The application of sediment quality guidelines and toxicity assessment to identify contaminant hotspots in an urbanised West Australian estuary.

This paper presents a tiered assessment approach that enabled identification, triage, interrogation and confirmation of significantly contaminated areas of an urbanised West Australian estuary. The spatial distribution of organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs) and bioavailable metals was determined in surficial sediments of the Swan-Canning Estuary through broad-scale screening (500 cores, 100 composite samples, 20 locations). The application of sediment quality guideline values (SQGVs) enabled ranking of locations through risk-based scoring and identification of contaminant hotspots. Subsequent targeted ecotoxicological and chemical assessment was undertaken at the highest scoring location in each tributary (80 cores, 16 composite samples, 3 locations, 16 sites). In the Canning tributary, Bull Creek sediments demonstrated the highest metal concentrations and greatest number of SQGVs exceeded. High-level toxicity was experienced in copepods and moderate toxicity in mussels (test sensitivity: copepod>mussel>amphipod). Toxicity-inducing contamination was attributable to two stormwater outfalls and limited to 300 m from points of discharge. In the Swan tributary, Claisebrook sediments demonstrated the highest concentrations of all PAHs, most OCPs and metals and the greatest number of SQGVs exceeded. High-level toxicity was reported in fish and mussels and moderate toxicity in copepods and amphipods (test sensitivity: fish>mussel>amphipod>copepod). Toxicity-inducing contamination included a stretch of estuary >1 km long, and two stormwater outfalls in the area were likely sources. The distribution and nature of PAH contamination suggested an additional source at Claisebrook. This combined chemistry and biological effects dataset provides critical information for the management of planned major development and concomitant estuary-bed disturbance in the coming decade.

Otolith microchemistry: Insights into bioavailable pollutants in a man-made, urban inlet.

Black bream (Acanthopagrus butcheri) were collected from an artificial inlet, Claisebrook Cove, Western Australia. Claisebrook Cove is adjacent to an historic contaminated site that was remediated during the 1990s. It was later identified as a priority area due to elevated levels of sediment contaminants including Zn, Cu, and Pb. Black bream were collected from this cove in 2005 and 2012 and their otoliths were analysed by laser ablation inductively coupled plasma mass spectrometry of the most recent growth zone. Levels of Zn and Mn, which are metabolically regulated, did not correlate with sediment contamination. However, reduction in sediment Cu levels over time coincided with reduced Cu otolith levels from 2005 to 2012. Results indicate that the elemental composition of the marginal edge of Black bream otoliths can identify bioavailable contaminants in an urban estuary and, with monitoring, can be utilized to establish long-term trends.

Performance of the thistle gall fly, Urophora cardui, in relation to host plant nitrogen and mycorrhizal colonization.

Many hypotheses have been developed to explain the adaptive nature of insect galls. One of these, the nutrition hypothesis, states that gall formers have advantages over other insects because gall tissue provides a better (higher quality) food source than unmodified tissue. However, this has rarely been experimentally tested. In a test of this hypothesis, we grew plants of Cirsium arvense (L.) Scop. in a factorial design with two main treatments: the addition of nitrogen (to enhance foliar N levels) and of fungicide (to reduce colonization of roots by arbuscular mycorrhizal fungi). Mycorrhizal fungi have been shown previously to reduce the N concentration of host plants. Plants were exposed to adult gall flies, Urophora cardui L., and maintained through one season to allow maturation of galls. Reduction of the percentage mycorrhizal colonization by fungicide resulted in an elevation of total stem N comparable to that achieved by N addition, but gall N concentration remained unchanged in all treatments. Nitrogen application elevated stem N levels when mycorrhizal fungi were present, but application of both compounds together did not result in any increase over either single treatment. Fungicide application resulted in larger galls, which contained more larval chambers, with more live, and heavier, larvae. However, the main effects of N were not significant, as N addition only increased fly performance on plants where mycorrhizas were not reduced. It is suggested that U. cardui gall inhabitants can manipulate N at an optimal level and thus might conform to a modified version of the nutrition hypothesis. Mycorrhizal colonization might reduce gall fly performance by delaying the appearance, or impairing the quality, of secondary nutritive tissue in the gall. Future tests of the nutrition hypothesis should include a consideration of the plant's mycorrhizal status.