Development and Validation of an On-Line Water Toxicity Sensor with Immobilized Luminescent Bacteria for On-Line Surface Water Monitoring.

Surface water used for drinking water production is frequently monitored in The Netherlands using whole organism biomonitors, with for exampleDaphnia magnaorDreissenamussels, which respond to changes in the water quality. However, not all human-relevant toxic compounds can be detected by these biomonitors. Therefore, a new on-line biosensor has been developed, containing immobilized genetically modified bacteria, which respond to genotoxicity in the water by emitting luminescence. The performance of this sensor was tested under laboratory conditions, as well as under field conditions at a monitoring station along the river Meuse in The Netherlands. The sensor was robust and easy to clean, with inert materials, temperature control and nutrient feed for the reporter organisms. The bacteria were immobilized in sol-gel on either an optical fiber or a glass slide and then continuously exposed to water. Since the glass slide was more sensitive and robust, only this setup was used in the field. The sensor responded to spikes of genotoxic compounds in the water with a minimal detectable concentration of 0.01 mg/L mitomycin C in the laboratory and 0.1 mg/L mitomycin C in the field. With further optimization, which should include a reduction in daily maintenance, the sensor has the potential to become a useful addition to the currently available biomonitors

Hydroacoustic assessment of pelagic stages of freshwater insects

Two independent surveys showed that aquatic insects can generate echoes comparable with the echoes of small fish. In the open water of two fishless mountain acidic waters of the Czech Republic, a very distinct population of well-defined single targets resembling fish (target strength –66 to –50 dB at 120 kHz) was discovered. These targets were found in the depth range of 5–7 m during the day (June–July 1997). At night, most targets were recorded by horizontal beaming (depth < 3 m). Towing of ichthyoplankton nets in these horizons revealed the presence of ‘water bugs’, Corixidae (Hemiptera), mostly genus Glaenocorisa. Target strengths of corixids was also verified by direct observations in an experimental tank, where it was possible to track side, dorsal and ventral aspects. In three Dutch reservoirs, Petrusplaat, Honderd-en-Dertig and De Gijster (area 100–300 ha, maximum depth 15–28 m, with fish presence) the targets of ascending dipteran pupae (Chironomidae, Procladius signatus) with target strength of –74 to –65 dB were observed by vertical beaming. The presence of pupae was verified by horizontally towed ichthyoplankton nets and by vertical plankton hauls inside the echosounder beam. The contribution of aquatic insects to the fish biomass was small but they can interfere in juvenile fish assessment

Development and Validation of an On-Line Water Toxicity Sensor with Immobilized Luminescent Bacteria for On-Line Surface Water Monitoring.

Surface water used for drinking water production is frequently monitored in The Netherlands using whole organism biomonitors, with for exampleDaphnia magnaorDreissenamussels, which respond to changes in the water quality. However, not all human-relevant toxic compounds can be detected by these biomonitors. Therefore, a new on-line biosensor has been developed, containing immobilized genetically modified bacteria, which respond to genotoxicity in the water by emitting luminescence. The performance of this sensor was tested under laboratory conditions, as well as under field conditions at a monitoring station along the river Meuse in The Netherlands. The sensor was robust and easy to clean, with inert materials, temperature control and nutrient feed for the reporter organisms. The bacteria were immobilized in sol-gel on either an optical fiber or a glass slide and then continuously exposed to water. Since the glass slide was more sensitive and robust, only this setup was used in the field. The sensor responded to spikes of genotoxic compounds in the water with a minimal detectable concentration of 0.01 mg/L mitomycin C in the laboratory and 0.1 mg/L mitomycin C in the field. With further optimization, which should include a reduction in daily maintenance, the sensor has the potential to become a useful addition to the currently available biomonitors