Physiology, niche characteristics and extreme events: Current and future habitat suitability of a rhodolith-forming species in the Southwestern Atlantic.

Given the ecological and biogeochemical importance of rhodolith beds, it is necessary to investigate how future environmental conditions will affect these organisms. We investigated the impacts of increased nutrient concentrations, acidification, and marine heatwaves on the performance of the rhodolith-forming species Lithothamnion crispatum in a short-term experiment, including the recovery of individuals after stressor removal. Furthermore, we developed an ecological niche model to establish which environmental conditions determine its current distribution along the Brazilian coast and to project responses to future climate scenarios. Although L. crispatum suffered a reduction in photosynthetic performance when exposed to stressors, they returned to pre-experiment values following the return of individuals to control conditions. The model showed that the most important variables in explaining the current distribution of L. crispatum on the Brazilian coast were maximum nitrate and temperature. In future ocean conditions, the model predicted a range expansion of habitat suitability for this species of approximately 58.5% under RCP 8.5. Physiological responses to experimental future environmental conditions corroborated model predictions of the expansion of this species' habitat suitability in the future. This study, therefore, demonstrates the benefits of applying combined approaches to examine potential species responses to climate-change drivers from multiple angles.

How experimental physiology and ecological niche modelling can inform the management of marine bioinvasions?

Marine bioinvasions are increasing worldwide by a number of factors related to the anthroposphere, such as higher ship traffic, climate change and biotic communities' alterations. Generating information about species with high invasive potential is necessary to inform management decisions aiming to prevent their arrival and spread. Grateloupia turuturu, one of the most harmful invasive macroalgae, is capable of damaging ecosystem functions and services, and causing biodiversity loss. Here we developed an ecological niche model using occurrence and environmental data to infer the potential global distribution of G. turuturu. In addition, ecophysiological experiments were performed with G. turuturu populations from different climatic regions to test predictions regarding invasion risk. Our model results show high suitability in temperate and warm temperate regions around the world, with special highlight to some areas where this species still doesn't occur. Thalli representing a potential temperate region origin, were held at 10, 13, 16, 20 and 24 °C, and measurements of optimal quantum field (Fv/Fm) demonstrated a decrease of photosynthetic yield in the higher temperature. Thalli from the population already established in warm temperate South Atlantic were held at 18, 24 and 30 °C with high and low nutrient conditions. This material exposed to the higher temperature demonstrated a drop in photosynthetic yield and significant reduction of growth rate. The congregation of modelling and physiological approach corroborate the invasive potential of G. turuturu and indicate higher invasion risk in temperate zones. Further discussions regarding management initiatives must be fostered to mitigate anthropogenic transport and eventually promote eradication initiatives in source areas, with special focus in the South America. We propose that this combined approach can be used to assess the potential distribution and establishment of other marine invasive species.

UVR and PAR absorbing compounds of marine brown macroalgae along a latitudinal gradient of the Brazilian coast.

Absorption spectra are indicative of biological sample chemical composition and can be used as a basis for the construction of descriptive and predictive models for biotechnological screening or assays. In marine algae, chemical composition can vary due to species-specific differences in biochemistry, as well as intra-specific responses to unique environmental variables. Different indices (UVCi, UVB+Ai and PARi) were proposed and calculated to evaluate how photoprotective compounds vary in 18 species of Phaeophyceae. In addition, they were correlated to abiotic factors. Through this technique, seven main peaks were detected in the absorbing spectra of marine brown algal extracts. The highest photoprotective indices values were found in species collected in tropical areas, where higher solar radiation is observed compared to the southern Brazilian coast. Considering additional abiotic factors, water temperature and nitrate concentration were negatively correlated with UV indices. PARi's indices were positively affected by nitrate. All species collected on the Brazilian coast have absorption peaks in the region of phenolic compounds and carotenoids, suggesting that tropical marine brown macroalgae may have developed an effective antioxidant defense system, suggesting adaptation to environments characterized by high solar radiation. UVR/PAR indices congregated essential information to possible future biotechnological screening, facilitating selection of high priority species or sites, fostering actions to enhance alternative sustainable management strategies of coastal environments.

Mitochondrial and plastid genome analysis of the heteromorphic red alga Mastocarpus papillatus (C. Agardh) Kützing (Phyllophoraceae, Rhodophyta) reveals two characteristic florideophyte organellar genomes.

Analysis of the marine red algal species Mastocarpus papillatus (C. Agardh) Kützing using paired-end 36 bp Illumina sequences resulted in the assembly of its complete mitochondrial and plastid genomes. The mitogenome is 25,906 bp in length and contains 50 genes, and the plastid genome is 184,382 bp with 234 genes. The mitochondrial and plastid genomes show high gene synteny with published Florideophyceae.