Laboratory-based Toxicity Tests Research Articles

Increased sensitivity of subantarctic marine invertebrates to copper under a changing climate - Effects of salinity and temperature

Stressors associated with climate change and contaminants, resulting from the activities of humans, are affecting organisms and ecosystems globally. Previous studies suggest that the unique characteristics of polar biota, such as slower metabolisms and growth, and the generally stable conditions in their natural environment, cause higher susceptibility to contamination and climate change than those in temperate and tropical areas. We investigated the effects of increased temperature and decreased salinity on copper toxicity in four subantarctic marine invertebrates using realistic projected conditions under a future climatic change scenario for this region. We hypothesised that these relatively subtle shifts in environmental stressors would impact the sensitivity of cold-adapted species to copper. The four test species were: a copepod Harpacticus sp.; isopod Limnoria stephenseni; flatworm Obrimoposthia ohlini; and bivalve Gaimardia trapesina. These species occupy a range of ecological niches, spanning intertidal and subtidal nearshore zones. We predicted that species would differ in their tolerance to stressors, depending on where they occurred within this ecological gradient. Organisms were exposed to the multiple stressors in a factorial design in laboratory based toxicity tests. Sensitivity estimates for copper (LC50) were calculated using a novel statistical approach which directly assessed the impacts of the multiple stressors. In three of the four species tested, sensitivity to copper was amplified by small increases in temperature (2-4 °C). The effects of salinity were more variable but a decrease of as little as 2 ppt caused a significant effect in one species. This study provides some of the first evidence that high latitude species may be at increased risk from contaminants under projected future climate conditions. This interaction, between contaminants and the abiotic environment, highlights a potential pathway to biodiversity loss under a changing climate.

A rapid amphipod reproduction test for sediment quality assessment: In situ bioassays do not replicate laboratory bioassays

An underlying assumption of laboratory-based toxicity tests is that the sensitivity and exposure of organisms in the laboratory is comparable to that in the field. We sought to make a comparison between field-based and laboratory-based sediment toxicity tests using a recently developed rapid amphipod reproduction test that encompasses gametogenesis, fertilization, and embryo development before hatching. The test species, Melita plumulosa, is an epibenthic, detritivorous amphipod native to Eastern Australia. Test sediments were sourced from Lake Macquarie, a large saltwater lagoon located 100 km north of Sydney (New South Wales, Australia) that has received heavy-metal pollution over many decades, primarily from a Pb/Zn smelter but also from collieries, coal-fired power stations, and urban areas. This has led to a north-south trace-metal concentration gradient, including Pb, Zn, Cd and Cu, in the sediments of Lake Macquarie. Sediments from these northern bays were demonstrated to reduce amphipod fecundity in laboratory-based tests. For the current study, the amphipod reproduction test has been modified for use in situ. In situ test chambers were deployed at the mouth of Cockle Creek, Lake Macquarie. Sediments that were demonstrated to reduce fecundity of M. plumulosa in the laboratory reproduction test were not similarly toxic when amphipods were exposed to the same sediments in situ. Factors related to the regular tidal renewal of overlying water likely altered exposure profiles in situ, including the provision of additional or alternative nutrition that obviated the need for amphipods to interact with the contaminated sediments, and a washout effect that prevented the accretion of dissolved zinc in the overlying water.

Competition modifies the response of organisms to toxic disturbance

Transient pollution events have the potential to cause both direct and indirect effects on exposed assemblages, but the test designs used in the majority of toxicity studies have precluded an examination of potentially important indirect effects. Field experiments conducted in marine epifau- nal assemblages have revealed that pulse chemical disturbances from copper decrease the densities of large solitary ascidians while increasing the densities of serpulid polychaetes. Field manipulative experiments were carried out to test whether the positive effects of transient pollution events repre- sent the response of serpulids to the release from competition for space (an indirect effect of the tox- icant) or a direct positive response to the putative toxicant. Three species of serpulid polychaetes (Ficopomatus enigmaticus, Hydroides sp., and Pileolaria pseudomilitaris) responded positively to pulse copper exposures in the presence of competition, but did not display any density response to pulse copper exposures in the absence of competition for space from other recruits. Pomatoceros tae- niata displayed no response to copper exposure in the presence of competition, but was dramatically reduced in density in the absence of competition for space. This was the only species deemed sensi- tive to the frequency and intensity of pollution disturbance employed. There was no indication of a direct positive effect of the toxicant on any serpulid, confirming the hypothesis that positive responses of serpulids to copper exposure in the whole assemblage are an indirect effect of the toxi- cant mediated through competition for space. Our results show that the interaction between a pollu- tion disturbance and competition for a limiting resource can modify the response of organisms to a toxicant. Such results could not be predicted from conventional laboratory-based toxicity tests and they suggest that small-scale ecotoxicological field tests are a useful tool in predicting the impacts of pollution events in complex systems.

Do amphipods have the same concentration‐response to contaminated sediment in situ as in vitro?

AbstractAn underlying assumption of laboratory‐based toxicity tests is that the sensitivity of organisms in the laboratory (in vitro) is comparable to that in the field (in situ). We tested this assumption by exposing estuarine amphipods (Chaetocorophium cf. lucasi) to a concentration series of cadmium‐spiked sediments in vitro and in situ for 10 d. In situ exposures were conducted within plastic‐mesh cages on an intertidal mudflat. To characterize exposure, we measured interstitial water cadmium concentrations (IWCd), acid volatile sulfide (AVS), and simultaneously extracted Cd (SEMCd) at the beginning and end of the exposures. Between day 0 and day 10, AVS decreased in both in vitro and in situ exposures, while IWCd levels declined less in vitro (median 27%) than in situ (median 76%). Despite more extreme conditions of temperature (10–36°C) and salinity (18–22%o) in situ, in vitro and in situ exposures showed comparable survival responses based on SEMCd/AVS (LC50 [95% CI]: 1.6 [1.46–1.78] and 1.8 [1.76–1.83], respectively), with the onset of marked mortality above a SEMCd/AVS value of about one and minimal survival (<5%) above a value of two. Based on IWCd concentrations, however, sensitivity was significantly greater in vitro (LC50 = 0.41 μg Cd/L [0.171–0.959], in situ LC50 = 1.6 μg Cd/L [1.15–2.16]). We concluded that, in our tests, amphipod sensitivity in vitro was equal to or greater than its sensitivity in situ.

Salinity tolerances of selected macroinvertebrates of the Sabie River, Kruger National Park, South Africa.

Salinization has been identified as the most important problem facing the managers of South African freshwaters. Laboratory-based toxicity tests were conducted to assess the tolerance of selected macroinvertebrates to elevated salt concentrations. Since the Kruger National Park is the focus of river research in South Africa, and the Sabie River is the least mineralized river in the park, 96-h acute toxicity tests were conducted using Sabie River water and an ephemeropteran mayfly Tricorythus sp. found in the river. Experiments were conducted inflowing water systems known as raceways. The tolerance of the mayfly to two sodium salts, sodium chloride and sodium sulphate, was assessed at a range of selected conductivity levels/concentrations. The results indicated that mortality cannot be linked only to conductivity or total dissolved solid(TDS) concentrations, but also to the nature of the salt. Sodium sulphate was considerably more toxic to Tricorythus sp. than sodium chloride. Causes of mortality and implications for the development of water quality guidelines for the natural aquatic environment are discussed.

Environmental impact of liquid wastes discharge in coastal waters

Discharge of liquid wastes to coastal and estuarine waters has been carried out for many years by most of the countries bordering the North Sea. This paper examines recent changes in public perception and corporate awareness of the responsibilities of industry for protection of the environment. The deficiencies of laboratory-based toxicity tests are discussed, and methods that are available for the quantitative evaluation of marine communities are outlined. The paper provides examples illustrating the use of such methods in monitoring the potential impact of liquid waste discharges and in defining strategies for effluent treatment.