Sclerochronology and modelling: combining annually resolved bivalve records and biogeochemical models to understand the shelf seas

Our coastal oceans are where many of the impacts of fishing, pollution and climate change are being, and will increasingly be felt. For example, by 2050, the World Bank estimates that climate impacts on tourism and fisheries alone will cost the global economy between 95 and 147 billion USD.

The vulnerability of coastal waters is now widely recognised, and in response innovative and extensive monitoring systems are being rolled out. However, we lack the past observations required to place recently observed change in context - is it caused by humans or nature? We also lack observations of long-term (decades) change, necessary for calibrating models used to look into the future and explore how coastal oceans may respond to different management strategies.

In this project, we will therefore extend the observational records back in time, and do this in such a way that we can make use of, and carefully test, models of coastal currents and ecosystems. Our past records will come from clam shells collected from the bottom of the North Sea and off the West coasts of England, Wales and Scotland.

These clams (or bivalves) live for many decades to hundreds of years. Samples we have worked on include the longest-lived animal ever found - over 500 years old. Each year bivalves grow a new band of shell material - much like a tree ring. Researchers have found that at different locations, the changing width of these bands records different aspects of how the environment has changed, probably mediated through a changing food supply.

So far no one has put all of the information from different locations together to come up with a single description of the overall factors controlling bivalve growth - and consequently no one has fully opened up their potential to reconstruct past changes in the environment. This has not previously been done because observations of the potentially important factors (plankton concentrations, nutrient concentrations etc.) are limited to a small number of sites, often far from where the bivalves have been collected.

We will use state-of-the-art 3D model simulations of the coastal ocean spanning the last 50 years, which reconstruct the changing ocean and ecosystem state by assimilating (taking in) ocean and/or atmospheric observations. By carefully identifying where and in what respects these models are doing a good job, we can supplement observations with information from the models, and identify what is ultimately causing the bivalve growth to vary.

Using this new understanding of the link between environmental change and bivalve growth change, we can interpret long (many decades to centuries) bivalve growth records, and reconstruct how our coastal waters have changes in the past. We can also build this understanding into models to allow us to predict how bivalve growth may change in the future.

This project requires a 3-way collaboration between the Universities of Exeter and Bangor and the Centre for the Environment, Aquiculture and Fisheries (Cefas) in Lowestoft. The University of Exeter is at the vanguard of climate change research, with expertise from climate to ecosystem modeling, and socioeconomic impacts to adaptation. Bangor University pioneers bivalve reconstruction techniques, including working with the 'longest-lived animal on Earth'. Cefas are recognised leaders in marine biological science, with a government remit to secure healthy and sustainable marine environments. Cefas run the UK's ocean model which most comprehensively simulates the biological and chemical processes on the sea-floor, and will make use of our findings to help meet the UK's marine environmental commitments.

By bringing together this expertise and understanding in climate, past environmental reconstruction and marine ecosystems, we hope to deliver the best possible tools for tacking emerging questions about the past, present and future impact of human activity on our coastal oceans.