Need a new search?

If you didn't find what you were looking for, try a new search!

The Journey of the Sargassum

There is a sea on the Planet Earth which has no shores.  It is over two million square miles in size, and it is completely distinct from its surrounding waters both oceanographically and ecologically.  It supports roughly a million tons of plant life, which provides habitat for over 100 species of fish and 140 species of invertebrates, and many of them occur nowhere else.  All this teeming abundance is in waters that are so nutrient poor that visibility can be a couple hundred feet on a good day.  If not for this astonishing ecosystem, in this astonishing sea without shores, this place would be an aquatic desert.

It’s called the Sargasso Sea.  It is contained by a clockwise gyre of four different ocean currents that circle between North America, Europe and North Africa, and it is about 1,000 miles across at its widest point.  Its sea level is three feet higher than the surrounding waters, and the waters are warmer and saltier.  The foundation of the ecosystem is a remarkable seaweed called sargassum (Sargassum natans and Sargassum fluitans), a highly unusual marine algae that is completely pelagic (free drifting).   It reproduces asexually through simple fragmentation, and it can do so easily, and anywhere it goes.  Because it is pelagic, it does not have to compete for precious real estate on the ocean bottom, and it also is not limited to shallow coastal waters like the benthic (attached) seaweeds, which not only have to find some substrate to attach to, but then have to be able to grow up into some light so they can photosynthesize.  Sargassum has none of those constraints, and it grows in great mats and windrows in a sprawling, mid-ocean world where the coastlines are hundreds of miles away and the bottom is sixteen thousand feet down.  It consumes carbon and produces oxygen in huge quantities.  It has been called the golden floating rainforest of the ocean.

Sail east from anywhere in the US or west from anywhere in Europe and you’ll probably have to cross it.  Sailors have known about it for centuries, and it has broken some strong hearts when the seaweed was sighted from shipboard by early explorers, and they thought they were approaching land.

For myself, I started reading up on it because, though we’ve always gotten a little sargassum on our beaches around here, recently it’s been hitting us in huge quantities.  It’s ugly.  It’s slimy.  It puts out hydrogen sulfide gas as it decomposes and it stinks.  The tourists are not pleased.  “WTF?” my friends are all asking me—but in that quaint way we older folks have of spelling things out completely.

 

*          *          *          *

 

SargassumTulumBeach
Sargassum on the Tulum Beach

Well, I knew this would be a tough one and I was right.  We’ve all read several articles in the popular press about this and none of them answer the question why, so I knew it wouldn’t be easy to find.  A week into it I muttered to myself that it might have been easier if I’d been looking up the meaning of life.  Then, on a whim, I did so.  It’s 42.  If you’ve read any Douglas Adams you already knew that.  But anyway, bear with me, because I did arrive at what I consider to be an answer, and getting there was a pretty good trip, not just through the life cycle of one of the most interesting seaweeds in the world, but also the amazing Sargasso Sea, the world’s ocean currents, climate change, and agricultural and urban runoff as measured in continent-fulls.

It used to be thought that the Sargasso Sea was a one-way destination for sargassum seaweed.  The model went like this:  The sargassum grows in the north-west Gulf of Mexico (they’ve always gotten some on the Texas beaches), and that was thought to be sort of its nursery.  Then the Gulf Stream current catches it and whips it around the southern tip of Florida and up the east coast of North America, and it settles out into the gyre that is the Sargasso Sea, and there the story ends.

 

The problem with that model is that it’s a one-way model—the sargassum goes in, and nothing comes out—and ecologists just hate one-way models.  To any ecologist with a proper reverence for the Interconnectedness of Everything (capital ‘I’, capital ‘E’), if you’re looking at a one-way system, you’ve only found half the system.  It wasn’t until last year that three Texas A&M scientists found what appears to me to be the other half.  They developed a way to identify sargassum in satellite photos.  If there is enough of it, it reflects wavelengths of light that jump right out at you if you use the right filter.  Even if there is not enough to be directly visible, its presence breaks surface tension and dampens wave motion, creating what the scientists call a “slick” on the water.  They started going through images, all the way back to the year 2000, which was the earliest year that the photos had enough resolution for this.  What they found was that every year, a weather occurrence called the Azores High Pressure System creates strong south-bound winds, and they don’t exactly disrupt this huge North Atlantic Gyre—but they jail-break a bunch of sargassum out of it.

SargassumLoopSystem2
The Sargassum Loop System

This expanded hugely the travels that we understood Sargassum to make.  When it breaks out of the gyre, it drops down through three different passages between the island nations that border the Caribbean on the north—between Cuba and Haiti, between Dominican Republic and Puerto Rico, and between Saint Thomas and Anguilla the sargassum is blown through the passages, and it ends up in the Caribbean, where the North Equatorial Current grabs it and sweeps it west down the same gun barrel that brings us our hurricanes—right at the Yucatan.  Then the Gulf Stream grabs it and carries it around the north-east tip of the Yucatan and into the Gulf of Mexico, where some of it continues around the south tip of Florida and up the East Coast again to complete the circuit, but a lot of it eddies backwards into the north-west Gulf of Mexico, where it reproduces wildly and buries the beaches in Texas.

They’re calling it the Sargassum Loop System, and it’s recent news, cutting edge science, and a pretty big discovery, but here’s why it doesn’t answer the question my neighbors are asking me:  There seems to be nothing new about it.  As far as the scientists can tell, sargassum has been travelling this circuit all along, and it had only resulted in occasional, and not very heavy, strandings of sargassum on our beaches.

But another study got my attention, and when you put the two together you have something.

In 2011, there was a huge episode of this, and in 2012 a scientist named Johnson and a couple of colleagues did a very clever thing.  You see, scientists have software models of ocean currents.  There is more than one, and people and institutions have worked hard on them, and they’re very detailed and sophisticated, and they do a pretty good job.  And Johnson et al had historical data about where the heavy loads of sargassum were, and on what dates.  So what they did, effectively, is they dropped some virtual sargassum in their software sea at a few of those places and dates, and then ran the tape backwards.

They were amazed at where it ended up.  It wasn’t anywhere near the Caribbean, and it wasn’t anywhere near the Sargasso Sea.  It wasn’t even anywhere near the Sargassum Loop System (which actually hadn’t been discovered yet).  It was in a huge, elongated eddy that lies just above the equator and reaches all the way from South America to Africa.  It’s called the North Equatorial Recirculation Region.  While the huge Equatorial Current is taking everything west, this eddy forms above it, bounded on its north by a weak, usually seasonal current called the North Equatorial Counter Current.  This explained why there had been landfalls not just here in the Caribbean, which has always gotten some sargassum, but also in places like Brazil, and even on the coast of Africa in places like Sierra Leone, where it had never been seen before and people didn’t know what in the heck they were looking at.  And the thing about this eddy, this North Equatorial Recirculation Region, is that it’s swimming in nutrients.  It’s west end is right at the mouth of the Amazon River.  It also gets iron-rich dust blown over from Africa, and coastal upwelling off that coastline as well.  According to their software models, the sargassum stayed there for a “considerable time,” and it just loved that place.  It grew exponentially, moving in eddy-like motions and sucking up all that warmth and all those nutrients and creating masses and masses of itself—and then the counter-current broke down.  The eddy vanished, the floodgates opened, and all that sargassum started across the Caribbean toward us.

SargassumNERRSave - Copy
North Equatorial Recirculation Region

It makes sense when you think about it, because the two biggest rivers in the Americas are the Mississippi and the Amazon.  Which brings us to the subject of continental run-off.

I’ve written before about eutrophication, when I did a piece on jellyfish.  It’s a word you’ll be hearing more of, unfortunately, as we pummel this planet harder and harder, and sure enough, it figures in this story too.  Looked at simply, eutrophication is when excess nutrients wash into a body of water and mess everything up.  The first thing that happens is an algae bloom, and that could be anything from phytoplankton to sargassum, and then as that stuff dies, the decomposition process robs the water of all its oxygen, and you end up with what marine biologists call a dead zone.  This happens in big ways and small ones—I know divers who can swim down our barrier reef and tell you resort by resort whose septic systems aren’t working.  But rivers like the Mississippi and the Amazon empty entire continents of their nutrients, and that now includes fertilizers, pesticides, industrial waste and discharge from sewage treatment plants.  You can see the dead zones on Google Earth now.  Look for the little dead fish icons.  They’re courtesy of William and Mary College and the World Resources Institute (and thank you, Google, for being willing to display them!)  The second biggest dead zone in the world is in a plume running west from the mouth of the Mississippi, which is why the sargassum grows so riotously in the north-west Gulf of Mexico, and man, if you think we’ve got problems, you should see the sargassum in Texas.  They get it on a classic Texan scale.  The piles on the beaches (called wracks) can be ten feet high there, especially around Galveston.  When it comes in, they call it the golden tide.

And sargassum isn’t the only seaweed going nuts from eutrophication.  On the Brittany coast in France, they got a green tide of sea lettuce (Ulva armoricana) in 2009 that off-gassed so much hydrogen sulfide that it killed a horse and rendered its rider unconscious.  In 2011 it returned and killed thirty-six wild boars.  The sensational press coverage left everyone with the impression that the seaweed was toxic (it’s not, but hydrogen sulfide is nothing to trifle with).  The cause was clear:  factory agriculture.  Nutrients come in (in animal feed) but they don’t go out (no one returns the manure to sender), so there’s a gargantuan net increase in the nutrients in the Brittany area, and they end up in the ocean.  Measures to curtail factory farming caused layoffs, closures and protests.  The tourist industry there is 5 million dollars per year.  The agriculture industry is 11.6.  They’re still fighting.

In China, on the shores of the notoriously eutrophic Yellow Sea, the largest green tide ever recorded hit the beaches of Qingdao three weeks before the Olympics and its sailing regatta.  The Chinese rose to it in impressive fashion:  In just three weeks they removed a million tons of Ulva prolifera from the beaches in an operation that involved 10,000 people and cost thirty million dollars.  Then they put up a boom to keep the stuff out that was thirty kilometers long.

 

*       *       *       *

 

Sargassum_natans
Sargassum Natans

So, the picture that’s shaping up in the mind of this amateur naturalist looks something like this:  The sargassum spends most of a year, or even more than a year, hanging out somewhere it has never been before, which is in the North Equatorial Recirculation Region, and it circles and blooms and circles and blooms. Then at some point, the countercurrent bounding it on the north dissipates, the eddying stops, and the sargassum floods out, rejoins the Sargassum Loop System and buries our beaches.  But there’s a huge question still unanswered, which, of course, is this:  How in the hell did sargassum start getting into the North Equatorial Recirculation Region?  Nobody knows.  Johnson and his team say that the causes “have not yet been elucidated,” but they suspect a link with global warming.

A voice in my head is going, I should have known.  Climate change, and eutrophication.  Both.

And they could both in theory be fixed, because the good news and the bad news here is that they’re both anthropogenic.  Anthropogenic is a scientific term meaning caused by humans.  But I prefer how the great Jimmy Buffet would put it:

It’s our own damn fault.

Now you know.

 

 

Copyright © 2015 Randy Fry
Sources:
-http://eol.org/pages/893154/overview
-http://precedings.nature.com/documents/1894/version/1/files/npre20081894-1.pdf
-http://research.tamu.edu/2015/04/21/app-uses-nasa-satellites-to-track-sargassum-along-texas-coastline/
-http://seas-forecast.com/
-http://mission-blue.org/2014/10/sargassum-inundates-the-beaches-of-the-caribbean/
-http://seas-forecast.com/Pages/stories/Papers/JeffFrazierthesisformatedforpublishingNEW.pdf
-http://www.readcube.com/articles/10.1038%2Fnature12860
-http://www.alertdiver.com/Sargassum-barometer-of-global-change
-http://www.usm.edu/gcrl/sargassum/docs/Sargassum.Invasion.of.the.Eastern.Caribbean.and.West.Africa.2011.pdf
-http://www.tandfonline.com/doi/abs/10.1080/2150704X.2013.796433#preview
-http://www.laht.com/article.asp?CategoryId=14091&ArticleId=2393072
By |2017-09-22T09:06:43-05:00July 21st, 2015|Nature Essays|41 Comments
Read More

The Secret Lives of Beaches

Why they come, why they go, and what sargassum means to them

I’ve always thought it would be fun if we could radio-tag a grain of sand.  You just never know where the thing has been, or what it’s made of, or where it’s headed from here.  Pick up a few grains and put them in the palm of your hand.  They might all have the same story, but it depends on the beach you’re standing on.  Some beaches are quite homogeneous, and the grains are all from the same source.  The gleaming black sands of the beaches of the Big Island in Hawaii are all from the lava that created that island.  The whitest beaches in the world, on the Emerald Coast in Florida, are all from Appalachian granite.  The beaches of our hometown of Monterey, California all come from the mouth of the Salinas River, and each grain has made that three-hundred-year, beach-to-dune-to-river-to-beach circuit several times.  But here on the east coast of the Yucatan, we’re inside a barrier reef, and each of those grains of sand in your hand probably tells a different story.  They might have been battered from some headlands, or washed from the mouth of an underground river, but more likely they have a biological origin.  They might come from the gut of a fish who ate a fish who ate some coral.  They could be shattered exoskeletons, or crushed shells,  or the carapaces of tiny plankton or the spicules that make up the skeletons of sponges—or they could be the pulverized bones of an oceanic giant.  They might have been body armor for an animal, but just as likely they protected a plant.  And they all come together, all these grains, into great sweeps and berms and ridges, into crests and dunes, streaming, blowing, getting stranded and then swept away again, farther downwind or down-shore.  They might blow inland and become marching systems of dunes, or wash outward and build shifting shallows and bars.  In the end what emerges from all this constant motion is one of the most transient landforms in the geological world, the one we all love so much.  Always in motion, always shape-shifting, always mesmerizing us and drawing us to it; often beautiful, always fascinating, and never, ever predictable.  You gotta love a beach, but you’ll never walk on the same one twice.

Beaches have been on our minds here in the Caribbean lately, as they’re assaulted by unprecedented heaps of sargassum seaweed.  Everyone wonders how to help them.  In my last posting, sargassum turned out to be a fascinating organism.  But what is a beach?

beach_fort_ord_dunes

Monterey Bay, Northern California
Photo by Elery S. Oxford CC BY 2.0, via Wikimedia Commons

Susan and I come from Northern California, where the beaches are subjected to big forces.  That coastline is exposed to that ocean, and that ocean is big, and the waves that hit it have been gathering momentum since the Gulf of Alaska.  They effortlessly lift oil tankers out of their way as they pass under, and then continue building steam as they barrel southeast over a “fetch” of some fifteen hundred miles.  What ends up hitting the headlands is explosive in its power, and thunderous in its tonnage.  A good-sized one can be felt underfoot, and beaches on that coast can gain and lose a hundred horizontal feet between summer and winter.  Susan and I have launched our ocean kayaks from charming pocket beaches  nestled into bluffs, then returned a few months later to find a notch in the cliffs and a few cobblestones.  And every beach is different.  There’s a place south of Carmel called Monastery Beach where the face of the beach is so steep and so coarse that a kayak won’t stick to it.  You have get in your kayak and get your paddle in your hands up on top of the crest, then shove off, ski down the berm, then launch through the surf.  It’s a sporting proposition.  And landing is even weirder.

A beach has body parts, but, as with any living thing, the body parts are always moving.  There is a face that the waves run up, then a crest, which is overtopped only by the larger ones.  There is a back beach which is largely flat, and that’s where the people lie around, or walk if they don’t want to dodge waves, and then behind that there will be another rise, sometimes called the storm beach, which is touched by waves only in the heaviest conditions.  There the sand will dry out enough that wind becomes the shaping force instead of water, and grains are carried up and over small obstructions and drop into the dead air behind them, and embryonic dunes are created, and the dunes begin to grow and march inland.  The underwater shallows and bars lead to the beach, which leads to the dunes, and all three act together to create a moving, shape-shifting rampart which protects the coast against heavy storms.  As conditions change, the sand is exchanged freely between the elements of this triad.  In stormy times, the beach is hit by rapid, back-to-back waves and the sand remains in suspension, getting no rest, until it is finally stripped away from the beach, creating bars and shallows just offshore, and those shallows cause the waves to break farther out, and blow their energy before hitting the coast.  In really heavy conditions, like the storm surge that accompanies a hurricane, sand will get stripped even from the dunes, and carried back out to sea again.  Then, when things are quieter, the beach is washed by smaller waves with longer periods between them, and the sand is carried back up and dropped and left, and the bars and shallows become beach again, and the beach heals and grows wider, and blows inland and replenishes the dunes.  It’s a resilient system, and it is resilient because it’s responsive, constantly in motion.  The reason it doesn’t break is because it bends.  But it only works as long as it has a source of sand.  Which brings us to longshore drift.

Longshore drift is what carries sand longwise up or down a coastline, and it is driven by the scalloping motion of waves angled slightly to the beach.  This is what replenishes miles of beaches downshore from something like a river mouth.  But sand is constantly leaving the system.  It can hit a submarine canyon  or a harbor mouth, or it can just get pulled out to sea beyond a depth called the depth of closure, where wave action no longer reaches it, and it is lost.  If you have barriers at each end of a beach, say a headlands at one end and a canyon at the other, you are in a closed system called a littoral cell, and if your source of sand, whatever that is, does not keep up with the amount of it that leaves your cell daily, your beach is eroding, and you will lose it.  It is called your sand budget, and every beach has one, and no beach gets to exceed it.  Damming and pumping rivers can put a beach outside of its means.  In our hometown of Monterey, California, the beaches are going away because the Salinas River is a ghost of its former self.

BeachesTuckersIslandCombined

The demise of Tucker’s Island Lighthouse, Oct. 12, 1927
(Photo courtesy of NOAA)

All of this makes beach dynamics famously treacherous to tinker with.  Many lives have been ruined when someone put a jetty or some other obstruction in the wrong place.  In the very simplest scenario, everything downshore from the obstruction stops getting replenished by longshore drift and begins to erode, but it gets way more complicated than that.  One time an entire island off the coast of New Jersey called Tucker’s Island just flat disappeared, and it was because they built a couple of jetties to try to save it.  It was actually very sad—in the early nineteen hundreds it had a lighthouse, two hotels, guest cottages and a number of residences on it, all managed by a pioneering family of hardy souls, who some say had created the first beach resort in the U.S.  But the island was eroding at its north end, so they built jetties across the inlet passage from it on the advice of an engineer from the University of Pennsylvania.  It had the effect of reversing a critical current and making things worse, and longshore drift began stripping the island away in earnest.  Three years later, the last structure to go was the lighthouse, and on October 12, 1927, it toppled into the sea.  The lighthouse keeper photographed the whole thing on his Brownie box camera.

Here inside the Mesoamerican Barrier Reef, the source of our sand is almost entirely the reef.  Some might come from outcrops or landslides, but for the most part creatures lived and died to give us this beautiful white sand.  In fact, they probably lived and died and then passed through a whole chain of other creatures, so to a large extent you’re walking on fish poop, but don’t dwell on that.  And that whole food pyramid is underpinned, as any food pyramid is, by those tireless primary producers, the photosynthesizers like the corals, the phytoplankton, the dune plants, the turtle grass, the coralline algaes—and the sargassum.  It all gets broken down by micro-organisms and eaten by burrowing invertebrates, which is why we have shore birds working the surf zone and rays snuffling the sandy bottoms, noshing crustaceans and creating more sand.  Some beaches require healthy rivers, and some require heavy surf pounding a headlands, but for us, it’s all about the reef.  It is the reef ecosystem that creates our beaches.  The reef is everything to us.

Sargassum is good for beaches in several ways, but sargassum does not become sand, at least not until you take an extremely long view of things.  Sargassum has some mineral content, especially if it is encrusted by bryozoans, which most of it is (bryozoans can be pictured as tiny, filter-feeding creatures living in symmetrically-ranked glass condominiums—they’re another story), but that’s still not  that much mineral content.  Those piles of sargassum will not become same-sized piles of sand.  But they will become organisms.  They will fertilize plants and feed animals that become food for other animals, and as it all makes its way up the food chain, and the creatures have to protect themselves from herbivores and predators, they all start to employ a cute trick:  They take calcium from the water around them, and the carbon that is the by-product of their own respiration, and they make calcium carbonate, CaCO3—it’s what every crab leg and coral frond is made of, and it’s what you are walking on when you stroll on the beautiful, powdered sugar beaches of somewhere like Tulum.  In that sense, yes—sargassum becomes sand.

*          *          *          *

BeachesCoralSandBermuda

The creatures who lived and died: This coral beach in Bermuda is coarse enough that you can make out the organisms who comprise it.
Photo by Siim Sepp CC BY-SA 3.0, via Wikimedia Commons

The first debate we’re all hearing these days is about whether to rake the beaches.  Raking the stuff up and carting it away is nice for us beachgoers, but questions are being raised about whether it is good for the beach.  Texas A&M University did the only study I could find on beach raking, and I was surprised by the results.  They monitored the elevation of several beaches on Galveston Island with surveying equipment, half of them raked and groomed in front of hotels, and half untended in less developed areas.  They found no difference in beach elevation after a year.   They issue a few caveats, to be sure.  They point out  that they measured only elevation, not horizontal width or beach slope.   And a year isn’t very long.  They’re calling for more studies.  But, according to this early data, raking seems not to be a crime.  But it is the second part of their study that paints the picture more broadly, and takes in that triad of bars, beaches and dunes.

In that part of the study they examined the effect of sargassum on dune plants, and those results were conclusive—there’s no doubt about it, dune plants like sargassum, or at least the subject of their study does, which is a common dune grass called bitter panicum (Panicum amarum).  And it likes it whether you wash it to remove the salt or not, whether you leave it on top of the sand or mix it in—sargassum is just great fertilizer.  The panicum grows bigger, and puts out more roots and stabilizes the dunes better.  Panicum actually prefers the stuff unwashed, and the scientists speculate that that’s probably due to other important nutrients staying in the mix—plants are typically limited by the availability of nitrogen, phosphorus and potassium.  It’s important to remember, though, that panicum is a dune plant, and is salt tolerant.  For use in your garden you’d probably want to wash the stuff.

The scientists do point out that sargassum is good for the beach as well as the dunes—it creates food and habitat and protects the sand from both wave and wind erosion—but in the end, they seem to recommend raking the beach, but then carting the stuff no farther than the base of the dunes and piling it there, and then, periodically (it doesn’t have to be daily) spreading it more broadly across the dunes for the benefit of the plants there.

People are asking me if sargassum can be eaten.  The answer is yes, but the reviews aren’t exactly glowing.  EatTheWeeds.com calls it “not a prime edible, but a plentiful one.”  But they do go on to offer several ideas for preparing it.

It has been suggested that we sell the sargassum.  Various species of brown algae are already harvested and used in numerous things, including bio fuels, food thickeners, pharmaceuticals, cosmetics, and extracts for medical uses.  There’s a whole industry out there (a couple of industry websites are here and here), and in fact they used to harvest sargassum live from the Sargasso Sea, and the practice was opposed by conservation organizations like the Sargasso Alliance, and was finally regulated in most U.S. waters.  But what if they could gather it from beaches?  Well, it still poses environmental problems.  It would mean heavy equipment on the beaches where the turtles nest, and generally it involves collecting the stuff in dump trucks, where the load can end up being eighty percent sand and water by weight.  Then you drive it away to process it somewhere else, and all the salt and sand ends up in landfills, and, according to most reports, the beach takes a beating.  But the University of Alicante in Spain has designed a system that is transportable.  A truck backs it onto your beach on a giant trailer, and the sargassum is put through a three-stage process right there, finally creating cleaned and dried bales of the stuff, all without leaving your beach.  As far as I can tell, this system has only been designed—one has not been built yet.

Beaches_1024px-Green_Sea_Turtle_grazing_seagrass

Green Sea Turtle (Chelonia mydas)
Photo by P.Lindgren CC BY-SA 3.0, via Wikimedia Commons

And, since they’re so close to everyone’s hearts around here including mine, I’ll close the article with a word about the turtles.  I’m very sorry to report that sargassum does kill sea turtles.  The Barbados Sea Turtle Project reports 42 dead, both greens (Chelonia mydas), which are endangered, and hawksbills (Eretmochelys imbricate), which are critically endangered.  In 2014, the National Marine Fisheries Service reported 20 live and 23 dead green turtles stranded in the sargassum on U.S. beaches.  The sargassum causes problems for them in several ways.  First of all, when you swim among the turtles somewhere like the wonderful waters of Akumal Bay, they are so graceful and beautiful in the water that it’s easy to forget that they’re actually air breathers.  They have to be able to get to the surface about every fifteen minutes, and a mat of sargassum pushed up against a coastline can get several feet thick, and if they cannot get up through it they will simply drown.  Even if they reach the air, they might remain entangled, and end up beached and helpless in the mass of seaweed.   It is also feared that nesting sea turtles will have trouble finding a clear patch of beach for a nesting site, and if their options are limited, they will get crowded together, and the result will be turtles digging up other turtles’ nests as they create their own.  And then, of course, the hatchling has to get back through it all to reach the water, and that’s a trek which is already the most perilous sixty seconds of her life.

And that’s a life that might go on to span eight decades.

Now you know.

Copyright © 2015 Randy Fry
Sources:
http://treasureislandtx.org/TIMUD/Seaweed%20Report.pdf
–http://www.eattheweeds.com/sargassum-not-just-for-breakfast-any-more-2/
https://seaweedindustry.com/
http://news.algaeworld.org/
http://www.loopnewsbarbados.com/content/sea-turtles-victims-sargassum-seaweed
http://www.barbadosseaturtles.org/
http://www.sanpedrosun.com/environment/2015/08/08/sargassum-linked-to-dead-fish-washing-onshore/
https://sandiego.surfrider.org/wp-content/uploads/2010/01/DynamicsofBeachSand2007.pdf
http://www.houstonchronicle.com/neighborhood/bayarea/news/article/Groups-Seaweed-could-be-killing-sea-turtles-5585589.php
Tucker’s Island, By Gretchen F. Coyle and Deborah C. Whitcraft

 

By |2017-11-12T11:51:36-06:00August 29th, 2015|Nature Essays|6 Comments
Read More

When Squids Fly

In this article I’m going to not tell you about cuttlefish.

We had dinner with Dave, Nancy and their daughter Sidney last night, here on our Caribbean coastline in Mexico, and all of us were remarking on the cuttlefish we’d been seeing out on the reef lately.  Cuttlefish are beautiful and enchanting little creatures, about nine inches long, with graceful tentacles hanging from their face, huge, mesmerizing eyes with W-shaped pupils, and an apron-like fin all the way around their body that undulates like a dust ruffle to propel them around.  They’re inquisitive, and whenever Susan and I come across a few, they will usually stay with us for a while as we swim.  Caribbean reefs are just full of beautiful and mysterious creatures, but Susan and I were becoming especially fond of these cuttlefish.

The specific question that had been intriguing Dave was why they always seem to occur in threes.  Susan and I had noticed this too.  You’ll see them in ones and twos now and then, but usually threes.  Fascinating.  I started digging.  What I learned was just amazing.  Here’s what I found out:

Cuttlefish don’t occur in the Caribbean.

“D’oh!” I said to my laptop monitor, and smeared my hand down my face.  It shows you how much I still have to learn about my new ecosystem.

No one’s sure why they don’t occur in the Caribbean.  Cuttlefish have one of the strangest distributions you can imagine.  They’re in the Atlantic and they’re in the Pacific—it’s not like they’re not in our oceans.  They’re on the European coastlines and the African coastlines and the Asian coastlines and even the Australian coastlines, but they do not touch the Americas.  The best guess is that they evolved in the old world, and then the big oceans got too cold and deep for them to cross, being warm water and shallow water creatures.  There’s a part of me that’s somewhat surprised that they haven’t managed to get introduced somehow, and start throwing things out of whack like the lionfish is doing.

What we’ve been looking at is called the Caribbean reef squid (Sepioteuthis sepioidea), and they look a lot like a cuttlefish—in fact, their scientific name alludes to the resemblance (cuttlefish being the order Sepiida).

Well, they may not be cuttlefish, but they are cephalopods, and cephalopods are my second-favorite mind-blowing organisms after jellyfish, so Dave, don’t be disappointed yet.  Trust me, Caribbean reef squids are fall-down-and-slap-the-ground amazing.  For one thing, they can fly.  More on that in a bit.

Cephalopods are the octopi, squid, cuttlefish and nautiluses.  They are a mash-up of legacy evolutionary traits and astonishing innovations not seen anywhere else.  They’re shellfish (mollusks) who took a bizarre evolutionary turn, and I hugely enjoy bizarre evolutionary turns, because they remind us that life on this planet is not following any grand scheme, and neither are we.  (We became us by accident too, believe me—and by the way, we only made it by the skins of our teeth.)

CaribbeanReefSquidBrown
Caribbean Reef Squid (Sepioteuthis sepioidea) Photo by Nhobgood Nick Hobgood CC BY

Cephalopods  can change color in a flash, by conscious control, using muscular contraction and pigment cells called chromatophores.  Their colors shimmer and dance across their bodies as you watch.  They can also change their texture instantaneously, going from silky smooth to rough and spiky in a blink, and they can change their shape to mimic other creatures or objects.  All that remains of their shell (ignoring the nautilus for now) is a beak a lot like a parrot beak, which is dead center between their tentacles (actually called arms) which they use to crunch the shells of their prey.  A large species of octopus can have roughly the intelligence of a dog or a cat, depending on who you talk to, and squids and cuttlefish have been studied less, but appear not to be far behind.

That intelligence level is not bad for a shellfish, and it fascinates scientists, because their brains and nervous systems are so radically different from our own, or from any mammal, or even bird or reptile.  They are such different creatures that in many ways intelligence in cephalopods can be considered a case of convergent evolution.  That’s where two species independently arrive at a similar solution to a problem.  Two thirds of their neurons are not even in the brain, but are out in the arms, which have a lot of autonomy in what they do.  It is not a centralized system like ours, and if you watch an octopus forage in a rocky reef, you’ll see this design at work—they are reaching into numerous crevices and hidey-holes simultaneously.  Clearly they’re thinking about eight things at once.

Two_Caribbean_Reef_Squid,_Bonaire,_Dutch_Antilles
Two Caribbean Reef Squids (in different moods)
 Photo by Clark Anderson CC BY-SA 2.5

You can put a crab in a jar, and an octopus will figure out how to unscrew the lid and get it out.  You can put the octopus in the jar, and he’ll figure out how to open it from the inside.  I don’t know if they’ve tried any of this with a squid or a cuttlefish.  An octopus named Otto in the Sea Star Aquarium in Coburg, Germany, got annoyed at the 2,000-watt spotlight that was left on all night above his tank, so he started hitting that thing with jets of water and shorting the place out.  I’m not making this up.  It threw the aquarium into crisis.  Everything went down including the pumps, and it threatened the lives of all the creatures in all the tanks, and it happened every night.  They had to stake the place out to figure out what the hell was going on.  Otto had other quirks:  He was fond of doing something a lot like juggling with the hermit crabs in his tank.  He would periodically rearrange everything in it (including the hermit crabs), and he liked to damage the glass by smacking it with rocks.  There are other stories from other aquariums.  They are talented escape artists, and will leave their tank at night to help themselves to dinner in the crab exhibit, returning to their own tank to eat, and then hiding the remains.

But the thing is, they don’t live long.  Sophisticated and intelligent though they are, one or two years is all you get if you’re a cephalopod.  It’s called being semelparous—they die immediately after they reproduce, and there’s not a thing you can do about it, and I remember this causing a lot of wet eyes around the Monterey Bay Aquarium from time to time when I was a docent there.  These creatures are aware, and they have personalities, and attachments get formed—and then they die.

 

*          *          *           *

 

In 2001, Sylvia Macia and her husband Michael Robinson, both marine biologists, were in a boat off Jamaica when a Caribbean reef squid burst out of the water with its fins flared outward and its arms held in a radial pattern, and it sailed to a height of six feet above the water over the course of a thirty-foot flight before dropping back in.  They were flabbergasted.  Flying fish do this (family Exocoetidae), and it’s a cute trick for predator evasion.  There’s no better way to befuddle your pursuer than to blast through a reflective ceiling and vanish.  But squid?  There had been a few rumors and folk tales, but hell, the ocean is just full of rumors and folk tales.  Thor Heyerdahl, who has (and deserves) some respect, reported squid occasionally falling on his raft Kon Tiki.  And now and then a biologist will find a squid dead on the floor next to his tank.  But those kinds of jumping mishaps can happen with any fish, including a goldfish.  This thing was flying.

They sent out a signal to the mollusk community.  Reports started trickling in.  Maybe this had been witnessed before, but people had assumed they were looking at flying fish.  I mean, let’s face it, a flying squid is just not something that has a cubbyhole in your brain.  But Macia and Robinson were marine biologists.  They knew what a Caribbean reef squid was.  Aware of the possibility now, scientists began paying attention with new eyes.  The sightings continued to mount.  But they were all anecdotal.  There were no photographs.  There was no proof.  The sightings seemed to be very rare, and the flights are so brief, and squid are nocturnal, and catching a flight on film was looking like it might be impossible.  They published a paper anyway, in 2004.  It was well received.  But they still had no proof.

Then, in 2009, a retired geologist named Bob Hulse was on a cruise ship off Brazil.  He was an amateur photographer, and he was packing a wildlife camera a lot like Susan’s.  He was shooting in burst mode, and at a high resolution, and he captured a handful of “unusual creatures” flying above the water.  Though it was not his field of science, he was observant enough to know that he was seeing something weird.  He forwarded the shots to the University of Hawaii, and they forwarded them to a scientist named Ronald O’Dor, now at Dalhousie University in Halifax, Canada, and that’s who started working with the best and, at the time, only photographic documentation of flying squid.  (They have since been photographed off Japan.)  He knew the data he was looking at was gold.  The exact interval between the frames was known, and he could calculate the velocity and the acceleration, and get a close look at the body parts.  He lit into the project.

What O’Dor is piecing together is amazing.  Cephalopods already have the jet propulsion thing dialed in.  That was known.  They jet around underwater, and blast away backwards as an escape technique.  They fill their body (mantle) with water and force it out under great pressure through an organ by their mouth called a funnel.  The funnel can be directed, like the nozzle of a guided missle, so they have control.   They extend their fins, and hold their arms out stiffly to create another flight surface, and they rocket through the air like little cruise missiles, trailing exhaust streams of water and steering with their flight surfaces.  Gliding is too tame a word for what they do.  They have a propulsion system onboard, and they have aerodynamic control.

This is breaking science (he presented his paper in 2012), so there is still lots of argument, but O’Dor now believes that they do not fly to escape predators—they do it to travel long distances.  They do it to escape the drag of the water.  He believes that it explains some long migrations that had always seemed implausible.  Using Hulse’s photographs, he calculated that they get five times the speed in the air that he had ever measured in the water from the same propulsive effort.  They fly.  They fly to get around.  But we never knew they did it, because they do it at night, when the birds aren’t out.

Six species of flying squid have now been identified.

The Caribbean reef squid was the first.

 

*          *          *           *

 

The Caribbean reef squid communicate with each other through color.  Over forty distinct patterns of color and shape have been identified, and that’s just for communication.  There are looks scientists call bars, belly stripes, dark arms, yellow flecked, speckled belly.  When they’re pissed off, their brow ridge turns metallic gold.  They layer the artwork, like imaging programmers do.  There will be a background, and then one or more patterns or shapes overlaid on top of it.  Scientists have modeled the whole thing in Photoshop, and given them names.  They can flash one message to a squid on their right, and a different one to a squid on their left.  The courtship display is a shimmering, moving background overlaid with zebra stripes.  Some scientists are arguing that they have both a vocabulary and a syntax, and that that constitutes language.  But only a few are saying that.  Language in animals is controversial.  It takes cojones to use the L-word in the scientific community.

They can imitate anything.  When they flee into open water they become pale.  When they flee into the coral they become rough-textured and brown.  When they’re stalking prey they can make themselves look like sargassum seaweed.  They can become a parrotfish by swimming backwards, holding their arms out like a tail and displaying eyespots on their rears.  Like all cephalopods, they can shoot out a cloud of ink to confuse a predator, and sometimes they’ll do this and then real quick make themselves look like an ink cloud next to the ink cloud.

They are very social.  They hang out in schools called shoals, and there is a hierarchical social structure, based mostly on size.  The shoal will have sentinels around its perimeter, all facing outward in different directions.  If a predator needs to be distracted or confused, one of the larger squid will rise to the challenge.  Mixed schools have been observed, with other species of squid present, and there is an association with two species of goatfish, who will forage on the bottom beneath the shoal of squid, protected by their vigilance, but it’s not clear what if anything the squid get out of it.

The young hide in the turtle grass beds, and the older ones like to shoal in the open water, and here, Dave, I’m circling back to your question.  When they come into a reef, it’s usually to mate.  To get the girl, a male must intimidate and out-display other males, and these face-offs will be going on in the coral, always in the presence of a female.  Two plus one makes three.  I’ll bet that’s what we’re seeing.

In the end, the winner approaches the girl.  At first she flashes an alarm pattern at him, but he persists, comforting her by blowing water across her, jetting away briefly, and then returning, in his shimmering, zebra-striped splendor.  This might go on for an hour.  Finally, when she has succumbed to his charms, he displays a special pulsating pattern and attaches a sticky packet of sperm called a spermatophore to her side, and leaves.

So in the end, it is she who performs the sexual selection for the species, choosing whether to use the spermatophore.  She can place it herself into her sexual organ, called a spermatangia–or she can discard it.  If she has deemed the male to be worthy of continuing his evolutionary journey, the next thing she does is find a place to lay her eggs.  Then she dies.  She never meets her children.

Now you know.

 

 

By |2017-05-24T00:03:04-05:00October 28th, 2014|Nature Essays|12 Comments
Read More
Go to Top