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The worldwide dispersal of the ectoparasitic mite Varroa destructor from its Asian origins has fundamentally transformed the relationship of the honey bee (Apis mellifera) with several of its viruses, via changes in transmission and/or host immunosuppression. The extent to which honey bee-virus relationships change after Varroa invasion is poorly understood for most viruses, in part because there are few places in the world with several geographically close but completely isolated honey bee populations that either have, or have not, been exposed long-term to Varroa, allowing for separate ecological, epidemiological, and adaptive relationships to develop between honey bees and their viruses, in relation to the mite's presence or absence. The Azores is one such place, as it contains islands with and without the mite. Here, we combined qPCR with meta-amplicon deep sequencing to uncover the relationship between Varroa presence, and the prevalence, load, diversity, and phylogeographic structure of eight honey bee viruses screened across the archipelago. Four viruses were not detected on any island (ABPV-Acute bee paralysis virus, KBV-Kashmir bee virus, IAPV-Israeli acute bee paralysis virus, BeeMLV-Bee macula-like virus); one (SBV-Sacbrood virus) was detected only on mite-infested islands; one (CBPV-Chronic bee paralysis virus) occurred on some islands, and two (BQCV-Black queen cell virus, LSV-Lake Sinai virus,) were present on every single island. This multi-virus screening builds upon a parallel survey of Deformed wing virus (DWV) strains that uncovered a remarkably heterogeneous viral landscape featuring Varroa-infested islands dominated by DWV-A and -B, Varroa-free islands naïve to DWV, and a refuge of the rare DWV-C dominating the easternmost Varroa-free islands. While all four detected viruses investigated here were affected by Varroa for one or two parameters (usually prevalence and/or the Richness component of ASV diversity), the strongest effect was observed for the multi-strain LSV. Varroa unambiguously led to elevated prevalence, load, and diversity (Richness and Shannon Index) of LSV, with these results largely shaped by LSV-2, a major LSV strain. Unprecedented insights into the mite-virus relationship were further gained from implementing a phylogeographic approach. In addition to enabling the identification of a novel LSV strain that dominated the unique viral landscape of the easternmost islands, this approach, in combination with the recovered diversity patterns, strongly suggests that Varroa is driving the evolutionary change of LSV in the Azores. This study greatly advances the current understanding of the effect of Varroa on the epidemiology and adaptive evolution of these less-studied viruses, whose relationship with Varroa has thus far been poorly defined. Author summary: Honey bees are plagued by many enemies, and the Varroa mite is one of the most important of these. Varroa hurts bees by feeding on their haemolymph, but more importantly, by facilitating the transmission and development of many viruses. The impact of Varroa on most honey bee viruses remains poorly understood. Here, we capitalized on the exceptional Azores setting, which contains islands with and without Varroa, to gain unprecedented insights into the complex mite-virus interactions. We uncovered a very heterogenous viral landscape, with one virus (SBV) occurring only on mite-infested islands, two (CBPV and DWV) on some islands, and two (BQCV and LSV) on every single island. While Varroa influenced the prevalence and/or diversity of all four viruses, its strongest effect was observed for LSV, with the mite leading to elevated LSV prevalence, loads, and diversity (number of variants and their relative abundance). Furthermore, we discovered a novel LSV strain and showed for the first time that the epidemiology of LSV-2, a major strain of LSV, is unambiguously linked to the presence of Varroa. Our findings not only deepen current scientific understanding of the mite-virus relationships but are also of value for assisting veterinary authorities in decision-making regarding the movement of bees across territories. [ABSTRACT FROM AUTHOR]

Climate change is enhancing the frequency of cyanobacterial blooms not only during summer but also in spring and autumn, leading to increased ecological impacts. The bacterioplankton community composition (BCC), in particular, is deeply affected by these blooms, although at the same time BCC can also play important roles in blooms' dynamics. However, more information is still needed regarding BCC during species-specific cyanobacterial blooms. The goal of this study was to assess BCC succession in a hypereutrophic shallow lake (Vela Lake, Portugal) during a warm spring using a metagenomic approach to provide a glimpse of the changes these communities experience during the dominance of Aphanizomenon-like bloom-forming species. BCC shifts were studied using 16S rRNA gene metabarcoding and multivariate analyses. A total of 875 operational taxonomic units (OTUs) were retrieved from samples. In early spring, the dominant taxa belonged to Proteobacteria (mainly Alphaproteobacteria—Rickettsiales) and Bacteroidetes (Saprospirales, Flavobacteriales and Sphingobacteriales). However, at the end of May, a bloom co-dominated by cyanobacterial populations of Aphanizomenon gracile, Sphaerospermopsis aphanizomenoides and Synechococcus sp. developed and persisted until the end of spring. This led to a major BCC shift favouring the prevalence of Alphaproteobacteria (Rickettsiales and also Rhizobiales, Caulobacteriales and Rhodospirillales) and Bacteroidetes (Saprospirales, followed by Flavobacteriales and Sphingobacteriales). These results contribute to the knowledge of BCC dynamics during species-specific cyanobacterial blooms, showing that BCC is strongly affected (directly or indirectly) by Aphanizomenon-Sphaerospermopsis blooms. [ABSTRACT FROM AUTHOR]

In this study, we gathered sequence data from the tRNAleu-cox2 intergenic mitochondrial (mtDNA) region concurrently with single nucleotide polymorphism (SNP) data from 91 loci of nuclear DNA (ncDNA). The data was obtained from 156 colonies sampled in six apiaries from four countries. The full dataset was analysed and discussed for genetic patterns with a focus on cytonuclear diversity and admixture levels. [ABSTRACT FROM AUTHOR]

Increases in carbon dioxide (CO2) and other greenhouse gases emissions are leading to changes in ocean temperature and carbonate chemistry, the so-called ocean warming and acidification phenomena, respectively. Methylmercury (MeHg) is the most abundant form of mercury (Hg), well-known for its toxic effects on biota and environmental persistency. Despite more than likely co-occurrence in future oceans, the interactive effects of these stressors are largely unknown. Here we assessed organ-dependent Hg accumulation (gills, liver and muscle) within a warming (▵ T = 4 °C) and acidification (▵ pCO2 = 1100 μatm) context, and the respective phenotypic responses of molecular chaperone and antioxidant enzymatic machineries, in a commercially important fish (the meagre Argyrosomus regius). After 30 days of exposure, although no mortalities were observed in any treatments, Hg concentration was significantly enhanced under warming conditions, significantly more so in the liver. On the other hand, increased CO2 decreased Hg accumulation and, despite negative effects prompted as a sole stressor, consistently elicited an antagonistic effect with temperature and contamination on oxidative stress (catalase, superoxide dismutase and glutathione-S-tranferase activities) and heat shock (Hsp70 levels) responses. We argue that the mechanistic interactions are grounded on simultaneous increase in excessive hydrogen (H+) and reactive oxygen species (e.g. O2-) free radicals, and subsequent chemical reaction equilibrium balancing. Additional multi-stressor experiments are needed to understand such biochemical mechanism and further disentangle interactive (additive, synergistic or antagonistic) stressor effects on fish ecophysiology in the oceans of tomorrow. [ABSTRACT FROM AUTHOR]

Wildfires have become a recurrent threat for many Mediterranean forest ecosystems. The characteristics of the Mediterranean climate, with its warm and dry summers and mild and wet winters, make this region prone to wildfire occurrence as well as to post-fire soil erosion. The wide recognition of wildfires as a driver for runoff and erosion in burnt forest areas has created a strong demand for model-based tools for predicting the post-fire hydrological and erosion responses and, in particular, for predicting the effectiveness of post-fire management measures to mitigate these responses. In this presentation, we will analyse how well hydrological and erosion model calibration can be transferred between burnt areas and treatments. To this end, we used data from three field experiments in north-central Portugal. The Colmeal experiment was carried out in two Maritime Pine stands following a 2008 wildfire, and tested the effectiveness of spontaneous needle cast and hydromulching. The Colmeal measurement and modelling results were published in Prats et al. (2016) and Vieira et al. (2018). The Castanheira de Pera study site was set up as a pilot station on post-fire erosion and its mitigation (spontaneous and manipulated needle cast), upon request from the national Institute of Nature Conservation and Forestry of Portugal (ICNF), following the so-called Pedrógão-Góis wildfire of June 2017 in central Portugal. The Loriga experiment was started only recently, in the framework of the EPyRIS SUDOE project, following a wildfire on 24 August 2018, and aims to assess the effectiveness of mulching with pine needles and with pine chips in a former Maritime Pine stand. Both mulch treatments explicitly targeted minimal application rates (1.3 and 2.6 Mg ha-1). In a nutshell, the Colmeal experiment showed that hydromulching was more effective than spontaneous needle cast to reduce overland flow generation but similarly effective to reduce erosion. The overall runoff coefficient decreased from 43 % under untreated conditions to 10 and 23 %, respectively, while soil losses dropped from 3.7 Mg ha-1 y-1 under untreated conditions to 0.5 and 0.4 Mg ha-1 y-1. The runoff and erosion rates of all three treatments could be predicted with reasonable accuracy by Morgan-Morgan-Finney model. The insights gained in the application of the three models to the Colmeal data set will now be applied to the initial data from Castanheira de Pera and Loriga experiment, in particular to assess the importance of local factors in the models' performance.Vieira, D.C.S., Serpa, D., Nunes, J.P.C., Prats, S.A., Neves, R., Keizer, J.J., 2018. Predicting the effectiveness of different mulching techniques in reducing post-fire runoff and erosion at plot scale with the RUSLE, MMF and PESERA models. Environmental Research 165: 365–378.Prats S.A., Malvar M.C., Vieira D.C.S., MacDonald L., Keizer J.J., 2016. Effectiveness of Hydromulching to reduce runoff and erosion in a recently burnt Pine plantation in Central Portugal. Land Degradation & Development. [ABSTRACT FROM AUTHOR]

Deformed wing virus (DWV) is a honey bee virus, whose emergence from relative obscurity is driven by the recent host-switch, adaptation, and global dispersal of the ectoparasitic mite Varroa destructor (a highly efficient vector of DWV) to reproduction on honey bees ( Apis mellifera ). Our study examines how varroa affects the continuing evolution of DWV, using the Azores archipelago, where varroa is present on only three out of the eight Islands, as a natural experimental system for comparing different evolutionary conditions and trajectories. We combined qPCR of 494 honey bee colonies sampled across the archipelago with amplicon deep sequencing to reveal how the DWV genetic landscape is altered by varroa. Two of the varroa-free Islands were also free of DWV, while a further two Islands were intriguingly dominated by the rare DWV-C major variant. The other four Islands, including the three varroa-infested Islands, were dominated by the common DWV-A and DWV-B variants. The varroa-infested Islands had, as expected, an elevated DWV prevalence relative to the uninfested Islands, but not elevated DWV loads, due the relatively high prevalence and loads of DWV-C on the varroa-free Islands. This establishes the Azores as a stable refuge for DWV-C and provides the most convincing evidence to date that at least some major strains of DWV may be capable of not just surviving, but actually thriving in honey bees in the absence of varroa-mediated transmission. We did not detect any change in DWV genetic diversity associated with island varroa status but did find a positive association of DWV diversity with virus load, irrespective of island varroa status., Competing Interests: The authors declare no conflicts of interest., (© The Author(s) 2024. Published by Oxford University Press.)