Biodiversity patterns of epipelagic copepods in the South Pacific Ocean: Strengths and limitations of current data bases.

Basin-scale patterns of biodiversity for zooplankton in the ocean may provide valuable insights for understanding the impact of climate change and global warming on the marine ecosystem. However, studies on this topic remain scarce or unavailable in vast regions of the world ocean, particularly in large regions where the amount and quality of available data are limited. In this study, we used a 27-year (1993-2019) database on species occurrence of planktonic copepods in the South Pacific, along with associated oceanographic variables, to examine their spatial patterns of biodiversity in the upper 200 m of the ocean. The aim of this study was to identify ecological regions and the environmental predictors explaining such patterns. It was found that hot and cold spots of diversity, and distinctive species assemblages were linked to major ocean currents and large regions over the basin, with increasing species richness over the subtropical areas on the East and West sides of the South Pacific. While applying the spatial models, we showed that the best environmental predictors for diversity and species composition were temperature, salinity, chlorophyll-a concentration, oxygen concentration, and the residual autocorrelation. Nonetheless, the observed spatial patterns and derived environmental effects were found to be strongly influenced by sampling coverage over space and time, revealing a highly under-sampled basin. Our findings provide an assessment of copepods diversity patterns and their potential drivers for the South Pacific Ocean, but they also stress the need for strengthening the data bases of planktonic organisms, as they can act as suitable indicators of ecosystem response to climate change at basin scale.

Influence of Biochar and Bio-Oil Loading on the Properties of Epoxy Resin Composites.

In this study, we evaluated the use of bio-oil and biochar on epoxy resin. Bio-oil and biochar were obtained from the pyrolysis of wheat straw and hazelnut hull biomass. A range of bio-oil and biochar proportions on the epoxy resin properties and the effect of their substitution were investigated. TGA curves showed improved thermal stability for degradation temperature at the 5% (T5%), 10% (T10%), and 50% (T50%) weight losses on bioepoxy blends with the incorporation of bio-oil and biochar with respect to neat resin. However, decreases in the maximum mass loss rate temperature (Tmax) and the onset of thermal degradation (Tonset) were obtained. Raman characterization showed that the degree of reticulation with the addition of bio-oil and biochar does not significantly affect chemical curing. The mechanical properties were improved when bio-oil and biochar were incorporated into the epoxy resin. All bio-based epoxy blends showed a large increase in Young's modulus and tensile strength with respect to neat resin. Young's modulus was approximately 1955.90 to 3982.05 MPa, and the tensile strength was between 8.73 and 13.58 MPa for bio-based blends of wheat straw. Instead, in bio-based blends of hazelnut hulls, Young´s modulus was 3060.02 to 3957.84 MPa, and tensile strength was 4.11 to 18.11 Mpa.

Microalgae as Raw Materials for Aquafeeds: Growth Kinetics and Improvement Strategies of Polyunsaturated Fatty Acids Production.

Studies have shown that ancient cultures used microalgae as food for centuries. Currently, scientific reports highlight the value of nutritional composition of microalgae and their ability to accumulate polyunsaturated fatty acids at certain operational conditions. These characteristics are gaining increasing interest for the aquaculture industry which is searching for cost-effective replacements for fish meal and oil because these commodities are one of the most significant operational expenses and their dependency has become a bottleneck for their sustainable development of the aquaculture industry. This review is aimed at highlighting the use of microalgae as polyunsaturated fatty acid source in aquaculture feed formulations, despite their scarce production at industrial scale. Moreover, this document includes several approaches to improve microalgae production and to increase the content of polyunsaturated fatty acids with emphasis in the accumulation of DHA, EPA, and ARA. Furthermore, the document compiles several studies which prove microalgae-based aquafeeds for marine and freshwater species. Finally, the study explores the aspects that intervene in production kinetics and improvement strategies with possibilities for upscaling and facing main challenges of using microalgae in the commercial production of aquafeeds.

Eurythenes atacamensis sp. nov. (Crustacea: Amphipoda) exhibits ontogenetic vertical stratification across abyssal and hadal depths in the Atacama Trench, eastern South Pacific Ocean.

Eurythenes S.I. Smith in Scudder, 1882 (Crustacea: Amphipoda) are prevalent scavengers of the benthopelagic community from bathyal to hadal depths. While a well-studied genus, molecular systematic studies have uncovered cryptic speciation and multiple undescribed lineages. Here, we apply an integrative taxonomic approach and describe the tenth species, Eurythenes atacamensis sp. nov., based on specimens from the 2018 Atacamex and RV Sonne SO261 Expeditions to the southern sector of the Peru-Chile Trench, the Atacama Trench (24-⁠21°S). Eurythenes atacamensis sp. nov. is a large species, max. observed length 83.2 mm, possesses diagnostic features, including a short gnathopod 1 palm and a chelate gnathopod 2 palm, and a distinct genetic lineage based on a 16S rRNA and COI phylogeny. This species is a dominant bait-attending fauna with an extensive bathymetric range, spanning from 4974 to 8081 m. The RV Sonne SO261 specimens were recovered along a 10-station transect from abyssal to hadal depths and further examined for demographic and bathymetric-related patterns. Ontogenetic vertical stratification was evident across the trench axis, with only juveniles present at abyssal depths (4974-6025 m). Total length-depth analysis revealed that the size of females was unrelated to depth, whereas juveniles followed a sigmoidal relationship with a step-up in size at depths >7200 m. Thus, these bathymetric trends suggest that juveniles and females employ differing ecological strategies in subduction trench environments. This study highlights that even dominant and ecologically important species are still being discovered within the abyssal and hadal environments. Continued systematic expeditions will lead to an improved understanding of the eco-evolutionary drivers of speciation in the world's largest ecosystem.

Epoxidation of Fatty Acid Methyl Esters Derived from Algae Biomass to Develop Sustainable Bio-Based Epoxy Resins.

The objective of this research was to investigate the development of epoxides from Chlorella vulgaris lipids to obtain a novel bio-based resin. The process involved the production of fatty acid methyl esters (FAMEs) by in situ transesterification of microalgal biomass, followed by epoxidation of the FAMEs to obtain bioresin. During the FAME production process, an assessment was made of the main factors affecting the production of unsaturated fatty acid methyl esters (UFAMEs), such as catalyst dosage and methanol:hexane volume ratio. For step epoxidation, an evaluation of the catalyst concentration, temperature and formic acid:hydrogen peroxide ratio was made. From the results obtained, UFAME production was maximized using 20 wt% of catalyst dosage and a volume ratio of 1:2 (v/v, methanol:hexane). Then, in the epoxidation stage, a higher yield was obtained using 1 wt% of catalyst with a volume ratio of 1:1 and maintaining a temperature of 70 °C. The bioresin was blended with neat epoxy resin (DGEBA) and cured with tetraethylenepentamine (TEPA). Bio-based resin was characterized via Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) to evaluate this material as an alternative source for oleochemistry.

Evaluation of different solvent mixtures in esterifiable lipids extraction from microalgae Botryococcus braunii for biodiesel production.

Non-polar and polar solvents as well as their mixtures were tested for the extraction of microalgae lipids and thus, to evaluate their effect on total and esterifiable lipids extraction yields with potential to be converted to biodiesel. The obtained results show an increase in lipids and esterifiable lipids extraction yields when non-polar and polar solvent mixtures were used. The higher esterifiable lipids extraction yield was 19.2%wt (based on dry biomass) using a chloroform-methanol mixture (75%v/v of methanol), corresponding to a 98.9%wt esterifiable lipids extraction. In addition, esterifiable lipids extraction yield of 18.9%wt (based on dry biomass) was obtained when a petroleum ether-methanol mixture (75%v/v of methanol) was used, corresponding to a 96.9%wt esterifiable lipids extraction.

Biodiesel synthesis by direct transesterification of microalga Botryococcus braunii with continuous methanol reflux.

Direct transesterification of Botryococcus braunii with continuous acyl acceptor reflux was evaluated. This method combines in one step lipid extraction and esterification/transesterification. Fatty acid methyl esters (FAME) synthesis by direct conversion of microalgal biomass was carried out using sulfuric acid as catalyst and methanol as acyl acceptor. In this system, once lipids are extracted, they are contacted with the catalyst and methanol reaching 82%wt of FAME yield. To optimize the reaction conditions, a factorial design using surface response methodology was applied. The effects of catalyst concentration and co-solvent concentration were studied. Hexane was used as co-solvent for increasing lipid extraction performance. The incorporation of hexane in the reaction provoked an increase in FAME yield from 82% (pure methanol) to 95% when a 47%v/v of hexane was incorporated in the reaction. However, the selectivity towards non-saponifiable lipids such as sterols was increased, negatively affecting biodiesel quality.