Background: Biological monitoring is the use of aquatic organisms to provide an early warning of the presence of toxic materials in water. Over the past 30 years, this concept has been applied to industrial, municipal, and groundwater effluents to help prevent hazardous waste spills or detect incomplete treatment processes; water treatment plants as a check on potable water supplies; and ecosystem monitoring to detect unknown, intermittent, or unmeasured contaminants. Early warning systems have the following basic characteristics:

• Organisms are held either in a laboratory or field situation under controlled conditions and exposed on a frequent or continuous flow basis to the wastewater or water being evaluated.
• A physiological or behavioral parameter of the organism is monitored by a recording device with the capability of responding to abnormal conditions indicated by the organism.
• The function of the monitor is primarily for detection of short-term changes in toxicity as opposed to chronic or cumulative effects of a toxicant.

The USACEHR has developed an automated biomonitoring system utilizing the ventilatory and body movement patterns of the bluegill (Lepomis macrochirus). Briefly, bluegills are placed in individual flow-through chambers containing a water input and drain system. Ventilatory signals from individual fish are monitored by electrodes suspended above and below each fish in a chamber. The electrical signals are amplified, filtered, and passed onto a personal computer for analysis. The ventilatory parameters measured are ventilatory rate, ventilatory depth, gill purge (coughing) frequency, and whole body movement as shown in the figure.

Figure 1. Bluegill ventilatory parameters.

Continuous biomonitoring is achieved by alternating between groups of fish which are "on-line" with groups of fish which have not been exposed to water which may contain a toxic material(s). If a ventilatory parameter or body movement of a certain number of fish becomes statistically different from control fish, an acute toxic response is considered possible. The biomonitoring program sounds an alarm so that the problem can be identified and corrective action taken.

Strengths of the System

• Rapid and reliable detection of developing toxic water conditions for several groups of materials, e.g., metals, cyanide, organic solvents, and several pesticides.
• Operates continuously and automatically.
• Produces results which are easy to interpret.
• Automatically takes a series of water samples when an acutely toxic response is considered possible.
• Can be accessed remotely (e.g., modem or satellite).
• System is reliable and requires little maintenance.

Limitations of the System

• Long-term effects caused by low levels of toxic materials with cumulative toxicity are not likely to be detected soon enough for the response to be useful.
• Certain materials are not readily detected, e.g., some anaesthetics, some pesticides, and low concentrations of some metals which are not acutely toxic.
• Changes in physical-chemical characteristics of the water (e.g., pH, temperature, dissolved oxygen, and hardness) can cause responses that appear to indicate acute toxicity.
• Depending on the application, certain physical-chemical parameters must be controlled to reduce false responses.

System Can be Used to Monitor

• Industrial effluents
• Effectiveness of industrial, municipal, and groundwater treatment plants
• Water quality
• Drinking water sources
• Aquaculture sources
• Near real-time monitoring of potentially toxic waterway conditions in aquatic ecosystems

Additional Information on Fish Biomonitoring Systems

USACEHR System: Addition information on the USACEHR biomonitoring system can be found at the USACEHR Fish Biomonitoring System web page and in the Old O-Field Groundwater Treatment Facility case study web page. The USACEHR biomonitoring system was recently used in the Chicamacomico River, a tributary of the Chesapeake Bay, to monitor for the presence of Pfiesteria which is an alga suspected of causing fish kills that have damaged local fisheries and may have the potential to affect people exposed while engaged in sport or commercial fishing, swimming, or other water-related recreational activities. The system was deployed as part of EPA's Environmental Monitoring for Public Access and Community Tracking (EMPACT) project.

Other Fish Biomonitoring Systems: Biological Monitoring, Inc. has two commercial fish biomonitoring systems which are similar to the system developed by USACEHR. The systems operate on a real-time basis and utilize ventilatory and body movement parameters. One model houses eight fish and the second houses 12 fish. Both systems can alarm and take water samples for chemical analysis when a toxic event occurs.

Bundesanstalt für Gewässerkunde (Koblenz) has a commercially available fish monitoring system using BehavioQuant®. The BfG Koblenzer Verhaltensfischtest mit BehavioQuant® utilizes a video camera system coupled to a personal computer to analyze changes in fish behavior. The flow-through system is programed to sound an alarm when toxicity occurs.

The electric organ discharges of weakly electric tropical fish have been used as an early warning system for monitoring water quality. As an example, a Brazilian flow-through system is based on the time characterization of the electric signal emitted by the fish which may vary as function of the physico-chemical quality of the ambient water. The electric signals of eight individually confined fish are sampled at one second intervals, amplified, and processed to detect unusual electrical behavior.

Information on Other Aquatic Biomonitoring Systems

Algae: Changes in algal population structure and distribution have been used for many years to draw conclusions about a water body's health, composition, and ecological status. Phytoplankton populations are typically estimated by measuring chlorophylla, the principle photosynthetic pigment present in all forms of algae. The measurements which are typically made with flurometers can be intermittent or continuous. This technology has recently been extended to evaluate toxic substances. bbe Moldaenke's (Kiel) bbe Algae Toximeter determines toxic substances in water on a quasi real-time basis. Algae, which are automatically and independently cultivated, are added to a water sample and the active chlorophyll concentration is measured. If the algae are damaged, e.g., by an herbicide which reduces activity of the algae, an alarm is induced. The measurement chamber is automatically cleaned after each sample.

Cladocerans: The swimming behavior of daphnids can be used to assess toxic materials in freshwater. Daphnia behavior is observed in flow-through systems via video camera. The pictures are analyzed on-line by an integrated personal computer for a modification of swimming behavior. An alarm is sounded when statistically significant modifications of swimming behavior occur. bbe Moldaenke's (Kiel) commercially available bbe Daphnien Toximeter is equipped with a continuously operating alga fermentor for feeding the daphnia. Bundesanstalt für Gewässerkunde (Koblenz) also has a commercially available daphnid monitoring system using BehavioQuant®. BfG's Daphnientest mit BehavioQuant® is similar to the bbe Daphnien Toximeter.

Bivalves: A number of bivalves have been used in real-time biomonitoring systems. The conceptual basis for the system lies in the behavioral defense mechanism of bivalves. Under normal conditions the shells of bivalves are mainly open to allow respiration and feeding. Under adverse environmental conditions the valves will close to exclude the irritant(s). The valve movement behavior is used as the biological effect parameter. The opening and closing of the valves of individual organisms are continuously monitored by high frequency electromagnetic induction sensors or proximity sensors linked to a data collection system to analyze the signals. Current valve movement behavior is compared with historic data from the same individual. If significant changes in behavior are detected, most biomonitoring systems are programmed to sound an alarm. Some systems are also further programmed to activate an automatic water sampler, taking a sample of water which can then be analyzed to evaluate toxicity. Real-time bivalve monitoring systems in both freshwater and seawater have been deployed in a number of applications throughout the United States, Canada, Europe, and Australia. Systems developed by academic institutions, (e.g., University of North Texas clam monitor), governmental agencies (e.g., ANSTO Mussel Monitor), and commercial firms (e.g., Delta Consult B.V. Mosselmonitor®) are available.

BehavioQuant®: BehavioQuant® is a video analysis system developed by GSF Research Center of Environment and Health (Neuherberg) and Metacom Gmbh (Munich). The system records the three dimensional movement patterns of animals in water. It is able to register up to 200 untagged objects and makes use of the integrative whole-animal behavioral response by recording and quantifying the spontaneous locomotor activity of the observed objects. The video signals are digitized and can be processed online or offline by the system software. To insure the continuous observation of individuals and register movements during the dark phase of a photoperiod, the system can be adapted with cameras which are able to handle normal as well as infrared light. The system can be used with up to 16 observation units which are sequentially processed by the system software. BehavioQuant® has been used in various commercial applications to monitor toxicity on a flow-through basis (e.g., BfG's Koblenzer Verhaltensfischtest mit BehavioQuant® and BfG's Daphnientest mit BehavioQuant®.