Ocean warming is pushing sea life into new territories

Once native to the rocky shores of Jeju Island, the top shell Turbo sazae is now moving north. Scientists at KIOST have linked the snail’s shifting range to rising sea temperatures driven by climate change.

Genetic evidence supports the snails’ expansion, showing shared ancestry between eastern and southern Korean populations.

A research paper published in the journal Animals reveals that this shift is not just recent. It is tied to deeper evolutionary history and ocean current dynamics.

“Climate change-driven rises in sea temperatures are a core variable in the impact of climate change on marine ecosystems,” said KIOST President Hyi Seung Lee.

Snails with shared ancestry

The researchers collected samples from six locations, including Jeju and the East Sea. Using mitochondrial DNA (COI), the team built haplotype maps to assess relatedness.

A dominant genetic type, called EJ1, appeared in 60% of Jeju individuals and 50% of East Sea ones. This strong overlap suggests these regions share more than just warm waters. They share a common genetic base.

Bayesian analysis dated the most recent common ancestor between these populations to between 9.7 and 23.3 million years ago.

Ocean currents and snail dispersal

The ancestral link between the snails reflects a long evolutionary history shaped by currents like the Kuroshio and Tsushima.

These ocean currents are central to the story. They carry larvae north during early planktonic stages. Turbo sazae larvae live in open water for 3 to 5 days before settling. That short window is enough to disperse widely along current paths.

This dispersal helps maintain genetic continuity between distant populations. That is why genetic differentiation between Jeju and the East Sea is low.

The study’s FST values and AMOVA results confirm that most genetic variation occurs within, not between, these groups.

Unique regions still shape genes

Despite shared ancestry, some sites showed early signs of divergence. Populations at Dokdo and Wangdolcho had site-specific haplotypes.

These locations have complex underwater topography and eddies that may trap larvae. This can limit outside gene flow and shape unique traits over time.

Dokdo, for instance, rises steeply from the ocean floor and is shaped by dynamic currents. These geographic features might create local barriers that influence how genes move. More research could clarify whether such structures truly restrict connectivity.

Warmer waters weaken snail immunity

Earlier studies suspected diet changes caused population drops in Jeju. Researchers thought urchin barrens affected feeding behavior. But recent findings show diet had little impact on physiology or reproduction.

Instead, warming waters weakened the snail’s immune function. In other words, climate change was the real driver of the snail’s population decline around Jeju.

This finding came from a second study published in the journal Marine Environmental Research. The study confirmed that higher sea temperatures compromise the snail’s immunity and make it more vulnerable to environmental stress.

Ocean warming shifts sea life habitats

Between 2009 and 2018, Turbo sazae expanded north at a rate of 12.4 km per year. That is a fast pace for a marine mollusk. It aligns with rising sea surface temperatures of 0.38°C per decade in the region. Warmer waters now support life where it once could not.

A marine desertification phenomenon called barren ground is also changing habitats. These zones lose kelp and become covered with white algae. Such shifts leave snails like T. sazae with fewer choices. They must move or decline.

Climate change and snail conservation

The study’s findings have practical implications. They show that Jeju acts as a source for new East Sea populations.

The shared genetics suggest that populations should not be managed as isolated units. Instead, integrated approaches should reflect their connectivity.

Yet, local differences still matter. Management plans must protect unique habitats, especially where signs of early genetic differentiation emerge. Monitoring, habitat conservation, and tracking larval dispersal are essential steps.

Snails adjusting to climate change

As the sea changes with the climate, snails and other inhabitants are changing too. Turbo sazae is adjusting, relocating, and surviving.

The science behind this shift not only charts the path of one species. It gives a broader glimpse into how ocean warming is reshaping sea life.

KIOST President Hyi Seung Lee said the findings will help deepen scientific understanding of how sea life distribution is changing and support ongoing efforts to protect marine ecosystems.

The study is published in the journal Animals.

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