‘Mini hotels’ for sea creatures reveal Hong Kong’s rich marine life

Scientists say it’s ‘disproportionately diverse’, with more unique species than the Red Sea and Indo-Pacific

They’ve been using autonomous reef monitoring structures to understand biodiversity as part of a global programme

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The HKU team has since 2015 been placing autonomous reef monitoring structures on the seabed that are later retrieved to see what has colonised them. Photo: Alex Reshikov

Published: 6:42pm, 23 Jun 2022

Deep down on Hong Kong’s seabed, marine scientists place “mini hotels” for shrimp, snails and sponges to move into and grow. And after a year or so, they are retrieved to see what has colonised them.

Since the programme began in 2015, the researchers have found that Hong Kong is “disproportionately diverse”, with more unique marine species than biodiversity hotspots the Red Sea and the Indo-Pacific region. Their work backs up the findings of an earlier University of Hong Kong study that the city’s waters are home to nearly 6,000 known marine species – a quarter of all such species recorded in China.

“We’re small, but as you go 10 kilometres from one place to the next, the whole community turns over,” said Shelby McIlroy, a research assistant professor at HKU’s School of Biological Sciences.

“The overlap of species from one place to the next is usually only about 20 to 30 per cent. That means around 70 per cent of [the animals found] from the genetics are unique to one site,” said McIlroy, who co-leads the local efforts of the Marine Global Earth Observatory (MarineGEO), a biodiversity monitoring programme.

The HKU team is part of a global network of scientists who use a standardised sampler deployed to the ocean floor to understand biodiversity in their coastal communities, including in Australia, Belize, Canada, Panama, Peru, Portugal and the United States.

The ARMS are stacks of PVC plastic plates that mimic the structure of the sea bottom. Photo: Alex Reshikov

The autonomous reef monitoring structures, or ARMS – which McIlroy calls “mini apartments for underwater” – are stacks of PVC plastic plates that mimic the structure of the sea bottom, which is hard to sample without destroying habitat. They provide hard surfaces, nooks and crannies that sea creatures like to live on, according to the Smithsonian Institution in the US, which started MarineGEO.