S. L. Kenefick

VARIABILITY OF THE HEPATOTOXIN MICROCYSTIN‐LR IN HYPEREUTROPHIC DRINKING WATER LAKES1

The patterns of occurrence of the peptide hepatotoxin microcystin‐LR (MC‐LR) was studied in three hypereu‐trophic hardwater lakes (Coal, Driedmeat, and Little Beaver) in central Alberta, Canada, over three open‐water seasons. MC‐LR concentration was based on high‐performance liquid chromatography detection and expressed as μg.g−1 of total plankton biomass, ng.L−1 of lake water, and μg.g−1 of Microcystis aeruginosa Kuetz. emend. Elenkin. MC‐LR was highly variable temporally (differences up to 3 orders of magnitude) within each lake over an individual year, between years in an individual lake, and between lakes in any year. Seasonal (within‐year) changes in MC‐LR concentration (expressed in the preceding units) were positively correlated to the abundance and biomass Of the cyanobacterium M. aeruginosa (r =0.60–0.77), total and total dissolved phosphorus concentration (r =0.46–0.59), pH (r=0.38–0.58), and chlorophyll a (r=0.25–0.59). Surprisingly, there was no relationship between MC‐LR concentration and water temperature (range: 7°‐24°C, r =‐0.13 to 0.02) and a negative correlation with nitrate concentration (r =–0.27 to ‐0.34). In two synoptic surveys examining spatial variability, MC‐LR concentrations were quite variable (CV of 185 and 36% between sampling sites for Coal and Little Beaver lakes, respectively). Spatial distribution of MC‐LR on any one day was correlated with the abundance and biomass of M. aeruginosa. Over a 24‐h period, MC‐LR concentration in M. aeruginosa decreased more than 6‐fold at night relative to daytime concentrations. In general, analytical and within‐site variation of MC‐LR was relatively small (CV < 4 and 9%, respectively) but greatest both within and between years in a lake followed by diel and spatial variation.

Occurrence and toxicological evaluation of cyanobacterial toxins in Alberta lakes and farm dugouts

Abstract The occurrence of neuro- and hepatotoxins produced by cyanobacteria (blue-green algae) was assessed in eight lakes and six farm dugouts, located in Alberta. Anatoxin-a, an alkaloid neurotoxin produced by Anabaena flos-aquae , was not detected in the lake blooms with gas chromatography-mass spectrometry (GC-MS). Algal blooms which contained Microcystis aeruginosa almost always had detectable concentrations of microcystin-LR, a peptide hepatotoxin, based on high performance liquid chromatography (HPLC) analyses. Bloom samples from the six farm dugouts contained no detectable quantity of either anatoxin-a or microcystin-LR. However, anatoxin-a and microcystin-LR were detected in algae isolated and subsequently cultured from two separate dugouts. Microcystin-RR was not detected in any bloom sample collected. Among three lakes studied in greater detail, the concentration of microcystin-LR present in the blooms was highly variable between lakes and temporally within each lake over the limited sampling period. Fast atom bombardment-mass spectrometry (FAB-MS) performed on a composite of several bloom samples from one lake confirmed the identity of microcystin-LR. Bioassays were performed with a subset of the bloom samples to determine acute toxicity to mice. Intraperitoneal injection of bloom extracts containing microcystin-LR resulted in a massive dose-dependent pooling of blood in the liver, shock and very rapid (as quickly as 50 min post-injection) death of injected mice.

Physiological toxicity, cell membrane damage and the release of dissolved organic carbon and geosmin by Aphanizomenon flos-aquae after exposure to water treatment chemicals

Reducing the level of dissolved organic carbon is an increasingly important goal in the treatment of drinking water. Dissolved organic carbon (DOC) compounds react with chemical disinfectants to form undesirable by-products, and DOC provides a substrate for bacterial growth. Chemicals used in water treatment processes and surface water reservoir management can cause the release of dissolved organics from photosynthetic aquatic organisms, and specific organic compounds can impart taste, odour and sometimes toxicity to treated water. Thus, chemical treatment of water may exacerbate the problem of dissolved organic carbon loading. The effects of several chemicals used at different stages of the water treatment process were studied on a nitrogen-fixing strain of the cyanobacterium Aphanizomenon flos-aquae. Chemicals included chlorine, potassium permanganate, aluminum sulphate, ferric chloride, calcium hydroxide, hydrogen peroxide and copper sulphate. Physiological effects on Aphanizomenon, as quantified by its ability to fix nitrogen, were compared with cell membrane damage (manifested as potassium release) and the release of organic cellular components, including DOC and the specific odour compound, geosmin. Aluminum sulphate and ferric chloride did not cause either physiological toxicity, cell membrane damage or the release of DOC at treatment usage concentrations. Calcium hydroxide at low levels and hydrogen peroxide caused physiological toxicity, but only limited membrane damage, DOC and geosmin release. Chlorine, copper sulphate and potassium permanganate caused physiological damage with concomitant release of both DOC and geosmin at concentrations lower than those currently used in water treatment. Consequently, these last three chemicals create potential water treatment problems by releasing DOC and specific problem compounds.

Actinomycetes as a factor in odour problems affecting drinking water from the North Saskatchewan River

Abstract In 1991 the numbers of actinomycetes in the water from the North Saskatchewan River, the colour of the water and the flow rate of the river were all found to increase coincidentally at the onset of spring runoff. These same conditions had previously been associated with odours in the treated water. When more than one hundred actinomycete isolates from water samples were tested for their ability to produce geosmin and 2-methylisoborneol, the majority were able to produce one or both of these odorous compounds. When representative actinomycete isolates were tested for their susceptibility to disinfection with chloramine under conditions commonly encountered in water treatment processes, they gave CT99 values varying from a low of 3.6 to a high of 92 (mg/l min). This wide range of sensitivities seen in the small numbers of isolates tested suggests that chloramine-resistant odour-causing organisms could escape the water treatment processes during the spring runoff period. Odour problems could result from having these organisms become established in the distribution system. In addition to their ability to produce geosmin or 2-methylisoborneol, we found that two of three actinomycete isolates tested were able to transform the common pollutant and disinfection by-product 2,4,6-trichlorophenol into the extremely odorous compound 2,4,6-trichloroanisole.