Hydrobiology: a new open access journal for the rapid dissemination of the latest discoveries on aquatic biodiversity and ecosystems

[Excerpt] We are pleased to announce the launch of Hydrobiology (ISSN 2673-9917) [1], a new open access journal that offers an excellent opportunity to establish an exciting forum for the discussion and dissemination of high-quality research in freshwater and marine biology, limnology, fisheries, oceanography, and aquatic ecology. We welcome innovative, hypothesis-driven papers on current scientific challenges as well as on new methodological tools and approaches to monitor aquatic biodiversity and ecosystems that tackle the socio-ecological complexity and the management of aquatic ecosystems

Proteomic analysis of aquatic microbial responses to nanoparticulate and ionic silver

Environmental biomarkers are the most promising next generation risk assessment tools, augmenting measurements of direct and highly sensitive responses at the cellular and sub-cellular levels. Silver nanoparticles (AgNPs) are among the mostly used nanoparticles and likely to be released in significant amounts to aquatic environments. Due to their antimicrobial properties, it is relevant to examine whether AgNPs can pose a risk to aquatic microbes in natural ecosystems. We used a bacterial strain, Pseudomonas sp. M1 (PsM1), isolated from sediments in a metal-polluted stream, to gain insights into the molecular mechanisms underlying its ability to deal with the toxic effects of AgNPs using a proteomic approach. We identified changes in the protein expression at AgNP concentrations inhibiting biomass production in 20% (EC20). After SDS-PAGE, the LC-MS/MS identified almost 200 proteins, about 50% of which increased its abundance under stress induced by AgNPs and Ag. Silver is known to react with proteins by combining with the thiol groups of enzymes, leading to protein inactivation. After AgNPs exposure, some of the upregulated proteins were associated with the degradation of transiently denatured and unfolded proteins, accumulated in the periplasm under stress conditions (e.g. periplasmic serine endoprotease). Exposure to AgNPs also induced proteins related to stress response, in particular, antioxidant enzymes, such as catalase-peroxidase and superoxide dismutase. The antioxidant response was consistent with our previous work suggesting that the ability to initiate an efficient antioxidant response is essential for the bacterium to cope with AgNP toxicity. We also found an increase in the proteins involved in amino acid (e.g. ornithine carbamoyltransferase) and energy metabolism (e.g. fructose-bisphosphate aldolase), which may reveal an AgNP-induced reorganization of the metabolic fluxes, that is compatible with an increased need of the bacterial cells to generate energy to support the defense mechanisms against AgNPs toxicity. An increased amount of chaperones (e.g. chaperone protein ClpB) was also found. These proteins play an essential role in the cell by assisting the correct folding of nascent and stress accumulated misfolded proteins and preventing their aggregation. AgNPs can likewise interact with elements of bacterial membranes, causing structural changes, dissipation of the proton motive + force, which is consistent with the increase in a specific porin with serine protease activity. Overall, PsM1’s response to the stress induced by AgNPs involved, among others, stress response proteins, proteins of the energy metabolism and transport proteins. Since the risk of the appearance of bacterial strains with augmented silver resistance is growing, it is highly recommended that the knowledge obtained from PsM1’s response to AgNPs be considered in future studies

The role of invertebrates and aquatic fungi on the decomposition of eucalyptus leaves in streams

Resumo da comunicação apresentada no XII Congresso da Association Española de Limnología - IV Congresso Ibérico de Limnologia. CIMAR, Universidade do Porto, 5-9 Julho 2004.Leaves entering in streams are subject to physical abrasion, invertebrate fragmentation and microbial degradation. Fungi, particularly aquatic hyphomycetes, dominate microbial leaf decomposition and condition the leaves, increasing their palatability for invertebrate shredders. The aim of this work was to study the relative role of invertebrates and aquatic fungi on leaf decomposition of Eucalyptus globulus Labill. in two rivers of Northwest Portugal with different water chemistry. For that purpose, leaf decomposition was followed in coarse-mesh and fine-mesh bags. Physical, chemical and microbial analyses of the stream water, as well as, biotic indices and diversity measures applied to the invertebrates associated with leaves showed that the Guisande River had better water quality than the Este River. Decomposition rates of eucalyptus leaves were significantly higher in the Guisande River (k = 0.019 to 0.029 dˉ¹) than in the Este River (k = 0.009 to 0.011 dˉ¹). Significantly higher fungal biomass (up to 790 μg ergosterol gˉ¹ AFDM) and sporulation rates (up to 370 conidia mgˉ¹ AFDM dˉ¹) occurred in the Guisande River in comparison with the Este River (fungal biomass up to 280 μg ergosterol gˉ¹ AFDM; sporulation rates up to 90 conidia mgˉ¹ AFDM dˉ¹). Correspondence analyses applied to aquatic hyphomycete and invertebrate assemblages discriminated the two rivers and higher richness in taxa was found in the Guisande River. In this river, leaf decomposition rate was significantly higher in coarse-mesh than in fine-mesh bags. However, in the Este River no significant differences were found between coarse-mesh and fine-mesh bags, which can be attributed to the absence of shredders and low current velocity in this river

Effects of increased temperature and aquatic fungal diversity on litter decomposition

This version thus not correspond to the final version of the journal. To assess the final version please go to: http://www.sciencedirect.com/science/article/pii/S1754504812000876Climate warming and biodiversity loss are two major factors threatening freshwaters. Aquatic hyphomycetes are fungi that play a key role in organic matter turnover in streams. To assess the impacts of temperature increase and aquatic hyphomycete diversity on plant-litter decomposition, we manipulated fungal assemblage composition at two levels of diversity (four and eight species) under ambient temperature of 16 º C and two regimes of temperature increase differing in 8 º C: abrupt versus gradual increase from 16 to 24 º C. The effects were evaluated on leaf-litter decomposition, fungal biomass and reproduction. Results showed faster leaf decomposition under increased temperature, but no differences were found between an abrupt and a gradual increase in temperature. Assemblage composition was the major factor controlling fungal biomass and reproduction, while fungal diversity was only critical to maintain reproduction.Fundação para a Ciência e a Tecnologia (FCT), através dos projectos: PTDC/CLI/67180/2006 (FCOMP-01-0124-FEDER-007112), TDC/AAC-AMB/117068/2010, e PEst-C/BIA/UI4050/2011

Are aquatic fungi able to evaluate microplastic impacts on leaf litter decomposition process?

Microplastics (MPs) have been recognized as a threat, and an ecotoxicological risk for aquatic ecosystems. MPs toxicity is determined by their physical and chemical properties, including particle size, shape, surface area or polymer type. Aquatic hyphomycetes are a group of fungi that have the greatest ecological effects on freshwater ecosystems, as they are involved in a key process on these ecosystems, the decomposition of plant litter in streams. These fungi have the ability to degrade and consequently transform leaf material into a more suitable food source for stream detritivores, being important mediators in the energy and nutrient transfer to higher trophic levels. The knowledge on the impacts of MPs on aquatic fungi and the processes they driven is very scarce, so the main goal of this study was to assess the impacts of different sizes of MPs (fragments, FR; and pellets, PE) on the leaf litter decomposition, measuring functional aspects such as leaf mass loss, fungal reproduction and activity of plant litter degrading enzymes. A microcosm experiment was used with monocultures and combinations up to three aquatic hyphomycetes species (Articulospora tetracladia, Tricladium splendens, and Heliscus lugdunensis), where concentrations of FR (0.5 and 2 g L-1) and PE (2 g L-1) were added. We expected that: i) the presence of FR could negatively affect all functional aspects; ii) the impacts of the PE could not be so strong as FR impacts, as PE has a bigger size than FR; iii) the traits of the fungal species would matter to face MP exposure because the traits of certain fungal species may be of greater importance than species number to maintain ecological processes. FR or PE led to a stimulation of leaf mass loss especially in combinations of two aquatic hyphomycetes. Consequently, the activity of degrading enzymes increased in the presence of 0.5 g L-1 FR and PE. Fungal sporulation rate increased in the presence of FR, especially for monocultures and combinations of three aquatic hyphomycetes, while the presence of PE decreased fungal sporulation in combinations of the three aquatic hyphomycetes. Our results showed the MPs influence in the activity and diversity of microbial decomposers, putting at risk the processes they drive in freshwaters. This suggest the aquatic hyphomycetes as potential microorganisms to be used to evaluate the MPs impacts on leaf decomposition process

Impacts of warming on aquatic decomposers along a gradient of cadmium stress

We evaluated the effects of cadmium and temperature on plant-litter decomposition by examining diversity and activity of aquatic fungi and leaf consumption by Limnephilus sp., a typical invertebrate shredder of Iberian streams. Freshly fallen leaves were immersed in a stream to allow microbial colonization, and were exposed in microcosms to a gradient of cadmium (≤11 levels, ≤35 mg L-1 ). Microcosms were kept at 15 ºC, a temperature typically found in Iberian streams in autumn, and at 21 ºC to simulate a warming scenario. The increase in temperature stimulated leaf decomposition by microbes, fungal reproduction and leaf consumption by the shredder. Conversely, increased cadmium concentrations inhibited fungal reproduction and diversity, and leaf consumption by the invertebrate. Cadmium concentration inhibiting 50% of fungal reproduction, microbial decomposition and leaf consumption by the shredder was higher at 15 ºC than at 21 ºC, suggesting that higher temperatures can lead to increased metal toxicity to aquatic decomposers.This study was supported by the Portuguese Foundation for Science and Technology through the projects PTDC/CLI/67180/2006 (FCOMP-01-0124-FEDER-007112) and PEst-C/BIA/UI4050/2011

Proteomic responses to nanoparticulate and ionic silver in fungi from metal-polluted and non-polluted streams

Enhanced production and usage of silver nanoparticles (AgNPs) raise concerns about their potential impacts in aquatic ecosystems. Effects of AgNPs and Ag+ were assessed based on the variations in the overall proteome and the activities of selected antioxidant enzymes in two fungal strains of Articulospora tetracladia, one isolated from a non-polluted stream (At72) and the other from a metal-polluted stream (At61). For that, fungi were exposed to concentrations of AgNPs and Ag+ affecting 20% of growth (EC20). A total of 432 proteins were identified, of which 172 belonged to At72 and 260 to At61; 71 were expressed in both strains. At72 had 58% and 52% of the proteins induced by AgNPs and Ag+, respectively. For At61, the percentages were higher ( ˜77%). The higher percentages of proteins suppressed by either Ag forms suggest higher stress in At72 than in At61, which is consistent with the background of this fungal strain. Major groups of proteins were related to carbohydrate metabolism, amino-acid and protein biosynthesis. Both Ag forms also induced stress-responsive proteins, including catalase and superoxide dismutase which remained consistent with the profile of their enzymatic activities. These results supported the ability of these fungi in initiating an efficient antioxidant response to cope with Ag-induced toxicity. Overall, the functional proteomic approach can be useful to get a mechanistic insight on the stress induced by AgNPs or Ag+ in aquatic fungi that play a key role in plant litter decomposition in stream

Proteomic responses to nanoparticulate and ionic silver in aquatic fungi

Enhanced use of silver nanoparticles (AgNPs) has inevitably resulted in their release into aquatic environments raising concern about the risk to aquatic biota and related ecological functions. Functional proteomics is an emerging technology that provides high-throughput analyses augmenting measurements of direct and highly sensitive responses at the cellular and sub-cellular levels. The impacts of AgNPs and its ionic precursor (Ag+ in AgNO3) at low exposure concentrations (close to environmental realism) on a fungal strain isolated from a non-polluted stream were assessed based on the variations in the overall proteome as well as in the activity of selected antioxidant enzymes. A total of 352 proteins were identified, but only 151 proteins were responsive (significantly up- or down-regulated relative to control) of which 65% presented matching alterations. Out of these 151 proteins, 62% increased abundance under stress induced by AgNPs and 56% under stress induced by Ag+. Exposure to both forms of silver induced proteins related to stress response, in particular, antioxidant enzymes. The antioxidant enzymatic responses were consistent with the proteomic responses, suggesting that the ability to initiate an efficient antioxidant response is essential for the fungus to cope with Ag-induced toxicity. Moreover, several proteins involved in the metabolism of carbohydrates, amino acids and lipids were altered. This evidence may reflect the need of generating energy to support the cellular defense mechanisms. Some of the significantly altered proteins were associated with the correct folding of nascent and stress accumulated misfolded proteins or degradation of transiently denatured and unfolded proteins preventing their aggregation. Others were related to the regulation of translation suggesting a compromised protein synthesis system. Overall, the functional proteomic approach can be useful to expand the knowledge on silver-induced stress responses in aquatic fung

Nano copper oxide is a threat to an endemic shredder of the Iberian Peninsula

FEDER-POFC-COMPETE and the Portuguese Foundation for Science and Technology supported this study (PEst-C/BIA/UI4050/2011, NANOECOTOX-PTDC/AAC-AMB/121650/2010) and A. Pradhan was supported by the Portuguese Foundation for Science and Technology (SFRH/BD/45614/2008)