National survey of molecular bacterial diversity of New Zealand groundwater: relationships between biodiversity, groundwater chemistry and aquifer characteristics.

Groundwater is a vital component of rural and urban water supplies in New Zealand. Although extensive monitoring of chemical and physical properties is conducted due to the high demand for this valuable resource, current information on its bacterial content is limited. However, bacteria provide an immense contribution to drive the biogeochemical processes in the groundwater ecosystem as in any other ecosystem. Therefore, a proper understanding of bacterial diversity is crucial to assess the effectiveness of groundwater management policies. In this study, we investigated the bacterial community structure in NZ groundwater at a national scale using the terminal restriction fragment length polymorphism (T-RFLP) molecular profiling tool and determined the relationships between bacterial diversity and groundwater chemistry, geological parameters and human impact. Considerable bacterial diversity was present and the community structures were strongly related to groundwater chemistry, and in particular to redox potential and human impact, reflecting their potential influence on determination of bacterial diversity. Further, the mean residence time of groundwater also showed relationships with bacterial community structure. These novel findings pertaining to community composition and its relationships with environmental parameters will provide a strong foundation for qualitative exploration of the bacterial diversity in NZ groundwater in relation to sustainable management of this valuable resource.

Dynamic groundwater monitoring networks: a manageable method for reviewing sampling frequency.

Optimization of a water quality network through a change in sampling frequency is the only way to increase cost-efficiency without any reduction in the robustness of the data. Existing techniques define optimal sampling frequency based on analysis of historical data from the monitoring network under investigation. Their application to a large network comprised of many sites and many monitored parameters is both technical and challenging. This paper presents a simple non-parametric method for reviewing sampling frequency that is consistent with highly censored environmental data and oriented towards reduction of sampling frequency as a cost-saving measure. Based on simple descriptive statistics, the method is applicable to large networks with long time series and many monitored parameters. The method also provides metrics for interpretation of newly collected data, which enables identification of sites for which a future change in sampling frequency may be necessary, ensuring that the monitoring network is both current and adaptive. Application of this method to the New Zealand National Groundwater Monitoring Programme indicates that reduction of sampling frequency at any site would result in a significant loss of information. This paper also discusses the potential for reducing analysis frequency as an alternative to reduction of sampling frequency.