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

Sandrine Ruitton,Valérie Michotey,Marc Verlaque,Delphine Thibault,Dorian Guillemain,Sylvain Roblet,Thierry Thibaut,Charles-François Boudouresque,Aurélie Blanfuné

doi:10.3390/w13162306

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.

Highlights

Non-indigenous species (NIS) are a part of global change
The Mediterranean Sea is considered the worldwide hotspot of biological invasions; it harbours almost 1000 NIS, more than 600 of which are definitively established [1,2,3,4]
They originate from different source regions, both warm waters and cold waters [5,6]

Summary

Introduction

The Mediterranean Sea is considered the worldwide hotspot of biological invasions; it harbours almost 1000 NIS, more than 600 of which are definitively established (introduced or invasive) [1,2,3,4] They originate from different source regions, both warm waters (e.g., the Red Sea) and cold waters (e.g., the Northwest Pacific) [5,6]. In view of the extent of the colonized area when it was discovered, totalling a dozen kilometres of shoreline, its introduction probably preceded 2002 This first in European waters in 2002, in the coastal lagoon of Thau (Occitania, France, Mediterra nean, [10]). This first intro duction is probably linked to the oyster farming facilities of Magallana giga2s o(fT1h1 unberg

Methods

Results

Conclusion