It’s 06:45 and dawn is beginning to break across the tranquil waters of the Dornoch Firth in the
Scottish Highlands. Home to the Glenmorangie Distillery for the last 180 years, one of Scotland’s
most northerly estuaries has seen enormous biodiversity change.

Its tranquil waters are far from still. But instead of teeming with plant and animal life, the water is
teeming with scientists and restoration ecologists. The team are members of the innovative Dornoch
Environmental Enhancement Project (DEEP), first initiated in 2014, which is aiming to reintroduce
four million European native oysters (Ostrea edulis), into the protected area by 2030. The species
became extinct in these and many other waters, probably due to overfishing, over 100 years ago.

The exemplar project aims to improve water quality and increase carbon storage whilst enhancing
marine biodiversity. Oysters naturally filter water as they feed and create microhabitats for other
marine life and enhance sediment deposits on the seabed, which increases an area’s biodiversity. 
Within a decade, it is hoped that the newly established reefs, together with Glenmorangie’s
anaerobic digestion plant, will account for 100 per cent of the organic material that the Distillery
releases into the Dornoch Firth.

DEEP is delivered through a ground- breaking partnership between The Glenmorangie Company,
Heriot-Watt University and the Marine Conservation Society. During our first phase, we trawled
archaeological records, ancient literature and fisheries records, then sampled shell material, to
show that oysters existed in the Dornoch Firth as far back as 10,000 years ago. This substantiated
our belief that reintroducing them was feasible. Since then, the process of recreating oyster
habitats has been optimised and the benefits of oyster restoration increasingly clarified, led by
scientific project lead Professor Bill Sanderson.

Oyster restoration efforts are growing across Europe as more is understood about the ecosystem
services provided by reefs. But with intact oyster reef habitats so rare, researchers like us have had
limited data to work with to help predict the biodiversity benefits of this marine conservation work –
until now.

Our new research has, for the first time, predicted the biodiversity gain of reintroducing European
native oysters. Writing in peer-reviewed scientific journal PLOS ONE, we studied the biodiversity of
Scotland’s last remaining native oyster fishery at Loch Ryan in south-west Scotland. The fishery,
which has been operating since 1701, uses a rotational harvest system where different areas are
fished each year and then left to repopulate for six years before they are fished again.

As well as giving our research a window into the past, it allowed us to predict what a future reef
might look like in the Dornoch Firth once oysters are fully restored. This was achieved by studying
the effect of oyster reef development and biodiversity gain at different stages after the Loch Ryan
oyster habitats had been fished.

In the study, three treatments were surveyed for faunal biodiversity, oyster shell density and oyster
shell percentage cover. Treatments were plots that had been harvested one year previously, two
years, and six years before the study began. The treatments were surveyed with SCUBA using a
combination of video transects and photo quadrats. Modelling was used to predict changes in the
Shannon-Wiener’s Diversity index, a globally recognised and popular measure of diversity, over time
since fishing.

Our findings from Loch Ryan demonstrate that biodiversity will likely double over a decade once
oyster restoration projects are complete. This means the population of species will increase in a
balanced way. The data has also shown a link between increased shell material as the oyster
population grows and increased biodiversity.

The last five years have seen a rapid increase in the number of restoration projects targeting
European native oyster habitats, many of which aim to improve biodiversity. As we push towards
our next milestone of 200,000 oysters restored to the Dornoch Firth by the end of 2024, these
findings are significant for DEEP but more broadly this research will help to inform the many marine
conservation projects around the world that have taken inspiration from this environmental
partnership in the Highlands of Scotland.

The Deep Science team in Heriot-Watt University’s Centre for Marine Biodiversity and Biotechnology
concentrates on the marine biodiversity research needed to support sensitive management and
sustainable development. Recent work focuses on biogenic reef restoration covering biodiversity,
blue carbon, water quality and the optimisation and up-scaling of marine restoration techniques. For
more information, visit www.hw.ac.uk

By Naomi Kennon, PhD candidate in restoration ecology, Heriot-Watt University