The lung of phanerogams under the water of Pals bay

Everything that happens above the ground is clearly visible: when it blooms, when it changes, when it ceases to be. We are told that the forests we walk through produce the oxygen we breathe, and we understand the importance of protecting them when we see the greenery vanish before our eyes. We are shown an image of how far the forest once stretched, and nostalgia stirs within us.

You can open your eyes underwater as you dive in the Gulf of Pals, yet you'll still see sand stretching to the horizon. And what if I told you that your parents didn't see the same underwater desert as you?

Let us go back further, to the close of the Mesozoic, 120 million years ago. A group of plants ventured to the seabed of the oceans to populate it with large settlements known by the names of Posidonia cretacea, Achaeozostera and Thalassocharis.

Although some fanerogamous plants abandoned their land-dwelling habits, the underwater environment did not prevent them from retaining roots, stems, leaves and flowers. But the new aquatic medium drove adaptation strategies, and today we can fortunately count between fifty and sixty species of these primitive plants.

Some of these live on the Costa Brava. Within Pals Beach and the Natural Park we currently find submerged fanerogam meadows, a priority Community interest habitat, on the coast of Montgrí (at cala Montgó, cala Ferriol, La Foradada and Cala Pedrosa), on the Medes Islands and in areas of l'Estartit, and on Racó Beach and the Red Island in Begur, and seagrass meadows of Cymodocea nodosa or gram from Estartit to the mouth of the Daró Vell River in front of the Basses d'en Coll, parallel to the coast. This meadow once stretched across the entire Pals Gulf to Racó, but it has suffered severe regression in recent decades and has almost disappeared from the Peripheral Protection Zone of the seabed of the Montgrí Natural Park, the Medes Islands and the Lower Ter.

But at Pals Beach you will have to imagine for yourself immense underwater meadows, fans of leaves brushing your dives alongside a great diversity of crustaceans, molluscs, algae, sponges, echinoderms (crabs) and fish swimming around you such as sardines, sea bass, bream, wrasses or scorpionfish. The seagrass meadows provide habitat, shelter and food for all these species.

Open your eyes wide, the fanerogams are in danger

Several phenomena are favouring the regression of phanerogamous grasslands:

The mechanical effects arising from marine dredging and excessive fishing activity., especially of trawling, of poorly aware fishermen's associations, which could apply techniques to minimise the negative impact of their activity, such as pelagic gate trawling.

The brutality of these practices not only damages sandbanks but also irreversibly harms the species living buried in the sand, the seagrass meadows, crustaceans and molluscs on the seabed; moreover, it destroys the rhizomes of the phanerogams, increases dune mobility and erosion. Although marine seagrass meadows are not found at depths below 30 metres, a depth at which bottom trawling and other industrial fishing methods (encircling or longline) do not take place, poor practices and excessive proximity to the shore often occur, damaging the meadows.

The continuous emission of pollutants, the excessive discharge of organic matter and nutrients from the River Ter, the former Daró and the rice paddies degrade the water and increase its turbidity at Pals Beach, making it difficult for light to reach the seabed for photosynthesis.. Contaminated waters do not promote the growth of meadows, as they require clean, low-nutrient water. The reduction of meadows compromises water quality, since they are genuine purifiers: they filter suspended particles and fix carbon and nitrogen.

The growing maritime traffic and coastal modification. The alteration of the coastline by the construction of infrastructure such as ports and breakwaters results in a reduction of habitat and a modification of sediment transport.

The mooring of vessels. In recent years, anchoring of vessels on the seagrass meadows of the Medes Islands and the coves of Montgrí has been prohibited, and buoys have been installed for vessels. The rest of the areas in the Pals Gulf that are in decline, such as the eelgrass meadow off the Gola del Ter, Mas Pinell, the Basses d'en Coll or Radio Liberty, or the seagrass meadows at the beach of the Grau, remain unprotected. In this link You can find a best practice guide.

The greater frequency and virulence of storms. The increase in the frequency and intensity of storms is accompanied by an increase in seagrass erosion, which negatively affects the seagrass beds, especially if they are already fragmented.

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The difficulty of maintaining the integrity of the seagrass during a violent storm such as Storm Gloria (15–25 January 2020) at Pals Beach is dramatic. Usually the impact is quite significant. It is precisely the seagrass meadows that protect the coast from storms and control erosion and sedimentation on the seabed.

The submerged fanerogam meadows give us

Each organism has a fundamental role forged over thousands of years within the ecosystem to which it belongs, and when it disappears, the great web adapts to keep breathing. Discover the exceptional qualities of phanerogamic meadows and how they contribute to the balance of what happens both below and above sea level, however strange that may seem to you:

A meadow of underwater vascular plants releases up to 20 litres of oxygen per day and square metre., while absorbing the carbon dioxide that so greatly contributes to global warming.

This large plant concentration produces biomass for other ecosystems.. Biomass provides shelter and is a safe breeding ground for many fish, cephalopods, gastropods, echinoderms and a long list of other marine species. A no less important portion of biomass reaches the beaches and contributes to terrestrial ecosystems.

Seagrass and eelgrass meadows stabilise the seabed. They counteract the movement of sediments caused by coastal currents. They weaken wave forces and reduce coastal erosion, especially during autumn and winter storms.

Fanerogams have very slow growth, with their rhizomes increasing by approximately one centimetre per year. For this reason, it is vitally important to preserve them.

The Drama of the Regression of Phanerogamous Grasslands

In the Mediterranean basin of the peninsula, by 2001 it was estimated that between 30 and 45 per cent of the seagrass meadow area had disappeared or was in an advanced state of deterioration. This plant is severely threatened and has been in decline since the mid-20th century.

At present there is still no complete or up-to-date bionomic mapping of the submerged coastline of Pals Beach, let alone of its evolution or the retreat of its fanerogamous meadow ecosystems, a basic tool for preventing their disappearance. We can only find the following studies with underwater maps that you can consult:

Mapping of the meadows of Cymodocea nodosa at Pals Golf Course – 2012

Bionomic mapping of the submerged coastline of the Medes Islands – 2011

Bionomic mapping of the submerged coastline of the Montgrí coast – 2010

It is unlikely we will ever again see seagrass meadow expanses on the seabed off Pals Beach as there were just a few decades ago, but we can help protect those that still remain scattered. For this reason We consider it necessary that a mapping of the entire Pals Gulf and the rest of the coastline be carried out urgently, along with a temporal monitoring programme from which appropriate protection measures can be taken.

Demand urgent protection for these habitats.

We need your support to prevent the regression of the phanerogamous grasslands at Pals Beach.

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We thank Alèssia Pons (biologist), Guillem Roca (Doctor of Marine Sciences) and the Friends of the Ant Islands in the writing of this article, who work tirelessly to alert us to the disappearance of posidonia, ghost fishing, the collateral effects of fishing gear, etc. We recommend following their work to stay up to date with everything happening both far out at sea and closer to shore, which, even after a dive, is hard to see and, above all, to understand.

Article creation date: 2 October 2022 – Last updated: 19 April 2022.

Header photograph by Alessiodl under a CC BY-NC-SA 2.0 licence.