Anne M. Taylor

Arsenic Species in a Rocky Intertidal Marine Food Chain in NSW, Australia, revisited

Environmental Context. The pathways by which arsenic is accumulated, biotransformed and transferred in aquatic ecosystems are relatively unknown. Examination of whole marine ecosystems rather than individual organisms provides greater insights into the biogeochemical cycling of arsenic. Rocky intertidal zones, which have a high abundance of organisms but low ecological diversity, are an important marine habitat. This study examines the cycling of arsenic within intertidal ecosystems to further understand its distribution and transfer. Abstract. The present study reports total arsenic and arsenic species in a short rocky intertidal marine food chain in NSW, Australia. Total mean arsenic concentrations increased up the food chain in the following order: 4 ± 2 µg g–1 in attached rock microalgae, 31 ± 14 µg g–1 in Bembicium nanum Lamarck, 45 ± 14 µg g–1 in Cellana tramoserica Sowerby, 58 ± 14 µg g–1 in Nerita atramentosa Reeve, 75 ± 15 µg g–1 in Austrocochlea constrica Lamarck (a herbivore) and 476 ± 285 µg g–1 in the carnivore Morula marginalba Blainville. Significant differences in arsenic concentrations of B. nanum, N. atramentosa and M. marginalba were found among locations and may be related to food availability, spawning or differences in age and/or size classes of individuals. Significant differences in arsenic concentrations were also found within locations among species, and increased in the order: rock microalgae < B. nanum < C. tramoserica < N. atramentosa < A. constricta < M. marginalba. Although small differences in total arsenic concentrations were found among locations for some gastropod species, arsenic species proportions were very consistent within gastropod species across locations. The majority of arsenic in Homosira banksii (macroalgae) was oxo-arsenoribosides, with thio-arsenoribosides making up ~10% of the total methanol–water extractable arsenic. The rock microalgae contained arsenobetaine (AB) (59 ± 5%) and arsenoribosides (36 ± 15%). The AB content of the herbivores B. nanum, N. atramentosa and A. constricta ranged from 71 to 95%, and that of the carnivore M. marginalba was 98%. Most gastropods contained thio-arsenosugars (up to 13 ± 3% of total extractable arsenic), with C. tramoserica containing higher proportions of thio-phosphate arsenoriboside (7 ± 2%) and lower proportions of AB (69 ± 4%). Glycerol trimethylarsonioribosides (1.4 ± 0.1%) were also found in most of the herbivorous gastropods. Oxo-dimethylarsinoylethanol (oxo-DMAE) was found in N. atramentosa (<1%).

Arsenic distribution and species in two Zostera capricorni seagrass ecosystems, New South Wales, Australia

Arsenic concentrations and species were compared in biota from two Zostera capricorni ecosystems. Mean arsenic concentrations were not significantly different for non-vegetative sediment, rhizosphere sediment, Z. capricorni blades, roots, rhizomes, epiphytes, amphipods, polychaetes, molluscs, crustaceans and fish, but were significantly different in detritus. Sediments and plant tissues contained mostly inorganic arsenic and PO4-arsenoriboside. Detritus contained mostly PO4-arsenoriboside. Fish tissues contained predominately arsenobetaine. Other animals had lower proportions of arsenobetaine and variable quantities of minor arsenic species. Bioconcentration but not biomagnification ofarsenicisoccurringwithnoevidenceofarsenichyperaccumulation.Theproportionofarsenobetaineincreasesthrough the food web and is attributed to a shift from a mixed diet at lower trophic levels to animals containing mostly arsenobetaineathighertrophiclevelsandthemoreefficientretentionofarsenobetaine,comparedtootherarsenic species.

Importance of Subcellular Metal Partitioning and Kinetics to Predicting Sublethal Effects of Copper in Two Deposit-Feeding Organisms

The role of subcellular partitioning of copper on the sublethal effects to two deposit-feeding organisms (41-day growth in the bivalve Tellina deltoidalis and 11-day reproduction in the amphipod Melita plumulosa) was assessed for copper-spiked sediments with different geochemical properties. Large differences in bioaccumulation and detoxification strategies were observed. The bivalve accumulated copper faster than the amphipod, and can be considered a relatively strong net bioaccumulator. The bivalve, however, appears to regulate the metabolically available fraction (MAF) of the total metal pool by increasing the net accumulation rate of copper in the biologically detoxified metal pool (BDM), where most of the copper is stored. In the amphipod, BDM concentration remained constant with increasing copper exposures and it can be considered a very weak net bioaccumulator of copper. This regulation of copper, with relatively little stored in detoxified forms, appears to best describe the strategy applied by the amphipod to minimize the potential toxic effects of copper. When the EC50 values for growth and reproduction are expressed based on the MAF of copper, the sensitivity of the two species appears similar, however when expressed based on the net accumulation rate of copper in the metabolically available fraction (MAFrate), the bivalve appears more sensitive to copper. These results indicate that describing the causality of metal effects in terms of kinetics of uptake, detoxification, and excretion rather than threshold metal body concentrations is more effective in predicting the toxic effects of copper. Although the expression of metal toxicity in terms of the rate at which the metal is bioaccumulated into metabolically available forms may not be feasible for routine assessments, a deeper understanding of uptake rates from all exposure routes may improve our ability to assess the risk posed by metal-contaminated sediments.

Distribution and Speciation of Arsenic in Temperate Marine Saltmarsh Ecosystems

This paper reports the distribution of total arsenic and arsenic species in saltmarsh ecosystems located in south-east Australia. We also investigated the relationship between arsenic, iron, and phosphorus concentrations in saltmarsh halophytes and associated sediment. Total mean arsenic concentrations in saltmarsh plants, S. quinqueflora and S. australis, for leaves ranged from 0.03 ± 0.05 to 0.67 ± 0.48 µ gg −1 and 0.03 ± 0.02 to 0.08 ± 0.06 µ gg −1 , respectively, and for roots ranged from 2 ± 2t o 6± 12 µ gg −1 and 0.39 ± 0.20 to 0.57 ± 1.06 µ gg −1 respectively. Removal of iron plaque from the roots reduced the arsenic concentration variability to 0.40-0.79 µ gg −1 and 0.95-1.05 µ gg −1 for S. quinqueflora and S. australis roots respectively. Significant differences were found between locations for total arsenic con- centrations in plant tissues and these differences could be partially attributed to differences in sediment arsenic concentrations between locations. For S. quinqueflora but not S. australis there was a strong correlation between arsenic and iron concentrations in the leaf and root tissues. A significant negative relationship between arsenic and phosphorus concentrations was found for S. quinqueflora leaves but not roots. Total mean arsenic concentrations in salt marsh animal tissues (7 ± 2-21 ± 13 µ gg −1 ) were consistent with those found for other marine animals. The concentration of total arsenic in gastropods and amphipods could be partially explained by the concentration of total arsenic in the dominant saltmarsh plant S. quinqueflora. Of the extractable arsenic, saltmarsh plants were dominated by arsenic(iii), arsenic(v) (66-99%), and glycerol arsenoribose (17-35%). Arsenobetaine was the dominant extractable arsenic species in the gastropods Salinator soilda (84%) and Ophicardelus ornatus (89%) and the crab Neosarmatium meinerti (89%). Amphipods contained mainly arsenobetaine (44%) with some phosphate arsenoribose (23%). Glycerol trimethyl arsonioribose was found in both gastropods (0.7-0.8%) and the visceral mass of N. meinerti (0.1%). These results show that arsenic uptake into plants from uncontaminated saltmarsh environments maybe dependent on plant iron uptake and inhibited by high phosphorus concentrations. Arsenic in saltmarsh plants is mainly present as inorganic arsenic, but arsenic in animals that eat plant detritus is present as organo arsenic species, primarily arsenobetaine and arsenosugars. The presence of glycerol trimethyl arsonioribose poses the question of whether trimethylated arsonioriboses are transitory intermediates in the formation of arsenobetaine.

Exposure-dose-response of Tellina deltoidalis to metal contaminated estuarine sediments 2. Lead spiked sediments

Lead accumulation in estuarine sediments, as a result of activities such as mining and ore smelting, and through urban runoff is a continuing problem in the increasingly developed world. Marine organisms accumulate lead, which is known to be highly toxic to biological processes and to degrade organism and ecosystem health. Here the relationship between lead exposure, dose and response was investigated in the sediment dwelling, deposit feeding, marine bivalve Tellina deltoidalis. Bivalves were exposed in the laboratory to individual lead spiked sediments at < 0.01, 100 and 300 μg/g dry mass, for 28 days and accumulated total tissue lead concentrations of 4, 96 and 430 μg/g, respectively. Subcellular fractionation indicated that around 70% of the total accumulated tissue lead was detoxified, three quarters of the detoxified lead fraction was converted into metal rich granules, with the remainder in the metallothionein like protein fraction. The majority of biologically active lead was associated with the mitochondrial fraction with up to a 128 fold increase in lead burden in exposed organisms compared to controls. This indicates lead detoxification was occurring but the organism was unable to prevent lead interacting with sensitive organelles. With increased lead exposure T. deltoidalis showed a suppression in glutathione peroxidase activity, total glutathione concentration and reduced GSH:GSSG ratios, however, these differences were not significant. Lead exposed T. deltoidalis had a significantly reduced total antioxidant capacity which corresponded with increased lipid peroxidation, lysosomal destabilisation and micronuclei frequency. The exposure-dose-response relationships demonstrated for lead exposed T. deltoidalis supports its potential for the development of sublethal endpoints in lead toxicity assessment.

Effects of lead-spiked sediments on freshwater bivalve, Hyridella australis: linking organism metal exposure-dose-response

Lead entering aquatic ecosystems adsorbs to sediments and has the potential to cause adverse effects on the health of benthic organisms. To evaluate the freshwater bivalve Hyridella australis as a bioindicator for sediment toxicity, their exposure-dose and response to lead contaminated sediments (< 0.01, 205 ± 9 and 419 ± 16 μg/g dry mass) was investigated in laboratory microcosms using 28 day exposures. Despite high concentrations of lead in the sediments, organisms accumulated low concentrations of lead in their tissues after 28 days of exposure (low treatment: 2.2 ± 0.2 μg/g dry mass, high treatment: 4.2 ± 0.1 μg/g dry mass), however, accumulated lead concentrations in lead exposed organisms were two fold (low treatment) and four fold (high treatment) higher than that of unexposed organisms (1.2 ± 0.3 μg/g dry mass). Accumulation of lead by H. australis may have occurred as analogues of calcium and magnesium. Labial palps accumulated significantly more lead than other tissues. Of the lead accumulated in the hepatopancreas, 83%-91% was detoxified and stored in metal rich granules. The proportions and concentrations of lead in this fraction increased with lead exposure, which suggests that lead detoxification pathway plays an important role in metal tolerance of H. australis. The biologically active lead was mainly present in the mitochondrial fraction which increased with lead exposure. Total antioxidant capacity of H. australis significantly decreased while lipid peroxidation and lysosomal membrane destabilation increased with lead exposure. This study showed a clear lead exposure-dose-response relationship and indicates that H. australis would be a good biomonitor for lead in freshwater ecosystems.

The Use of Two Marine Gastropods, Austrocochlea constricta and Bembicium auratum, as Biomonitors of Zinc, Cadmium, and Copper Exposure: Effect of Tissue Distribution, Gender, Reproductive State, and Temporal Variation

Abstract This investigation examined the influence of tissue distribution, gender, reproductive state, temporal variation, salinity, and water temperature on zinc, cadmium, and copper tissue concentrations in two intertidal gastropods, Austrocochlea constricta and Bembicium auratum. More of the variability in total zinc, copper, and cadmium concentrations of both species was explained by trace metal variability in digestive/gonad tissue than by variability in somatic tissue metal concentration. Although there was significant temporal variation in tissue trace metal concentrations, gender, reproductive state, salinity, and water temperature individually did not account for these differences. It was not possible to entirely disentangle the interactions of several concurrent processes such as spawning and mass gain and loss; however, these do not appear to be confounding factors for the use of these gastropods as biomonitors for the comparison of trace metal concentrations between populations at different locations.

Effects of cadmium accumulation from suspended sediments and phytoplankton on the Oyster Saccostrea glomerata

Metals are accumulated by filter feeding organisms via water, ingestion of suspended sediments or food. The uptake pathway can affect metal toxicity. Saccostrea glomerata were exposed to cadmium through cadmium-spiked suspended sediments (19 and 93μg/g dry mass) and cadmium-enriched phytoplankton (1.6-3μg/g dry mass) and cadmium uptake and effects measured. Oysters accumulated appreciable amounts of cadmium from both low and high cadmium spiked suspended sediment treatments (5.9±0.4μg/g and 23±2μg/g respectively compared to controls 0.97±0.05μg/g dry mass). Only a small amount of cadmium was accumulated by ingestion of cadmium-enriched phytoplankton (1.9±0.1μg/g compared to controls 1.2±0.1μg/g). In the cadmium spiked suspended sediment experiments, most cadmium was desorbed from sediments and cadmium concentrations in S. glomerata were significantly related to dissolved cadmium concentrations (4-21μg/L) in the overlying water. In the phytoplankton feeding experiment cadmium concentrations in overlying water were <0.01μg/L. In both exposure experiments, cadmium-exposed oysters showed a significant reduction in total antioxidant capacity and significantly increased lipid peroxidation and percentage of destabilised lysosomes. Destabilised lysosomes in the suspended sediments experiments also resulted from stress of exposure to the suspended sediments. The study demonstrated that exposure to cadmium via suspended sediments and to low concentrations of cadmium through the ingestion of phytoplankton, can cause sublethal stress to S. glomerata.

Recent history of sediment metal contamination in Lake Macquarie, Australia, and an assessment of ash handling procedure effectiveness in mitigating metal contamination from coal-fired power stations

This study assessed historical changes in metal concentrations in sediments of southern Lake Macquarie resulting from the activities of coal-fired power stations, using a multi-proxy approach which combines (210)Pb, (137)Cs and metal concentrations in sediment cores. Metal concentrations in the lake were on average, Zn: 67 mg/kg, Cu: 15 mg/kg, As: 8 mg/kg, Se: 2mg/kg, Cd: 1.5 mg/kg, Pb: 8 mg/kg with a maximum of Zn: 280 mg/kg, Cu: 80 mg/kg, As: 21 mg/kg, Se: 5 mg/kg, Cd: 4 mg/kg, Pb: 48 mg/kg. The ratios of measured concentrations in sediment cores to their sediment guidelines were Cd 1.8, As 1.0, Cu 0.5, Pb 0.2 and Zn 0.2, with the highest concern being for cadmium. Of special interest was assessment of the effects of changes in ash handling procedures by the Vales Point power station on the metal concentrations in the sediments. Comparing sediment layers before and after ash handling procedures were implemented, zinc concentrations have decreased 10%, arsenic 37%, selenium 20%, cadmium 38% and lead 14%. An analysis of contaminant depth profiles showed that, after implementation of new ash handling procedures in 1995, selenium and cadmium, the main contaminants in Australian black coal had decreased significantly in this estuary.

Bioavailability and toxicity of zinc from contaminated freshwater sediments: Linking exposure-dose-response relationships of the freshwater bivalve Hyridella australis to zinc-spiked sediments

To evaluate the use of the freshwater bivalve Hyridella australis as a potential biomonitor for zinc contamination in freshwater sediments, the bioavailability and toxicity of zinc contaminated sediments (low 44 ± 5, medium 526 ± 41, high 961 ± 38 μg/g dry mass) were investigated in laboratory microcosms for 28 days by examining H. australis exposure-dose-response relationships. Zinc concentrations in sediments and surface waters were measured as zinc exposure. Zinc in whole organism soft body tissues and five individual tissues were measured as organism zinc dose. Sub-cellular localisation of zinc in hepatopancreas tissues was investigated to further understand the zinc handling strategies and tolerance of H. australis. Total antioxidant capacity, lipid peroxidation and lysosomal membrane stability were measured in hepatopancreas tissues as zinc induced biomarker responses. Accumulated zinc concentrations in whole body tissues of H. australis reflected the zinc exposure and exhibited exposure dependent zinc accumulation at day 28. Gills accumulated significantly higher zinc concentrations than other tissues, however, no significant differences in zinc accumulation between treatments were detected for any of the individual tissues analysed. Analysis of individual tissue zinc concentrations, therefore, may not offer any advantages for monitoring bioavailable zinc in freshwater environments with this organism. Relationships between tissue zinc and calcium concentration suggest accumulation of zinc by H. australis may have occurred as an analogue of calcium which is a major constituent in shell and granules of unionid bivalves. A high percentage of accumulated zinc in the hepatopancreas tissues was detoxified and stored in metallothionein like proteins and metal rich granules. Of the zinc accumulated in the biologically active metal pool, 59-70% was stored in the lysosome+microsome fraction. At the concentrations tested, increasing zinc exposure resulted in decreasing total antioxidant capacity and measurable increases in the sublethal effects, lipid peroxidation and lysosomal membrane destabilisation, were observed. Based on exposure-dose analysis, H. australis partially regulates zinc uptake and weakly exhibits bioavailability of zinc in freshwater environments, however, exposure-response analysis shows zinc induced toxicological effects, suggesting the potential of this organism as a biomonitor for zinc in heavily contaminated freshwater environments.