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PARENT SESSION

PW17 Control and Regulation of Non-idigenous Species
Exhibit Hall
8:00 AM - Wednesday

(PW266) Mesocosm experiments for evaluating potential ballast water treatment systems.

Herwig, R1, Cordell, J1, Perrins, J1, Ferm, N1, Grocock, J1, Blatchley III, E2, 1 University of Washington, Seattle, WA, United States2 Purdue University, West Lafayette, IN, United States

ABSTRACT- The introduction of non-indigenous aquatic organisms from one region of the world to another has caused ecological change and sometimes serious economic consequences. The transport of ballast water is a major vector for the transfer of non-indigenous aquatic species. Presently, nations and states are attempting to address the issue by implementing laws that mandate oceanic ballast water exchange (BWE). Most regulators and environmental scientists consider BWE a temporary solution, so research to develop ballast water treatment systems is being pursued. Large amounts of money have been spent to perform shipboard experiments with potential technologies. Generally, these experiments have no or little replication in their experimental design. The purpose of our research was to develop and use intermediate-scale or mesocosm experiments to evaluate potential ballast water treatment systems. For our experiments, we used 75-gallon (280-liter) tanks at a marine laboratory located on Puget Sound, Washington. Four replicate mesocosms were used for each treatment dose and a set of control mesocosms were established. We used mesocosms to examine the following potential ballast water treatments: ultraviolet (UV) light, ozone, and SeaKleen®. For each of these treatments, we determined the efficacy by using natural populations of Puget Sound organisms. To increase the sensitivity of our analyses, we increased the concentration of mesozooplankton that were naturally present in Puget Sound seawater to a higher but realistic level. Not surprisingly, the different treatments and doses had different effects on the variety of organisms present in Puget Sound seawater. For example, UV light resulted in the rapid decline of viable heterotrophic bacteria, but these organisms rebounded to their original population levels after a few days. At the same UV dose, mesozooplankton appeared normal immediately after treatment, but gradually became moribund or dead after several days to a week. Experiments were conducted during different times of the year. Mesocosm experiments can be designed to evaluate potential treatment systems by monitoring changes in individual taxa or communities of organisms following treatment, as they are held in dark mesocosms, similar to storage in a ballast tank. Investigators can also use mesocosms to evaluate the impact of treated water on natural assemblages that would be found in receiving waters.

Key words: non-indigenous species, ballast water, mesocosms, treatment technologies


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