Abstract
The marine red algae Asparagopsis armata is an invasive species gaining competitive advantage by releasing large amounts of toxic compounds to the surrounding invaded area. The main objective of this study was to evaluate the effects of this invasive seaweed on marine invertebrates by exposing the common prawn Palaemon elegans and the marine snail Gibbula umbilicalis to the exudate of this seaweed. The seaweed was collected and placed in a tank for 12 h in the dark in a 1:10 ratio. Afterwards the seawater medium containing the released secondary metabolites was collected for further testing. Lethal and sublethal effects of A. armata were investigated. Biochemical biomarker responses associated with energy metabolism (lactate dehydrogenase, LDH; electron transport system activity, ETS; lipid, protein and carbohydrate content) were analysed. The biomarker responses showed physiological status impairment of invertebrates after exposure to low concentrations of this algal exudate. The highest concentrations of exudate significantly increased lipid content in both organisms. In the shrimp, protein content, ETS, and LDH were also significantly increased. By contrast, these parameters were significantly decreased in G. umbilicalis. A behavioural impairment was also observed in G. umbilicalis exposed to A. armata exudate, reducing feeding consumption. These results represent an important step in the research of natural toxic exudates released to the environment and prospective effects of this seaweed in invaded communities under increasing global change scenarios.
Highlights
Introduction in published maps and institutionalRapid globalization and increasing trends of trade and travel have accelerated marine biological invasions by transporting species to areas outside their native range
Acute toxicity tests revealed that A. armata exudate affects both species, with P. elegans being more tolerant than G. umbilicalis with significantly higher LC50 (F2,100 = 53.03, p < 0.001) (Figure 1)
Feeding activity was affected in G. umbilicalis (F6,49 = 5.304, p < 0.001; Figure 2A) when exposed to A. armata exudate at 0.07% (Dunnett’s p = 0.022), 0.47% (Dunnett’s p < 0.001), and 0.87% (Dunnett’s p < 0.001)
Summary
Introduction in published maps and institutionalRapid globalization and increasing trends of trade and travel have accelerated marine biological invasions by transporting species to areas outside their native range. Asparagopsis armata Harvey, 1855 (Bonnemaisoniales, Rhodophyta) is a red seaweed native to Western Australia, and nowadays is distributed throughout Europe in the Atlantic and Mediterranean basin, where it is highly invasive [2] This seaweed possesses chemical defence mechanisms that are critical for its invasiveness, based on the synthesis and storage of an array of secondary metabolites, which include more than 100 halogenated compounds such as haloforms, haloacids, and haloketones [3]. The pungent aroma of this alga is attributed to an essential oil that is composed mainly of bromoform with smaller amounts of other bromine-, chlorine-, and iodine-containing methane, ethane, ethanol, acetaldehydes, acetones, 2-acetoxypropanes, propenes, epoxypropanes, acroleins, and butenones, stored in vacuoles within gland cells [5] These potent biological effects of these compounds can induce significant changes in terms of native community composition [6], including in rock pools [7], favouring A. armata in a given niche. These organisms inhabit the upper intertidal zone on rocky shores where A. armata is often found attached to the substrate, or unattached (drifting), and releasing its chemical exudates
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