Posted on April 23 2019
Some think the best way to survive a fight, or a really bad set of circumstances, is to be tough as nails. Be strong, nimble, street-smart, quick, and very determined. In some fights, however, the best quality to possess is adaptability. We live in a changing world. Seasons change, weather changes, the climate shifts to wetter or dryer, colder or warmer, and all the plants and animals of the world react to these new circumstances and become transformed by the pressures of natural selection. It’s a long-term thing, functioning since life first emerged on the planet. We’re going through change now, and while it’s nothing new, the problem we face is the rate of change. Evolution is not a rapid process, and it cannot keep up. The climate will do what it will, heating or cooling as chemical and thermal influences shape it—it’s just a physical condition. The biota, however, operate with that mysterious quality called life, and each has come to its own strategy for survival within the confines of its habitat. Changes in heat and moisture and chemistry are crucial to living things that count on stability, or at least an acceptable range of conditions. Outside of those limits, organisms start to die.
As this world morphs too quickly into a different regime of climates, there will be losers and survivors. Mobility will be key for many, but even those who can move to more favorable locales, ones still within those acceptable parameters, may find that their food species haven’t made the transition along with them, for one reason or another. The world is a complicated, interdependent web of life, and changing up the operating rules creates chaos. So who will manage to maneuver within a changed world? People often cite cockroaches, rats, and fleas as likely survivors because they have learned how to exist, and thrive, alongside humans, and seem impossible to eradicate. They’re familiar to us because we see so much of them, but in another realm live another suite of creatures who are not having much trouble with rapid change, and in fact, seem to find it no problem.
They live in the sea, and while so many other ocean species are suffering from heightened warmth, increased salinity, and chemical changes in the seawater, these climate winners, jellyfish, swim merrily along. Well, it’s hard to say whether they’re merry, since jellyfish, more properly called jellies, have no brain. As such they have no cleverness or wisdom to guide them to safer water. They have no eyes with which to see, or teeth with which to bite, nor claws to scratch. No tough hide either—they’re jellies, for Pete’s sake! But somehow, jellies have emerged as pre-eminent adapters to a warming world. It may help that they have been around for hundreds of millions of years and seen their share of changes. Their phylum, Cnidaria, has largely maintained its ocean habitat and general body form all this time because it works so well. Jellies are relatively uncomplicated animals, and sometimes a simple talking drum beats an iPhone to get a message across. They can tolerate a wide range of both water temperature and salinity, and their food source is pretty low on the food chain, mostly zooplankton, small invertebrates, eggs, and small fish, all killed by stinging cells. They don’t actively attack on the hunt, but they do swim by slow jet propulsion to a variety of depths to better encounter their prey: whatever happens to swim or drift into their tentacles.
These qualities have enabled jellies to get along just fine in normal circumstances, and when others are beginning to suffer under new extremes, they sail on. The massive ocean deposit of nutrients in runoff from farms and cities leads to phytoplankton blooms which then suck all the oxygen out of broad areas in the ocean. This condition, called hypoxia, kills off most sealife in the zone, but little affects the jellies. Ocean acidification due to increased CO2 in the atmosphere spells trouble for shellfish and corals, but once again, jellies aren’t much bothered. While these chemical changes to the sea are grudgingly tolerated by jellies, the fact that our current temperature trend is toward the warmer is actually much to their advantage. The heating seas increase their metabolism, feeding, and reproductive rates, and it helps them live longer. This has resulted in jelly population blooms in certain places, creating noticeable effects. Desalination plants and oceanside power plants that rely on seawater for cooling have at times sucked in so many jellies that their pumps became clogged. Likewise, the engines on huge aircraft carriers have been fouled by thousands of the floating animals at sea.
The Chinese have found it enough of a problem that they devised a shredding net to chop up the jellies into small pieces. It is dragged behind a smaller lead ship, making a clearer path for the larger ships that might choke on the biomass. China is reaping a bit of what it has sown, however, as its enormous appetite for shark fins and meat has decimated populations of those key jelly predators. Overfishing in general tends to scoop up some species that could compete with jellies for food and better hold their numbers in check. And once again, instant karma has found fishermen in search of fish occasionally collecting huge loads of jellies in their nets, which at this time have little marketable value. Humans also contribute to jelly success by the large and growing number of structures such as drilling platforms and wind power towers that are placed out at sea. Their hard, vertical surfaces are ideal for polyps, the non-swimming stage of the jelly lifecycle, to settle upon and attach to. These unnatural nurseries provide an entirely new opportunity for open-ocean proliferation of their kind.
So, thanks in part to our unintended help, some jelly species are experiencing problematic explosions in their numbers in certain areas worldwide, leading some to worry that the oceans are going to be taken over by them. Calmer analysis of the situation suggests that such a scenario is not currently happening, but the fortunes of jellies are definitely looking up. There is much we do not know about jellies and how they interact with their environment. We don’t even know how many different kinds there are—new species are found all the time. You might think the “new arrivals” would be tiny, previously unnoticed forms. After all, many of them are practically see-through. Just a few years ago, though, an uncataloged jelly washed up in Tasmania. Though animals of its description had reportedly been seen at sea before, the beaching of one particular specimen really caught everyone’s attention, probably because it was a good five feet in diameter. Presumed to be a relative of what are called the lion’s mane jellies, its gooey, runny structure puts it in the group known colloquially as “snotties.” Not a particularly endearing name for a creature that is obviously successful at what it does and has been doing it for so many years outside of our knowledge. If jellies of many species all over the planet continue with that successful adaptability, and if we humans keep on doing what we do, we may expect to see more and more jellies in the ocean in the future, for better or worse.
Are you itching to get to Tasmania to catch a glimpse of a snottie? Get this beautiful wall map and poster of all sorts of Australian wildlife. It’s a National Geographic original, available from Maps.com.
caption: Simple parts, simple strategy—float and swim casually, and collect the food that comes by.
source: Wikimedia Commons: Zina Deretsky, National Science Foundation; converted into modified SVG by Whidou and KDS4444 (Public domain)
caption: Within this basic body plan, the variations seem endless. Example variation #1
source: PublicDomainPictures.net: Linnaea Mallette (Public domain)
caption: Example variation #2
source: Pexels: Pawel Kalisinski (Pexels)
caption: Example variation #3
source: Wikimedia Commons: Andrea (CC by 2.0 Generic)
caption: Example variation #4
source: Flickr: NOAA Ocean Exploration and Research (CC by SA 2.0 Generic)
caption: Jelly blooms, whether part of a natural cycle or stoked by human activity, can cause problems. Masses of blue blubber jellies like these once clogged the intake pipes of the USS Ronald Reagan, a major aircraft carrier, as she cruised into Brisbane harbor.
source: Wikimedia Commons: Via Fernandez (CC by SA 3.0 Unported)
caption: Under the right conditions, even a jelly can leave a fossil print. They’ve been around forever, and will be for some time to come.
source: Wikimedia Commons: James St. John (CC by 2.0 Generic)