THE MIRACLE OF OYSTERS

Understanding the miracle of OYSTERS

RESTORING WITH NATURE: WHAT ARE WE LEARNING FROM OYSTERS? BY PROF. ANAMARIJA FRANKIĆ

Nature has been teaching us about design miracles and solutions for years – how to live resilient, healthy, loving lives creating conditions conducive to clean water, air, soil, food and biodiversity. Amazing! There is nothing more relaxing to me than to dive into water, fresh or salty, and reconnect with nature’s energy, absorbing it, recharging and sharing her wisdom. Unfortunately, we are continuously alarmed by the loss of biological diversity and one very common species captured my interest for many decades. Today, I am still learning from this marine bivalve – the oyster.

Did you know that oyster reefs are the most endangered coastal habitat globally? Imagine the amazing bivalve shells piling up to seven metre high reefs and spreading thousands of hectares in area, building three dimensional structured habitats in every sea and along every coast of every continent. Presently, as there are practically no existing oyster reefs it is hard to image the vast oyster populations globally and their benefits to our coastal ecosystems.

 The beach at Arklow, Co. Wicklow

" DECLINES IN OYSTER REEF POPULATION ARE MAINLY DUE TO ANTHROPOGENIC ACTIVITIES THAT LEAD TO OVER-HARVESTING, HABITAT DESTRUCTION, COASTAL WATER POLLUTION AND DISEASE SPREAD."

Oysters have diversified into hundreds of species adapted to specific coastal marine and estuarine environments, becoming one of the world’s most significant coastal engineers. Oysters have been evolving for about five hundred million years, shifting with temperature changes and sea level rises, adapting to natural changes through the Ice Age, until the present Anthropocene Era. We know today that one adult oyster can filter between one to two hundred litres of water per day!

Unfortunately, global oyster populations and their reef habitats have been reduced by approximately 85% in many coastal ecoregions and by 99% in most bay areas (estuaries). Declines in oyster reef population are mainly due to anthropogenic activities that lead to over-harvesting, habitat destruction, coastal water pollution and disease spread. When the harmony of a natural system is harmed, it is more prone to diseases. This amazing, healthy food source is a delicacy for humans and a keystone species in nature which is now missing from one of the most important niches in nature – coastal and marine systems.

Oyster reefs are formed through the gregarious settlement of oysters, preferably on their own shells or any other calcium carbonate substrate. As ecosystem engineers, oyster reefs enhance biodiversity by harbouring juvenile and smaller fish species, creating natural coastal buffer zones absorbing wave energy, and preventing erosion. We should not undermine their ability to reverse present water pollution and ocean acidification, although it is hard to visualise their historic abundance in the global marine environment because we don’t have a single example of a healthy oyster reef to learn from.

Throughout their lifespan, oysters help reduce turbidity and improve photosynthesis in deeper waters, promoting the growth of submerged aquatic vegetation (SAV). The symbiotic relationship between deep water oyster habitats and SAV supports synergistic ecosystem benefits including sediment stabilisation, habitat creation and improved water quality. Interestingly, along some coastlands, oysters prefer to settle in the vicinities of salt marshes. These three keystone coastal systems (salt marsh, oyster reef and SAV) act in unison to create some of the most biologically productive areas known.

Natural systems that love to work together with oyster reefs vary globally and include mangroves, coral reefs, rocky shorelines, kelp, mud flats, sandy beaches and dunes. Essentially, every natural coastal and marine system requires filterfeeders and healthy waters.

NATIVE OYSTER REEF RESTORATION IRELAND (NORRI) In 2019, we initiated the Native Oyster Reef Restoration Ireland (NORRI) project to restore Ostrea edulis, the endangered native European flat oyster. Historically, this oyster species was established along 80km of reefs from Wicklow Head to Ravens Point, Co. Wexford. Arklow in Co. Wicklow was the main port for oyster fisheries in the 1800s, with a harvest of forty million oysters by 1863. Today, the whole of Ireland lands just over two million native oysters per year. Every single harbour in the world has a similar story. The oyster reefs are gone but remind us of their presence with accumulated oyster shells along the beaches.

Together with the local community we set up the NORRI initiative to restore their historic beds. We have selected two suitable sites for oyster reef restoration, along Wicklow’s coastal marine area and the main goal is to establish two no-take areas, with Biomimicry LivingLabs (see https://biomimicry.org/livinglabs-savin-hill/). With support from Wicklow County Council, County Wicklow Partnership and the local community, NORRI hopes to reintroduce this species and restore oyster reefs so that Wicklow and neighboring counties can once again benefit from the presence of this native, keystone species in the Irish Sea.

Unfortunately, due to the pandemic and lockdowns, we had to postpone practical biomimicry workshops as well as our pilot project. We held a two-day workshop in Arklow, in March 2020 with 40 participants and we are going to organize the second online workshop in March this year. Hopefully, we will be able to start the oyster restoration pilot project this summer in Arklow.

What can you do? First, say thank you to oysters when you eat them next. Second, please bring shells back to the sea where they belong. One in a million oyster larvae might find a home to settle on them.

For more information visit www.norri.ie or search for NORRI Project on YouTube to watch their documentary.