Polluted Field Sites Research Articles

Thermal stress reduces carbonate production of benthic foraminifera and changes the material properties of their shells

Abstract In shallow marine environments, benthic foraminifera are important foundation species and carbonate producers. Understanding their response to future climate is often drawn from their acclimation potential in short laboratory experiments, thereby limiting our understanding of migration, species replacement, and adaptive potential. To overcome this challenge, we examine two species of benthic foraminifera from a thermally polluted field site mimicking future warming. This site and a control station cover 13–36°C causing both warm and cold stress to the local species. Computer Tomography reveals that under heat stress, even with acclimation, Lachlanella significantly reduced its shell volume. In contrast, Pararotalia calcariformata did not reduce its shell volume but reduced the relative amount of calcite with respect to shell volume and changed its reproduction cycle from twice to once per year. Raman spectroscopy indicates that thermal conditions alter the chemical composition of the calcite shells of both species. Calcification during thermal stress creates alterations in the crystal structure that are unexpectedly more prominent under cold stress than warm stress indicating warming might positively affect the shell's protective function. Supported by previous laboratory experiments and observations from the geological record, our results provide new perspective to the effect of warming on benthic foraminifera.

The Effects of More Realistic Forms of Lead Heterogeneity in Soil on Uptake, Biomass and Root Response of Two Brassica species

The spatial heterogeneity of soil constituents is known to have significant impacts on plant growth and plant uptake of nutrients and contaminants, yet studies have rarely used patterns of heterogeneity based on those found in the field. Heterogeneity refers to how lumpy materials are distributed in the soil, whilst homogeneity is the uniformity in the distribution of such materials. We identified patterns of lead contamination at historically polluted field sites and conducted pot trials using field–based parameters to determine the pattern of distribution of lead within the pots. We examined plant Pb uptake and growth in simulated low, medium and high heterogeneity environments as well as a control homogeneous treatment. We found a significant effect of Pb spatial heterogeneity on uptake and biomass of two Brassica species (Brassica napus and Brassica juncea), both candidate species for phytoremediation projects. Biomass was 4 to 5 fold lower in the high heterogeneity treatment and total plant Pb uptake as Pb mass in (µg) was 40 to 80% lower, compared to the homogeneous treatment. Plant lead concentration (mg/kg) increased by a factor of 2 with increasing heterogeneity. Peak uptake was observed in low and medium heterogeneity treatments of B. napus and B. juncea respectively. We also explored roots behaviour in the high heterogeneity treatment and found variation in root mass by 20 to 80% between concentric patches with significant (P < 0.05) differences between patches and species. High proportion of roots (40 to 50%) were proliferated in patches of lower Pb concentration. The tap root was a greater proportion of root in B. napus, which was absent in B. juncea. Results suggest that root morphology of this plant species might be a factor influencing the placement of roots in concentric patches and consequently the overall root response to Pb spatial heterogeneity. This is an indication that the root response could be realistic of that experienced by plants in field conditions. Generally result showed that spatial heterogeneity of Pb has a significant effect on plant growth and biomass. This study also demonstrated that the presence and extent of in situ heterogeneity of Pb in soil plays an important role in Pb uptake by plants. This work has implications for improving the phytoremediation of Pb contaminated land, phytomining, the reliability of risk assessment/models of human exposure to Pb and the quality of trace mineral content of agricultural produce.

Spatial heterogeneity of dechlorinating bacteria and limiting factors forin situ trichloroethene dechlorination revealed by analyses of sediment cores from a polluted field site

Microbiological analyses of sediment samples were conducted to explore potentials and limitations for bioremediation of field sites polluted with chlorinated ethenes. Intact sediment cores, collected by direct push probing from a 35-ha contaminated area, were analyzed in horizontal layers. Cultivation-independent PCR revealed Dehalococcoides to be the most abundant 16S rRNA gene phylotype with a suspected potential for reductive dechlorination of the major contaminant trichloroethene (TCE). In declining abundances, Desulfitobacterium, Desulfuromonas and Dehalobacter were also detected. In TCE-amended sediment slurry incubations, 66% of 121 sediment samples were dechlorinating, among them one-third completely and the rest incompletely (end product cis-1,2-dichloroethene; cDCE). Both PCR and slurry analyses revealed highly heterogeneous horizontal and vertical distributions of the dechlorination potentials in the sediments. Complete reductive TCE dechlorination correlated with the presence of Dehalococcoides, accompanied by Acetobacterium and a relative of Trichococcus pasteurii. Sediment incubations under close to in situ conditions showed that a low TCE dechlorination activity could be stimulated by 7 mg L(-1) dissolved carbon for cDCE formation and by an additional 36 mg carbon (lactate) L(-1) for further dechlorination. The study demonstrates that the highly heterogeneous distribution of TCE degraders and their specific requirements for carbon and electrons are key issues for TCE degradation in contaminated sites.

Are laboratory derived toxicity results informative for field situations? Case study on earthworm populations contaminated with heavy metals

The relevance of laboratory tests on toxicants for field situations is often disputed given that laboratory tests are conducted under, next to the toxicant stress, optimal conditions which are not expected in field situations. In this paper we confront the results of laboratory tests on growth, reproduction and survival of earthworms, in a polluted and a reference field soil with a field inventory of earthworms. The field inventory includes population density, biomass and demographic composition in life stages measured monthly over a period of one year. The field inventory showed that density and biomass was higher at the polluted field site, a result in conflict with the extrapolation of the laboratory tests that showed a decrease in population growth rate by 23% at this site compared to the reference. The field inventory and laboratory derived results agreed in the demographic composition of the population with more individuals in the younger age class at the polluted site compared to the reference. Abiotic and biotic conditions that differ between sites and could possibly explain the lower earthworm biomass and density at the reference site are discussed. We suggest that predation by the two to five times higher densities of meadow birds in spring may have caused the lower density and biomass of earthworms at the reference site.

Modeling the Impact of a Benzene Source Zone on the Transport Behavior of PAHs in Groundwater

Aquifers at industrial sites are commonly characterized by a multitude of contaminant source zones. Conceivably, dissolved contaminants originating from an up-gradient residual nonaqueous phase liquid (NAPL) source zone may be transported along the groundwater flow path into another residual NAPL source zone down-gradient. However, if and how contaminants from different zones may affect one another with regard to dissolution and transport has thus far been unknown. To identify and understand such potential interactions, the numerical model BIONAPL3D was applied to simulate the behavior of six dissolved polycyclic aromatic hydrocarbons (PAHs), stemming simultaneously from an up-gradient NAPL source zone, when they encounter a down-gradient NAPL source zone. The down-gradient NAPL source zone was assumed to be a residual benzene phase with a saturation of 10%. When the dissolved PAHs entered the benzene source zone, the aqueous PAH concentrations declined significantly due to their partitioning into the residual benzene phase. As benzene rapidly dissolved intothe aqueous phase,the PAHswere resolubilized with negligible impact due to benzene co-solvency. The degree of resolubilization was much smaller than the initial loss due to partitioning into the benzene phase. Thus, the PAHs formed a new residual NAPL phase that, over time, replaced the original benzene source zone. The new NAPL phase continued to grow even after all of the benzene was dissolved. Our modeling approach is the first theoretical demonstration of a significant interaction of contaminants emanating from multiple source zones. It should be regarded as a starting point to consider source zone interactions at polluted field sites.

Expression of cytoskeletal proteins, cross-reacting with anti-CYP1A, in Mytilus sp. exposed to organic contaminants

The possible use of cytoskeletal components as biomarkers of organic pollution in mussels has been investigated. Responses of non-muscular actin and tropomyosin (TM), two bivalve proteins that were recently demonstrated to cross-react with anti-fish-CYP1A, were analysed in digestive tissue of blue mussels ( Mytilus sp.) exposed to a wide range of organic contaminants. The results were evaluated with ELISA and Western blot assays, utilising commercial monoclonal antibodies, and compared with expression of Hsp70, a marker of chemical stress. Furthermore, mussels were sampled from the Baltic Sea at sites with different degrees of pollution to assess the expression of these proteins, and to monitor seasonal changes in relation to energy reserves and water temperature. The results demonstrated that expression of microsomal actin was significantly higher ( p < 0.02) in mussels exposed to a brominated flame retardant (BDE-47), and lower, however not significantly, in specimens exposed to crude oil, alone and spiked with alkylphenols and PAHs. Hsp70 was strongly induced in all exposure groups, which also included bisphenol A and diallylphthalate. Furthermore, microsomal actin exhibited seasonal variations, and expression was negatively correlated with water temperature. No correlation was seen between actin and the microfilament-binding protein TM, indicating that regulation of these two cytoskeletal components are not coupled. Furthermore, parallel and significant ( p < 0.05) up-regulations of TM and Hsp70 were seen in individuals sampled from a strongly polluted field site, whereas the seasonal analysis showed that TM expression was positively correlated with energy reserves (total glycogen content) in mussels, suggesting the use of TM as a marker of growth. In conclusion, this study has demonstrated the cytoskeleton to be a target of contaminants in mussels, calling for further attention. Exposure-induced increase of microsomal actin can be interpreted either as stimulated actin synthesis, or re-arrangements of the dynamic microfilaments.

Bioturbation effects of Chironomus riparius on the benthic N-cycle as measured using microsensors and microbiological assays

Chironomus riparius (Diptera) larvae were added to laboratory microcosms containing defaunated sediments sampled at 2 NO 3 -polluted field sites. Following a 3 wk incubation, the larval influence on the sedimentary nitrogen conversions was studied using microsensors (O 2 , NO 3 - , NH 4 + ) and microbial bulk parameters (microbial biomass, community respiration). At the sediment surface the chironomid larvae fed on particles (deposit-feeding layer), while in the subsurface zone the larvae moved through the sediment and ventilated transient or permanent burrows (ventilation layer). In the deposit-feeding layer of the chironomids, NO 3 - production and NH 4 + consumption were lower and microbial biomass decreased. In the ventilation layer of the chironomids, NO 3 - and NH 4 + conversion maxima were shifted downwards, and both microbial biomass and community respiration were increased. The observed changes in the vertical stratigraphy of the benthic microbial community were ascribed to the depth-specific larval behaviour as: (1) particle ingestion and removal of adhering microorganisms in the deposit-feeding layer; and (2) stimulation of subsurface microorganisms due to an increased supply of O 2 and NO 3 - along with larval ventilation.

Bioindication Potential of Carbonic Anhydrase Activity in Anemones and Corals

Activity levels of carbonic anhydrase (CA) were assessed in anemones Condylactis gigantea and Stichodactyla helianthus with laboratory exposures to copper, nickel, lead, and vanadium, and also in animals collected from polluted vs pristine field sites. CA activity was found to be decreased with increase in metal concentration and also in animals collected from the polluted field site. Preliminary assessments to adapt the CA assay for use in the widespread coral Montastraea cavernosa show decreased CA activity in specimens from the polluted field site and provide an avenue for future research aimed at more thoroughly describing coral CA activity for potential application in bioindication.

Apparent induction of a cytochrome P450 with immunochemical similarities to CYP1A in digestive gland of the common mussel (Mytilus galloprovincialis L.) with exposure to 2,2′,3,4,4′,5′-hexachlorobiphenyl and Arochlor 1254

The induction of a cytochrome P450 with immunochemical similarities to CYP1A, and accompanying changes in microsomal NADPH-dependent benzo[a]pyrene (BaP) metabolism, were examined in digestive gland of the common mussel (Mytilus galloprovincialis L.) with exposure to 20 ppb water-borne polychlorobiphenyl (PCB) mixture (Arochlor 1254) for 4 or 10 days, or 4 days after a single injection into the mantle cavity of the mixed-type inducer PCB congener 2,2′,3,4,4′,5′-hexachlorobiphenyl (CB-138; 2.5 μg g−1 wet weight). Whole animal tissue levels of PCB following water-column exposure or injection were similar to those for mussel species from polluted field sites, viz. 0.8 to 1.9 μg g−1 wet weight. Levels of microsomal CYP1A-immunopositive protein increased 59% (CB-138) and 72% (Arochlor 1254; 10 days exposure) as determined by Western blot analysis using polyclonal antibodies to hepatic CYP1A of perch (Perca fluviatilis). No changes were seen in levels of digestive gland CYP1A-like mRNA 4 days after injection of CB-138 as determined by Northern analysis using cDNA to hepatic CYP1A1 of rainbow trout (Oncorhynchus mykiss). The increases in levels of CYP1A-immunopositive protein were accompanied by a shift in microsomal NADPH-dependent BaP metabolism towards phenol and diol and away from dione production, the former increasing from 32 to 85% of total free metabolites. The marked decrease in dione production (which is the major BaP metabolite formed in control microsomes) resulted in no increase in total microsomal BaP metabolism with exposure to PCBs. The Type I ligand α-naphthoflavone markedly inhibited microsomal phenol but had no affect on dione production, whereas the Type II ligand clotrimazole markedly inhibited dione, but had much less effect on phenol production. The overall results are interpreted in terms of the existence of an inducible CYP1A-like enzyme catalysing predominantly 2-electron monooxygenation leading to epoxide (and hence phenol and diol) formation, and a constitutive non-inducible cytochrome P450 catalysing predominantly 1-electron oxidation leading to dione formation. Both Arochlor 1254 or CB-138 produced cellular damage in the digestive gland in the form of decreased epithelial digestive cell height and decreased lysosomal membrane stability.

A New Laboratory Technique for Studying the Effects of Heavy Metals on Bryophyte Growth

A novel, non-destructive method for measuring moss gametophyte growth rates is presented. Standard 2-cm moss gametophores are supported vertically on Velcro strips held within a clear perspex box, with their bases resting in liquid. Shoots sampled from the field were either continuously exposed to test solutions via their cut bases, or by preliminary pulse-immersion. Growth was assessed by linear extension, or final dry mass, and showed different patterns and sensitivities to heavy metals using the two exposure methods. A biologically appropriate assessment of toxicity was established, using tissue concentrations comparable to material from polluted field sites, by considering the cellular location of heavy metals in shoots. A linear relationship was established between apical growth and intracellular Zn concentration recovered in the newly produced gametophyte tissue, irrespective of the method of exposure or Zn concentration in the remaining or original shoot portion. The limitations and ambiguity associated with many heavy-metal monitoring and toxicity studies are addressed, and the advantages and further applications offered by this growth system are discussed.

Sulphate and antioxidants in needles of Scots pine (Pinus sylvestrisL.) from three SO2‐polluted field sites in eastern Germany

summaryNeedles from young and mature Scots pine trees (Pinus sylvestirs) were collected at three field sites in eastern Germany, i.e. Menz, Taura, and Gossa, which differed in SO2pollution. Current and previous year's needles from the polluted sites Taura and Gossa (yearly mean af SO2: 26 ppb) contained approximately 100‐120 μmol sulphate g−1d. wt, whereas needles tram the unpolluted site, Menz (yearly mean of SO2: 3 ppb) contained 30‐65 μmol sulphate g−1d. wt. The apoplastic sulphate content was in the order of o.3‐1% of total sulphate and corresponded to concentrations of 0.6‐1.2 mM in needles from Mtnz and to 1.5–2 mn in needles from Gossa. In needles from the polluted sites the contents of glutathione, cysteine, γ glutamyleysteine, and soluble protein were higher than in needles from Menz. Despite the clear increases in sulphur‐containing compounds, pigment content and activities of superoxide dismutase, total peroxidase and apoplastic peroxidase (on the basis of d. wt) were not significantly different. When enzymatic activities were related to protein, lowest activities were found in needles from the site with the highest SO2‐pollution. The results show that it is not possible to use the activities of peroxidases or superoxide dismutases as biomarkers for SO2‐mediated stress in pine needles. It remains open whether the needles from the polluted sites suffered from greater oxidative stress than the needles from the less polluted site.

Allozyme polymorphism and protein profile in Orchesella bifasciata (Collembola): Indicative of extended metal pollution?

Allozyme variation and protein profiles of Orchesella bifasciata (Collembola) populations collected from a range of metal polluted forest soils were compared using starch gel and polyacrylamide electrophoresis. The purpose of the work was to examine whether simple biochemical expressions for genetic differences can be used to distinguish individuals collected at a metal polluted field site from those collected at an unpolluted site. Significant differences were observed between populations in allele and genotype frequencies and in survival rates, but there was no significant correlation between the genetic differences and the metal concentration in the litter. The absence of consistent effects of metals on the allozyme and protein pattern may be explained by a high degree of genetic exchange between the populations, selection pressures other than metals dominating the genetic variation among populations or simply an absence of selection at the studied, or at any linked loci. The genetic homogeneity among populations was high, and the value of Nei's genetic distance ranged from 0.001 to 0.016. Calculations of genetic divergence ( F ST indicate that less than 2% of the total variation in O. bifasciata was due to genetic differences between populations. If this value is translated to a number of migrants, the populations may exchange 10–50 individuals per generation. Among the 32 identified proteins two (120 and 189 kDa) were detected at a significantly higher frequency in individuals from the metal polluted soil. Classical stress proteins in the range of 60–80 kDa were not detected. It is suggested that the resolution of one-dimensional gel electrophoresis is too low to distinguish a resistant population from a non-resistant without prior experimental exposure to high metal concentrations.