Impacts of The Invasive Seaweed <em>Asparagopsis armata</em> Exudate on Rockpool Invertebrates

Abstract

The marine red algae Asparagopsis armata is an invasive species which competitive advantage arises from the production and release of large amounts of toxic compounds to the surrounding invaded area, reducing the abundance of native species. 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 macroalgae. The seaweed was collected and placed in tanks, for 12 hours, in the dark in a 1:10 ratio. Afterwards the media containing its secondary metabolites was collected for further testing. Lethal and sublethal effects of A. armata were investigated. Biochemical biomarkers responses associated with energy metabolism (lactate dehydrogenase, LDH; electron transport system activity, ETS; content in lipids, proteins and carbohydrates) were analysed. The biomarker responses showed invertebrates&amp;rsquo; physiological status impairment after exposure to low concentrations of this algae exudate. Highest concentrations of exudate significantly increased lipid content in both organisms. In the shrimp, protein content, ETS, and LDH were also significantly increased. On the contrary, these parameters were significantly decreased in G. umbilicalis. A behavioural impairment was also observed in G. umbilicalis exposed to A. armata exudate, with reduction in 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.

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

“…Although we did not measure some peroxisomal enzymes (such as CAT) in the muscle tissue, a correlation between lipids metabolism and peroxisomal enzyme activities has been previously described [71]. On the other hand, and in agreement with our results, an increase in lipid content of G. umbilicalis exposed to A. armata exudate was observed and related with a concomitant decrease in feeding activity, leading to less energy expenditure [17]. On the other hand, the enzymatic activity of LDH, that plays an important role in the anaerobic pathway of energy production and is responsible for the reduction of pyruvate to lactate in glycolysis [72], was not altered.…”

“…Mussels' survival decreased to 50% when exposed to only about 3.67% of exudate. Similar 96h-LC50 values were reported by Silva et al [17] for the gastropod G. umbilicalis (2.79%) and the prawn P. elegans (5.04%). Another study comparing the communities of peracarid species inhabiting A. armata and Corallina elongata, a red macroalga native from the Atlantic coast and abundant in the subtidal zone of Azores [67], showed that even though A. armata hosts a diversity of crustacean assemblages [6], its presence might lead to an impoverishment of epifaunal peracarid.…”

“…For example, it was demonstrated that A. armata halogenated metabolites deterred feeding by two marine mesograzers (Hyale nigra and juvenile abalone Haliotis rubra) [16]. Exposure to its exudate caused physiological status impairment in exposed Palaemon elegans and Gibbula umbilicalis, as well as feeding inhibition in this gastropod [17].…”

The Effects of the Invasive Seaweed <em>Asparagopsis Armata</em> on Native Rock Pool Communities: Evidences from Experimental Exclusion

“…Asparagopsis armata produces very high amounts of secondary metabolites including volatile components as phenolic compounds [24], which toxicity to invertebrates, and seaweeds has often been associated to the invasive process [25,26]. These phenolic compounds from seaweeds have also shown to vary throughout the year [27], while the release of defensive compounds may also be altered by several abiotic factors such as temperature, light, and nutrient availability [28].…”

“…Due to their nature, grazers play an important role in structuring macroalgal assemblages, but secondary metabolites (terpenes, phenolic compounds, etc.) of A. armata ought to affect the palatability, or acceptability to herbivores [25,26]. Many of the gastropod species are microherbivores that feed on the biofilm established on the macrophyte fronds.…”