The Japanese alga Polysiphonia morrowii (Rhodomelaceae, Rhodophyta) on the South Atlantic Ocean: first report of an invasive macroalga inhabiting oyster reefs

M. Emilia Croce,Elisa R. Parodi

doi:10.1007/s10152-014-0384-5

Abstract

Conspicuous tufts of the filamentous algae Polysiphonia Greville inhabit the reefs of Crassostrea gigas on the Atlantic Patagonian coast. The population was recorded for the first time in 1994 and identified as P. argentinica. This study exhaustively investigated the morphology and reproduction of specimens and the seasonality of the population. The results revealed the identity of the specimens as the invasive Japanese macroalga Polysiphonia morrowii Harvey, on the basis of several striking features: the setaceous and tufted thalli, the corymbose growing apices, the endogenous axillary branches, the urceolate cystocarps and the sharply pointed branches. Sexual reproduction was evidenced; however, fertile male gametophytes were absent in the samples. The population was found almost all year round, but its abundance became higher in autumn and winter. The present study constitutes the first record of this invasive macroalga on the South Atlantic Ocean; the fourth record of an exotic macroalgal species on the Atlantic Patagonian coast; and the first record of an invasive species related to the establishment of C. gigas in Atlantic Patagonia.

Highlights

Polysiphonia Greville is a widespread genus of red macroalgae of which numerous species have been recognized (Menez 1964; Hollenberg and Norris 1977; Womerseley 1979; Kapraun and Rueness 1983; Yoon 1986)
The results revealed the identity of the specimens as the invasive Japanese macroalga Polysiphonia morrowii Harvey, on the basis of several striking features: the setaceous and tufted thalli, the corymbose growing apices, the endogenous axillary branches, the urceolate cystocarps and the sharply pointed branches
The present study constitutes the first record of this invasive macroalga on the South Atlantic Ocean; the fourth record of an exotic macroalgal species on the Atlantic Patagonian coast; and the first record of an invasive species related to the establishment of C. gigas in Atlantic Patagonia

Summary

Introduction

Polysiphonia Greville is a widespread genus of red macroalgae of which numerous species have been recognized (Menez 1964; Hollenberg and Norris 1977; Womerseley 1979; Kapraun and Rueness 1983; Yoon 1986). Members of this genus are characterized by filamentous and often delicate thallus that grows within intertidal and subtidal habitats, ranging from turbid estuaries to clear waters (Adams 1991). There is evidence that filamentous invasive macroalgae such as Polysiphonia are able to produce changes in the biodiversity of native ecosystems, providing substrate for the settlement of protozoa, colonial diatoms and early stages of macroalgae, increasing the complexity of the ecosystems that they invade (Thomsen et al 2006)

Objectives

Methods

Results

Conclusion