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Development and Testing of Instrumented Incubator-Emergence Traps
As of 2006, this project is no longer current. Please see the Research Programs page for a list of current research projects.
Co-Investigator:
Steve Ruberg
External Collaborators:
Tom Johengen, CILER
Capt. Philip Jenkins, Jenkins and Associates, Ontario
Ballast tanks are the leading vector for aquatic invasive species invasions worldwide. Among the legislative and administrative responsibilities assigned directly or by inclusion to the Department of Commerce by the Nonindigenous Aquatic Nuisance Species Prevention and Control Act of 1990, the National Invasive Species Act of 1996, and Executive Order 13112 (1999), are support of research to develop measures for preventing new introductions and controlling existing invasions, support for research to cover all aspects of aquatic nuisance species, support for the interagency Aquatic Nuisance Species Task Force (NOAA is co-chair), and development of alternative technologies to treat ballast water. The research priorities identified by the Great Lakes Panel on Aquatic Nuisance Species in 1996 and again in 2000 included vessels with "no ballast on board", which are usually referred to as "NOBOB" vessels. This project will enhance our ability to assess invasion risk posed by NOBOB vessels.
Under the NOBOB Program, the goal of Task 2 is to assess whether biota (including resting stages) resident in ballast tank residual water and sediment can invade the Great Lakes under actual ship operating conditions. We proposed to examine this by experimentally filling a NOBOB tank and then repeatedly sampling the ballast tank (water column) as the ship travels through the Great Lakes. However,experience has taught us that regular access to ballast tanks, especially double bottom tanks, is very difficult to maintain on an operating vessel, making our original plan to obtain daily samples untenable. In addition, the port-to-port schedule of these vessels is subject to change at the last minute, complicating our ability to run a well-planned experiment. Finally, it became problematic how to find organisms originating from the ballast residuals in the experimental tank against the background of the biota already contained in the local ballast water used to flood the tanks.
As a result of these difficulties, we are taking what we believe is a new and novel approach involving the use of "Incubator-Emergence traps" (IETraps) to test for zooplankton hatching from resting eggs in residual sediment under ballast tank operating conditions during the experiment. The traps address the difficulty of trying to detect the presence of newly hatched organisms against the huge background of organisms present in the incoming water, and the limitation of sampling due to tank access.
Figure 1: Incubator-Emergence Traps designed for NOBOB Task 2. The interior of each trap is lined with Nitex plankton mesh of an appropriate mesh size.
Procedure
IETraps traps are constructed of 6" diameter PVC sewer components (Figure 1). Large holes in the body and tops allow for passage of water, but are lined with Nitex plankton mesh selected to prevent hatched organisms from escaping the trap, and also to prevent outside organisms from entering the trap. Traps are mounted on dense PVC sheets, 3 to a sheet. Each trap is seeded with a pre-measured amount of residual sediment, either collected from the ship conducting the experiment, or from previously collected sediment residual with a laboratory determined density and viability of resting eggs (in the latter case, sediments are chosen from NOBOB Task 1 that are known to contain resting stages of organisms already in the Great Lakes). Each experiment consists of two trays of 3 traps each, providing 4 replicates and 2 controls, a sterilized sediment control and a live animal control. The live animal controls consist of adding 20 Lumbriculus and 20 Hyallela (both organisms are prevalent in the Great Lakes), provided by Dr. Peter Landrum, to a "control" trap which contains a sterilized sample of the test sediment, so we can evaluate survivorship of live animals within a trap. At the end of the experiment the number of live animals in the controls are counted, and all water and sediment samples are collected from the other traps and preserved for examination.
The Problem: One limitation to this experimental design is that we are not sure of the conditions inside the traps during the experiment. The plankton mesh can easily become clogged with fine particulates, thus restricting water exchange (flushing) with the interior of the trap, which could lead to low-oxygen or anaerobic conditions. The live animal control partially addresses this, but if there is a partial or full mortality of the animals, we have no way of knowing if it was due to deteriorated conditions inside the traps.
The Solution: A viable solution would be to instrument several of the traps with internal sensors connected to a data-logger system that could record basic environmental parameters (temperature, conductivity/salinity, oxygen) over the course of the experiments.
Proposed Work
GLERL's Marine Instrumentation Laboratory will modify an IETrap provided by the NOBOB Program to mount a commercially available instrument to the trap such that the sensors (temperature, conductivity, oxygen) reside inside the body of the trap and are sealed from the external environment. A twin system will be mounted to the PVC tray immediately adjacent to the test trap. This instrumented IETrap will be deployed in the bottom of a ballast tank during regular Task 2 experiments starting late summer 2003. Power is supplied by a self-contained internal battery pack and data from the sensors is recorded on an internal data logger.
Deployment is made at the first or earliest port of call in the Great Lakes for which a ballast tank is accessible. After deployment is complete, the ballast tank is flooded with at least 2 meters of water depth, if possible. The test ballast tank is maintained with water covering the traps for the duration of the voyage in the Lakes. At the last or next-to-last port of call, the ballast tank is emptied and the traps retrieved for analyses.
We hope to conduct at least two experiments with instrumented traps before the end of the CY2003 Great Lakes shipping season.
Last updated: 2006-03-30 mbl