Methyl mercury concentrations in edible fish and shellfish from Dunedin, and other regions around the South Island, New Zealand.

Methyl mercury (MeHg) concentrations were determined in edible fish and shellfish available in local markets in Dunedin, New Zealand. While most of the fish species were sourced in Dunedin, some specimens of fish were also collected from waters off Picton, around Stewart Island and also off-shore of the South Island in the Puysegur and Subantarctic regions. The concentrations of MeHg were analysed in 25 different fish species and shellfish (103 muscle tissue samples). Total mercury (HgT) levels were also analysed in a few (n=12) selected fish samples. Most of the Hg was in the form of MeHg (≥ 96%). Higher MeHg concentrations were found in fish at higher trophic levels, particularly in predatory fish species such as ling, school shark, spiny dogfish and albacore tuna. Concentrations of MeHg in all samples ranged from 0.002 to 2.515 µg MeHg/g.

Two novel non-destructive biomarkers to assess PAH-induced oxidative stress and porphyrinogenic effects in crabs.

Two novel, non-destructive assays were developed to evaluate contaminant-induced lipid peroxidation (thiobarbituric acid-reacting substances, TBARS, levels) and haem biosynthesis disruption (porphyrin excretion) in decapod crabs. A laboratory experiment was conducted whereby pie-crust crabs (Cancer novaezelandiae) were fed cockles (Austrovenus stutchburyi) collected from a contaminated and reference site and TBARS levels and porphyrin excretion determined using fluorometric analysis in urine samples. Pyrene metabolite levels were also measured in the same urine samples to assess polycyclic aromatic hydrocarbon (PAH) exposure. Contaminant-exposed crabs exhibited elevated urinary TBARS and porphyrin levels and a strong correlation was found between these two assays and the urinary pyrene metabolite concentrations. However, there was large within-treatment variability, which precluded a clear separation between the control and the impacted group. Nevertheless, consistency in the direction of the response shows that the biomarkers reflect pollutant levels and validates the use of these simple techniques from human medicine for environmental assessments.

Non-destructive assessment of polycyclic aromatic hydrocarbon (PAH) exposure by fluorimetric analysis of crab urine.

The detection of urinary polycyclic aromatic hydrocarbon (PAH) metabolites by fluorescence spectrophotometry is particularly effective as a practical means to assess PAH exposure in decapod crabs. However, the practical application of this technique has thus far only been tested for the European shore crab (Carcinus maenas) and only a few field studies have been conducted in heavily polluted areas. The present study evaluated the adaptability of this method as a rapid, cost-effective and non-destructive biomonitoring tool for the New Zealand crab species, Macrophthalmus hirtipes (stalk-eyed mud crab). A field gradient could be detected among the sites and different input sources of PAH contamination could be discerned through the differentiation of pyrogenic and petrogenic PAH signatures. The present study shows that the fluorescence screening method is sensitive to relatively low levels of PAH contamination and more broadly applicable to smaller crab species than C. maenas, for which the technique was developed.

Determination of labile Cu(2+) in fresh waters by chemiluminescence: interference by iron and other cations.

Analysis of labile Cu(2+) in fresh waters using the Cu(2+)-catalysed oxidation of 1,10-phenanthroline by superoxide anion radical has been investigated. It was found that certain metal ions, notably Fe(3+), Fe(2+) and Pb(2+) enhance the chemiluminescence (CL) intensity of this reaction by up to an order of magnitude when present in the muM concentration range. This enhancement is considered to arise through coordination of the metal ion to 1,10-phenanthroline, which prevents free rotation of the benzene rings in the excited state intermediate thought to be responsible for light emission. This introduces a potential interference when analyzing fresh waters, which usually contain Fe(3+) concentrations of this magnitude. However, the enhancement effect saturates at about 4muM Fe(3+), so that reliable results can be obtained if the water sample is supplemented with Fe(3+) to reach this level. Application of the enhanced technique to a river water, and a reservoir to which CuSO(4) had been added to control algal growth, are described. In both cases, only a small fraction of total dissolved Cu(2+) is labile with respect to the chemiluminesence method.