The Science of Sustainability

Ocean Overrun With Gentle Gelatinous Salps

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In situ picture of salps underwater. Photo by Lars Plougmann.

A salp colony underwater – photo by Lars Plougmann

What looks like a jellyfish but is closely related to humans? The answer is an oceanic animal called a salp, and right now the waters off California are teeming with unprecedented numbers of these creatures.

Salps are essentially transparent jet-propelled tubes. Their life cycle alternates between solitary swimmers, each smaller than your hand, and aggregated colonies that can grow longer than a bus.

Shimada 2012 Pyrosoma, Carinaria, and salps

The pink tubes in the upper left are pyrosomes, a close relative of salps that have also increased in abundance. To the right of the pyrosomes is a transparent sea snail that preys on salps–these sea snails were unusually large this year. The rest of the tray is full of Salpa fusiformis, the "brown-eyed salp." Photo by Matthew Birk.

As individuals, salps are innocuous. They don't sting. They don't hunt. They're gentle plankton eaters. But as populous blooms, salps can wreak havoc. So far this year their sheer gelatinous mass has shut down one nuclear power plant and destroyed two fishing nets.

The NOAA Southwest Fisheries Science Center in Santa Cruz has surveyed the central California coast every spring since 1983, gathering information on individual fished species and on the ecosystem in general. The 2012 survey took the ship Bell M. Shimada from San Diego to Newport between May 6 and June 17.

"We've had wild salp catches over the last few weeks," wrote research fishery biologist John Field in a message from the boat to colleagues back on shore. "No one from the survey has ever seen anything like it."

Each time the scientists dragged a trawl net through the water, they caught an average of 30,000 salps. Prior to 2012, the maximum salp catch for a single trawl was 235 in 1999. This year, some hauls held over half a million.

Shimada 2012 midwater trawl net covered in salps

Trawl net covered in salps – photo by Matthew Birk

And that was when they could even use the nets. "For the first time in the history of the survey," wrote research fishery biologist Keith Sakuma, "both the primary and backup midwater trawl nets were ripped apart due to the sheer number of salps in the water." Often they had to cancel the trawls because there were simply too many salps.

So what does such a freak salp bloom mean? It's tempting to dredge up the "jellyfish gone wild" hypothesis–the idea that gelatinous creatures are taking over the oceans because they can adapt to human pollution. But as MBARI scientist Steven Haddock has pointed out, historical data for most species isn't good enough to be certain of an increase in numbers or a significant tolerance for pollution. Furthermore, in the case of California salps, there's reason to believe shifts in abundance are driven by natural oceanwide changes.

Over the course of decades, the Pacific Ocean alternates between "warm" and "cool" phases. During a warm phase from 1977-1998, salps declined in abundance; the trend reversed after 1998 with a shift to a cool phase. Yet none of the years since 1998 have shown salp numbers even close to the banner year of 2012. Scientists will surely be seeking further explanations and waiting to see how long the bloom continues.

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Category: Biodiversity, Biology, Blog, Environment

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Danna Staaf

About the Author ()

Danna is a marine biologist, a science writer, a novelist, an artist, and an educator. She helped found the outreach program Squids4Kids, illustrated The Game of Science, and has blogged at Squid A Day since 2009. She holds a BA in Creative Studies from the University of California, Santa Barbara, and a PhD in Baby Squid from Stanford. She lives in San Jose with her husband, daughter, and cats.
  • http://www.facebook.com/stephen.yang Stephen Yang

    What makes these things "closely related to humans"? Aside from their ability to adapt to our pollution?

  • http://www.facebook.com/Aignatius Wendy Peabody

    This is so fascinating! And yes, it begs the question, how are they related to humans, is it their DNA?

  • http://twitter.com/jimwharton Jim Wharton

    Salps are pelagic (open water) tunicates. Some tunicates (though not salps) have a larval phase that resembles a tadpole, complete with a stiff notochord along their "back" (a backbone precursor). Tunicates belong to the same phylum as we do, Chordata.

    • realityanvil

      So salps, though tunicates, DON'T have a notochord? Don't they have a nerve net, as opposed to a central nervous system? So how can they be considered chordates?
      "Chordata" seems an absurdly long way up the chain to assert "close" kinship. After all, aren't jellyfish only one level further removed? It seems to be another case of some writer failing to have command of the facts. A lamentably common trait.

    • realityanvil

      Does the "notochord" surround a nerve pathway, or is it simply a structural affectation? I don't see how a salph could at one point have a central nerve and then mature away from that feature.

  • http://www.facebook.com/nowwithlasernostrils Izzy Evangelique

    The only similarity between salps and humans is that salps are biologically more similar to vertebrates than they are polyps (like jellies).

  • Joanne

    We have had incredible numbers here in Orange County since the end of July. See videos and pictures of four species we found here – up 4 rows from the bottom of the page, under Class Thaliacea (Salps) at http://nathistoc.bio.uci.edu/Intertidal.htm#Tunicates

    • http://cephalopodiatrist.com Danna Staaf

      Wow, the bloom continues! Very cool, thanks for sharing.

  • nancy

    They are showing up in Oregon the size of a mans hand

  • iphelta thei

    They are related to humans because they are classified in the Phylum Chordata based on the presence of a larval notochord, among other characteristics. About 3% of chordate species are tunicates (Subphylum Urochordata). The salps (Class Thaliacea, Order Salpida) include the most commonly encountered pelagic tunicates.

    • realityanvil

      OK, quick question: Where is the cord? Is there a central nerve? I would have suspected a nerve net, but not a central cord.
      Shouldn't asserting that they're "related to humans" should require much more commonality than simply sharing a phylum? After all, jellyfish are only one division removed from that. We share a common kingdom with them, don't we?

  • http://twitter.com/beroe beroe

    If you see salps or other jellies, send your reports to jellywatch.org so they go into our database…

    • realityanvil

      What sea creatures feed on salps? Whales? The article doesn't bother to tell us.

  • http://twitter.com/Aquilagrande Knut Holt

    So, salps like cool water? Mayby the Earth is cooling and not warming up as we are told by the authorities?

    • http://twitter.com/aboutgeology Andrew Alden

      Have you heard the expression, "grasping at straws"? That's you.

      • http://www.abicana.com/ Knut Holt

        Not at all. I wish it to be warmer, but the recent data show that the Earth is actually cooling since at least a decade back.

        • realityanvil

          Warmer temps = millions of acres in Siberia and Central Canada being opened up to food production. If environmentalists want to legitimately contribute to saving the world in a real sense, they should pull the electric meter from their homes TODAY, sell any motorized vehicles they own, and neuter themselves. Lead by example, boys!

      • realityanvil

        Beats being "Gored". Actually world temps have been flat for a decade, as opposed to Gore's skyrocketing income stream from the gullible Alden family, as well as from the oil companies (network sale to oil-rich sheikdom-derived Al Jazeera).

  • sfwmson

    I know some human's I'd like to slap, but not salps!

  • Kim Vincent

    Is there an update on this story? I was scuba diving back in October 2012 at Montasery Beach and was pleasantly surprised by a salp bloom – made the water really clear. I would love to know when salp blooms occur (makes for better scuba diving!)

  • Elisabeth

    I saw thousands of colonies of these in the waters around Anacapa Island (off the coast of Ventura, CA) a couple weeks ago.

  • realityanvil

    Thanks! It sounds like you finished a course of study I had only considered, but gave up with regret due to the low pay for beginning graduates. I still find it fascinating.

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  • coconutgirl

    Oh my gosh I just discovered these all over the beach of Northern California, eureka/Manila area. My son said his feet burned after walking on the beach. It was very disturbing to see the beach so covered with gelatinous creatures…