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

Abstract

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.

Factors Shaping the Pattern of Seasonal Variations of Microcystins in Lake Xingyun, a Subtropical Plateau Lake in China

“…In our study, the maximum MC concentration reached as high as 42.12 lg l -1 during the warm season and was considerably higher than those of Microcystis blooms in other regions of the world (Kotak et al 1995(Kotak et al , 2000Lahti et al 1997;Haney and Ikawa 2001). The concentration we measured greatly exceeded the safety limit for drinking (1 lg l -1 ) and recreation water (20 lg l -1 ) provided by the WHO.…”

“…However, only a few studies addressed the significance of direct environmental influences on microcystin production by Microcystis (Wicks and Thiel 1990;Kotak et al 1995Kotak et al , 2000Jacoby et al 2000). Such studies on cyanobacterial toxins in natural algal blooms are still lacking from subtropical China, especially in the Chinese plateau lakes.…”

Growth, toxin production, active oxygen species and catalase activity of Microcystis aeruginosa (Cyanophyceae) exposed to temperature stress

“…M. aeruginosa was monitored in the area (Giannuzzi et al, 2012) and MCs were detected in drinking water . From our results we may predict that increasing temperatures up to 29°C (projected higher mean water temperature under climate change) could produce a decreased total MC cell quota in M. aeruginosa but leading to higher proportions of the more toxic MC-LR variant (Kotak et al, 1995). Therefore, continued climatic warming could lead to a dominance of M. aeruginosa populations including blooms that contain a greater percentage of cells with high concentrations of MC-LR.…”

Field Studies on the Environmental Factors in Controlling Microcystin Production in the Subtropical Shallow Lakes of the Yangtze River

“…They reported that total microcystin production was positively correlated with Chl a and solar radiation, and the microcystins-YR, -LR, -YA and -LA were negatively correlated with Chl a and the concentration of soluble reactive phosphorus. Kotak et al (1995) reported that microcystin-LR content of cyanobacteria in three Canadian lakes was positively correlated with the concentrations of total phosphorus, dissolved phosphorus and Chl a; and negatively correlated with that of nitrate. Vézie et al (1997) reported the total amount of microcystin was positively correlated with the concentration of Chl a in water, and negatively correlated with solar radiation.…”

“…Phytoplankton and zooplankton were identified based on descriptions of Prescott (1978) and enumerated with a microscope equipped with a calibrated micrometer (Kotak et al 1995).…”