Rapid Spread of the Invasive Brown Alga Rugulopteryx okamurae in a National Park in Provence (France, Mediterranean Sea)

Abstract

The temperate Northwest Pacific brown alga Rugulopteryx okamurae (Dictyotales, Phaeophyceae) was first discovered in 2002 in the Mediterranean Sea in the Thau coastal lagoon (Occitania, France) and then again in 2015 along the southern side of the Strait of Gibraltar, where it was assigned with invasive status. We report here on the first occurrence of the species in the Northwest Mediterranean Sea in Calanques National Park (Marseille, France) in 2018. By 2020, a large population had developed, extending over 9.5 km of coastline, including highly protected no-take zones. The seafood trade, with R. okamurae used as packing material for sea urchin Paracentrotus lividus shipments from Thau Lagoon, could be the vector of its introduction into the Marseille area. As observed in the Strait of Gibraltar, R. okamurae is spreading rapidly along the Marseille coasts, suggesting an invasive pathway. The subtidal reefs are densely carpeted with R. okamurae, which overgrows most native algal species. Fragments of the alga are continuously detached by wave actions and currents, sedimenting on the seabed and potentially clogging fishing nets, and thus, impacting artisanal fishing or washing up on the beaches, where they rot and raise concern among local populations.

The invasive brown seaweedRugulopteryx okamurae(Dictyotales, Ochrophyta) continues to expand: first record in Italy

“…The fact that the first records of R. okamurae in Sicily have been found very close to an important port strongly support this explanation. The species could have been introduced through ballast water from other points in the Mediterranean that share shipping routes with the port of Palermo or may be the destination of fishing activities carried out in other invaded areas of the Mediterranean, like Marseilles, where R. okamurae is well established (Ruitton et al 2021). Also in this case, the results of the favorability model support this second hypothesis, since proximity to fishing ports, although it was the last variable to enter the model, contributes to explaining the current distribution of the species.…”

“…The first record as an invasive species was on the Spanish coast of the Strait of Gibraltar in 2016 (Altamirano et al 2016, 2017), on the African coast (Ceuta, Spain) and then on the European coast. Since then, the species has been spreading both towards the Mediterranean Sea and the Atlantic Ocean, being already present other than in Spain (Altamirano et al 2016; García Gómez et al 2020), in Morocco (El Aamri et al 2018), Portugal (Liulea et al 2023) and France (Ruitton et al 2021), having even reached different Macaronesian islands such as the Azores (Faria et al 2021), Madeira (Bernal-Ibáñez et al 2022) and the Canary Islands (REDEXOS 2022). Its limit in the Mediterranean is currently found on the coast of Marseilles, in France (Ruitton et al 2021).…”

“…Since then, the species has been spreading both towards the Mediterranean Sea and the Atlantic Ocean, being already present other than in Spain (Altamirano et al 2016; García Gómez et al 2020), in Morocco (El Aamri et al 2018), Portugal (Liulea et al 2023) and France (Ruitton et al 2021), having even reached different Macaronesian islands such as the Azores (Faria et al 2021), Madeira (Bernal-Ibáñez et al 2022) and the Canary Islands (REDEXOS 2022). Its limit in the Mediterranean is currently found on the coast of Marseilles, in France (Ruitton et al 2021). The species has a high capacity for vegetative proliferation as well as for dispersal, which gives it a high capacity to produce large amounts of biomass that can be moved by currents (García-Lafuente et al 2023; Mateo-Ramírez et al 2023) or helped by human vectors such as fishing or maritime transport (MITECO 2022), and which can end up forming important wracks on the coasts.…”

A Concise Review on the Potential Applications of Rugulopteryx okamurae Macroalgae

“… ( a ) R. okamurae brown macroalgae growing in Mediterranean Sea (adapted from [ 21 ], published by MDPI in 2021 with CC BY 4.0 permission). ( b ) Photograph of R. okamurae alga collected from the coast of São Miguel Island, with brightfield microscopic micrographs being taken to highlight details of the different regions of the alga.…”

The Impact of Sargassum Inundations on the Turks and Caicos Islands

“…A similar situation has been reported from Provence, France, where the benthic algae Rugulopteryx okamurae has increased, forming large floating mats that inundate beaches. The main impacts there are on fisheries who have lost catch due to clogged nets, and the hydrogen sulfide (H 2 S) produced by the rotting algae causing concern to local residents and water users [33]. In China, a bloom of Ulva prolifera occurred a few weeks before the Olympic sailing competition, leading to extensive clean-up efforts and losses for aquaculture operations [34,35].…”