Marine bioinvasion prevention : understanding ballast water transportation conditions and the development of effective treatment systems

Abstract

Man’s impact on the Earth is constantly increasing due to ever progressing technological developments. One of our major impacts is the transportation of organisms to new habitats, leading to alterations of existing ecosystems. Mechanisms responsible for the transportation of marine organisms are mainly associated with the shipping industry e.g. hull fouling, sea chests and ballast water. Ballast water has long been recognised as one of the major mechanisms by which aquatic organisms are transported to new environments. In 2004 the International Convention for the Control and Management of Ships’ Ballast Water and Sediments was adopted and measures were implemented to reduce and control the number of future invasions. This thesis has addressed aspects relevant to the future prevention of organism transport via ballast water. Firstly, during ballast water uptake organisms are exposed to potential damage whilst passing through a centrifugal pump. Upon reaching the ballast tanks they are stored in dark, confined conditions. These processes are not intended to damage individuals, but both could potentially kill organisms and reduce the discharge of live individuals. Both processes were examined in isolation to determine their effect on plankton survival. To manage ballast water introductions water treatment technologies have been investigated to determine their ability to kill plankton. This study assessed three technologies: a stainless steel 40μm screen filter, a UV light and a chlorine based chemical, for their potential in ballast water treatments. A further challenge facing researchers involved in developing ballast water treatment systems is accurately assessing the resulting mortality in plankton from treatments. Five common viability assessment methods were investigated and their application on test organisms and natural populations examined. This thesis concludes that no significant mortality was caused to plankton by a centrifugal pump, and phytoplankton are able to survive long periods in dark confined conditions. Thus these processes will not prevent viable organisms reaching new destinations. The three treatments assessed were all effective on two iii test species and could be utilised in large scale treatment systems on board vessels to minimise introductions. Finally, while viability is difficult to assess in plankton using viability stains it is possible to obtain accurate information if the methods used are properly optimised prior to use.