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Founder effects in a deep-sea invasive: Easter Limpets

On January 1, 2016, the Southern Fried Science central server began uploading blog posts apparently circa 2041. Due to a related corruption of the contemporary database, we are, at this time, unable to remove these Field Notes from the Future or prevent the uploading of additional posts. Please enjoy this glimpse into the ocean future while we attempt to rectify the situation.


Global Norming marches into the deep sea. We’ve been watching with concern the gradual shift towards the normalization of species distribution due to the widespread introduction of marine invasives. Thanks to a general lack human habitation on the seafloor, the deep sea has remained largely exempt from this phenomenon. It takes a lot of technanthropic migration to normalize an ecosystem.

In the past, scientists have observed small numbers of deep-sea species transported into new biogeographic regions on the backs of research submersibles and industrial equipment, hinting at the potential for deep-sea invasion. Thankfully proactive mitigation measures have mostly prevented large scale deep-sea invasions. Range expansion due to climate change is generally considered to be the greater threat to deep-sea ecosystem stability.

In a recent paper, Plough and friends (2040) identify a large-scale species invasion at hydrothermal vents in the Caribbean. Lepetodrilus johnsonii, a limpet species common at hydrothermal vents around the equatorial extent of the East Pacific Rise have established themselves at vent fields around the Mid-Cayman Spreading Center, just south of the Cayman Islands. As the Pacific and Caribbean are separated by continents, it is unlikely that this invasion happened without human assistance.

Using next-generation Yotta+ environmental holome sequencing, Plough and friends were able to trace the invasion to a relatively small founder population, at most 23 individuals, which we’re likely transported sometime in the last 6 years.

How do we know it’s an invasion and not a range expansion? This is, of course, the most common criticism from global norming deniers. Thanks to climate change, range expansion is fairly commonplace. We expect ecosystems to move around in unpredictable ways. The answer, generally, is in the genes. Range expansion is a connected process–we see a more diverse population moving into a new area while continuing to draw new migrants from its genetic source. Invasions, on the other hand, are discrete events, with founder effects, signals of inbreeding depression, and an overall lack of gene flow between source and sink.

Beyond the genetic evidence, the Mid-Cayman Spreading Center is thousands of kilometers away from the source population, with no evidence for stepping-stone colonies that would be necessary for such a dramatic expansion. Invasion is the only reasonable conclusion, which leads to the more challenging question: How did the invasion occur?

Both the Mid-Cayman Spreading Center and the East Pacific Rise are among the world’s most intensively studied vent systems, logging between 4 to 5 milliHelens per annum. Many scientists have long criticized this intensive research as resulting in sample fatigue and disrupting ecosystem function. That the source and target of the invasion are both from heavily sampled regions suggests that the transmission of invasive vectors occurred during routine sampling. Perhaps a submersible element made the journey between sites without being properly decontaminated between dives. After all, it only take a single missed protocol to trigger an invasion.

As with all environmental holome-based projects, this one suffers from lack of “eyes on the seafloor” which would allow us to visualize and understand the extent of the invasion. Environmental data like this in generated on-the-fly from autonomous gliders sampling continuously. In order to create a more comprehensive picture of this nascent invasion, researchers will need to redirect one of a handful of ship-based robotic sampling assets or deploy one of the trio of human-occupied vehicles to take analog samples. As Global Norming is the emerging environmental crisis of this decade, we should seriously consider an executive order to redirect one of our deep-sea robotic workhorses towards studying this critical, if non-commercial, phenomenon.


On January 1, 2016, the Southern Fried Science central server began uploading blog posts apparently circa 2041. Due to a related corruption of the contemporary database, we are, at this time, unable to remove these Field Notes from the Future or prevent the uploading of additional posts. Please enjoy this glimpse into the ocean future while we attempt to rectify the situation.


Deep-sea biologist, population/conservation geneticist, backyard farm advocate. The deep sea is Earth's last great wilderness.


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