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Southerly light winds. Manta trawls

From last afternoon onwards the wind has backed to a fair Southwesterly first, then to an even better Southerly. Though becoming lighter and lighter, resulting in the slowing down of our progress, it allows us to change the North-northeasterly course we had to a direction that actually bring us closer to our destination at Easter Island. 

The combination of prevailing winds and the rotation of the planet’s effect on the atmosphere and water masses produce large-scale circular current systems in the oceans called gyres. Present in all the world’s oceans, the one directly related to our voyage is the South Pacific Gyre, a counterclockwise oceanic circulation comprised between the Equator, Australia, South America, and the clockwise circulating Antarctic Circumpolar Current in the south. 

For a while, we have been following the part of this oceanic circulation that runs northwards along the Chilean coast, and now we are starting to get deeper into the open Pacific waters westwards. An area between the southern edge of the Southeasterly Trade winds, and the Westerlies to the south. 

The trade winds in the Tropical South Pacific typically blow from the southeast, but they often don't start until a few hundred miles or so west of the Galapagos. Closer to the South American mainland the winds are less well defined, as we are finding out for ourselves. 

Typically the Low-Pressure Systems pass South of this zone, then coming up to lower latitudes above the continental America and Argentinean coast, while to our Westward use to sit a large High-Pressure system. The last few days we have been under the influence of the northern edge of one of those Depressions and now, sailing in a northwesterly direction the Europa gets closer to the High-Pressure area sitting in the middle of the South Pacific. 

A climate pattern that produces steady Southeasterly trade winds blowing in the Pacific tropical areas, helping sailing ships to go into its waters in a westerly direction. Although they start to blow north of our planned itinerary, they are not a problem for our trip as this is our general heading for the next months of Pacific exploration, but a characteristic that presents a substantial disadvantage if the course to take is eastwards. But contrary to this, towards the east it was the gradual expansion of the native population of the Melanesian and Polynesian islands. A deed that puzzled scholars and explorers, to which Captain Cook found a plausible explanation by discussing the issue with a Tahitian navigator:  

Cook chose the "East Indias" as the origin point for the Polynesian migration because a linguistic sailing with Cook as his botanist was Joseph Banks, who had studied philology at Oxford, and who later was to become president of the Royal Society. On board the ship was a small library containing published accounts of previous voyages through the Pacific, and in these accounts were short lists of words from islands scattered from Southeast Asia eastwards into the Pacific as far as the western edge of Polynesia. By comparing the list of Tahitian words he compiled with these other vocabularies, Banks was able to show how Tahitian was directly related to languages spread across the Pacific to the Southeast Asian islands of the "East India’s". 

Cook saw only one obstacle to accepting a Polynesian origin in island southeast Asia: the proposed migration trail led through tropical latitudes, and in the tropics easterly trade winds normally prevail. Whereas these would make it relatively easy for voyagers from South America to sail westward with the wind into the Pacific, steady trade winds would seem to present a formidable obstacle for any voyagers sailing eastward across the ocean. Yet, because he saw no cultural resemblance between the islanders he had met and the native Americans, Cook rejected the idea of an American origin of the Polynesians. The trail of linguistic evidence clearly marked the direction of migration, and he therefore sought to explain how canoe voyagers could have moved eastward into the Pacific against the direction of the trade winds. 

Tupa'ia supplied the solution to this apparent dilemma: he told the puzzled Cook that during the months of November, December, and January the trades frequently died down and were replaced by spells of westerly winds, and that the Tahitians then used these westerly winds to sail to the east. From that crucial bit of intelligence, Cook constructed his seaman's explanation for how Polynesia was settled from the west that takes into account both the oceanic environment and Polynesian nautical abilities: the early voyagers worked their way eastward from the Asian side of the Pacific, moving from island to island, by exploiting seasonal westerly wind reversals. 

William Henry Giles Kingston. “Captain Cook. His Life, Voyages and Discoveries”. 1871 

To the south of the Southeasterly Trades and towards the center of the ocean, the middle of the oceanic gyres accumulate water and show little movement, being a much less productive environment than coastal and upwelling areas. Quiet zones and relatively poor on nutrients and marine life, but where litter and debris tend to gather. Microplastics are common in waters and on the beaches near the center of those gyres. The larger marine debris shows a similar distribution pattern. The most affected sites, including many of the world’s most remote islands, are starting to monitor the amount of plastic washed up on their beaches and join beach clean-up projects. 

Initiatives that Europa plans to join during her voyage along the South Pacific, when she will call on different islands on her way. Aboard, selected scientists join us as well during the next months to study and contribute to the present knowledge of the microplastic distribution in this ocean. And today the winds and weather were suitable, light enough to deploy once more their equipment for that purpose. In the morning the manta trawl is rigged and soon the ship is dragging it alongside collecting samples on the water surface. A procedure that if possible will take place every three days. The catch is filtered through different mesh sizes and the final result shows a wonderful diversity of planktonic organisms and also the presence of microplastics. Today less plankton was caught in comparison with three days ago, and their diversity has changed too. Less of the gelatinous plankton was present, a decrease also followed by crab and other crustacean larvae. On the other hand, Portuguese man o’ war are still in the samples, now together with their relatives by the wind sailors. Some fishes came up too with the trawl, including deep sea species, that usually inhabit the abyssal depths of the ocean, but they migrate to surface waters during the night for feeding, diving back to the depths during the day to avoid predation.  

But the samples also contained synthetic fibers, small bits of colored plastic, and a bead of expanded polystyrene.  

Polystyrene is one of the most used plastics and in its expanded form is widely used on packaging. The white small round pellets are very light and are easily blown off with the wind and float when in the water, representing an important amount of the litter that accumulates along shorelines and free-floating in the oceans. It is nonbiodegradable and, mistaken as a food source, terrestrial, fluvial, and marine wildlife can suffer health issues when they eat them in large amounts. 

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