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Background Microalgae biomass is regarded as a potential feedstock for bioenergy purposes through anaerobic digestion (AD). Even though AD is a well-proven technology, the use of new feedstocks requires in-depth studies. A lot of research has been conducted assessing methane yield without paying attention to the anaerobic microbiome and their activities. For such a goal, the present investigation was designed to link methane yield to those two later sludge characteristics. In this sense, different anaerobic sources were tested, namely adapted to microalgae biomass and adapted to sewage sludge. Results Despite the registered differences for the anaerobic microbiome analysis and specific methane activities towards model substrates, sludge adapted to digest sewage sludge did not affect the methane yield of Chlorella sorokiniana and Scenedesmus sp. Opposite to that, sludge samples adapted to digest microalgae exhibited a concomitant increase in methane yield together with increasing digestion temperatures. More specifically, the values attained were 63.4 ± 1.5, 79.2 ± 3.1 and 108.2 ± 1.9 mL CH4 g COD in−1 for psychrophilic, mesophilic and thermophilic digestions, respectively. While psycro- and mesophilic digestion supported similar yields (most probably linked to their anaerobic microbiome resemblance), the values attained for thermophilic digestion evidenced the usefulness of having a highly specific microbiome. The relative abundance of Firmicutes, particularly Clostridia, and Proteobacteria together with an important abundance of hydrogenotrophic methanogens was highlighted in this inoculum. Conclusion Overall, this study showed that working with tailored anaerobic microbiome could help avoiding pretreatments devoted to methane yield enhancement.

The consortia formed by microalgae and bacteria developed during semi-continuous operation of photobioreactors treating domestic wastewater was characterized by means of flow cytometry and DGGE techniques. While microalgae population was dominated by the inoculated wild strain Chlorella sorokiniana, the bacterial community included as activated sludge was totally replaced by microbial groups exhibiting adaptations to illuminated environments. The quantification conducted by flow cytometry evidenced bacterial population displacement favoring pigmented and photoheterotrophic groups. This fact was correlated with DGGE analysis that showed the dominance of Rhodobacteraceae family during steady state conditions and disappearance of Rhizobiaceae family present in the inoculum. This particular bacterial community composition was related with the limited organic matter consumption detected in the experimental reactors, estimated in removal rates of 64.2 ± 4.8% of biodegradable chemical oxygen demand present in primary treated wastewater. In conclusion, the dominance of photoheterotroph and pigmented bacteria reduced the metabolic capability of the photobioreactor resulting in insufficient wastewater treatment with regard to discharge regulations.

The geographical spreading of new fishing activities and the increasingly deeper locations of these activities have shown the worldwide distribution of gerionid crabs and new descriptions of Chaceon taxa. However, incomplete penetrance, variable expressivity, and phenotypic overlap make the morphometric identification of these species difficult. In this study, partial sequences of the cytochrome c oxidase subunit 1 (COI) and 16S mitochondrial ribosomal RNA (16S rRNA) genes have been analyzed in Chaceon species from the Eastern Central and South Atlantic and compared with sequences of species from Western Atlantic. Our results corroborate the proposed morphological species and highlight the significant separation of the Eastern Atlantic species and those from Atlantic coasts of South America for both markers (97% Bayesian posterior probability, BPP / 83% Bootstrap replicates, BT). Interestingly, Chaceon sanctaehelenae shows a closer relationship with the species of the American coast than with those from the Eastern Atlantic. On the other hand, while COI marker clearly separates Chaceon atopus and Chaceon erytheiae species (99 BPP / 91% BT), these species share haplotypes for the 16S rRNA marker, pointing to a recent speciation process. Moreover, a close relationship was observed between Chaceon maritae and Chaceon affinis (94% BPP / 77% BT). The topologies of the trees obtained indicate that the ancestor of this genus was closer related to those species from South America than to those from the Eastern Atlantic., SI

Atlantic bluefin tuna (Thunnus thynnus) are highly migratory predators whose abundance, distribution, and somatic condition have changed over the past decades. Prey community composition and abundance have also varied in several foraging grounds. To better understand underlying food webs and regional energy sources, we performed stomach content and stable isotope analyses on mainly juvenile (60–150 cm curved fork length) bluefin tuna captured in foraging grounds in the western (Mid-Atlantic Bight) and eastern (Bay of Biscay) Atlantic Ocean. In the Mid-Atlantic Bight, bluefin tuna diet was mainly sand lance (Ammodytes spp., 29% prey weight), consistent with historic findings. In the Bay of Biscay, krill (Meganyctiphanes norvegica) and anchovy (Engraulis encrasicolus) made up 39% prey weight, with relative consumption of each reflecting annual changes in prey abundance. Consumption of anchovies apparently declined after the local collapse of this prey resource. In both regions, stable isotope analysis results showed that juvenile bluefin tuna fed at a lower trophic position than indicated by stomach content analysis. In the Mid-Atlantic Bight, stable isotope analyses suggested that >30% of the diet was prey from lower trophic levels that composed, Sí

This study explores the relationship between a seamount located in the Cantabrian Sea known as Le Danois Bank (El Cachucho fishing ground), the first offshore Marine Protected Area (MPA) in Spain, and the Spanish albacore (Thunnus alalunga) surface fishery that operates during the summer and autumn months. The geographical distribution of catch per unit effort (CPUEs), expressed by number, showed that August and September were the months with the highest catches in the El Cachucho area, however, annual variability existed. Nominal CPUE series obtained from both logbook data and fishing interviews revealed that higher CPUEs were achieved inside the MPA during some fishing seasons, but there was no consistency in the data, since spatial and temporal variability were shown. The spatial distribution of monthly CPUE data was characterized by means of geostatistical analysis. Albacore schools tended to aggregate in mesoscale patches of similar dimensions but the location of these aggregations was non-stationary both in space and time. This supports the hypothesis that albacore are not randomly spatially distributed, but that they concentrated in certain areas where they find suitable conditions of food availability.

Skin and gill parasites found in juvenile Atlantic bluefin tuna (Thunnus thynnus) caught in the Bay of Biscay, northeast Atlantic, were examined with the aim of finding biological tags. The degree of infection of different microhabitats was analyzed and the annual prevalence by species of parasite obtained. Of the specimens examined, 98% had parasites, and the gills were by far the most infected microhabitat, followed by the skin and the pectoral fin. Within the gill cavity, parasites were most commonly found in the afferent margins of the primary lamellae. Three species of Copepoda were identified, two species of Monogenea, and eleven Digenea. Thus, ten species (Digenea: Didymozoidae) and a new host record for Copiatestes thyrsitae (Digenea: Syncoeliidae) were recorded in Thunnus thynnus. The suitability of the different external parasites found is discussed and gill didymozoids are put forward as useful biological tags. Confusing taxonomy within this digenean family makes species identification of the different morphotypes difficult. However, their habitat specificity in hosts can be a good tool to differentiate morphotypes and characterise host individuals.