A series of artificial, concrete rockpools, bolted onto harbour walls in Poole and the Isle of Wight have provided a safe habitat for an abundance of marine life, scientists have found.
The findings show that this could be an effective way to improve coastal ecosystems by helping nature to thrive in urban ports and harbours.
A team from Bournemouth University installed 114 of the artificial rockpools – shaped like a typical bathroom sink - across three sites in 2020. For the past three years they have been monitoring the species that inhabit them and comparing the results to species residing on the sea wall.
“As our coastlines become more developed, marine species are seeing their natural habitats replaced by sea defences which are harder to colonise,” explained Jess Bone, PhD researcher at Bournemouth University. “Sea level rise is also compounding the problem and is squeezing their habitats into smaller and smaller spaces. We wanted to see if giving them more rockpools could offer them a lifeline in the face of these challenges,” she added.
Rockpools retain water during low tide which creates a vital refuge for marine life, providing shelter, food and a nursery habitat. Mobile species like fish and prawns can remain safely immersed in water in the rockpools when the tide goes out.
Jess and the team have spotted 65 different species making use of the 45 artificial rockpools installed on a seawall at Sandbanks, including the protected native oyster Ostrea edulis.
Other species found include crabs, barnacles, molluscs, small fish, sea squirts and 25 types of seaweed.
This compares to 40 species that were found in whatever cracks and crevices they could find on the harbour wall.
Inquisitive bass – an important species for the local fishing industry – were also seen investigating the pools during high tide.
“At low tide, we found that the rock pools provided a haven for squishy species, like sea squirts and sponges that would dry out on the seawall and not survive,” explained Jess. “Similarly, they helped delicate species, like bryozoans and some finer seaweeds, that would get bashed about by waves on the seawall and would not survive either.”
Further environmental benefits could come from increased biomass - the weight of all living material - in the rockpools, predominantly because of bigger specimens of seaweed. “More biomass means more carbon being removed from the atmosphere and excess nutrients being removed from the water - which can be a problem in Poole Harbour, causing low levels of oxygen,” Jess explained.
The artificial rockpools were manufactured by Isle of Wight based eco-engineering company Artecology from low-carbon concrete. To make sure they resembled a natural environment, they were hand finished with rough surfaces and the moulds were lined with giant bubble wrap to create further crevices.
“This project has shown how rockpools can help us to ensure nature can continue to survive in urban coastal spaces. They also give residents a chance to connect with nature, learning more about the wealth of wildlife just off the harbour’s edge and the role it plays in preserving our natural environment.” Jess concluded.
The project has formed part of the €4.6million Marineff project (MARine INfrastructure EFFects). Marineff is funded by the European Union and involves universities and partners in the South of England and North of France exploring ways to protect and enhance coastal ecosystems.
You can watch Jess explain more about what she's found in the rock pools in the video below.