News | 23 November 2023

The BioMARathon detects 34 invasive species, 40 protected species, and the unprecedented presence of the west African fiddler crab on the Catalan coast

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This citizen science event tripled observations in its third year, surpassing 60,000 photographs and species identifications. 

The observations are now accessible to the entire scientific community / CC BY-NC 4.0 DEED Xavier Salvador (MINKA).
The observations are now accessible to the entire scientific community / CC BY-NC 4.0 DEED Xavier Salvador (MINKA).

This year's BioMARathon has detected a total of 34 invasive species, 40 protected species, and the unexpected presence of the West African fiddler crab (Afruca tangeri), not previously seen on the Catalan coasts. The total observations along the Catalan coast have exceeded 60,000, three times more than the previous year, solidifying it as one of Catalonia's most successful citizen science events.

The activity has been supported by scientists from the Institut de Ciències del Mar (ICM-CSIC) to validate and analyze observations of various marine species submitted by over 300 volunteers. The images, with corresponding geolocation and validated species identification, have been published on the citizen science platform MINKA, providing access to the entire scientific community.

The positive results of the three editions held so far have led to the creation of one of Catalonia's most extensive marine biodiversity databases, documenting the appearance of new species on the Catalan coasts. Over these three years, a total of 1,900 marine species have been cataloged, indicating significant marine biodiversity along the Catalan coast. This achievement would not have been possible without the help of the public, highlighting the significant impact of citizen science on advancing knowledge and research.

Invasive and Protected Species on the Catalan Coast

Out of the 1,440 species recorded during this year's BioMARathon, 34 are invasive. Additionally, a specimen of the West African fiddler crab (Afruca tangeri), previously only seen near the Strait of Gibraltar, has been observed in Catalonia for the first time, penetrating deeper into the Mediterranean basin.

Regarding invasive species, notable mentions include the green alga Caulerpa cylindracea, gradually spreading to new areas, and the appearance this year along the Catalan coast of the species Asparagopsis taxiformis, a red alga typically found in the southern peninsular coast but proliferated in certain areas of Catalonia. Experts suggest both could pose a threat to native species by competing for space and resources. Specifically, Caulerpa cylindracea poses a threat to the Posidonia meadows, Cymodocea nodosa, and Zostera noltei.

The BioMARathon also captured images of 40 protected species, including various rays such as the undulate ray (Raja undulata) and the mobula ray (Mobula mobular), categorized as endangered by the IUCN and included in various international directives. Other protected species include the red coral (Corallium rubrum), heavily affected by water warming and currently regulated in exploitation. Finally, several protected seagrasses were identified, playing a crucial role in ecosystem formation, erosion prevention, and carbon dioxide storage.

Additionally, the BioMARathon facilitated the collection of information on rarely observed marine species near the coast, such as the bluntnose sixgill shark (Hexanchus griseus), several specimens of which were stranded on the beach, likely due to accidental capture. The common dolphin (Tursiops truncatus) was seen hunting just meters from the beach in Gavà, and an instance of the loggerhead sea turtle (Caretta caretta) laying eggs on the beach was identified.

Finally, this year's results highlight the impact of soft coral colonies such as the sea fans Eunicella singularis and Paramuricea clavata due to prolonged and intense marine heatwaves this summer. These findings align with those obtained by the citizen science platform Observadores del Mar, also coordinated by ICM-CSIC.

BioMARathon: Beaches Teeming with Life

The BioMARathon is a citizen science event aimed at monitoring marine and coastal biodiversity in Catalonia through a friendly competition between the provinces of Girona, Barcelona, and Tarragona. From April to October 2023, various snorkelling and diving activities were organized in these provinces to photograph as many living beings as possible, regardless of knowing to identify the species and upload the images to the MINKA citizen science platform.

In Barcelona's case, the collected observations will update marine biodiversity information in the Barcelona City Biodiversity Atlas and create a new layer for molluscs and crustaceans in this atlas.

The BioMARathon results, involving also the Catalan Federation of Underwater Activities FECDAS), Anèl·lides – Serveis ambientals marins, Plàncton Diving, and European projects MINKE, ANERIS, ECS and GUARDEN, will be officially presented at an online event on November 30. The event will showcase the impressive biodiversity of the Catalan coast and identify the challenges facing the Catalan marine ecosystem.