Ernest Hemingway knew how to make seaweed sexy. In his classic, The Old Man and the Sea, he describes an encounter with a particular macroalgae: “they passed a great island of Sargasso weed that heaved and swung in the light sea as though the ocean were making love with something under a yellow blanket,...”

Sargasso, that sultry seaweed portrayed by Hemingway, covered Inkwell and State beaches last weekend. The sustained onshore winds pushed piles of the plant onto the beach where it blanketed the sand.

Appearing as piles of small round beads, the question of whether those were eggs of some marine species or seeds from maritime plant was asked by my sidekick. Neither. Those are air bladders, called pneumatocysts, and are an integral part of sargassum. These gas-filled pockets provide buoyancy to the algae so that it can float in ocean waters. Being at the sea’s surface allows for photosynthesis, which provides the plant’s food and energy.

Normally afloat, sargassum travels with the tides and currents and is usually found in mats or masses of individual plants. The largest mats are most commonly found in more southern areas, especially around the Sargasso Sea, the weed’s namesake.

Marine biologist Sylvia Earle called those expansive carpets of sargassum a “golden floating rainforest” due to their importance as habitat for many other organisms. More than one hundred species call sargassum mats home including fish, crustaceans, invertebrates and even baby sea turtles, which use them for shelter and to acquire foodstuff hidden among the algae’s leaves and bladders.

The last fact was particularly ironic, since my reason for being on the beach was to examine a deceased leatherback turtle that had washed up in the swashline below the wrack of sargassum. The solemn moment had me imagining the weed protecting the turtle as a youngster and, now, providing shelter at its end of life.

The word Sargasso reputedly hails from a Portuguese root sarga, a type of grapes, describing those pneumatocysts. Even with that origin, don’t think that this seaweed is purple. As a brown alga, it ranges through the brown hues from light tan to dark chocolate shades.   

A variety of floating and sessile sargassum species exist, though differentiating them can be challenging. Also called gulf weed, the washed-up masses can be problematic when they overwhelm a beach and begin to rot, causing odor and unhappy beachgoers.

Some intrepid foragers claim that this is an edible seaweed, offering varied suggestions for ways to eat and enjoy what is likely a very salty sidedish. Fresh, cooked, pickled, smoked and dried are all methods offered up. However, the fact that it is described as bitter and an “acquired taste” says enough for me to assume that it might be a delicacy worth declining. And a warning that this seaweed can be dangerous if covered with toxic blue-green algae sealed the deal.

Sargassum can reproduce sexually (with floating sperm contacting an attached ova) or by fragmentation. Its cells are totipotent, meaning that any fragment can regenerate into an entire plant. So, as racy as Hemingway’s description was, the reality is much more G-rated, innocent and wholesome.

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature and The Nature of Martha’s Vineyard.