, Na) as well as δ 18 O and δ 13 C for both species within each year differed sig- nificantly among mangrove and seagrass stations within islands (p < 0.001). Classification success for French grunt and schoolmaster juvenile areas within St. Croix across years ranged from 87 to 92% and from 76 to 77%, respectively, whereas in Puerto Rico, classification success for French grunt and schoolmaster for the 2 years ranged from 80 to 84% and 84 to 87%, respectively. Classification success between mangrove and seagrass habitats (stations combined) in Puerto Rico for French grunt ranged from 84 to 91%, and for schoolmaster ranged from 94 to 99%. In St. Croix, classification success for French grunt was 95 to 96%, and for schoolmaster was 86 to 89%. The percentages of French grunt subadults collected from forereef stations in St. Croix, identified as having resided as juveniles in man- grove habitats in 2006 and 2007, were 40 and 68%, respectively, while for Puerto Rico, these percent- ages were 70 and 74%. By contrast, for schoolmaster almost 100% of all fish in both islands resided as juveniles in mangrove habitats in both years. This study contains the first direct evidence of postsettle- ment fish movement connecting mangrove habitats to the reef using otolith chemistry.

Trace element accumulation in Cassiopea sp. (Scyphozoa) from urban marine environments in Australia

Jellyfishes are robust, short-lived animals, tolerant to a wide range of environmental conditions and pollutants. The benthic jellyfish, Cassiopea sp. was collected from five locations along the north and eastern coast of Australia and analysed for trace elements to determine if this species has potential as a marine biomonitor. Both the oral arm and bell tissues readily accumulated aluminium, arsenic, barium, cadmium, chromium, copper, iron, manganese and zinc above ambient seawater levels. In contrast, lithium appeared to be actively regulated within the tissues while calcium, magnesium and strontium reflected the ambient environment. The multi-element signatures showed spatial variation, reflecting the geographical separations between locations, with locations closer together showing more similar elemental patterns. The combination of bioaccumulative capacity, life history traits and biophysical aspects indicate that this species has high potential as a biomonitor in coastal marine systems.

An evaluation of the site specificity of soil elemental signatures for identifying and interpreting former functional areas

Soil multi-element analysis is now a routine technique employed to help answer questions about space use and function in and around archaeological sites. The pattern of enhancement of certain elements, including P, Pb, Ca, Zn, and Cu, has been shown by numerous studies to correlate closely with the archaeological and historical record. Interpretation of these soil signatures, however, has generally been more problematic. One approach to the problem has been the use of ethnographic or “known” sites to guide interpretation, but how confidently can results from one site be extrapolated to another? This study of abandoned farms tests the site specificity of soil multi-element signatures of past space use through the use of discriminant models. Data analysis suggests that one to one comparisons of similar sites are much less accurate (38% accuracy) than comparisons based on a wider range of sites (59.3% accuracy), even when the latter have contrasting geology. The results highlight the importance of individual anthropogenic practices during occupation and abandonment in the development of diagnostic soil geochemical signatures.

Multi-element signatures of stream sediments and sources under moderate to low flow conditions

Abstract This study assesses a simple sediment source tracing method using major- (Al, Ca, Fe, K, Mg, Mn, Na, P, Si, Ti) and trace-element (Ba, Be, Ce, Co, Cr, Mo, Nd, Pb, Sr, Th, V, Y, Zn) signatures of stream suspended particulate matter (SPM), bed sediments and soils in a small agricultural catchment in NE Scotland. Whilst most erosion studies characterise the large amounts of material mobilised at the highest flows, this study aimed to assess properties of sediments during moderate to low flow periods. These occur more frequent than intense storms and are important in linking stream sediments, near-channel sources and aquatic ecosystem impacts. Data were transformed by multivariate statistical methods to compare elemental signatures of SPM (ranging from 3 to 53 mg L −1 in the stream) and stream bed sediments with a limited number of near-channel source soils. Increased concentrations of Ce, Nd, Th and Y in subsoils contributed to the ability to discriminate between surface fieldslope and stream bank erosion sources. Stream bed sediments showed close matches with compositions of stream bank and arable surface soils, but signatures of SPM differed greatly from any of the sources. Large concentrations of Cr, Pb and Zn in SPM, particularly during summer (677, 177 and 661 mg kg −1 , respectively) exceeded water quality standards and were linked to an accumulation of trace elements associated with biological material. The potential for within-stream alteration of SPM in relation to erosion sources was confirmed by changes in the nature of the SPM organic matter observed by IR spectroscopy. Thus the potential is shown for multi-element signatures to give information on catchment sediment sources to aid land management decisions, given careful consideration of the effects of in-stream alteration of eroded material. However, this combined information may be beneficial to process understanding linking land use and stream ecosystems at critical ecological periods.

Multi-element otolith chemistry of juvenile sole ( Solea solea), whiting ( Merlangius merlangus) and European seabass ( Dicentrarchus labrax) in the Thames Estuary and adjacent coastal regions

Estuaries are regarded as valuable nursery habitats for many commercially important marine fishes, potentially providing a thermal resource, refuge from predators and a source of abundant prey. To assess the extent of estuarine use by juvenile (0+) common sole ( Solea solea), whiting ( Merlangius merlangus) and European seabass ( Dicentrarchus labrax) we: (1) developed techniques to distinguish between estuarine and coastally-caught juveniles using otolith chemistry; and (2) examined the accuracy with which multi-elemental signatures could re-classify juveniles to their region of collection. High-resolution solution-based inductively coupled plasma mass spectrometry (HB-SB-ICPMS) was used to quantify 32 elements within the juvenile otoliths; 14 elements occurred above detection limits for all samples. Some elemental distributions demonstrated clear differences between estuarine and coastally-caught fish. Multivariate analysis of the otolith chemistry data resulted in 95–100% re-classification accuracy to the region of collection. Estuarine and coastal signatures were most clearly defined for sole which, compared to bass and whiting, have low mobility and are less likely to move from estuarine to coastal habitats between larval settlement and later migration to adult stocks. Sole were the only species to reveal an energetic benefit associated with an estuarine juvenile phase. The physiological ability of bass to access upper estuarine regions was consistent with some elemental data, while the high mobility and restricted range of whiting resulted in less distinct otolith chemistries.

Using stylet elemental signatures to determine the population structure of Octopus maorum

A novel method was used to investigate the population structure and dispersal patterns of Octopus maorum, an octopus species with a planktonic larval stage, which forms a distinct and large aggregation in southeast Tasmania. Single and multi-elemental signatures within the ‘early life history’ region of the stylet (an internal ‘shell’) were used to determine levels of connectivity and the common origins of individuals collected from 5 locations across Tasmania, South Australia and New Zealand. Using laser ablation inductively coupled plasma-mass spectrometry (LA ICPMS) the stylets were analysed for 12 elements, 8 of which were found to be excellent spatial discriminators. There was evidence of population structuring within the O. maorum population, with a distinct separation of the aggregation site in southeast Tasmania from other groups. Octopuses from the aggregation shared a common origin and appeared to be coming from a local neighbouring source. The 2 northern sample locations shared a similar elemental signature, which could be due to either similar water chemistries or long-distance dispersal. This study presents the first insights into the population structure of O. maorum, and provides vital information for the sustainable management of this species. Furthermore, this technique will have direct application to other more heavily fished octopus species around the world.

Characterizing natal source population signatures in the diadromous fish Galaxias maculatus, using embryonic otolith chemistry

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 343:273-282 (2007) - DOI: https://doi.org/10.3354/meps06886 Characterizing natal source population signatures in the diadromous fish Galaxias maculatus, using embryonic otolith chemistry Nicole C. Barbee*, Stephen E. Swearer Department of Zoology, University of Melbourne, Parkville, Victoria 3010, Australia *Email: nbarbee@unimelb.edu.au ABSTRACT: One of the greatest empirical challenges in studies of marine metapopulations is assessing the role of connectivity in maintaining local populations. The use of natural tags in body structures such as otoliths has led to significant improvements in our understanding of dispersal dynamics; however, the real knowledge gap remains our ability to identify the origins of dispersing larvae. In the present study we show that embryonic otoliths of a diadromous fish native to southeastern Australia, Galaxias maculatus, can be used to quantify unique natal elemental signatures and identify potential source populations spread out along a contiguous coastline. Using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS), we analysed embryonic otoliths from G. maculatus hatchlings from 10 rivers across coastal Victoria, Australia. We found significant differences among rivers in the concentrations of all 8 elements analysed (B, Mg, Mn, Zn, Cu, Sr, Ba, Pb). More importantly, significant differences among rivers in the multi-element signature of hatchling otoliths indicate that sites separated by 10s to 100s of km can be discriminated with a high degree of confidence. Our results show that these methods can be successfully applied to examine questions of population connectivity within metapopulations of diadromous species. KEY WORDS: Otolith chemistry · LA-ICPMS · Galaxias maculatus · Diadromy · Natal signatures Full text in pdf format PreviousNextCite this article as: Barbee NC, Swearer SE (2007) Characterizing natal source population signatures in the diadromous fish Galaxias maculatus, using embryonic otolith chemistry. Mar Ecol Prog Ser 343:273-282. https://doi.org/10.3354/meps06886 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 343. Online publication date: August 07, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Use of vegetation and soil in mineral exploration in areas of transported overburden, Yilgarn Craton, Western Australia: a contribution towards understanding metal transportation processes

Five sites were selected in the semi-arid northern Yilgarn Craton (Jaguar VHMS Cu-Zn-Ag, Moolart Well Au, Rumour Au, Gossan Hill VHMS Cu-Zn-Au and McGrath North Au deposits) to test the use of vegetation as an exploration sampling medium in areas of transported overburden. A variety of vegetation samples (litter, roots, bark, branch wood and phyllodes) were collected from Mulga ( Acacia aneura ) plants. In addition, the soil from 10–20 cm below surface was sampled and analysed following total, partial and selective digests to investigate any potential chemical signature of bedrock mineralization at surface. At all sites, selective extractions of the &lt;250 μm fraction of soil show either no expression of buried mineralization or, where present, only a weak or ambiguous signature. In contrast, the vegetation survey shows a multi-element signature in different plant organs. Branches show very low anomaly contrasts or none at all. Phyllodes and bark generally show weak to moderate anomaly contrasts. Litter shows the greatest anomaly contrast of all plant material. There is also an enrichment in metals and an expression of the bedrock mineralization with good anomaly contrast in the uppermost soil horizon (0–4 cm) at Jaguar and this may indicate some mixing of litter and soil by bioturbation, and fixing on organic material, and Fe and/or Mn oxides. This contrasts with greater depths (10–20 cm) where no significant metal enrichment appears to have occurred, suggesting that most contained metals were fixed near-surface and do not percolate deeper into the profile. This is possibly due to slow decomposition of litter in arid terrains, with continuous loss of soil and fine litter particles by wind erosion and bush fires. Our data support the hypothesis that vegetation plays an important role in bringing metals to surface in areas with a semi-arid to arid climate and a low water-table.

Population structure of red drum ( Sciaenops ocellatus ) as determined by otolith chemistry

To examine current genetic-based paradigms pertaining to the structure and possible philopatry of red drum populations, we used solution-based inductively coupled plasma-mass spectrometry (ICP-MS) to analyze the otolith chemistry of juvenile red drum (Sciaenops ocellatus) from eight different estuaries in the Gulf of Mexico (Gulf) and the North Atlantic Ocean. One estuary (Tampa Bay, Fla.) was sampled in three different years. Analyses of variance for five elemental ratios (Mg/Ca, Mn/Ca, Zn/Ca, Sr/Ca, Ba/Ca) were all significantly different between estuaries, as was a multi-element signature (MANOVA, Pillai’s trace F 50, 1020=19.41, P<0.0001). We also found that red drum from the Gulf could be distinguished from those taken from the Atlantic Ocean with 99.5% accuracy, likely due to differences in water chemistry between these water masses. A discriminant function developed using these elemental ratios was more than 80% accurate in assigning juvenile red drum to their natal estuary, or in the case of Tampa Bay, to the correct year of spawning. We also used laser ablation ICP-MS to examine the otolith core chemistry of adult red drum collected from spawning aggregations near Tampa Bay. Using a discriminant function analysis with a calibration data set derived from juvenile signatures, we found that 75% of the adult cores matched the juvenile signal established for Tampa Bay 1982. Although preliminary, the results presented here suggest that red drum may return to their natal estuary to spawn, which has been postulated from genetic data.

Accumulation of radionuclide and metal contaminants in flesh and osteoderms of estuarine crocodiles (crocodylus porosus): Pathways and histories of catchment-specific exposure

Flesh and osteoderms of estuarine crocodiles (C. porosus) from Kakadu National Park, Northern Australia, were analysed for a range of metals, including uranium, to assess their capability for accumulation, in relation to their catchment-specific exposure to i) uranium mine effluents and mineralisation and ii) lead shot ammunition through their consumption of fauna shot by the traditional owners of the Park. Uranium in osteoderms was significantly (PO.05) elevated in the East Alligator River catchment, that contains the Ranger and Jabiluka uranium mine sites, relative to two other adjacent catchments. The mean concentrations of other elements in flesh and osteoderms were also significantly (P<0.05) different between catchments. Linear discriminant analysis was used to demonstrate that multi-element signatures in both flesh and osteoderms could be used to classify individual crocodiles to their respective catchments. This approach may be useful for the identification of source catchments of itinerant 'nuisance crocodiles' that find their way into Darwin Harbour, close to dense human habitation. Lead concentrations were significantly (P<0.05) enhanced in flesh and osteoderms of crocodiles sampled within two areas hunted with guns using Pb ammunition. Enhanced ratios of Pb:Ca in the annual laminations of their osteoderms are consistent with their history of continual exposure to elevated anthropogenic Pb sources. Subsequent experimental studies have demonstrated the ability of the crocodilian stomach to retain ingested Pb shot, that is readily solubilised and absorbed into the blood and then archived in the contemporary osteodermal lamination.

A multi-element profile of house dust in relation to exterior dust and soils in the city of Ottawa, Canada

This paper presents multi-element profiles of indoor dust versus exterior soils and dusts from 50 residences located in 10 neighborhoods across Ottawa, the capital city of Canada. Mercury concentrations were determined using nitric–sulphuric acid digestion and cold vapor AAS. Concentrations of 31 other elements were determined using nitric–hydrofluoric acid digestion and ICP-MS. Comparisons of household dust, garden soil and street dust at the individual residence scale and at the community scale were based on a consistent 100–250 μm particle size fraction. Results showed housedust samples to contain significantly higher concentrations of many key elements, including lead, cadmium, antimony and mercury, than either street dust or garden soil samples. Also, housedust profiles revealed a distinct multi-element signature in relation to exterior dust and soil samples. Interestingly, garden soil contained higher concentrations of aluminum, barium and thallium than either house or street dust. Geometric mean concentrations (mg/kg) of these elements in household dust/garden soil were: lead 233/42; cadmium 4.42/0.27; antimony 5.54/0.25; mercury 1.728/0.055; aluminum 24281/55677; barium 454/763; and thallium 0.14/0.29. Street dust contained lower geometric mean concentrations than garden soil for 23 out of a total of 32 elements. In general, indoor/outdoor concentration ratios varied widely from one element to another, and from one residence to another within the community. In the case of Ottawa, which is a city with a low concentration of heavy industries, it would be difficult-to-impossible to accurately predict indoor dust concentrations based on exterior soil data. It is concluded that dust generated from sources within the house itself can contribute significantly to exposures to certain elements, such as lead, cadmium, antimony and mercury.