Quantitative Variations of Intracellular Microcystin-LR, -RR and -YR in Samples Collected from Four Locations in Hartbeespoort Dam in North West Province (South Africa) During the 2010/2011 Summer Season

Bhekie B Mamba,Titus A.M Msagati,Elbert A Mbukwa

doi:10.3390/ijerph9103484

Bhekie B Mamba, Titus A.M Msagati + Show 1 more

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https://doi.org/10.3390/ijerph9103484

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Abstract

The Hartbeespoort (HBP) Dam is a reservoir used for agricultural, domestic supply of raw potable water and recreational activities in South Africa’s North-West Province. Eutrophication and cyanobacterial blooms have long been a cause of water-quality problems in this reservoir. The most prevalent bloom-forming species is Microcystis aeruginosa, often producing the toxin microcystin, a hepatotoxin which can negatively impact aquatic animal and human health, and poses a problem for potable water supply. Algal samples were collected monthly from four pre-determined sites in the dam during the summer months (December 2010–March 2011). Intracellular microcystins (MCs) were extracted using SPE C18 cartridges, followed by separation, identification and quantification using LC-ESI-MS techniques. Quantitative variation studies of MCs were conducted with respect to MC congener isolated, sampling site and month. Three main MC congeners (MC-RR, -LR and-YR) were isolated, identified and quantified. In addition, three minor MCs (MC-WR, MC-(H4)YR and (D-Asp3, Dha7)MC-RR were also identified, but were not quantified. The MC dominance followed the order MC-RR>MC-LR>MC-YR across all sites and time. The maximum and minimum concentrations were 268 µg/g and 0.14 µg/g DW for MC-RR and MC-YR, respectively, of the total MCs quantified from this study. One-way ANOVA showed that there were no significant differences between average MC concentrations recorded across months (P = 0.62), there was, however, a marginally-significant difference in concentrations among MC congeners (P = 0.06). ANCOVA revealed a highly significant interaction between sites and MC congeners on MC concentration (P < 0.001).

Highlights

Hartbeespoort Dam is situated in the North-West Province of South Africa
The ADDA group has been utilised in various methods for the identification of microcystins as described in Msagati et al [13], these include ELISA [14], HPLC-UV/PDA [15,16,17,18,19], LC-electrospray ionisation source (ESI)-MS [18,19], etc
In terms of quantitative studies on MCs commissioned and funded by the Water Research Commission (WRC), South Africa, including some recent works, the results presented were mainly based on total microcystin concentrations expressed as MC-LR equivalence using immunoassay or biochemical methods [25,50]

Summary

Introduction

Hartbeespoort Dam is situated in the North-West Province of South Africa. The reservoir is fed by the waters of the Crocodile and Magalies Rivers (Figure 1) and has a mean depth of 9.6 m, maximum depth of 45.1 m and surface area of 20 km. Hartbeespoort Dam is renowned for its poor water quality and is arguably one of the World’s worst examples of eutrophication, due to the high nutrient loads which enter the system and have overburdened the reservoir basin for decades. The ADDA group [6] is highly conserved in microcystins (and nodularins) and stable against physiological replacements by other amino acids. Due to this stability, the ADDA group has been utilised in various methods for the identification of microcystins (and nodularins) as described in Msagati et al [13], these include ELISA [14], HPLC-UV/PDA [15,16,17,18,19], LC-ESI-MS [18,19], etc. In positive mode LC-ESI-MS the ADDA group gives a characteristic fragment ion at m/z 135 corresponding to the [phenyl-CH2CH(OCH3)]+ ion [13]

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