Seven sq. meters of a HK oyster reef can filter up to just one Olympic swimming pool of water in a solitary working day — ScienceDaily

Gains of oyster reefs

Hong Kong was once house to thriving shellfish reefs, but due to a combination of components which include over-exploitation, coastal reclamation and pollution, shellfish populations have declined considerably. Restoring oyster reefs along urbanized coastlines can mitigate some of the environmental problems normal of coastal enhancement, these types of as destruction from storm surge and reduction of biodiversity.

“Globally, we have shed 85% of shellfish reefs, earning it the most endangered maritime habitat on earth,” mentioned Marine Thomas, Conservation Task Supervisor, for TNC in Hong Kong. “Most people affiliate oysters with food stuff, but considerably less nicely-regarded is that oysters build reef habitats that support coastal marine existence. Only by restoring these misplaced habitats can we start off to bring again some of the involved environmental rewards.”

A most important advantage that healthful oyster reefs contribute to coastal environments is their role as all-natural water purifiers: This new research found that, just 7 m² of Hong Kong oyster reef can filter up to a single Olympic swimming pool of water each and every working day a one Hong Kong oyster (Crassostrea hongkongensis) can filter up to 30 liters of drinking water per hour at summer time temperatures, amongst the optimum filtration fees recorded of any oyster species.

Even extra importantly, oyster reefs supply habitat and nursery grounds for a lot of native species that are otherwise dropped from our shores. A further the latest SWIMS examine executed in partnership with TNC discovered that these reefs house six instances additional species than bare muddy shores. The investigate identified over 80 species on intertidal muddy shores in Deep Bay, 95% of which have been observed in oyster reefs, and almost 60% of which had been exclusively found in people reefs.

Oyster reefs restoration

“A past SWIMS research uncovered that Hong Kong is home to somewhere around 6,000 marine species and 26% of all marine species in China. This new study adds to that checklist, as we’ve determined a small crab previously not observed in Hong Kong. This shows us just how less than-analyzed these ecosystems are,” stated Dr Bayden D Russell, an Affiliate Director of SWIMS and Affiliate Professor in the Analysis Division for Ecology and Biodiversity, HKU.

A further advantage of restored reefs is improved generation of commercially and recreationally beneficial fish and crabs.

More, demonstration of productive restoration in a single of Asia’s coastal mega-metropolitan areas can also act as design, furnishing proof for the environmental and societal rewards of ecological restoration within the region.

In some areas of the world, oyster reef restoration has only been productive by transplanting juvenile oysters cultivated in hatcheries into the wild. Even so, this new research demonstrates that purely natural recruitment of oysters in Hong Kong is substantial, that means that restoration could possibly be accomplished with no the need for hatchery-reared oysters.

“We ended up enthusiastic to uncover substantial purely natural recruitment ranges which implies that oyster reef restoration is possible with no hatchery intervention,” explained Dr Russell. “We believe that this recruitment is due to the fact common oyster farming in the Pearl River Delta has preserved populations of indigenous oysters in the system in spite of the reduction of oyster reefs and these farms could perhaps act as a resource of larvae.”

In evaluating 10 web sites exactly where compact remnant shellfish habitats are uncovered in Hong Kong, the examine also observed that substantial oysters (further than 1 yr outdated) are incredibly difficult to come across in the wild, thanks to on-likely harvesting pressures.

“Though we are thrilled by the biological feasibility of restoration, unfortunately the human aspect remains our greatest challenge to provide these habitats back again at scale. Shellfish habitats are nevertheless severely under protected in Hong Kong, with quite minor community recognition of their ecological value. Wild harvesting is a enormous difficulty — as quickly as oysters or mussels are big adequate to try to eat, somebody will harvest them. We are doing the job with Govt on attaining a lot more security and recognition for these significant ecosystems and hope to incorporate them in the next Hong Kong Biodiversity System and Motion System (BSAP),” mentioned Ms Thomas.