Using and improving benthic ecosystem models to understand the future of seafloor communities

Seafloor communities are an important part of the ocean’s food chain and play a role in long-term seafloor carbon burial. They are almost wholly dependent on sinking organic carbon, or marine snow, from surface ecosystems for food. Climate change and ocean acidification are forecast to impact these surface ecosystems, potentially with implications for seemingly remote deep-sea communities [1]. Seafloor sampling remains difficult and good datasets are relatively limited. However, we now have datasets from multiple field sites of organisms from the smallest to the largest multicellular animals. These datasets have been used to construct a size-based model that uses sinking marine snow to drive seafloor community biomass at these disparate sites [2]. Recent work applying this model at the global scale has investigated how community biomass will change under different climate scenarios, and concluded that the role of potential changes in seafloor POC flux is critical. However, the model overlooks a number of environmental factors known to affect organism metabolism, including temperature and oxygen, and simplifies both the important role of seafloor bacteria and the ecological interactions between size classes [3]. More generally, the model is based on limited seafloor sites whose representativeness of the wider seafloor is unclear.

The project will make use of the Benthic Organisms Resolved In Size (BORIS) seafloor community model developed at NOC [2]. Research work will principally involve running and modifying this model and analysing its output, particularly in comparison to observations from diverse sites. The model currently operates within the MATLAB software package, which facilitates the management and analysis of simulations. An important part of the project will be the inclusion of data from more recently studied seafloor sites to improve the model’s parameterisation and “universality”. This will involve the use of a genetic algorithm, also within MATLAB, to tune the model to better fit existing and new seafloor observations. The model will additionally be developed and extended to investigate the importance of currently omitted or simplified ecophysiological factors. These include well-understood variables such as temperature and oxygen, but also food web interactions such as predation. The wider significance of the work for understanding seafloor communities into the future will be investigated by forcing the model with POC fluxes produced by global marine biogeochemistry models. These will include the UK Earth System Model, UKESM1, whose marine biogeochemistry is under development at NOC, and also international models used in IPCC climate change projections.

The SPITFIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the National Oceanography Centre. Specific training will include:

The operation and analysis of the BORIS model [2], including methods for parameter optimization
The analysis and use of seafloor benthic community data
Theory and practice of benthic ecology
Handling and use of global-scale earth system model outputs from IPCC simulations
Where possible, an opportunity to go to sea on a research cruise to learn about making shipboard measurements of seafloor communities