Por qué proteger esta planta marina que está desapareciendo es fundamental en nuestra lucha por salvar el clima y la biodiversidad.

Levanté la roca y mi llave había desaparecido. Era un mediodía de julio y el calor de los Cayos de la Florida era agobiante. Estaba empapado y tenía algas marinas en el cabello. Mi teléfono, billetera, agua potable, llave del hotel, gafas de sol y todo lo demás, con excepción de mi traje de baño mojado y mi cámara submarina, estaban en el caluroso automóvil de alquiler, que estaba cerrado. Sabía que había puesto el llavero allí, y había estado observando el área desde el agua. Nadie podría haberla tomado y me preguntaba, incrédulo, dónde demonios podría estar.

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’s first known omnivorous sharks. A central question facing scientists was how much of the seagrass nutrient content the sharks were taking in.

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’ 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’ nutrient intake meant we would “need 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.”¹

Los tiburones consumidores de plantas son solo un ejemplo de cómo la ciencia cambia nuestro parecer de los pastos marinos y pone de manifiesto su importancia.

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 — some Zostera marina crece en el Ártico y puede sobrevivir bajo el hielo.

A few weeks before I ended up keyless in the Florida heat, I was wearing a drysuit but still shivering in 35°F (1.7°C) 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.

In the early 1990s one of the world’s 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’t 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.

Many of the world’s 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

Al igual que los tiburones cabeza de pala, los bacalaos del Atlántico son tímidos cuando hay personas. Preparé mi equipo fotográfico submarino en un trípode en frente de una exuberante área de pastos marinos y me alejé, y con la mano congelada agarré el disparador remoto.

A tiny Atlantic cod would occasionally flit in front of my lens, and I’d 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.

Off the Spanish coast of the Mediterranean Sea, I swam among one of the oldest and largest seagrass species on the planet — Posidonia oceanica. The plant’s 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.

Los pastos marinos están disminuyendo en todo el mundo. Algunas estimaciones sugieren una pérdida total de hasta un 7 por ciento al año durante la década de 1990 y principios de la década de 2000.³ Factores como polución, desarrollo costero, menor claridad del agua, algunas actividades de pesca, acciones de amarre y prácticas de navegación, y, desde luego, el cambio climático, se encuentran entre aquellos que contribuyen a la disminución.

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 “JJ” 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.

Los beneficios de proteger los pastos marinos no deben subestimarse. Los pastos marinos purifican el agua, ayudan a proteger contra la erosión costera, ayudan a mantener las pesquerías de pequeña escala que sustentan comunidades y aumentan las poblaciones de peces y la biodiversidad. Absorben mucho más carbono por área que los bosques terrestres y reducen la acidificación del océano. Tener pastos marinos saludables se traduce en un océano más próspero.

With so much going for it, why aren’t dive tourists flocking to explore seagrass meadows? I’ve encountered toothy sharks and crocodiles, lovable dugongs and turtles, amazing seahorses and octopuses, strange lumpfish and horseshoe crabs, and many others among seagrass.

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 — 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’s do what we can to protect our seagrass — that’s one key we don’t want to lose.

Notes

1. Leigh SC, Papastamatiou YP, German DP. Seagrass digestion by a notorious ‘carnivore.’ 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

2. Importance of seagrass. Florida Fish and Wildlife Conservation Commission. myfwc.com/research/habitat/seagrasses/information/importance

3. Salinas C, Duarte CM, Lavery PS, et al. Seagrass losses since mid-20th century fueled CO₂ emissions from soil carbon stocks. Global Change Biology 2020; 26(9):4772–4784. doi.org/10.1111/gcb.15204. onlinelibrary.wiley.com/doi/full/10.1111/gcb.15204

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Explore más

Mire este video para obtener más información sobre la función de los pastos marinos en el cambio climático. https://youtu.be/zY2WCPwkmog

© Alert Diver — Q3/Q4 2021