Cracking the shell secret to help shellfish farmers
Shellfish are a significant source of food, yet we know very little about how they make their shells and how environmental factors affect them. The EU-funded CACHE project is finding out how shellfish produce their shells, how this production varies according to their environment, and what this means for the future of shellfish farming.
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As more carbon dioxide (CO2) makes its way into the atmosphere, so our oceans absorb it and the oceans get warmer. In seawater, CO2 forms carbonic acid, which makes the ocean more acidic. This oceanic acidification places many animals that build shells or skeletons of calcium carbonate at serious risk, explains CACHE project coordinator Melody Clark.
Shellfish are a significant source of food, with aquafarmers producing more than 160 million tonnes of shellfish each year. Asia and Europe are the main producers of shellfish, and just a few species account for as much as 70-98% of all shellfish production. Putting all our eggs in one basket places the entire shellfish industry at risk of disease and sensitivity to climate change, points out CACHE researcher Phoebe Stewart-Sinclair.
And according to the CACHE project, it is important to protect shellfish not only for food security but for biodiversity reasons. Other uses include reducing industrys CO2 emissions (the very pollutant putting shellfish at risk), and as a calcium supplement for hens that need 10g of calcium per day to stay healthy and to produce eggs. Other potential applications include agricultural liming agents, topsoil and mulch for gardening, and in concretes and other building materials.
Prising open the secrets of shells
A team of 10 PhD researchers, plus three junior and three experienced researchers from across Europe are collaborating in the CACHE project, which has received a Marie Curie grant to create a training network. They are investigating calcium production in four commercial shellfish species: blue mussels, great scallops, Pacific oysters and clams. The researchers are located in England, Germany, France, Portugal, Scotland, Belgium and Sweden.
Thanks to the Marie Curie collaboration and mobility exchange, we have been able to take samples of those species of shellfish from locations across Europe Scotland, Sweden, and the Baltic. This has enabled us to look at the natural populations of species and how they vary across sites, reports Clark. Where possible, the researchers have shared and used the same samples for research on multiple aspects of shells, using different approaches, for more scientifically reliable results.
Although shells are a fantastic source of calcium, we actually dont know how shellfish make their shells, she says. The CACHE project is looking at many aspects of this question from mollusc proteins (in Paris), shell genetics (Cambridge, England), and the movement of calcium across cell membranes (in Gothenburg, Sweden) to the development of shellfish lava, the production of shells and the mobilisation of calcium (in Kiel, Germany).
Information about the shells genes, proteins, size and shape can give researchers an indication of how much shell a mollusc can produce under different conditions. When a broad range of disciplines intersect in this way, Marie Curie investment into research can push a field of study forward at a rapid pace, comments Clark.
Future impact on shellfish farming
There is much media hype about the potentially devastating effects of oceanic acidification on aquafarmers. But farmers want to know how this acidification will affect the species they cultivate in the oceans they farm. CACHE PhD students are working with aquafarmers who have provided access to their sites. They too want answers!
Identifying strains that have thicker shells, as well as the effects that different environments have on these shells and their thickness, are focal points of this project. Salinity and acidification both affect the thickness of shells, for example. The researchers have found that some individual mussels and species of mussels have thicker shells, even in oceans with lower pH. These mussels are better at coping with acidification due to their genetic make-up, reports Clark.
In Scotland, a CACHE researcher is exploring how depth affects the thickness and the uniformity of the shells that hang on a rope in aquafarming. When shells are of a uniform shape and thickness, they are easier to process; the research is intended to identify farming practices that can help to optimise aquaculture farming.
The findings of the CACHE project could have a significant impact on shellfish farming; they could tell farmers what species are more resilient and what locations / environmental factors will better support and improve production, explains Clark. And they could even help researchers take shells into areas as diverse as agriculture and construction.