Monitoring Extreme Impacts of Rugulopteryx okamurae (Dictyotales, Ochrophyta) in El Estrecho Natural Park (Biosphere Reserve). Showing Radical Changes in the Underwater Seascape

Abstract

The invasive macroalga Rugulopteryx okamurae represents an unprecedented case of bioinvasion by marine macroalgae facing the European coasts. Since the first apparition of the species in the Strait of Gibraltar in 2015, its fast dispersion along the introduced habitats constitutes a real challenge to develop monitoring strategies that ahead of its impacts. The present study uses three different approaches to address impacts on the benthic ecosystems, at the same time offers relevant data for future management actions in El Estrecho Natural Park (PNE). Information obtained by monitoring permanent sentinel stations revealed a significant loss in resident species coverage after the moment of maximum growth in 2017. Thus, despite coverage of R. okamurae did not strongly varied in the latter years, impacts generated remain high in the habitats studied. Estimations of the invasive species coverage by combining cartographic image analysis and in situ data predicted a major occupation (over 85% coverage) between 10 and 30 m, coinciding with the maximum rocky surface areas (m2) mapped on the PNE. Furthermore, a Citizen Science research collaboration evidenced impacts on the benthic seascape through an ad hoc exploration of images that allowed a “before” and “after” comparison of the invasion process in the same geographic locations. This has made it possible to graphically demonstrate severe changes in the underwater seascape and, therefore, the general impact of this new biological invasion. The spatial colonization estimations combined with the impacts reported by both scientific [Sessile Bioindicators in Permanent Quadrats (SBPQ) sentinel stations] and civilian (Citizen Science) monitoring methodologies claim the urgent development of further studies that allow the design of monitoring strategies against R. okamurae expansion across the Mediterranean and Atlantic waters.

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

“…The question of how Rugulopteryx okamurae spreads remains unresolved. In Thau Lagoon, Marseille (France) and Spain, no gametophytes have ever been observed so far [10,13,16], as they were in its source area (Japan [25]). Asexual reproduction with vegetative propagation by forming propagules (proliferous branchlets arising on the thallus surface) that grow into new plants appeared to be the main mode of reproduction in sink areas [17].…”

“…In only one year, R. okamurae became the most abundant species and carpeted the native community, leading to an increase in the number of dead colonies of the red gorgonian Paramuricea clavata (Risso, 1826) and a significant decline in the cover of the red alga key species Mesophyllum expansum (Philippi) Cabioch and M.L. Mendoza (Corallinaceae) [16,39,40].…”

“…In 2015, R. okamurae was, for the first time, recorded in the Mediterranean open sea in the southern (Ceuta, Spain, and Morocco) and northern (Spain) sides of the Strait of Gibraltar, where it quickly became invasive [12][13][14][15]. From 2015 to 2020, R. okamu rae exhibited extensive northerly and southerly geographical expansion from these two initial locations, along both the Atlantic and the Mediterranean coasts, ranking among the most invasive NIS in the Mediterranean Sea [14,16].…”

Processing and Characterization of Bioplastics from the Invasive Seaweed Rugulopteryx okamurae

“…The Spanish Mediterranean coasts and those of the Strait of Gibraltar present a highly favorable environment for the species, favoring its expansion and an increase in the derived impacts. Consequently, on 1 December 2020 it was included in the Spanish Catalog of Invasive Exotic Species since it represents one of the main threats to biodiversity in the Mediterranean, due to its ability to spread and adapt [4].…”

Diterpenoids from the Brown Alga Rugulopteryx okamurae and Their Anti-Inflammatory Activity

“…In recent years, R. okamurae has invaded the southwestern coasts of Europe, in particular the coasts of the Strait of Gibraltar [26]. The alga has experienced a proliferation so quick and massive that in a few years it has become a dominant species, which covers large areas of ocean bottom and produces tons of beach cast material [26,27].…”