Contaminants may affect marine organisms through various pathways with impacts evident across a variety of spatial and temporal scales. Organisms may encounter short pulsed exposures which contaminate surface waters for hours to days, or more persistent but patchy contamination of benthic habitats throughout their entire life-cycle. This thesis examines the responses of epifauna associated with macroalgae to a pulsed exposure of contaminants (storm-water input) and to chronic contamination via metal accumulation within temperate algal beds. The effects of storm water were monitored during a two-year survey of Sydney Harbour which sampled epifauna before and after heavy rainfall. Epifaunal assemblages declined throughout the harbour following storm events but for the most part these declines were not attributable to storm-water runoff. However, transient (< 4 d) and localized impacts of storm water upon physico-chemical characteristics of recipient water and some epifaunal groups were identified around storm drains. A novel field dosing technique tested the relative importance of freshwater and associated metals as causative agents of behavioural avoidance and direct mortality responses. Strong avoidance of storm-water plumes was found which could be entirely explained by freshwater inundation, with no additional effects of metals. No direct mortality was observed following brief exposures. Contaminants introduced by storm water may accumulate within the tissues of macroalgae and potentially pose persistent threats to epifauna. Colonisation of epifauna was reduced on algae with enhanced copper levels, and the nesting behaviour, feeding and survival of an abundant amphipod were all negatively affected by copper load. Subsequent field surveys identified sufficient copper, lead and zinc contamination in Sydney Harbour algal beds to pose direct toxic threats to epifauna. The abundance of herbivorous amphipods correlated negatively with the copper content of a common algal species. However, differences in metal accumulation between algal species resulted in spatially variable levels of contamination. Small-scale patchiness of contaminants within these landscapes may allow populations of mobile species to persist if contaminated hosts are avoided. In summary, epifaunal assemblages appeared resilient to storm-water pulses. Recovery of affected groups was rapid and large fluctuations in abundance appear to be part of the natural flux of epifaunal communities. In contrast, assemblages responded strongly to algal-bound contaminants and this has emerged as an important pathway of contaminant exposure and impact within algal habitats.
| Identifer | oai:union.ndltd.org:ADTP/257537 |
| Date | January 2008 |
| Creators | Roberts, David A, School of Biological, Earth & Environmental Sciences, UNSW |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://unsworks.unsw.edu.au/copyright, http://unsworks.unsw.edu.au/copyright |
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