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Treatment options to mitigate transport of harmful algal species and pathogens via ships' ballast water and shellfish translocation


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Gregg, Matthew David 2009 , 'Treatment options to mitigate transport of harmful algal species and pathogens via ships' ballast water and shellfish translocation', PhD thesis, University of Tasmania.

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The worldwide transfer of non-indigenous invasive aquatic organisms via ships'
ballast water and shellfish translocation has been widely shown to cause significant
ecological, economic and human health impacts. In 2004 the International Maritime
Organisation (IMO) adopted the International Convention for the Control and
Management of Ships' Ballast Water and Sediments. This legislation (still to be
ratified) requires all ships to introduce by 2016 approved systems capable of treating
ballast water to strict microbial standards. The latter has reinvigorated interest in the
application of chemical biocides, because mechanical separation and physical
treatment are unable to kill bacteria. The present work examined the effectiveness of
several proposed chemical ballast water treatment options using toxic dinoflagellate
resting cysts, vegetative marine microalgae and bacteria as model organisms.

The chemicals tested included the ballast water biocides Peraclean®Ocean and
SeaKleen®, the chlorine dioxide biocide Vibrex ®and the hull antifouling agent
Econea®. All biocide tests were conducted using filtered seawater (28 %o) and natural
estuarine water ranging in salinity from 23.7-28.6%o. Peraclean®Ocean was
biodegradable within 2-6 weeks, could effectively eliminate vegetative microalgae at
100 ppm, inactivated resting cysts of marine dinoflagellates (Gymnodinium
catenatum, Alexandrium catenella, A. pseudogonyaulax, Protoceratium reticulatum)
at 200-2000 ppm, and could control bacterial growth of Escherichia coli,
Staphylococcus aureus, Listeria innocua and Vibrio alginolyticus at 125-250 ppm.
SeaKleen®eliminated vegetative microalgae at 2 ppm and could control
dinoflagellate cysts at 6-20 ppm but displayed poor bactericidal properties (100-200
ppm required) and poor biodegradability. The burial of dinoflagellate cysts in 0.5 and
1 mm of ballast tank sediment severely reduced the effectiveness of Peraclean ®
Ocean and SeaKleen®. Vibrex®is not a suitable treatment option due to the need for
hydrochloric acid as an activator, however it was found to be the most effective
against bacteria (complete inhibition at 15 ppm) indicating that onboard chlorine
dioxide generators may provide an effective bacterial treatment. Econea®controlled
vegetative microalgae at 0.5 ppm but failed to inactivate G. catenatum cysts even at a
concentration of 1000 ppm, suggesting that the product lacks the penetrability required to infiltrate the walls of dinoflagellate cysts. The applicability of ballast
water biocides is limited by factors such as cost, biological effectiveness, reduced
efficacy in the presence of sediments and lower water temperatures (6°C compared
to 17°C), and possible residual toxicity of the discharged ballast water.

Translocation of bivalve shellfish for outgrowing purposes or to establish new
shellfisheries also poses a significant risk for transport of harmful algae. This study
showed that viable microalgal cells of A. catenella, Cryptoperidiniopsis brodyi, G.
catenatum, Karenia papilionacea, Kryptoperidinium foliaceum, Pfiesteria
shumwayae and cysts of G. catenatum can readily pass through the digestive tract of
adult Pacific oysters and blue mussels. Several treatment options currently used by
shellfish farmers for controlling fouling and pathogens were tested against Pacific
oysters. Vegetative cells of A. catenella, G. catenatum and K. fohaceum could not be
eliminated from the digestive tract of Pacific oysters following 24 h immersion in
freshwater or by 48 h exposure to hydrogen peroxide (400-600 ppm) or chlorine
dioxide (40-60 ppm). Depuration in filtered seawater for 7 days was identified as the
only effective treatment option. Recommendations for future research, along with
potential alternative treatment options, are identified and discussed.

Item Type: Thesis - PhD
Authors/Creators:Gregg, Matthew David
Copyright Holders: The Author
Copyright Information:

Copyright 2009 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Available for library use only and copying in accordance with the Copyright Act 1968, as amended. Thesis (PhD)--University of Tasmania, 2009. Includes bibliographical references

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