Real Time Whole Organism Biomonitoring

Real-time whole organism biomonitoring involves the use of organisms as sentinels in the environment. One underlying disadvantage of the methods previously discussed is their dependence on temporally discrete or a composite of discrete sampling of waters to be assayed. Contamination of source waters is often episodic; therefore, monitoring must be continuous and 'time relevant' to provide valuable information to stakeholders. The techniques have been variously described as on-line, continuous, real time, and time relevant. Essentially, some observable physiological or behavioral parameter of a group of organisms or single cells is measured and analyzed using computer technology. The historical example of this is the canary in the coal mine.

The science of real-time biomonitoring has become more sophisticated and useful, as technology has progressed. The concept is based on principle 3, only living material can measure toxicity. Many of these systems rely on changes in the behavior of the test organisms to signal that the environment has changed. For example, one such system relies on the gape behavior of bivalves to monitor the environment. Under nonstressful conditions, bivalves tend to behave in an uncoordinated way over brief periods of time. However, all bivalves share the same defensive behavior of isolating vulnerable tissues by closing shells. It is this coordinated response to changing environmental conditions that is the trigger resulting in further action (Figure 12).

In addition to bivalves, systems based on fish, algae, and water fleas have been developed. Current available online toxicity monitors use biota ranging from single cells to whole organisms. Spectroscopic methods are used to measure fluorescence in monocultures of the luminescent bacteria Vibrio fischeri and algae Chlorella vulgaris, and indigenous algal communities. Swimming behavior in the Cladocera D. magna and various species of fish is used as an endpoint. Myoelectric action potentials are measured in the fish Lepomis macrochirus. Results of single contaminant laboratory exposures indicate that exposures of short duration (1-2 h) elicit responses similar in concentration to those of longer-term (48-96 h) acute assays, and sometimes approach chronic values.

A system response can be used to signal a water sampler to start taking samples of the water associated with the change in behavior. The water samples can then be analyzed using the TIE methods discussed earlier and if the response is due to the increased level of a toxicant, it may be possible to trace the likely sources of the toxicant and take some corrective action to reduce or remove the toxicant. This approach works best if a watershed is instrumented so the potential sources can be narrowed to a certain subwa-tershed. These techniques received an elevated visibility following a massive chemical spill on the Rhine River in

Figure 12 Bivalve mounted on a rack positioned in front of an industrial proximity sensor. A steel washer is attached to the free-moving valve of the mussel. When the mussel moves the small electromagnetic field emitted by the proximity sensor is disturbed and based on that disturbance researchers can tell the position of the valve, that is, is it open or closed.

Figure 12 Bivalve mounted on a rack positioned in front of an industrial proximity sensor. A steel washer is attached to the free-moving valve of the mussel. When the mussel moves the small electromagnetic field emitted by the proximity sensor is disturbed and based on that disturbance researchers can tell the position of the valve, that is, is it open or closed.

1986 that resulted in the virtual death of the river from the Swiss/German border to its mouth in The Netherlands. European authorities invested heavily in the development of the Rhine early warning system that is now a model for current source water and distribution system protection efforts in the US and elsewhere.

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