Thanks to GLRI funding, the University of Wisconsin-Superior’s Great Waters Research Collaborative (GWRC) has been working with shipping companies to collect data on board Laker vessels. Laker vessels are commercial vessels that operate exclusively on the Great Lakes. Laker vessels are not major contributors of novel invaders into the Great Lakes. They can accelerate the secondary spread of introduced aquatic nuisance species via discharge of ballast water. In many cases, environmental risk associated with the ballast water vector can be substantially reduced through installation and operation of a ballast water management system.
GWRC worked with six Great Lakes vessels to install and assess operational performance and biological efficacy of ballast water management systems. The vessels also collect ultraviolet transmittance data in the ports they visit throughout the shipping season. Ultraviolet transmittance is a measurement of water clarity, i.e., how easily UV light travels through the water, and varies from port to port. Some vessels use ultraviolet (UV) treatments as part of their ballast water management systems. For UV light to neutralize organisms, it must be able to reach them. The spatial and temporal data will inform system developers about the challenges unique to the Great Lakes.
During the 2024 season, GWRC will be adding a vessel utilizing screen filtering technology to the sampling schedule. This will allow researchers to examine the reduction in organisms provided by a filter alone. Initial data analysis has shown that operational performance of the UV systems tested relates closely to the clarity of the water taken on. Both UV and chlorination treatment systems are highly effective at treating organisms in the smaller size classes but are less effective at treating larger organisms although they typically reduce the larger organisms by several orders of magnitude.