Open Google Earth, enter the coordinates 54°43’04″S 71°39’03″W or 46°20’36″S 51°44’49″E and press the enter key. We are in Chilenear the Alberto de Agostini National Park or on thePossession Islandthe island of the sub-Antarctic archipelago of the Crozet Islands. Now zoom in a bit and try to answer the question: what are those ribbon-like things that seem to float on the surface of the sea? Someone must have thought of making a videowhich has become viral on social networks. Whether they are banks of fish or huge mammals marine close to the coast? Of course they are not sirensnor any mythological creature. In fact, taking a look at the scientific literature, the answer is clear. What from a satellite appear as emerging filamentous clusters are huge expanses of kelp. Let’s see in detail what these algae are and how it is possible that they are visible from Google Earth.
What are kelp and where are they found?
The kelpalso called giant kelp, it’s abrown algae large in size that grows close to the coast in salty, shallow, nutrient-rich waters. There are about 30 species different types of kelp around the world (the most common belonging to the genera Macrocystis, Nereocystis, Laminaria, Lessonia, Saccharin, Alaria, Ecklonia) distributed mainly in the temperate-cold areasThey are easily found along the Pacific, Arctic and Northern European coasts, and also grow in the Southern Hemisphere along the coasts of Chile, Southern Africa and Australia where They form enormous and very important marine ecosystems.
These algae can reach truly impressive lengths: from 6 to 53 meters. This allows them to skillfully reach the surface of the water and develop horizontally (see image with diagram). As a result, you can see these enormous expanses of very long algae even from Google Earth.
The fronds of these “giant” algae when they reach the ocean surface they can be easily seen from low-altitude aerial platforms although it is not always possible to distinguish them clearly. Factors such as the reflection of the sunthe presence of waves, sediments, dissolved organic matter or phytoplankton blooms can contribute to water reflectance and alter outputs and interpretation.
These dense floating crowns visible on the surface are anchored to the ground to form algal columns similar to enormous underwater cathedralswhich exploit sunlight to grow and spread in the three-dimensionality.
Along the Chilean coasts the most abundant kelp species is Lessonia trabeculata known locally as huiro pole. It is a habitat and refuge for over 150 species including many elasmobranchs (sharks and rays) that use these vertical structures as a site for spawning.
The most widely distributed species of seaweed on the planet is, however, Macrocystis pyriferacommonly called giant algae: extends from the temperate and subpolar coasts of South America, western North America, South Africa, Australia, New Zealand, to the South Atlantic.
Although they extend almost as far as the eye can see and, given their size, are quite easy to observe with the naked eye, in some marine ecoregions consistent and detailed data is still missing on the distribution of kelp forests, especially at high latitudes in the Southern Hemisphere.
Why are kelp forests important?
Kelp forests grow in dense clumps, forming structures equivalent to terrestrial forests. They extend from the depths towards the surface creating immense underwater “columns” that become habitats for a large number of species. Kelp forests, in addition to being a very important primary energy sourcethey are some habitat formersecosystem engineers: they create the three-dimensional space and the suitable substrate for organic colonization. They modify and protect the seabed and the water column surrounding area as well as increasing the complexity and sustenance of the food webs marine and coastal.
I am among the most diverse marine ecosystemshosting an enormous biodiversity on both the animal and plant fronts. The seabed beds as well as the “foliage” canopies become a place of refuge, protection, feeding and nursery for fish, sea otters, seals, crabs, sea urchins and other invertebrates. Not to mention the birds and the importance that these algae also have for humans.
Underwater forests offer a wide variety of benefits, better known as ecosystem services: They are the habitat of commercially important fish species and provide the development of raw materials sought after by the food and pharmaceutical markets. They are used for the production of fish and livestock feed, cosmetics and as food in traditional and modern cuisine. They produce oxygen and store carbonremove nitrogen and regulate nutrient supply.
The Kelp Trade
There kelp harvesting It is legally regulated, but there are no specific restrictions on the morphological characteristics to be considered: if at a commercial level this condition can be considered irrelevant in some cases, it can have an important impact on the organic communities that base their survival on marine forests.
In addition to trade, the overfishing, pollution And rising sea temperatures affect the survival, abundance and density of kelp, as well as imbalances in the marine food web. It has been estimated that over the last 50 years these factors have led to a 40-60% damage to kelp forests.
Of the total kelp harvested annually (which has a global economic contribution of US$500 billion), much of it is used in production of medicines, cosmetic products (shampoo, toothpaste), condiments and foods (sweets, puddings, dairy products). Alginate, a substance naturally produced by seaweed, is in fact used as a stabilizer. Kelp is also used as a feed in the farmed fisheries sector.
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