Search

The invasive green algae Caulerpa taxifolia (M. Vahl) C. Agardh, 1817 and Caulerpa cylindracea Sonder, 1845 are widely diffused in the Mediterranean Sea, where they compete for space with the endemic seagrass Posidonia oceanica (Linnaeus) Delile, 1813, a keystone species in Mediterranean marine biodiversity. The present study aims to explore the possible effects of bioactive metabolites from the invasive algae on the seagrass, which may imply an allelopathic action. In particular, the study focuses on the effects of the algal alkaloid caulerpin and the sesquiterpene caulerpenyne. Changes in leaf growth, chlorophyll content, and leaf protein expression of P. oceanica genets under treatments were evaluated after 28 days of cultivation in mesocosms. Caulerpenyne strongly inhibited the growth of adult leaves and the formation of new ones, while inducing the elongation of the intermediate leaves and increased total chlorophyll content; on the contrary, caulerpin did not significantly influence leaf growth and the formation of new ones. A total of 107 differentially accumulated proteins common to the two treatments were also identified using the proteomic approach. Both molecules induced cells to maintain homeostasis, enhancing the amino acid metabolism or fatty acid biosynthesis. Despite these disruptions, P. oceanica demonstrated a more efficient response to stress induced by caulerpin, stimulating the biosynthesis of essential amino acids to maintain cellular homeostasis and mitigate damage caused by reactive oxygen species (ROS). Overall, obtained results supports the possible role of caulerpenyne, and not caulerpin, as an effector in allelopathic interactions among invasive Caulerpa species and P. oceanica in the Mediterranean. [Display omitted] • CAU metabolite influenced leaf renewal and longevity in P. oceanica genets, in mesocosm • CYN exerted a strong phytotoxic effects, hindered leaf formation, damaged adult leaves, and stressed leaf meristems. • P. oceanica effectively showed resilence to CAU-induced stress by boosting essential amino acid biosynthesis. • The mesocosm trial results were consistent with observed allelopathic interactions between P. oceanica and Caulerpa species in natural environments. [ABSTRACT FROM AUTHOR]

Sargassum muticum , an invasive macroalgae in Europe, was employed as material for third generation bioethanol production. As a first step, autohydrolysis was chosen as an eco-friendly pretreatment, seeking for a high enzymatic susceptibility of the solid phase and high content of hexoses as glucose, galactose and mannose, in both liquid and solid phases, which can be subsequently transformed in ethanol via fermentation. Besides, the search of a minimum consumption of energy in the pretreatment is also a key challenge in bioethanol production. At optimum conditions of autohydrolysis pretreatment, more than 90% of the glucan was recovered in the solid phase (while the other 10% appeared as glucooligosaccharides and glucose in the liquid phase). In the enzymatic hydrolysis carried out with the solid phases, glucan to glucose conversions of 94 and 89% were obtained, with the solid mixed with water and the whole slurry, respectively. Moreover, the whole slurry experiments, where all hexoses present in the raw material (glucose, galactose and mannose) from the solid and the liquid phases are fermented, allows to reach maximum ethanol yields of 80% (14.10 g of ethanol/L) referred to the theoretical yield, in a short time. • Autohydrolysis is a suitable pretreatment for bioethanol production from Sargassum. • Almost 100% of hexoses are recovered in the optimum conditions. • Glucan to glucose conversion above 90% was achieved in enzymatic hydrolysis assays. • SSF without nutrients reached 80–95% theoretical ethanol yield in less than 10 h. [ABSTRACT FROM AUTHOR]

The increasing spread of Undaria pinnatifida has caused concern in many parts of the world in recent decades, and this alga has been listed as invasive in the introduced countries. Its most recent spread in Europe was reported on Sylt island in the northern Wadden sea (German Bight, Eastern North Sea) between 2016 and 2017. Its direct origin remained unknown. In the present study, we obtained the mitochondrial DNA sequences including the partial coding region of cox3 and intergenic noncoding loci tatC - tLeu , atp8-trnS and trnW-trnI from one drifting population and one attached population of U. pinnatifida on Sylt and compared them with the available sequences published in previous studies. For the concatenated sequences of atp8-trnS and trnW-trnI , two haplotypes (Up01 and Up03) were detected in Sylt populations with Up01 being the dominant haplotype, which was most similar to the haplotype composition identified previously in European populations. For the concatenated sequences of cox3 and tatC - tLeu , two haplotypes (H1 and H9) were found in Sylt populations and they were the same as those identified previously in Brittany, France. These results suggest that European populations were most likely the direct origin of the newly established U. pinnatifida population on Sylt. The combined use of these sequences will be a robust tool to infer the origins of newly established populations of this seaweed in the future. • Undaria population from Sylt has similar haplotypes to other European populations. • European populations are the direct origin of the Undaria population invading Sylt. • The mitochondrial sequences are informative for tracing the origin of Undaria. [ABSTRACT FROM AUTHOR]

The red seaweed Agarophyton vermiculophyllum is an invasive species native to the north-west Pacific, which has proliferated in temperate estuaries of Europe, North America and Africa. Combining molecular identification tools, historical satellite imagery and one-year seasonal monitoring of biomass and environmental conditions, the presence of A. vermiculophyllum was confirmed, and the invasion was assessed and reconstructed. The analysis of satellite imagery identified the first bloom in 2014 and revealed that A. vermiculophyllum is capable of thriving in areas, where native bloom-forming species cannot, increasing the size of blooms (ca. 10%). The high biomass found during the peak bloom (>2 kg m−2) and the observation of anoxic events indicated deleterious effects. The monitoring of environmental conditions and biomass variability suggests an essential role of light, temperature and phosphorous in bloom development. The introduction of this species could be considered a threat for local biodiversity and ecosystem functioning in a global change context. • The presence of A. vermiculophyllum is confirmed for the Republic of Ireland. • Bloom development is constrained by P, not N limitation. • This alien species can bloom in areas where native bloom forming species cannot. • Free satellite imagery can be used to reconstruct A. vermiculophyllum invasion. • Biomass followed a seasonal pattern, with peak bloom occurring in summer. [ABSTRACT FROM AUTHOR]