Physical and ecological effects of rehabilitating the geothermally influenced Waikite Wetland, New Zealand

Temporal dynamics of geothermal microbial communities in Aotearoa-New Zealand

Microbial biogeography studies, in particular for geothermal-associated habitats, have focused on spatial patterns and/or individual sites, which have limited ability to describe the dynamics of ecosystem behaviour. Here, we report the first comprehensive temporal study of bacterial and archaeal communities from an extensive range of geothermal features in Aotearoa-New Zealand. One hundred and fifteen water column samples from 31 geothermal ecosystems were taken over a 34-month period to ascertain microbial community stability (control sites), community response to both natural and anthropogenic disturbances in the local environment (disturbed sites) and temporal variation in spring diversity across different pH values (pH 3, 5, 7, 9) all at a similar temperature of 60–70°C (pH sites). Identical methodologies were employed to measure microbial diversity via 16S rRNA gene amplicon sequencing, along with 44 physicochemical parameters from each feature, to ensure confidence in comparing samples across timeframes. Our results indicated temperature and associated groundwater physicochemistry were the most likely parameters to vary stochastically in these geothermal features, with community abundances rather than composition more readily affected by a changing environment. However, variation in pH (pH ±1) had a more significant effect on community structure than temperature (±20°C), with alpha diversity failing to adequately measure temporal microbial disparity in geothermal features outside of circumneutral conditions. While a substantial physicochemical disturbance was required to shift community structures at the phylum level, geothermal ecosystems were resilient at this broad taxonomic rank and returned to a pre-disturbed state if environmental conditions re-established. These findings highlight the diverse controls between different microbial communities within the same habitat-type, expanding our understanding of temporal dynamics in extreme ecosystems.

Quantitative assessment of the environmental risks of geothermal energy: A review

Over recent decades, the use of geothermal energy for heating supply and power generation has increased significantly across the world, owing to its low carbon emissions. However, a series of emerging environmental risks from geothermal energy development and operation have been drawing increasing attention from governments and the publics. In this context, the present study provides an overview of methods for quantitatively assessing the environmental risks of geothermal energy. These include seismic hazards, human health, ecological damage and economic loss. The constraints on constructing assessment frameworks are also discussed. Furthermore, a preliminary concept for an integrated framework is proposed to assess environmental risks of geothermal energy comprehensively from multiple perspectives. To enhance the accuracy and reliability of the proposed framework, a data-sharing platform needs to be built to develop multi-disciplinary modeling further.