ARC have been making steps forward in oyster restoration recently. We found out that we can stick oysters to Reef Cubes, with no significant effect on their survival. The results come from a short study completed with the Marine Biological Association (MBA), in Plymouth. We were lucky enough to make use of their new aquarium setup the Smart Experimental Array (SEA), to lay some laboratory groundwork for our future restoration efforts.
So what’s the point? Well, the European native oyster has seen massive declines in range and numbers over the last two centuries or so. They’re an extremely important species because they create a complex habitat in the form of oyster reefs. Unfortunately, most of Europe’s oyster reefs have effectively been ransacked and destroyed. So there’s a lot of talk about habitat restoration these days – in order to combat the biodiversity crisis we find ourselves in – and at ARC Marine we see engineering projects as a great opportunity to put restoration in to practice.
The Smart Experimental Array at the Marine Biological Association.
Previous research has found that concrete reef units can be highly beneficial for oyster restoration projects. The material itself can provide a hard surface that young oysters can settle and grow on in high abundance (Graham, Palmer and Pollack, 2017). Having a durable structure can also help stabilise the surroundings so that newly released oysters or any extra shell material for them to grow on isn’t washed away (Frederick et al., 2016). Also, being raised on a reef structure improves the filtration rate of newly released oysters, compared to being on the sea floor (Sawusdee et al., 2015). Reef Cubes have open internal spaces, so they have a greater surface area to volume ratio. This means that there’s more space for oysters to grow on the inside and outside of them. Fluid dynamics modelling has also indicated that the flow speeds up through the Reef Cubes, which means plenty of water – hopefully containing nutrients and oxygen – is provided to species living inside.
Four live native oysters attached to a 0.3m sided Reef Cube. Image credit: BBC Spotlight.
The question remains though as to how we should release the oysters with Reef Cubes. The aim is to create self-perpetuating populations but to start there often has to be be a reintroduction stage. There are many options at our disposal ranging from elaborate cages to simply ‘sprinkling’ the oysters loosely over the cubes. To explore some of these options in more detail we developed our experimental research project with the MBA, attaching oysters to the cubes and monitoring their survival. For further information on the research please get in touch to request a fact sheet or check out this short clip recorded by the BBC (https://youtu.be/b-Ei-SVROxU).
We now have a growing body of evidence for the use of Reef Cubes in oyster restoration. We’ve shown that young oysters – called spat – will settle on the Reef Cubes surfaces. Reef Cubes came first in the 2019 Offshore Innovation Challenge for effective oyster structure designs. Oysters were then grown on a Reef Cube in the Netherlands and released in the waters near Brouwersdam. And now, we have evidence that adult oysters will survive transplantation inside and on the Reef Cubes. Hopefully, we can take the momentum from these results into our projects and deliver a meaningful biodiversity gain to our clients.
Thanks again to the staff at the MBA and Emily Deery at the Marine Business Technology Centre (MBTC) for running the tanks and monitoring the oyster’s survival. Thank you also to the European Regional Development Fund for funding the SEA – facilitating this innovative research – and to Fal Oyster Ltd. for supplying healthy oysters for the experiment.
Oyster spat that have settled on Reef Cubes surfaces in a spat pond. Image credit: Tony Legg at the Jersey Oyster Co.
On the release of oysters with a Reef Cube into Dutch waters by the Rich North Sea project: https://www.derijkenoordzee.nl/nieuws/in-nederland-gekweekte-platte-oesters-uitgezet-in-zee
Frederick, P. et al. (2016) ‘Reversing a Rapid Decline in Oyster Reefs: Effects of Durable Substrate on Oyster Populations, Elevations, and Aquatic Bird Community Composition’, Journal of Shellfish Research, 35(2), pp. 359–367. doi: 10.2983/035.035.0210.
Graham, P. M., Palmer, T. A. and Pollack, J. B. (2017) ‘Oyster reef restoration: substrate suitability may depend on specific restoration goals’, Restoration Ecology, 25(3), pp. 459–470. doi: 10.1111/rec.12449.
Sawusdee, A. et al. (2015) ‘Improvements in the physiological performance of European flat oysters Ostrea edulis (Linnaeus, 1758) cultured on elevated reef structures: Implications for oyster restoration’, Aquaculture, 444, pp. 41–48. doi: 10.1016/j.aquaculture.2015.03.022.