Toxicity thresholds of nine herbicides to coral symbionts (Symbiodiniaceae)

Over 30 herbicides have been detected in catchments and waters of the Great Barrier Reef (GBR) and their toxicity to key tropical species, including the coral endosymbiotic algae Symbiodiniaceae, is not generally considered in current water quality guideline values (WQGVs). Mutualistic symbionts of the family Symbiodiniaceae are essential for the survival of scleractinian corals. We tested the effects of nine GBR-relevant herbicides on photosynthetic efficiency (ΔF/Fm′) and specific growth rate (SGR) over 14 days of cultured coral endosymbiont Cladocopium goreaui (formerly Symbiodinium clade C1). All seven Photosystem II (PSII) herbicides tested inhibited ΔF/Fm′ and SGR, with toxicity thresholds for SGR ranging between 2.75 and 320 µg L−1 (no effect concentration) and 2.54–257 µg L−1 (EC10). There was a strong correlation between EC50s for ΔF/Fm′ and SGR for all PSII herbicides indicating that inhibition of ΔF/Fm′ can be considered a biologically relevant toxicity endpoint for PSII herbicides to this species. The non-PSII herbicides haloxyfop and imazapic did not affect ΔF/Fm′ or SGR at the highest concentrations tested. The inclusion of this toxicity data for Symbiodiniaceae will contribute to improving WQGVs to adequately inform risk assessments and the management of herbicides in tropical marine ecosystems.

Human pharmaceuticals in Ontario's environment: a review of management opportunities

Pharmaceuticals have been detected in water throughout the developed world. Some, while at low concentrations, can negatively affect freshwater wildlife. This thesis explores the level of risk that pharmaceuticals pose to Ontario’s environment, and possible challenges and opportunities for government action to address this issue. In addition to a literature review, this work replicates an earlier similar study by collecting information directly from seven purposefully selected Ontario experts. Results make it clear that pharmaceuticals pose some risk, but a consensus cannot be reached on the level of risk. With limited financial resources, it is difficult to prioritize pharmaceutical removal over other environmental problems without a clear understanding of the harm that pharmaceuticals pose. Nevertheless, there are opportunities for government action. Ontario could follow what British Columbia has done; it developed a Water Quality Guideline for pharmaceuticals that must be considered by government when making decisions that could affect water quality.

Human pharmaceuticals in Ontario's environment: a review of management opportunities

Pharmaceuticals have been detected in water throughout the developed world. Some, while at low concentrations, can negatively affect freshwater wildlife. This thesis explores the level of risk that pharmaceuticals pose to Ontario’s environment, and possible challenges and opportunities for government action to address this issue. In addition to a literature review, this work replicates an earlier similar study by collecting information directly from seven purposefully selected Ontario experts. Results make it clear that pharmaceuticals pose some risk, but a consensus cannot be reached on the level of risk. With limited financial resources, it is difficult to prioritize pharmaceutical removal over other environmental problems without a clear understanding of the harm that pharmaceuticals pose. Nevertheless, there are opportunities for government action. Ontario could follow what British Columbia has done; it developed a Water Quality Guideline for pharmaceuticals that must be considered by government when making decisions that could affect water quality.

Toxicity thresholds of three insecticides and two fungicides to larvae of the coral Acropora tenuis

Tropical marine ecosystems, such as coral reefs, face several threats to their health and resilience, including poor water quality. Previous studies on the risks posed by pesticides have focused on five priority herbicides; however, as the number of pesticides applied in coastal agriculture increases, a suite of ‘alternative’ pesticides is being detected in tropical nearshore waters. To improve our understanding of the risks posed by alternative pesticides to tropical marine organisms, the effects of three insecticides (diazinon, fipronil, imidacloprid) and two fungicides (chlorothalonil, propiconazole) were tested on larval metamorphosis of the coral Acropora tenuis. A. tenuis larvae were affected by all five pesticides and the reference toxicant copper. The no effect concentration (NEC) and the 10% and 50% effect concentrations (EC10 and EC50, respectively) for larval metamorphosis were estimated from concentration-response curves after 48 h exposure. The NEC, EC10 and EC50 (in µg L−1), respectively, of each pesticide were as follows: chlorothalonil (2.4, 2.8, 6.0); fipronil (12.3, 13.9, 29.1); diazinon (38.0, 40.8, 54.7); imidacloprid (263, 273, 347); and propiconazole (269, 330, 1008). These toxicity thresholds are higher than reported concentrations in monitoring programs; however, these data will contribute to improving water quality guideline values, which inform the total risk assessments posed by complex contaminant mixtures to which these pesticides contribute.

Diatom–water quality thresholds in South Australian streams indicate a need for more stringent water quality guidelines

Water quality guidelines are an important tool that guide stream protection. In South Australia, as in other Australian states, guidelines have been set using statistical properties of physical and chemical stressors in reference streams. Given that water quality guidelines are designed to protect ecosystems, biologically based guidelines are more desirable. In this context, we investigated diatom–water quality relationships in South Australian streams. Our analysis focused on electrical conductivity (EC) and total phosphorus (TP), which explained significant variance in diatom assemblages. Threshold indicator taxa analysis was conducted to determine thresholds of diatom community change along EC and TP gradients. There were significant declines in the relative abundance of sensitive species at an EC of ~280μScm–1 and a TP concentration of 30μgL–1. The TP threshold is considerably lower than the trigger value in South Australia’s guidelines (100μgTPL–1). The change in species composition in relation to EC is considerably lower than the upper limit of the water quality guidelines (which range from 100 to 5000μScm–1). Hence, particularly in the case of TP, but also for EC, the current water quality guideline trigger values are too high in South Australia, and indeed in other temperate Australian states.