Settlement and Spreading of the Introduced Seaweed Caulacanthus okamurae (Rhodophyta) in the Mediterranean Sea

Antonella Petrocelli,Katia Sciuto,Marion A Wolf,Adriano Sfriso,Ester Cecere

doi:10.3390/d12040129

Antonella Petrocelli, Katia Sciuto + Show 3 more

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https://doi.org/10.3390/d12040129

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Abstract

In this study, we report the first finding of the non-indigenous seaweed Caulacanthus okamurae (Rhodophyta) in the Ionian and Adriatic Seas (Mediterranean). Specimens were identified through molecular analyses based on the plastid ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) marker. The sequences obtained during this study represent the first molecular evidence of the presence of this taxon in the Mediterranean Sea. Stable populations have been detected in some areas of the Mar Piccolo of Taranto (Italy) and in the whole lagoon of Venice, forming dense patches of low turf that reach high biomasses. Turf-forming algae are common in the intertidal zones of tropical regions, but are rare in temperate ones. The particular environmental conditions of transitional water systems, such as the Mar Piccolo of Taranto and the Venice Lagoon, together with the water temperature increase observed in the last years could have favored the settlement and spread of this introduced species.

Highlights

Caulacanthus Kützing is a small genus of the order Gigartinales and includes three taxonomically accepted species [1]
The rbcL sequences obtained from the 15 Caulacanthus isolates examined in this study were all identical among them
Sequences of the investigated Italian samples were included in a well-supported clade (100NJ/100MP/100ML) with two sequences of C. okamurae from South Korea and Atlantic Spain

Summary

Introduction

Caulacanthus Kützing is a small genus of the order Gigartinales and includes three taxonomically accepted species [1]. The type species of the genus, Caulacanthus ustulatus (Mertens ex Turner) Kützing, was believed to have a cosmopolitan distribution in the Eastern Atlantic and the Indo-Western Pacific until 2002. Observations of the reproductive structures [4,5] and phylogenetic analyses [2] supported the validity of C. okamurae as a distinct species, representing the Indo-Western Pacific lineage of C. ustulatus. This small turf-forming seaweed, first described from Japan by Yamada [6], is native to China, Korea and Taiwan [1].

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