Amanda J Reichelt-Brushett

The Effect of Copper on the Settlement Success of Larvae from the Scleractinian Coral Acropora tenuis

Abstract This study examined the effect of copper on the settlement success of planula larvae of the reef-building coral Acropora tenuis during 1994 and 1996 at Magnetic Island, Great Barrier Reef. Copper concentrations of 2, 10, 20 μg l−1 did not inhibit larval settlement after 48-h exposure. However, copper concentrations of 42 μg l−1 and 81 μg l−1 significantly reduced settlement success of A. tenuis larvae after 48-h exposure compared with controls using normal seawater. At 200 μg l−1 copper, all larvae died. EC50 values for the effect of copper on A. tenuis larval settlement were calculated from the 1996 results using measured copper concentrations. The 48-h EC50 was 35 μg l−1 with an upper and lower 95% confidence limit of 37 μg l−1 and 32 μg l−1, respectively. The 48-h NOEC value for both experiments was 20 μg l−1 copper. These experiments provide some of the first data on sub-lethal effects of trace metals on tropical marine organisms, and demonstrate that relatively low copper concentrations impair or inhibit settlement of coral larvae.

Trace metals in the living and nonliving components of scleractinian corals

Trace metals in coral tissue and skeleton have been investigated in various ways since the early seventies. More recently it has been suggested that the symbiotic zooxanthellae may play an important role in the accumulation and regulation of trace metals. Furthermore gamete development and mucus production may influence the metal accumulation and loss in corals. Many studies have attempted to use the annual growth bands in coral skeletons to investigate historical pollution events. However the relationship between the metal concentrations in the surrounding environment and the incorporation of this into coral skeleton is not well understood. This paper explains a method for investigating metal loads in coral tissue, zooxanthellae and skeleton. Furthermore, it presents new information suggesting that zooxanthellae accumulate most metals (Al, Fe, As, Mn, Ni, Cu, Zn, Cd, Pb) in greater concentrations than the coral tissue. Coral skeletons had consistently lower metal concentration than the zooxanthellae, tissue and gametes. The loss of zooxanthellae during stress events may have a significant contribution to the total metal loads in corals. The use of corals as biomonitors should carefully factor in zooxanthellae densities and gamete development before conclusions are drawn.

Electroacoustic isoelectric point determinations of bauxite refinery residues: different neutralization techniques and minor mineral effects.

Bauxite refinery residue (BRR) is a highly caustic, iron hydroxide-rich byproduct from alumina production. Some chemical treatments of BRR reduce soluble alkalinity and lower residue pH (to values <10) and generate a modified BRR (MBRR). MBRR has excellent acid neutralizing (ANC) and trace-metal adsorption capacities, making it particularly useful in environmental remediation. However, soluble ANC makes standard acid-base isoelectric point (IEP) determination difficult. Consequently, the IEP of a BRR and five MBRR derivatives (sulfuric acid-, carbon dioxide-, seawater-, a hybrid neutralization, i.e, partial CO(2) neutralization followed by seawater, and an activated-seawater-neutralized MBRR) were determined using electroacoustic techniques. Residues showed three significantly different groups of IEPs (p < 0.05) based around the neutralization used. Where the primary mineral assemblage is effectively unchanged, the IEPs were not significantly different from BRR (pH 6.6-6.9). However, neutralizations generating neoformational minerals (alkalinity precipitation) significantly increased the IEP to pH 8.1, whereas activation (a removal of some primary mineralogy) significantly lowered the IEP to pH 6.2. Moreover, surface charging curves show that surfaces remain in the ±30 mV surface charge instability range, which provides an explanation as to why MBRRs remove trace metals and oxyanions over a broad pH range, often simultaneously. Importantly, this work shows that minor mineral components in complex mineral systems may have a disproportionate effect on the observable bulk IEP. Furthermore, this work shows the appropriateness of electroacoustic techniques in investigating samples with significant soluble mineral components (e.g., ANC).

Development of a chronic, early life-stage sub-lethal toxicity test and recovery assessment for the tropical zooxanthellate sea anemone Aiptasia pulchella

There is an urgent need to identify additional tropical marine species and develop sensitive sub-lethal and chronic toxicity test methods for routine ecotoxicology. The tropical symbiotic sea anemone Aiptasia pulchella is a suitable species for use in ecotoxicology and here we have assessed the effects of trace metal exposures on the development of asexually produced A. pulchella pedal lacerates to a juvenile stage. Concentrations of 55 µg/L for cadmium, 262 µg/L for cobalt, 5 µg/L for copper, and 269 µg/L for zinc were estimated to inhibit normal development by 50 percent after 8-d exposures, and are among the most sensitive available toxicity estimates for marine organisms. This work illustrates the potential value of this species and sub-lethal toxicological endpoint for routine ecotoxicology in tropical marine environments.

Recent mercury contamination from artisanal gold mining on Buru Island, Indonesia--potential future risks to environmental health and food safety.

In November 2011 gold was found at Mount Botak, Buru Island, Mollucas Province, Indonesia. Since 2012 mercury has been used to extract the gold requiring large volumes of water and resulting in deposition of mercury into Wamsait River and Kayeli Bay. Total mercury in waste ponds was over 680 mg/kg. In sediments at the mouth of the local river and a small feeder creek >3.00 mg/kg and >7.66 mg/kg respectively. River and bay sediments were proportionately higher in available mercury than elemental mercury and more strongly bound mercuric sulfide compared to that in trommel waste. This preliminary investigation raises concerns about the long term distribution and speciation of mercury. The floodplain is an important agricultural resource, and Mollucas Province is recognised nationally as the centre for Indonesian fish stocks. Challenges for management include communicating the potential future risks to the community and leaders and identifying mechanisms to reduce mercury waste.

Bioaccumulation of metals in Eisenia fetida after exposure to a metal-loaded bauxsol™ reagent

The present study investigated the acute toxic effects of a metal-loaded Bauxsol reagent (MLBR), containing more than 6,450 mg kg(-1) of bound metal, on the earthworm Eisenia fetida. Bauxsol is manufactured by Virotec Global Solutions of Gold Coast, Queensland, Australia. The E. fetida were exposed to 0, 10, 20, 40, 60, and 80% treatments of MLBR plus cow manure for 28 d. Good motility and no mortality of E. fetida were found in all treatments after 28 d of exposure. The greatest bioaccumulation of metals by E. fetida occurred in the 20 and 40% MLBR treatments. The bioaccumulation of metals in the worms and bioaccumulation factors (BAFs) were less than the reported toxicity thresholds to cause mortality and less than the reported BAF for moderately contaminated soils, indicating that metals bound to Bauxsol reagents are mostly nonbioavailable. Analyses of the 20% MLBR treatment at 28 d using a sequential extraction procedure showed that more than 95% of the metals are bound within the Fe/Mn oxide fractions. However, changes occurred in metal fractionation after exposure to E. fetida for Cd/Cr, and Fe/Mn. The data also showed that the exchangeable (1 M MgCl2) and the toxicity characteristic leaching procedure extractant are useful as indicators of metal bioavailability from MLBR to E. fetida.

Geochemistry and mercury contamination in receiving environments of artisanal mining wastes and identified concerns for food safety

Abstract Artisanal small‐scale gold mining (ASGM) using mercury (Hg) amalgamation has been occurring on Buru Island, Indonesia since early 2012, and has caused rapid accumulation of high Hg concentrations in river, estuary and marine sediments. In this study, sediment samples were collected from several sites downstream of the Mount Botak ASGM site, as well as in the vicinity of the more recently established site at Gogrea where no sampling had previously been completed. All sediment samples had total Hg (THg) concentrations exceeding Indonesian sediment quality guidelines and were up to 82 times this limit at one estuary site. The geochemistry of sediments in receiving environments indicates the potential for Hg‐methylation to form highly bioavailable Hg species. To assess the current contamination threat from consumption of local seafood, samples of fish, molluscs and crustaceans were collected from the Namlea fish market and analysed for THg concentrations. The majority of edible tissue samples had elevated THg concentrations, which raises concerns for food safety. This study shows that river, estuary and marine ecosystems downstream of ASGM operations on Buru Island are exposed to dangerously high Hg concentrations, which are impacting aquatic food chains, and fisheries resources. Considering the high dietary dependence on marine protein in the associated community and across the Mollucas Province, and the short time period since ASGM operations commenced in this region, the results warrant urgent further investigation, risk mitigation, and community education. HighlightsMercury contamination of sediments and seafood due to artisanal gold mining.Considerable risks to human and ecosystem health are identified.Results emphasise the urgent need for risk mitigation and community education.

The effects of metals of emerging concern on the fertilization success of gametes of the tropical scleractinian coral Platygyra daedalea.

The demand for nickel and cobalt as important commodities has increased significantly over the past decade and a decline in the global nickel sulphide reserves has resulted in a shift toward the exploitation of the less favourable nickel laterite ores. These deposits, which are found associated with cobalt, are located predominantly in the tropical regions of the world where there is limited understanding of the toxicities of their extracted products and wastes. This study investigated the effects of nickel, cobalt and combinations of nickel and cobalt on the fertilization success of the common and widespread scleractinian coral Platygyra daedalea. We also present the first assessment of the effect of copper on fertilization success of this species. The EC50 value for copper was 33 μg L(-1) (95% confidence limits: 30-37 μg L(-1)) and is consistent with published values for other coral species. Our results provide the first EC50 value for the effect of nickel on fertilization success in a scleractinian coral, with an estimated value of 1420 μg L(-1) (95% confidence limits: 1160-1780 μg L(-1)). Concentrations of cobalt as high as 2500 μg L(-1) did not significantly reduce fertilization success nor did combinations of nickel (500 μg L(-1)) and cobalt (up to 1000 μg L(-1)). These are important findings given the emerging nickel-cobalt mining industry in the tropics and provide much needed toxicity data regarding the early-life histories of ecologically relevant tropical marine species.

Effects of carp, gambusia, and Australian bass on water quality in a subtropical freshwater reservoir.

Abstract Freshwater systems are frequently compromised by excessive macrophyte biomass and cyanobacterial blooms associated with eutrophication and possibly exotic fish. The effects of piscivorous Australian bass (Macquaria novemaculeata), planktivorous gambusia (Gambusia holbrooki [Girard]), and benthivorous carp (Cyprinus carpio L) on water quality in Emigrant Creek Dam (ECD), Australia, were studied in 20 experimental enclosures (depth 1 m, volume 3.2 m3), stocked at a density of 1875 kg/ha. Fish additions had immediate effects on water quality, except for bass, which merely recycled preexisting water column nutrients. Water turbidity, total suspended solids (TSS), total nitrogen (TN) and total phosphorus (TP) concentrations, and chlorophyll a (Chl-a), were all significantly higher in gambusia, but more so in carp enclosures. Assuming a linear relationship, mean daily Chl-a increases in carp enclosures were 4.6 μg/L/100 kg carp/ha. Moreover, Chl-a (>90 μg/L) was positively correlated with TP (r2 = 0.91), TN (r2 = 0.89), TFe (r2 = 0.96), and TMn (r2 = 0.83) in carp enclosures; however, Fe and Mn resuspension from sediments does not seem to be a principal mechanism affecting total phytoplankton biomass. Macrophyte, epiphyte, and periphyton biomass were also significantly lower in carp enclosures, a consequence of sediment and nutrient resuspension, dietary excretion, and macrophyte damage. In the absence of carp, epiphytes, periphyton, and macrophytes competed with phytoplankton for available nutrients, providing a critical stabilizing role. Exotic fish removal may prove to be an effective management tool in subtropical systems to maintain high water quality.

Factors affecting the toxicity of trace metals to fertilization success in broadcast spawning marine invertebrates: a review

Significant amounts of trace metals have been released into both nearshore and deep sea environments in recent years, resulting in increased concentrations that can be toxic to marine organisms. Trace metals can negatively affect external fertilization processes in marine broadcast spawners and may cause a reduction in fertilization success at elevated concentrations. Due to its sensitivity and ecological importance, fertilization success has been widely used as a toxicity endpoint in ecotoxicological testing, which is an important method of evaluating the toxicity of contaminants for management planning. Ecotoxicological data regarding fertilization success are available across the major marine phyla, but there remain uncertainties that impair our ability to confidently interpret and analyse these data. At present, the cellular and biochemical events underlying trace metal toxicity in external fertilization are not known. Metal behavior and speciation play an important role in bioavailability and toxicity but are often overlooked, and disparities in experimental designs between studies limit the degree to which results can be synthesised and compared to those of other relevant species. We reviewed all available literature covering cellular toxicity mechanisms, metal toxicities and speciation, and differences in methodologies between studies. We conclude that the concept of metal toxicity should be approached in a more holistic manner that involves elucidating toxicity mechanisms, improving the understanding of metal behavior and speciation on bioavailability and toxicity, and standardizing the fertilization assay methods among different groups of organisms. We identify opportunities to improve the fertilization assay that will allow robust critical and comparative analysis between species and their sensitivities to trace metals during external fertilization, and enable data to be more readily extrapolated to field conditions.