How Does Mytilus galloprovincialis Respond When Exposed to the Gametophyte Phase of the Invasive Red Macroalga Asparagopsis armata Exudate?

Sónia D Coelho,Maria D Bordalo,Amadeu M V M Soares,Hugo C Vieira,Jacinta M M Oliveira,Rui J M Rocha,Sílvia F S Pires,Andreia C M Rodrigues

doi:10.3390/w13040460

Abstract

Asparagopsis armata is classified as an invasive species in Europe. Through the exudation of secondary metabolites, this macroalga holds a chemical defence against consumers, with potential toxic effects to native rocky shore communities. This study aims to evaluate the potential impact of A. armata (gametophyte) exudate in a native species, the mussel Mytilus galloprovincialis, in terms of biochemical and organismal effects. The 96 h-LC50 was 3.667% and based on it, exudate concentrations (0.25; 0.5; 1; 2%) were determined to further sublethal experiments. These sublethal concentrations caused no oxidative damage in the digestive gland since lipid peroxidation and protein carbonylation were not affected. Nevertheless, there was a significant rise in the electron transport system activity and total glutathione content in muscle, suggesting an increased non-enzymatic antioxidant capacity and consequent energy consumption to cope with potential pro-oxidant compounds. This might have contributed to the observed decline in cellular energy allocation of the exposed mussels. At the organismal level, clearance capacity declined along the concentration gradient. Moreover, the number of functional byssuses decreased with increasing concentrations and a significant reduction in their attachment strength was observed. These findings suggest that the presence of A. armata may compromise M. galloprovincialis integrity in the invaded coastal areas.

Highlights

Published: 10 February 2021The continuous proliferation of invasive seaweeds has grown a great concern considering their impacts on native marine communities, mainly because they naturally threaten the availability of resources compromising the natural ecosystem functioning [1]
The present study focused on the exposure of M. galloprovincialis to different concentrations of the exudate of A. armata and helped to evaluate the potential impact on the local ecosystems’ integrity promoted by the presence of this invasive macroalga
There is evidence that the main effects may be a consequence of the biologically-active metabolites present in the A. armata exudate with strong antiherbivore, antifungal and antibiotic activity [16,64,65,66], especially volatile halocarbons such as bromoform, dibromomethane, 1,2-di-bromoethylene, dibromochloromethane and tribromoethylen [39], there is still a poor understanding on the impact this invasive seaweed may have in the surrounding biota

Summary

Introduction

Published: 10 February 2021The continuous proliferation of invasive seaweeds has grown a great concern considering their impacts on native marine communities, mainly because they naturally threaten the availability of resources compromising the natural ecosystem functioning [1]. The red marine macroalgae Asparagopsis armata Harvey, 1855 (Bonnemaisoniales, Rhodophyta), native from southern Australia and New Zealand, is identified as an invasive species and widely distributed in the Mediterranean and Atlantic coasts of Europe including Portugal [2,3] This temperate alga can overcome the ecological barriers and colonise diverse environmental conditions, mainly due to its fast growth rate, lack of predators and its effective spread, both through the tetrasporophyte floating balls and the gametophyte phase that hooks onto floating material [4,5]. A. armata sets mainly in the coastal low intertidal zone extending to the upper meters of the subtidal zone [3,6] It competes for resources (mainly space and nutrients) with specific native species, such as epifaunal assemblages.

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