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Water quality standards have been set for waterways in Australia and many other countries to help ensure survival of aquatic species. In Australia, the standards have been based on extensive evaluation of the available research into effects of different contaminants on a range of animals including mussels, oysters, sea urchins and various fin fish. However it seems that a potential ‘canary in the mines’ has been overlooked. | Dr Jacquelle Gorski’s research at RMIT has found that concentrations of heavy metals such as copper and mercury set by the standards are toxic to developing abalone.
Jacquelle focussed on six key trace metals known to be pollutants of waterways. She first evaluated their impacts on the healthy development of the different stages of abalone from the larvae through to the juveniles.
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The next stage was to determind whether the present water quality standards for these metals are appropriate for abalone. Even up to the 1980s metal pollution in marine waters worldwide as a major issues, typically associated with coastal or river areas where industry was established. The situation has improved especially in Australian waters. However, in the USA there are still some major hot spots for metal pollution and their local wild abalone has virtually disappeared.
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Abalone have a long life cycle and in the wild adult abalone may be five years of age. The cycle commences with the release of egg and sperm into the water column. The rapid development from fertilzed egg, through larval stages to a miniature of the adult form is illustrated in the following series of photographs by Jacquelle Gorski all at magnification x 100 of the abalone species Haliotis rubra. |
| Abalone have a long life cycle and are a very slow growing species. In the wild, adults may reach up to ten years of age. The cycle commences with the release of egg and sperm into the water column. Once fertilised, the egg undergoes rapid development over five days to become a tiny abalone with foot and developing shell, crawling over the substrate to find a suitable place to settle for their adult existence.
Left: Egg approximately 1.5 hours post fertilisation.
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| Jacquelle selected abalone to study because of the lack of research or comprehensive information about their sensitivity to heavy metals She worked with one of the Port Phillip Bay abalone farms, using their brood stock for her toxicity studies.
The six metals chosen included copper, zinc and iron - three essential metals that are needed for the healthy development of all life forms - and three nonessential metals that predominantly are associated with industry: cadmium, mercury and lead.
Right: Haliotis rubra trochophore larvae 31h post-fertilisation with the developing shell and internal organs becoming more organised.
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| Jacquelle was more interested in concentrations that would produce abnormalities rather than those that were fatal. Of the six metals, mercury was the most toxic followed by copper.
An interesting finding was that even at very low concentrations, abnormalities in the development of the abalone larvae were produced that resembled those produced by bacteria.
The larvae are very simple organisms that continually take in water from their surroundings and so are particularly vulnerable to effects from contaminants or bacteria in the water column.
Left: Normal Haliotis rubra trochophore larvae after 48 hours development.
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| Right: Abalone larvae after 48h development exposed to metals.
The juvenile abalone are by contrast more robust to environmental contamination and were found to be able to protect themselves to some extent from higher concentrations of some of the metals by partitioning them away from sensitive organs and tissues.
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Why are abalone so susceptible compared with other species such as oysters, mussels and fish? This may relate to their evolution in waters free from metal contaminants and so have not had the opportunity to adapt to lesser quality waters. |
| Oyster and mussels by contrast can survive in quite polluted waters, and are commonly found growing around sewer outlets and mariners. Australian water quality guidelines for marine waters appear to be perhaps the most stringent in the world. However Jacquelle Gorski’s findings with copper and mercury on developing abalone showed that the concentrations that she found impacted adversely on the abalone are comparable to those set by the Australian guidelines for the protection of 99 percent of marine species.
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| As a result she would like abalone to be considered in the revision of the guidelines since otherwise, abalone may end up being part of the one percent of species that are not protected by the guidelines.
Above: Haliotis rubra veliger larvae 120h post-fertilisation now able to crawl using the enlarged propodium.
Right: Metamorphosed Haliotis rubra with the appearance of the adult.
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