On some beaches, it is common for algae and marine plants to wash up on the sand from the water by currents and waves, especially during storms. A scientific team, which includes an expert from CEAB-CSIC, has explained the ecological role of these remains. They did so in an article published in the journal Frontiers for Young Minds.

The arrival on the coast of remains of native marine plants (such as posidonia or Cymodocea) is a phenomenon that is part of the natural cycle and is important for the health of coastal ecosystems. However, it is often not perceived as such, but rather judged as “negligence”, as rubbish, which must be removed quickly.

In a scientific article in the journal Frontiers for Young Minds, marine ecology researchers, including Òscar Serrano from the CEAB-CSIC’s aquatic macrophyte group detail the ecological functions of these remains.

In the publication they begin by explaining that they are made up of dead marine plants, such as algae and marine plants. The amount that accumulates on beaches varies greatly throughout the world, from just 0.1 kg per metre of coast to more than 300 kg.

These remains originate in seaweed meadows – in seaweed meadows and in seaweed forests. The leaf litter is carried to the coast by the tides, waves and wind, and is deposited on the sand or returns to sea. At each moment of this “journey”, the remains perform a series of functions that are key to maintaining coastal ecosystems in good condition.

The importance of these remains of marine plants

– Home: one of its “functions” is to be a home and/or refuge for small animals, mostly invertebrates, such as isopods and amphipods, crustaceans that look similar to shrimp. Fly larvae and other insects are also found there, as well as numerous microorganisms. It becomes an excellent home as it provides security against many predators and protects against difficult conditions such as, for example, excessive temperature or solar radiation. Some of these organisms live only in these remains, so respecting them is the only way to preserve these species.

– Food: Most of the animals that live in these remains are detritivores, which means that they love to eat dead plant material (detritus). The fact that it is moist and contains microorganisms makes the process easier for them. Bacteria and fungi, among others, in addition to breaking down the detritus making it more digestible, become another source of food for the detritivores. In turn, these small animals that feed on the remains of marine plants become food for other organisms such as beetles or spiders that live in the sand, fish in the water and even birds that frequent these areas. These remains therefore support an entire food network on the beach and in shallow waters.

– Fertilizer: when they decompose they also become food. The nutrients end up reaching terrestrial environments or returning to the sea, enriching and helping to keep these ecosystems in good condition. They therefore contribute to the birth and growth of more plants and animals, to keeping the environments alive and healthy.

– Natural barrier: if left on the beach, these remains help to minimise erosion and protect the coastline from storms.

Despite the clear ecological importance of this vegetation that reaches the sand, these remains are often not appreciated. With the mistaken idea that a healthy beach is a white beach without any “obstructions”, they are often removed, even using heavy machinery, causing a negative impact on ecosystems, and without even giving any practical use to all the removed material. A way of doing things that should be avoided whenever possible.

Fortunately, there are more and more municipalities (in the Balearic Islands and in other parts of the Catalan countries we have numerous examples) that respect the recommendations derived from scientific evidence and choose NOT to remove dead posidonia leaves or the remains of other marine plants, taking into account that beaches are natural habitats, spaces of transition between water and land that are dynamic and at the same time also very fragile.

The exception to the recommendation not to remove these remains is when, in specific points, huge quantities accumulate in very high smoking mountains – due to the gases arising from the decomposition process. In these cases, removal ends up being necessary, but it must be carried out in the right measure and with methods of minimum impact, which avoid damaging the environment. Also, trying to give another use to this vegetation. Very often, the enormous accumulations are the result of the breakdown of the balance produced by human activities that cause the death of our seaweeds, as well as the uncontrolled proliferation of invasive species such as the algae aisática that has spread unchecked along the Andalusian coast.

Read the entire scientific article, here.