Adrian Croucher

Python scripting libraries for subsurface fluid and heat flow simulations with TOUGH2 and SHEMAT

Numerical simulations of subsurface fluid and heat flow are commonly controlled manually via input files or from graphical user interfaces (GUIs). Manual editing of input files is often tedious and error-prone, while GUIs typically limit the full capability of the simulator. Neither approach lends itself to automation, which is desirable for more complex simulations. We propose an alternative approach based on the use of scripting. To this end we have developed Python libraries for scripting subsurface simulations using the SHEMAT and TOUGH2 simulators. For many problems the entire modeling process including grid generation, model setup, execution, post-processing and analysis of results can be carried out from a single Python script. Through example problems we demonstrate some of the potential power of the scripting approach, which does not only make model setup simpler and less error-prone, but also facilitates more complex simulations involving, for example, multiple model runs with varying parameters (e.g. permeabilities, heat inputs, and the level of grid refinement). It is also possible to apply the developed methods for extending the functionality of graphical user interfaces. Basing our approach on the Python language makes it simple to take advantage of other libraries available for scientific computation, with sophisticated analysis of results often a matter of a single function call. We envisage many other possible applications of the approach, including linking with geological modeling software, running stochastic ensembles of models and hybrid modeling using multiple interacting simulators.

Temperate marine protected area provides recruitment subsidies to local fisheries

The utility of marine protected areas (MPAs) as a means of protecting exploited species and conserving biodiversity within MPA boundaries is supported by strong empirical evidence. However, the potential contribution of MPAs to fished populations beyond their boundaries is still highly controversial; empirical measures are scarce and modelling studies have produced a range of predictions, including both positive and negative effects. Using a combination of genetic parentage and relatedness analysis, we measured larval subsidies to local fisheries replenishment for Australasian snapper (Chrysophrys auratus: Sparidae) from a small (5.2 km2), well-established, temperate, coastal MPA in northern New Zealand. Adult snapper within the MPA contributed an estimated 10.6% (95% CI: 5.5–18.1%) of newly settled juveniles to surrounding areas (approx. 400 km2), with no decreasing trend in contributions up to 40 km away. Biophysical modelling of larval dispersal matched experimental data, showing larvae produced inside the MPA dispersed over a comparable distance. These results demonstrate that temperate MPAs have the potential to provide recruitment subsidies at magnitudes and spatial scales relevant to fisheries management. The validated biophysical model provides a cost-efficient opportunity to generalize these findings to other locations and climate conditions, and potentially informs the design of MPA networks for enhancing fisheries management.