Seagrass Halodule uninervis / Thick seagrass between the shore and the reef at Wakaya, Fiji / This image has been used under the creative commons licence on ScienceNetwork WA.

Song of the Seagrass

Seagrass, the ocean’s early warning system, may well be our secret weapon in the fight against climate change.

In the early twentieth century, coal miners would carry canaries in cages with them as they descended into the cavernous depths of mines. As long as the canaries kept singing, the miners would continue working. If the canaries stopped singing, it was usually because they had died, alerting the miners about the presence of carbon monoxide and other toxic gases.

In a way, our oceans also come equipped with their own canaries. And while corals may be the best known example, seagrasses are an important early warning system of underwater environmental degradation that we have ignored for far too long.

Although seagrasses are often mistaken for seaweed or algae, they have leaves, roots, and veins, and produce flowers and seeds. They photosynthesize just like their monocotyledon cousins: grasses, lilies, and palms. Seagrasses are found off the coast of every continent on Earth except Antarctica. There are seventy-two species of seagrasses which — aside from a few exceptions — flourish in shallow waters where sunlight is plentiful, at depths of 1 to 3 meters. Yet worldwide, seagrass beds are disappearing. Recent studies have estimated that globally, seagrass coverage is being lost at a rate of 1.5 percent per year. Alarmingly, that translates to approximately two football fields of seagrass lost each hour.

Another study estimates that 29 percent of seagrass meadowshave died off in the past century. It is a trend that Dr. Rahanna Juman, wetlands ecologist and deputy director of the Institute of Marine Affairs in Trinidad and Tobago, has observed firsthand.

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