Mysterious masses of seaweed assault Caribbean islands

first_img Sea of trouble A satellite map from May shows abundant Sargassum across a swath of the Caribbean and tropical Atlantic that was largely free of floating seaweed until 2011. HELENE VALENZUELA/AFP/Getty Images (MAP) N. Desai/Science; (DATA) M. Wang, C. Hu, University of South Florida 0.00% PUERTO RICO This dead green sea turtle (Chelonia mydas)—an endangered species—was found tangled in Sargassum on the island of Barbados on 8 June. Carla Daniel In retrospect, 2011 was just the first wave. That year, massive rafts of Sargassum—a brown seaweed that lives in the open ocean—washed up on beaches across the Caribbean, trapping sea turtles and filling the air with the stench of rotting eggs. “It presented immense challenges,” says Hazel Oxenford, a fisheries biologist at The University of the West Indies in Cave Hill, Barbados. Before then, beachgoers had sometimes noticed “little drifty bits on the tideline,” but the 2011 deluge of seaweed was unprecedented, she says, piling up meters thick in places. “We’d never seen it before.”Locals hoped the episode, a blow to tourism and fisheries, was a one-off. But a few years later “it came back worse,” Oxenford says. Now, the Caribbean is bracing for what could be the mother of all seaweed invasions, with satellite observations warning of record-setting Sargassum ​blooms and seaweed already swamping beaches. The Barbados government declared a national emergency on 7 June. “It’s catastrophic,” says James Franks, a marine biologist at The University of Southern Mississippi in Ocean Springs, who is one of many scientists trying to explain why a part of the ocean that was once seaweed-free is now rife with Sargassum. “Right now there’s [another] huge mass impacting Puerto Rico, and that’s the last thing they need.”Before 2011, open-ocean Sargassum was mostly found in the Sargasso Sea, a patch of the North Atlantic enclosed by ocean currents that serves as a spawning ground for eels. So when Sargassum first hit the Caribbean, scientists assumed that it had drifted south from the Sargasso Sea. But satellite imagery and data on ocean currents told a different story. Click to view the privacy policy. Required fields are indicated by an asterisk (*) Since 2011, tropical Sargassum blooms have recurred nearly every year, satellite imagery showed. The new source region is encircled by currents running clockwise from South America to Africa and back again. From January to May, that loop breaks down and westward flows sweep Sargassum up the Brazilian coast toward the Caribbean. “All along the way, the Sargassum is blooming and growing,” Franks says.Yet in satellite data prior to 2011, the region is largely free of seaweed, says Chuanmin Hu, an oceanographer at the University of South Florida in St. Petersburg and the senior author of a 2016 study that examined satellite data from 2000 to 2015. That sharpens the mystery of the sudden proliferation. “Nobody has a definite answer,” Hu says. Nutrient inputs from the Amazon River, which discharges into the ocean around where blooms were first spotted, may have stimulated Sargassum growth. But other factors, including changes in ocean currents and increased iron deposition from airborne dust, are equally plausible. It’s all “educated speculation,” Hu says. Jim Gower, a remote-sensing expert with Fisheries and Oceans Canada who is based in Sidney, British Columbia, and his colleagues looked for spots on the ocean’s surface that reflected unusual amounts of near-infrared light, a part of the spectrum that plants don’t harvest. Data from May 2011 showed a huge patch of floating plants, presumably Sargassum, off the coast of Brazil—far to the south of its normal habitat. By September, it stretched from the Caribbean all the way to the coast of Africa, the team reported in 2013.To confirm that the Sargassum fouling Caribbean beaches in 2011 came from the tropical Atlantic, east of Brazil, Franks and his colleagues traced the likely path of seaweed masses backward through time. First, they compiled records of locations where Sargassum came ashore. Then, using information about surface currents, they calculated its likely source. “Invariably, in all of those instances, it tracked back to the [tropical] region,” says Franks, who reported the findings in 2016. “None of it ever tracked northward into the Sargasso Sea.” Country * Afghanistan Aland Islands Albania Algeria Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia, Plurinational State of Bonaire, Sint Eustatius and Saba Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory Brunei Darussalam Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, the Democratic Republic of the Cook Islands Costa Rica Cote d’Ivoire Croatia Cuba Curaçao Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands (Malvinas) Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard Island and McDonald Islands Holy See (Vatican City State) Honduras Hungary Iceland India Indonesia Iran, Islamic Republic of Iraq Ireland Isle of Man Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, Democratic People’s Republic of Korea, Republic of Kuwait Kyrgyzstan Lao People’s Democratic Republic Latvia Lebanon Lesotho Liberia Libyan Arab Jamahiriya Liechtenstein Lithuania Luxembourg Macao Macedonia, the former Yugoslav Republic of Madagascar Malawi Malaysia Maldives Mali Malta Martinique Mauritania Mauritius Mayotte Mexico Moldova, Republic of Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Norway Oman Pakistan Palestine Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Qatar Reunion Romania Russian Federation Rwanda Saint Barthélemy Saint Helena, Ascension and Tristan da Cunha Saint Kitts and Nevis Saint Lucia Saint Martin (French part) Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Sint Maarten (Dutch part) Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and the South Sandwich Islands South Sudan Spain Sri Lanka Sudan Suriname Svalbard and Jan Mayen Swaziland Sweden Switzerland Syrian Arab Republic Taiwan Tajikistan Tanzania, United Republic of Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Venezuela, Bolivarian Republic of Vietnam Virgin Islands, British Wallis and Futuna Western Sahara Yemen Zambia Zimbabwe BARBADOScenter_img Sign up for our daily newsletter Get more great content like this delivered right to you! Country Sargassum ocean coverage in May 2018 >0.1% By Katie LanginJun. 11, 2018 , 5:20 PM Email Mysterious masses of seaweed assault Caribbean islands Some clues may come from the seaweed itself. Most of the Sargassum that’s blooming off the coast of Brazil has broader blades than the weed in the Sargasso Sea, says Amy Siuda, a biological oceanographer at Eckerd College in St. Petersburg, Florida, who has examined hundreds of samples. Siuda is currently working with colleagues to figure out if the broad-blade form—which historically was rare in tropical areas—is a separate species. Figuring out the conditions that promote its growth could be key to explaining the proliferation, she says.In the meantime, the Caribbean is struggling to cope as yearly bouts of Sargassum become “the new normal,” says Iris Monnereau, a regional project coordinator for the Food and Agriculture Organization of the United Nations in Christ Church, Barbados. She’s particularly worried about this year, noting that the blooms visible in satellite imagery dwarf those of previous years. “You can’t solve the problem; you can’t put up a wall or anything,” she says. “It’s difficult to go forward.” Bilbao BRAZIL AtlanticOcean Deep drifts of Sargassum seaweed swept ashore on Guadeloupe in April.last_img