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Sargassum: the queries answered

As children we are told stories of old that over time have become legendary tales of monsters, dragons, pain and misery, usually ending with the words “and to this day no one really knows what happened” –– and thus the myth is born.

But we don’t often expect those stories to come full circle manifesting themselves in present-day life, backed up by scientific and academic rigour, with physical examples right on our doorsteps.

But that is exactly what has happened with stories of the Sargasso Sea –– so named for the floating masses of sargassum weed that propagate and fertilize without needing a reef or the ocean floor for housing or grounding. Folklore tells us that seafarers and mariners were vexed by these tangled masses, which made navigating that ocean –– and more importantly the North Atlantic Gyre –– tedious, if not a tad mysterious. And there began its mystery around the 1500s or earlier.

Professor Hazel Oxenford having a bit of fun ascending from a snorkel through floating Sargassum weed.

Professor Hazel Oxenford having a bit of fun ascending from a snorkel through floating Sargassum weed.

Yet to discuss this with fishermen off Consett Bay in the north of Barbados, they will tell you pretty much the same thing. Instead of becoming tangled in oars and anchors, the dense thick weed gets itself into the crevices of engines and motors, leaving the smaller fishing vessels adrift, with no way to get farther out to sea or to come ashore. The problem with legends, as they turn to myths, is that we can now separate fact from fiction –– and in this case it was not the North Atlantic Gyre, which is the circular rotation of water within a basin that is driven by the wind.

In the Northern Hemisphere wind blows from east to west at the Equator, pushing surface water to the north-west. As it rises and makes its way to about 30 degrees latitude, the wind shifts directions and blows from west to east, changing the path of the surface water to turn back down towards the sout-heast. This continuing pattern results in a slow clockwise rotation of water across the entire Pacific Ocean. Nor could 15th century Portugese seafaring explorers reasonably blame the floating masses of weed on the surface for uneasy going in that location. We now know it was most likely the calm winds of the horse latitudes –– subtropical latitudes between 30 and 38 degrees both north and south of the Equator.

What does all this have to do with the stinking piles of seaweed on beaches lining Barbados’ north and south-eastern coasts, about which much has been written and said but no one seems to be able to definitively do anything about? Actually more than you would think, as I found out in a fascinating chat with Hazel Oxenford, professor of marine ecology and fisheries at the Centre for Resource Management and Environmental Studies (CERMES) of the University of the West Indies, Cave Hill Campus.

A game of hide-and-seek among the whispy Sargassum on the surface is just what this lucky turtle hatchling is in the mood for.

A game of hide-and-seek among the whispy Sargassum on the surface is just what this lucky turtle hatchling is in the mood for.

It probably takes longer to recite her title than it does to walk the full floor space of her office; but what it lacked in grandeur it more than made up for it scientific explanation and years of tedious research.

In typical journalism fashion, I came out of the gates, guns blazing with the point-blank, who-dunnit question: is all of this because of global warming? Well, if I was looking for a headline-grabbing closed-end answer I was swimming around the wrong gyre, so to speak.

To start with, this recent influx is not an isolated incident, nor can it be divorced from a similar phenomenon in 2011. The bombardment of Sargassum weed along the shores of the Caribbean has been quietly studied and tracked by CERMES and Professor Oxenford in conjunction with the University of Mississippi in the United States since then.

“It was believed that Sargassum weed grew and lived . . . and stayed in the Sargasso Sea, but research more recently has shown that that can’t possibly be because a centre gyre is free of nutrients and really it can’t grow; it can only sustain itself, and it sustains itself by all the creatures living in it defecating and so on, producing the nutrients that it then uses to grow and sustain itself,” explained the diminutive blonde professor in one breathless sentence.

A bank of healthy floating Sargassum weed creates a live, moving ecosystem while leaving the water below clear and nutrient-rich.

A bank of healthy floating Sargassum weed creates a live, moving ecosystem while leaving the water below clear and nutrient-rich.

So the first myth is debunked. This journalist was humbled and Sargasso lessons were now in session. Still gnawing on the “where does it come from?” question, the professor whipped out her satellite imaging tracking slides and explained: “It first blooms in the Gulf of Mexico where the Mississippi [River] flows out here with a lot of nutrients, so there’s very high nutrient input from the Mississippi.”

The colour-coded tracking slides showed current patterns from March, May, July, September, November and February of 2011 in gradually sloping loops outward from and back towards the Gulf of Mexico. So in fact “the Sargasso Sea weed blooms in the Gulf of Mexico and then comes up with the current, goes around the Atlantic and gets stuck in the middle [of the North Atlantic Gyre which causes the weed to collect and stay in the Sargasso Sea]”, she explained.

The key point here is that the natural flow of current has nothing to do with the islands of the Caribbean in the main. The professor conceded that “yes, Bahamas get it all the time because that’s the Sargasso Sea weed and some of the northern islands like Puerto Rico and Haiti might get it occasionally, but we don’t get it down here because the currents have nothing to do with us down here”. Second myth debunked; and a clue that scientists and researchers are playing catch-up and scratching their proverbial heads just like beach regulars are because the 2015 influx is from a new source entirely.

“We assume that its blooming, that its propagating in the first place along the Equator off the Amazon; so the Amazon is the real nutrient source.”

That is one suggestion being bandied about; but there is another. Oxenford animatedly explained that “another possible source of nutrients is the Equatorial upwelling. So when you get the South Equatorial Current and the North Equatorial Current, they are meeting and then pulling apart. So they are basically drawing up deep water along the Equator”.

“And so the deep water from the Equator brings up the nutrients that are stuck in the bottom. So right along the Equator you get that high nutrient source.”

Feeling like I was being swept along by the current of her detailed explanation, to me, the murky waters became much clearer. We were heading to the 2000’s biggest environmental whipping stick: climate change. But the avid scuba diver was quick not to lay blame at the feet of either theory. At first it was thought to have been a sort of perfect environmental storm, a series of

chance occurrences leading to the 2011 landfall. But with two new options for possible sources for the 2015 landfall and near shore damage in the Caribbean archipelago, scientists and researchers at CERMES and at other research hubs are now prone to connect the two.

So that was the “where” question decidedly out of the way. Now to the how?

How do we manage it when we don’t know how long it is here for? How much more is coming? And should we learn to expect this as a regular occurrence?

So I put the questions to the lively sun-tanned blonde and she quickly cautioned that help was on the way through a closed-door think tank session to be held on Monday, when stakeholders brainstorm about how to handle the Sargassum weed in the here and now, while deploying students and research assistants to study its chemical make-up, life expectancy and impact on reef quality when it dies and rots on the ocean floor.

Knowing that the discussion was fast approaching a dissertation, rather than research for a single column, I asked about the one species whose health and longevity with respect to the Sargassum influx had created the loudest hue and cry: sea turtles. Stressing this was merely her perspective, Professor Oxenford tackled the issue of compromised turtle nesting sites.

“The Sargassum when it builds up on the beaches, yes, it will cause a problem for nesting adults. It’ll make it much more difficult to climb on to the beach. In fact, if the seaweed builds up on the back of the beach, it will make it very difficult for them to dig the nest, and it may well impact the temperature of the nest or the bacteria that are present in the nest. So it may affect hatching success.

“The Barbados Sea Turtle Project staff members would be able to tell us a lot more about that,” she opined.

On the matter of hatchlings –– which already have a high mortality rate –– going down the beach, Professor Oxenford said, they would indeed “get trapped in it trying to get to the sea and won’t make it”.

“I expect the population of crabs will build up because of the Sargassum on the beach, as they are probably the main predators of the hatchlings when they are trying to reach the sea. But on the other hand, those that do reach the sea, instead of swimming for perhaps two or three days looking for shelter, will find shelter more or less straight away. So it’s very difficult to say in the long term what the impacts will be.”

Each question begat another until I realized the simple truth of the matter: we simply don’t know how long the seaweed will be around; so that makes it hard for us to manage it.

Swimming furiously for answers is the staff at CERMES and researchers at the University of Mississippi with whom the professor is working to answer these questions and inform those who are charged with acting upon them.

But for now perhaps the “live and let live” adage is the best approach to adopt or steepen one’s learning curve in the process about the place that was once called The Golden Rainforest Of The Sea.

2 Responses to Sargassum: the queries answered

  1. Tony Webster August 15, 2015 at 9:44 am

    Thanks be BT…and also to the goodly professor and her students. Looking-out forsome quality, and practicable, scientific advice on either a solution, or intelligent ameliorations.

  2. Matthieu B November 23, 2015 at 10:32 am

    Interesting explanations.


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