Increased nutrient loading and eutrophication are common problems for lakes globally (Carpenter et al., 1998; Smith & Schindler, 2009). New Zealand is no exception, where 30% of lakes >1 ha have very poor to extremely poor water quality (Van Bunnik et al., 2007). Many of the iconic lakes in the well-known, geothermally active Rotorua region of New Zealand exhibit the adverse affects of eutrophication, including harmful algal blooms, bottom water hypoxia, reduced clarity (Hamilton et al., 2010) and loss of aquatic biodiversity (Hamilton, 2004; Burns, Mcintosh & Scholes, 2009). These lakes are important to New Zealand both economically and culturally (Edgar, 2009).