{"id":39620,"date":"2022-08-04T00:01:31","date_gmt":"2022-08-04T07:01:31","guid":{"rendered":"https:\/\/hakaimagazine.com\/?post_type=custom_news&p=39620"},"modified":"2022-08-04T08:38:30","modified_gmt":"2022-08-04T15:38:30","slug":"eelgrass-is-still-reeling-from-the-last-ice-age","status":"publish","type":"custom_news","link":"https:\/\/hakaimagazine.com\/news\/eelgrass-is-still-reeling-from-the-last-ice-age\/","title":{"rendered":"Eelgrass Is Still Reeling from the Last Ice Age"},"content":{"rendered":"

Over much of the past two million years, thick ice sheets blanketed the land and sea across vast swaths of the planet. Around 12,000 years ago, this frigid era began to lessen its icy grip. But the world is, to this day, recovering from the effects of the last glaciations. Relieved of its glacial burdens, the ground itself is gradually rebounding. Melting that began with the Ice Age\u2019s wane is ongoing, making the oceans minutely fresher. And in the Atlantic Ocean, eelgrass is still trying to regain the genetic diversity it lost when ice isolated it from the Pacific.<\/p>\n

Throughout the northern hemisphere, Zostera marina<\/em>\u2014commonly known as eelgrass\u2014is the backbone of coastal ecosystems from the Mediterranean to the Arctic. Eelgrass meadows protect the coast, store carbon, and support a host of organisms, from economically important herring, sea bass, and lobsters to vulnerable species such as sea turtles and dugongs. Zoom in closer, and you\u2019ll find a metropolis of algae and tiny invertebrates clinging to each gently swaying blade. \u201cEelgrass is like the Serengeti of the sea,\u201d says Emmett Duffy, an ecologist at the Smithsonian Institution.<\/p>\n

\u201cThe plants are covered with what looks like black sand, but it\u2019s these tiny little snails that are just all over the place,\u201d Duffy says.<\/p>\n

Eelgrass originated in the Pacific Ocean between 10 and five million years ago, descending from a rare group of flowering plants that colonized the sea. It only spread to the Atlantic Ocean starting around 3.5 million years ago, before the most recent ice age hit and ice sheets separated the two oceans. And now, eelgrass is in decline because of disease<\/a>, environmental degradation, and other causes. Duffy and his colleagues wanted to know if eelgrass\u2019s past is putting limits on its possible futures.<\/p>\n

For their new study<\/a>, Duffy and an international team worked on 50 eelgrass sites throughout the northern hemisphere, surveying meter-square patches of seafloor, collecting samples, and measuring the biomass of the algae and invertebrates living on the eelgrass. Geneticists reconstructed parts of the eelgrass genome, looking for similarities and differences between and within the eelgrass living in the Pacific and the Atlantic Oceans.<\/p>\n

Visually, eelgrass ecosystems look different in the Pacific and the Atlantic. The Pacific has sparse forests of meter-high eelgrass, while the Atlantic has shorter, denser meadows. Atlantic eelgrass meadows also support more invertebrates than the Pacific\u2019s tall forests.<\/p>\n

But the most striking differences aren\u2019t visible to the naked eye. As their research shows, eelgrass ecosystems in the Atlantic have far less genetic diversity than in the Pacific. Duffy links that back to eelgrass\u2019s initial migration from the Pacific to the Atlantic and the onset of Arctic ice not long afterward.<\/p>\n

\u201cCrossing the Arctic at that earlier, warmer time was probably a very difficult journey,\u201d Duffy says. Few plants were successful, limiting the genetic diversity of Atlantic Ocean eelgrass from the get-go. The onset of Pleistocene ice effectively sealed Atlantic eelgrass off from the Pacific, and repeated glacial cycles shaped eelgrass from there.<\/p>\n

\u201cThe biggest surprise, and the most important result for me, was that an event from tens to hundreds of thousands of years ago is still affecting this globally distributed plant,\u201d Duffy says.<\/p>\n

Atlantic eelgrass\u2019s lack of genetic diversity might be bad news for its ability to survive climate change. Without an assortment of potential adaptations to lean on, eelgrass might fail. Given enough time, Atlantic eelgrass could eventually evolve to have the same breadth of diversity as its Pacific counterparts. Unfortunately, the swift pace of climate change may not give it that chance.<\/p>\n

\u201cIt\u2019s assumed that species will simply move,\u201d Duffy says. \u201cBut sometimes, as we\u2019ve seen with eelgrass, it\u2019s only a small part of the population that makes it through, and the characteristics of those pioneers can be quite different from the larger population that they came from. \u2026 You don\u2019t just establish the same population at a different latitude.\u201d<\/p>\n

To Nicole Kollars, an ecologist at Northeastern University in Massachusetts who was not involved in the paper, the research \u201craises a lot of questions about what that [genetic diversity] means for the resilience of eelgrass to climate change.\u201d She adds, \u201cI think it opens up a lot of questions for us to tackle over the next 20, 30 years.\u201d<\/p>\n

People could lend eelgrass a helping hand, Kollars says, either by moving seeds and plants around to increase gene flow or by using eelgrass nurseries to support restoration efforts. For her, the study serves as an important reminder that the past can be a window to the future.<\/p>\n","protected":false},"excerpt":{"rendered":"

Over much of the past two million years, thick ice sheets blanketed the land and sea across vast swaths of the planet. Around 12,000 years ago, this frigid era began to lessen its icy grip. But the world is, to <\/p>\n

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