The undulating “forests” of the sea

Hidden beneath the waves, marine “forests” are vital ecosystems for life in the oceans and to balance the planet’s climate. Composed mainly of giant algae such as kelp, these underwater “forests” are as important as their counterparts on dry land. Get to know them better.

Along the Portuguese coast, the “forests” of the ocean swing sumptuously at a great distance from unsuspecting bathers. Nothing more, nothing less than an amalgam of the famous kelp, an English word that means large brown algae belonging to the order Laminariales – an order with the largest presence in Europe – with an illustrious list of names such as laminaries, sargassum, slime-belt or golf. With about thirty known genera and seven species spread like a marine jungle throughout Portugal: Laminaria hyperborea, Laminaria ochroleuca, Saccorhiza polyschides, Saccharina latissima, Phyllariopsis brevipes, Phyllariopsis purpurascens and an invasive Japanese algae known as Undaria pinnatifida. 

Kelp is formed in cold water coastal areas, with temperatures below 20 degrees, where it is not only possible to add a vast wealth of nutrients but also to receive consistent sunbathing. This combination of cold and heat favours the creation of life and helps the flowering of these algae.

But despite the strands of light falling on the water, these forests look like something out of an aquatic horror movie. However, this notion could not be further from reality, and the most astonishing confrontation takes place with funny and intrigued seals. More importantly, these places are extremely versatile and peaceful, true “forests” that protect, provide food and serve as a basis for several marine inhabitants to reproduce in privacy.

The “algaeritm”

This ocean maternity develops in relatively shallow waters with plenty of sunlight. The more turbid the water, the more complicated the process of photosynthesis. In addition to this ability to manage and foster small ecosystems, kelp is extremely effective in capturing and fixing carbon dioxide in the atmosphere, releasing only oxygen, identical to the process that occurs in true forests on land. They excel in efficiently retaining nutrients in the water, helping to reduce the acidity of the seas and mitigate the impact of waves on the coast, thereby slowing rock erosion.

These algae are the point of origin and extraction for products used in the food, pharmaceutical, cosmetic or even fertiliser industries.

This is an essential species for the entire ecosystem, and it is important to understand it and the way it reproduces and spreads to form habitats.

Although algae can be considered plants, in essence, they do not reflect the physicality of the species we know at the terrestrial level.

Without any roots, stems, leaves or flowers, kelp have blades, stipe and a base. To better understand this by visual association, the blades are the leaves, the stem, and the base is the structure next to the soil, attached to the rocky bottom. But, unlike terrestrial plants, this base doesn’t have the ability to absorb nutrients from the soil.

The blades with their flat formations absorb nutrients and perform photosynthesis, retaining carbon dioxide and other mineral salts to produce new organic matter, simultaneously creating biomass and oxygen. Growth takes place at the base of the blades, taking advantage of the tissues of perpetual division, renewing from the bottom up. In other words, the extremities are always the oldest and most worn areas.

The reproduction of these algae is visible only to the “microscopic” eye, with the elements called phase, composed of a few cells that we can call spores. Some spores turn into male gametes – spermatozoon – and others into female gametes – eggs – which, when united and attracted by a sex hormone, form a sporophyte that grows and becomes an algae visible to all.

Here at sea

Life in the algae can be as frenzy as a metropolis in rush hour. As we mentioned, it can be a safe and highly favourable place for the reproduction of the species, but also a frantic hunting ground, with a menu of the day always focused on seafood. Some of the tenants of these “cities” are sea bass, sea bream, wrasse, groupers, crabs or seals.

But as in any “city”, conflict can always be lurking. It is possible to witness algae hunting by a group of molluscs, such as the nudibranchs of the Polycera quadrilineata species.

Send kelp

With the advancement of pollution, climate change, overfishing and the invasion of exotic species, there is a need to revisit these mysterious forests and detail how best to preserve them and help maintain the natural balance.

Globally, efforts are being made to recover degraded areas of kelp forests, using assorted techniques such as algae replanting and improved water quality. Portugal has been following this trend since 2008. There are citizen science projects such as  FindKelp, in charge of bringing together a series of divers, underwater fishermen and professionals from the environment, in order to detail a map of the species of algae along the Portuguese coast. Through this cartographic process, methods are developed to understand the future development of these species.

There is a huge risk of kelp becoming extinct from the ocean, especially in Portugal, with serious consequences for the entire marine ecosystem, reducing not only carbon retention but also the ability to generate several species of fish. Fortunately, there is always a ray of sun touching the ocean floor, this time in the form of innovative projects such as  Seaforest Portugal, an organisation fighting relentlessly to achieve the goal of reversing this bleak prognosis, with a progressive methodology of algae planting that has been gradually implemented on the Portuguese coast.

What is this approach in practical terms? We have the example of the Alentejo coast: brown algae of the species laminaria ochroleuca were placed in bags, possessing some breeding dark spots. From here, they are expected to release seeds capable of sticking to the rocks and starting to generate new algae.

Another of Seaforest Portugal’s objectives is to create an awareness network in schools, diving centres and respective regional communities in the country, drawing everyone’s attention to the importance and function of brown algae. These scholars are also divers and tireless observers of the growth or decline of algae in the future of nature.

Did you know that…

• Kelp can grow and survive in places like Antarctica? Because of the icy waters that preserve many nutrients.
• It is an algae that grows very fast, about a centimetre a day.
• Rising temperatures, marine pollution, as well as fishing and physical damage from the use of nets by fishing activities, are preventing the growth of these algae and, therefore, the retention of nutrients.