Toxicity of copper to three common subantarctic marine gastropods.

Investigating the impacts of contamination on high latitude ecosystems includes determining the sensitivity of key taxa to contaminants. Unique characteristics, arising from adaption to cold and stable temperatures has likely resulted in marine biota at the poles being particularly sensitive to contamination in comparison to related species at lower latitudes. We aimed to determine the sensitivity of three species of common and ecologically important subantarctic gastropods to copper. This is the first study to investigate the sensitivity of subantarctic marine gastropods to contamination. We determined sensitivity by exposing each species to a range of copper concentrations by establishing mortality and sublethal endpoints. Sensitivity to copper was highly species specific. Laevilittorina caliginosa was relatively tolerant, with no response at Cu concentrations up to 1488µg/L following 7 d of exposure, while two species (Cantharidus capillaceus coruscans and Macquariella hamiltoni) were highly sensitive with 7 d Cu LC50 estimates of 33µg/L and 78µg/L respectively. In a global comparison of gastropod sensitivity data, these two species were highly sensitive to copper, highlighting the vulnerability of polar ecosystems to contamination.

Determining the sensitivity of the Antarctic amphipod Orchomenella pinguides to metals using a joint model of survival response to exposure concentration and duration.

Developing water quality guidelines for Antarctic marine environments requires understanding the sensitivity of local biota to contaminant exposure. Antarctic invertebrates have shown slower contaminant responses in previous experiments compared to temperate and tropical species in standard toxicity tests. Consequently, test methods which take into account environmental conditions and biological characteristics of cold climate species need to be developed. This study investigated the effects of five metals on the survival of a common Antarctic amphipod, Orchomenella pinguides. Multiple observations assessing mortality to metal exposure were made over the 30 days exposure period. Traditional toxicity tests with quantal data sets are analysed using methods such as maximum likelihood regression (probit analysis) and Spearman-Kärber which treat individual time period endpoints independently. A new statistical model was developed to integrate the time-series concentration-response data obtained in this study. Grouped survival data were modelled using a generalized additive mixed model (GAMM) which incorporates all the data obtained from multiple observation times to derive time integrated point estimates. The sensitivity of the amphipod, O. pinguides, to metals increased with increasing exposure time. Response times varied for different metals with amphipods responding faster to copper than to cadmium, lead or zinc. As indicated by 30 days lethal concentration (LC50) estimates, copper was the most toxic metal (31 µg/L), followed by cadmium (168 µg/L), lead (256 µg/L) and zinc (822 µg/L). Nickel exposure (up to 1.12 mg/L) did not affect amphipod survival. Using longer exposure durations and utilising the GAMM model provides an improved methodology for assessing sensitivities of slow responding Antarctic marine invertebrates to contaminants.

Can juvenile corals be surveyed effectively using digital photography?: implications for rapid assessment techniques.

The widespread decline of coral reefs requires integrated management measures across whole regions. Knowledge of demographic processes of reef organisms is important for informed management, yet current techniques for assessing such processes are time consuming, making it impractical to gather relevant information over large scales. We tested the usefulness of digital still photography as a rapid assessment technique to estimate coral recruitment--an important process in coral reef recovery. Estimates of the density and diversity of juvenile hard corals from digital images were compared with direct visual estimates from the same plots made in the field. Multiple plots were sampled on four reefs from a range of locations on Australia's Great Barrier Reef. On average, estimates of juvenile densities from photographic images were lower, in both absolute and relative terms, than that estimated from images. This was the case whether colonies <20 mm or <50 mm in diameter were considered. Overall differences between methods were generally greater at reefs where recruitment was higher, though proportional differences (density from images/density from direct visual census) still varied among reefs. Although the ranking of taxa, in terms of their densities, from the two methods were similar, the density of common genera was generally underestimated in images, and the occurrence of 'unknown' taxa was higher. We conclude that photographic images do not constitute a reliable rapid assessment method for estimating the spatial patterns in the density or diversity of juvenile hard corals.