{"id":19441,"date":"2021-12-07T15:20:26","date_gmt":"2021-12-07T20:20:26","guid":{"rendered":"https:\/\/wordpress.world.dan.org\/?post_type=dan_alert_diver&p=19441"},"modified":"2023-06-06T17:44:32","modified_gmt":"2023-06-06T21:44:32","slug":"celebrating-seagrass","status":"publish","type":"dan_alert_diver","link":"https:\/\/world.dan.org\/fr\/alert-diver\/article\/celebrating-seagrass\/","title":{"rendered":"C\u00e9l\u00e9bration de l'herbe de mer"},"content":{"rendered":"

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Pourquoi la protection de cette plante marine en voie de disparition est essentielle dans notre lutte pour sauver le climat et la biodiversit\u00e9.<\/h2>\n\n\n\n

J'ai soulev\u00e9 la pierre et ma cl\u00e9 avait disparu. Il \u00e9tait midi en juillet, et la chaleur des Keys de Floride \u00e9tait oppressante. Je d\u00e9goulinais d'eau sal\u00e9e et j'avais des algues dans les cheveux. Mon t\u00e9l\u00e9phone portable, mon portefeuille, mon eau potable, la cl\u00e9 de l'h\u00f4tel, mes lunettes de soleil et tout le reste, \u00e0 l'exception de mon short de surf et de mon appareil photo sous-marin, \u00e9taient enferm\u00e9s dans la voiture de location surchauff\u00e9e. Je savais que j'avais mis le porte-cl\u00e9s l\u00e0, et j'avais surveill\u00e9 la zone depuis ma place dans l'eau. Personne n'aurait pu la prendre, et je me demandais avec incr\u00e9dulit\u00e9 o\u00f9 elle pouvait bien se trouver.<\/p>\n\n\n\n

I had been sitting in a seagrass meadow, hoping a shy bonnethead shark would swim in front of my lens. These small hammerheads were reclassified in 2018 as the world\u2019s first known omnivorous sharks. A central question facing scientists was how much of the seagrass nutrient content the sharks were taking in.<\/p>\n\n\n\n

In one study led by Samantha Leigh, Ph.D., of California State University, Dominguez Hills, researchers fed captive bonnethead sharks a 90 percent seagrass diet for three weeks. Analysis of the sharks\u2019 digestion showed they could get nutrients from the seagrass and exhibit growth on a primarily vegetarian diet. Since other marine omnivores have had positive effects on food webs, the researchers posited that the sharks\u2019 nutrient intake meant we would \u201cneed to reevaluate the roles of bonnethead sharks in seagrass ecology because they could be responsible for significant grazing and nutrient transport within fragile seagrass ecosystems.\u201d1<\/sup><\/p>\n\n\n\n

\"Un
Un banc de poissons se nourrit d'herbes marines.<\/figcaption><\/figure>\n\n\n\n

Les requins mangeurs de plantes ne sont qu'un exemple de la fa\u00e7on dont la science change notre vision des herbiers marins et r\u00e9v\u00e8le leur importance.<\/p>\n\n\n\n

Seagrasses are different from algae and seaweed; they are more akin to flowering plants that grow on land. About 72 species are found in coastal seas on every continent except Antarctica, stretching from the equator to cool and cold areas \u2014 some Zostera marina<\/em> <\/em>pousse dans l'Arctique et peut survivre sous la glace.<\/p>\n\n\n\n

A few weeks before I ended up keyless in the Florida heat, I was wearing a drysuit but still shivering in 35\u00b0F (1.7\u00b0C) water in Newfoundland, Canada. I had joined a small team of scientists from Fisheries and Oceans Canada (DFO) who have been monitoring the eelgrass and fish populations for decades.<\/p>\n\n\n\n

In the early 1990s one of the world\u2019s largest fisheries collapsed. A 1992 moratorium on cod fishing cost more than 30,000 jobs in Newfoundland. The Atlantic cod population had been mismanaged and was severely overfished. In the nearly 30 years since then, the population hasn\u2019t returned to levels where commercial fishing can operate as it once did. Having ample seagrass habitats in which juveniles can hide and feed is one key to increasing cod numbers.<\/p>\n\n\n\n

\"tortue
Une tortue de mer verte rencontre par hasard un chercheur d'herbes marines aux Bahamas.<\/figcaption><\/figure>\n\n\n\n

Many of the world\u2019s major fisheries species depend on seagrass at some point in their life cycle. About 70 percent of the fishery species in Florida, for example, spend some time in seagrass.2<\/sup><\/p>\n\n\n\n

Comme les bonnets, les cabillauds de l'Atlantique sont timides avec les gens. J'ai install\u00e9 mon appareil photo sous-marin sur un tr\u00e9pied devant une zone luxuriante d'herbes marines et j'ai recul\u00e9, tandis que ma main gel\u00e9e saisissait le d\u00e9clencheur \u00e0 distance.<\/p>\n\n\n\n

A tiny Atlantic cod would occasionally flit in front of my lens, and I\u2019d snap a picture. I joked with the team between dives and sips of hot chocolate how I was on my way to sunny Spain after this, simultaneously attempting to warm them up and make them jealous.<\/p>\n\n\n\n

Off the Spanish coast of the Mediterranean Sea, I swam among one of the oldest and largest seagrass species on the planet \u2014 Posidonia oceanica<\/em>. The plant\u2019s root system is connected beneath the seafloor and stretches for more than 9 miles (14.5 km). Scientists estimate this organism could be up to 200,000 years old. The species is slow to recover from loss and has declined due to climate change and other human activity. Researchers are gathering data on its loss and areas where it is not declining, hoping that a better understanding will help reverse the trend.<\/p>\n\n\n\n

\"Cicatrices
Les cicatrices d'h\u00e9lice, comme celles-ci dans les Keys de Floride, peuvent couper les racines et infliger des dommages \u00e0 long terme \u00e0 la prairie.<\/figcaption><\/figure>\n\n\n\n

Les herbiers marins sont en d\u00e9clin dans le monde entier. Certaines estimations font \u00e9tat d'une perte globale allant jusqu'\u00e0 7 % par an au cours des ann\u00e9es 1990 et au d\u00e9but des ann\u00e9es 2000.3<\/sup> Des facteurs tels que la pollution, le d\u00e9veloppement c\u00f4tier, la diminution de la clart\u00e9 de l'eau, certaines pratiques de p\u00eache, d'amarrage et de navigation, et, bien s\u00fbr, le changement climatique, sont parmi ceux qui contribuent au d\u00e9clin.<\/p>\n\n\n\n

In May 2019 I joined a team of volunteers and researchers from the Virginia Institute of Marine Science (VIMS) as they continued a 20-year seagrass restoration project using a technique developed by VIMS professor Robert \u201cJJ\u201d Orth, Ph.D. His seeding system is incredibly effective and has reestablished more than 9,000 acres of healthy eelgrass that has shown signs of developing into a full ecosystem. This method may be promising for regrowth elsewhere, but protecting what we still have should be the priority.<\/p>\n\n\n\n

On ne saurait trop insister sur les avantages de la protection des herbiers marins. Les herbiers marins purifient l'eau, contribuent \u00e0 la protection contre l'\u00e9rosion c\u00f4ti\u00e8re, aident \u00e0 maintenir les p\u00eacheries \u00e0 petite \u00e9chelle qui soutiennent les communaut\u00e9s, et augmentent les populations de poissons et la biodiversit\u00e9. Elle s\u00e9questre beaucoup plus de carbone par surface que les for\u00eats terrestres et r\u00e9duit l'acidification des oc\u00e9ans. Des herbiers marins en bonne sant\u00e9 sont synonymes d'un oc\u00e9an plus sain.<\/p>\n\n\n\n

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A volunteer with the Nature Conservancy grabs a handful of eelgrass flowering shoots to gather seeds for the world\u2019s largest seagrass restoration project.<\/figcaption><\/figure>\n\n\n\n

With so much going for it, why aren\u2019t dive tourists flocking to explore seagrass meadows? I\u2019ve encountered toothy sharks and crocodiles, lovable dugongs and turtles, amazing seahorses and octopuses, strange lumpfish and horseshoe crabs, and many others among seagrass.<\/p>\n\n\n\n

Back in Florida, a single bonnethead shark eventually swam up to my camera, took a quick look and disappeared. I had one usable photograph after nine days of patience. I never found my key. A crab probably dragged it down one of the many nearby holes \u2014 perhaps it was a bit of revenge from nature. If we let ourselves destroy too much of nature, I worry about its revenge against all of us. Let\u2019s do what we can to protect our seagrass \u2014 that\u2019s one key we don\u2019t want to lose.<\/p>\n\n\n\n

Notes<\/strong><\/h5>\n\n\n\n

1. Leigh SC, Papastamatiou YP, German DP. Seagrass digestion by a notorious \u2018carnivore.\u2019 Proceedings of the Royal Society B. 2018; 285(1886). doi.org\/10.1098\/rspb.2018.1583. royalsocietypublishing.org\/doi\/full\/10.1098\/rspb.2018.1583<\/a><\/em><\/p>\n\n\n\n

2. Importance des herbiers marins. Florida Fish and Wildlife Conservation Commission (Commission de conservation de la faune et de la flore de Floride). myfwc.com\/research\/habitat\/seagrasses\/information\/importance<\/a><\/em><\/p>\n\n\n\n

3. Salinas C, Duarte CM, Lavery PS, et al. Seagrass losses since mid-20th century fueled CO2<\/sub> provenant des stocks de carbone du sol. Biologie du changement global<\/em> 2020; 26(9):4772\u20134784. doi.org\/10.1111\/gcb.15204. onlinelibrary.wiley.com\/doi\/full\/10.1111\/gcb.15204<\/a><\/em><\/p>\n\n\n\n

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En savoir plus<\/strong><\/h2>\n\n\n\n

Regardez cette vid\u00e9o pour en savoir plus sur le r\u00f4le des herbiers marins dans le changement climatique.<\/p>\n\n\n\n

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