CSIRO PUBLISHING www.publish.csiro.au/journals/mfr Marine and Freshwater Research, 2009, 60, 25–33 Distribution of the cyanobacterial toxins cylindrospermopsin and deoxycylindrospermopsin in a stratified lake in north-eastern New South Wales, Australia Sally Everson A,D,E , Larelle Fabbro A , Susan Kinnear B , Geoff Eaglesham C and Paul Wright D A Centre for Environmental Management AHS BLG 6, CQUniversity, Rockhampton, Qld 4702, Australia. B Institute for Sustainable Regional Development, CQUniversity, Rockhampton, Qld 4702, Australia. C Queensland Health and Scientific Services, 39 Kessels Road, Coopers Plains, Qld 4108, Australia. D Tweed Shire Council,Tweed Laboratory Centre, Enterprise Avenue, South Tweed Heads, NSW 2486, Australia. E Corresponding author. Email: sallye@tweedlab.com.au Abstract. This paper describes the vertical water column distribution of the cyanobacterial toxins cylindrospermopsin and deoxycylindrospermopsin in a water body containing the cyanobacteria Aphanizomenon ovalisporum and Cylindro- spermopsis raciborskii. The study site was Cobaki Village Lake, a small stratified anthropogenic lake in north-eastern New South Wales,Australia. Water quality analysis indicated that stratification and oxygenation of the water column were significant in both the distribution of the cyanobacterial populations and their associated toxin concentrations. Toxin was distributed throughout the entire water column, but the highest concentrations were recorded in the hypolimnion. Maximum toxin concentrations were detected in February 2007 (38.2 μgL −1 cylindrospermopsin (CYN) and 42.2 μgL −1 deoxy- CYN). The relative distribution of CYN and deoxy-CYN paralleled the distribution of NH 3 H and NO X within the water column, with oxygenated chemical species dominating above 15 m and de-oxygenated chemical species dominating below 15m. Cyanobacterial cell concentrations were highest in the oxic, warm and low conductivity waters of the epilimnion and cyanobacterial species succession was associated with nutrient and trace-metal depletion in this surface layer. These research findings are directly relevant to the management of water supplies affected by toxic blue-green algal blooms, particularly with respect to the considered placement of off-take devices to avoid layers of cyanobacterial cell and toxin concentrations. Additional keywords: Aphanizomenon ovalisporum, blue-green algae, cyanobacteria, Cylindrospermopsis raciborskii, ecotoxicity, stratification. Introduction Cylindrospermopsin (CYN) is an alkaloid toxin that was first isolated from Cylindrospermopsis raciborskii (Ohtani et al. 1992). The toxin is also produced by Aphanizomenon oval- isporum (Banker et al. 1997; Shaw et al. 1999), Anabaena bergii (Fergusson and Saint 2000), Umezakia natans (Harada et al. 1994), Raphidiopsis curvata (Li et al. 2001), Apha- nizomenon flos-aquae (Preußel et al. 2006), Lyngbya wollei (Seifert et al. 2007) and Anabaena lapponica (Spoof et al. 2006). Cylindrospermopsin has been found to be highly toxic following intraperitoneal injection and oral exposure (Ohtani et al. 1992; Seawright et al. 1999; Shaw et al. 2000) and the inhibition of protein synthesis is an important mechanism with respect to the toxicity (Froscio et al. 2003). In vitro stud- ies of the toxicity of the analogue deoxy-cylindrospermopsin (deoxy-CYN) have demonstrated cytotoxicity and inhibition of protein synthesis similar to that produced by CYN (Neumann et al. 2007). Cylindrospermopsis raciborskii occurs in a wide range of water bodies worldwide (Padisák 1997). In tropical Australia, C. raciborskii produces high cell concentrations in waters featur- ing high pH (8.1), warm surface water temperatures (28–32 ◦ C), a stable water column and long retention times (Branco and Senna 1994; Boland and Griffiths 1996; McGregor and Fabbro 2000). Cylindrospermopsis raciborskii often forms maxima in cell concentration at depth (Fabbro and Duivenvoorden 1996), which contrasts with the scum formation and surface cell accu- mulation normally associated with other cyanobacteria, such as Microcystis (White et al. 2003) and Anabaena circinalis (Bormans et al. 1997). Aphanizomenon ovalisporum has been detected in algal blooms in Israel (Pollingher et al. 1998), Australia (Shaw et al. © CSIRO 2009 10.1071/MF08115 1323-1650/09/010025