Fine sediment on leaves : shredder removal of sediment does not enhance fungal colonisation

Inorganic fine sediments are easily carried into streams and rivers from disturbed land. These sediments can affect the stream biota, including detritivorous invertebrates (shredders) and impair ecosystem functions, such as leaf litter decomposition. We hypothesized that fine sediment (kaolin) deposited on leaves would reduce or suppress fungal development, reducing decomposition rates of leaves. Moreover, we predicted that shredders would act as ecosystem engineers by perturbing sediment deposition, reducing its impact on decomposition and fungi. We used a fully crossed experimental design of sediment addition (control, 400 mg L-1) and shredders (none, Gammarus, Potamophylax) in laboratory aquaria. Leaf mass loss, sus- pended solids, microbial respiration, fungal biomass and spore production were measured. Sediment addition had no significant effects on the leaf mass remaining nor on shredders’ consumption rates. However, sediment slightly reduced fungal assemblage richness and the sporulation rate of three fungal species. The presence of shredders sub- stantially increased the resuspension of fine sediments ([300%),resultinginhighersuspendedloads.However,the action of shredders did not have a significant effect on fungal biomass nor on leaf mass loss. Even if shredders did not enhance fungal colonisation, they affected the settle- ment of fine sediment, serving as allogenic engineers. Our study suggests that concentrations of fine sediment of 400 mg L-1 with short exposure times (192 h) can have some effect on leaf decomposition

Bottom-up effects of streambed drying on consumer performance through changes in resource quality

Stream flow intermittency and subsequent streambed drying, which already occurs in most biomes worldwide, is expected to increase in many regions due to both climate change and increased water demand. We studied the effects of streambed drying on leaves and epilithic biofilm and their effects on potential consumers. In the field, resources were conditioned according to the following treatments: (i) continuously submerged (PERM), (ii) submerged, exposed to the dry streambed and then submerged again (INT), or (iii) conditioned in the dry streambed and only allowed instream conditioning for 1 week (DRY, only for leaves). The results showed that drying affects resource quality, and the effects on biofilm were more severe than those on leaves. Both DRY leaves and INT biofilm showed lower microbial colonization and nitrogen accrual, whereas INT leaves had similar characteristics to PERM leaves. Drying resulted in decreased shredder and herbivore consumption rates and detritivore growth. Our results suggest that bottom-up effects of drying through changes in resource quality can constrain detritivore growth in temporary streams, potentially affecting stream secondary production and invertebrate-mediated organic matter cycling under a drier climate scenario

El Nino southern oscillation and seasonal drought drive riparian input dynamics in a Mediterranean stream

Inland waters substantially contribute to global carbon fluxes, and within them, low-order forested streams are important processors of allochthonous organic matter (OM) inputs. Leaf litter quantity and quality are expected to change in response to global change (e.g., climate change, land use change) but few long-term studies exist to better understand these shifts. The goal of this study was to assess the quantity and quality of OM sources to determine which global and local environmental factors control the dynamics of OM at the reach scale. The study was performed on a Mediterranean stream edged by a deciduous riparian forest over a 10-yr-time period. Riparian inputs, benthic and transported OM, and its carbon and nitrogen content were determined. The quantity of riparian inputs (912 +/- 56 g dry mass m(-2) yr(-1)) was comparable to temperate regions with deciduous riparian forests, but the Mediterranean climate determined the different dynamics of these inputs. El Nino Southern Oscillation was strongly related to the interannual variability in riparian inputs through changes in precipitation. The annual amount of inputs depended on previous cumulated nonflow periods, with successive nonflow periods causing a progressive decrease in riparian inputs. The distribution of inputs throughout the year followed either a unimodal or bimodal pattern according to the absence or presence of a nonflow period in summer. In addition, drought caused lower quality (higher carbon : nitrogen molar ratio) riparian inputs. Changes in the quantity and quality of OM were explained by both present and past local and global factors

Biochemical quality of basal resources in a forested stream: effects of nutrient enrichment

We studied biochemical changes in biofilm and suspended particulate and dissolved organic matter (OM) during the leaf emergence period (March-May 2008) in a forested headwater stream in response to a long-term (4 years, 2004-2008) experimental nutrient enrichment study. This study compared results from one reach upstream of the enrichment point and one reach downstream using moderate nutrient concentrations (nitrogen, N, from 388 to 765 μg L−1 and phosphorus, P, from 10 to 30 μg L−1, resulting in N:P ratios of 85-56). During the spring of 2008, we analysed the chlorophyll content, elemental composition (carbon, C, and N), bacterial density, and extracellular enzyme activities along with their biochemical composition (amino acids, fatty acids and sterols) on biofilm and OM. Nutrients caused changes in the biochemical composition of the biofilm, while changes in the OM were subtle. The C:N ratio of the biofilm decreased with nutrient enrichment likely due to the increase in protein (non-essential amino acids). The polysaccharide and total and essential fatty acid contents were higher when nutrient enrichment coincided with greater light availability. The peptidase extracellular activity was higher in the fertilised reach at early spring, while phosphatase activity decreased at late spring. The suspended and dissolved OM composition did not change due to the nutrient addition, likely due to the lower water residence time in the reach. Headwater systems are highly dynamic, and the biochemical composition of the biofilm changed in response to changes in nutrients but also to light in this study. These changes, although moderate, could influence higher trophic levels through modifications in their diet. This experiment exemplifies how small land use shifts may affect headwater streams

Drought effects on resource quality in a Mediterranean stream: fatty acids and sterols as indicators

Seasonal droughts in Mediterranean streams shape their physical, chemical, and biological characteristics. Thus, droughts have the potential to alter resources at the base of the food web, which in headwater streams are primarily allochthonous and secondarily autochthonous organic matter (OM). In the present study we assessed the quality of basal resources in a Mediterranean stream during a drought episode before and after a non-flow period (NF). Fatty acids (FA) and sterols were analyzed in the benthic substrata (leaves and sand and cobbles biofilm) and transported OM (particulate and dissolved fractions). FA and sterols were selected as indicators of resource quality because they include essential molecules for consumers and may be used as biomarkers of OM sources. The drying-rewetting process determined a general reduction in the total and essential FA of benthic substrata and transported particulate OM, and a shift from predominantly autochthonous to allochthonous OM. Furthermore, the sterol composition did not change between the drying and rewetting phases and the rewetting did not cause the leaching of FA in dissolved OM. The epilithic biofilm and leaves were the most important sources of essential FA and sterols, while the sand biofilm was the poorest source of these lipids. Our conclusions enhance the understanding of the mechanisms underlying the effects of droughts on basal resource quality in streams

Mosquito alert: leveraging citizen science to create a GBIF mosquito occurrence dataset

The Mosquito Alert dataset includes occurrence records of adult mosquitoes collected worldwide in 2014-2020 through Mosquito Alert, a citizen science system for investigating and managing disease-carrying mosquitoes. Records are linked to citizen science-submitted photographs and validated by entomologists to determine the presence of five targeted European mosquito vectors: Aedes albopictus, Ae. aegypti, Ae. japonicus, Ae. koreicus, and Culex pipiens. Most records are from Spain, reflecting Spanish national and regional funding, but since autumn 2020 substantial records from other European countries are included, thanks to volunteer entomologists coordinated by the AIM-COST Action, and to technological developments to increase scalability. Among other applications, the Mosquito Alert dataset will help develop citizen science-based early warning systems for mosquito-borne disease risk. It can also be reused for modelling vector exposure risk, or to train machine-learning detection and classification routines on the linked images, to assist with data validation and establishing automated alert systems

Early-Career Coordinated Distributed Experiments: Empowerment Through Collaboration

Este artículo contiene 7 páginas, 1 tabla, 3 figuras.Coordinated distributed experiments (CDEs) enable the study of large-scale ecological patterns in geographically dispersed areas, while simultaneously providing broad academic and personal benefits for the participants. However, the effective involvement of early-career researchers (ECRs) presents major challenges. Here, we analyze the benefits and challenges of the first CDE exclusively led and conducted by ECRs (i.e. ECR-CDE), which sets a baseline for similar CDEs, and we provide recommendations for successful CDE execution. ECR-CDEs achieve most of the outcomes identified in conventional CDEs as well as extensive benefits for the young cohort of researchers, including: (i) receiving scientific credit, (ii) peer-training in new concepts and methods, (iii) developing leadership and communication skills, (iv) promoting a peer network among ECRs, and (v) building on individual engagement and independence. We also discuss the challenges of ECR-CDEs, which are mainly derived from the lack of independence and instability of the participants, and we suggest mechanisms to address them, such as resource re-allocation and communication strategies. We conclude that ECR-CDEs can be a relevant tool to empower ECRs across disciplines by fostering their training, networking and personal well-being.The authors were supported by the following founding: NC the support of the Beatriu de Pinós postdoctoral program of the Government of Catalonia’s Secretariat for Universities and Research of the Ministry of Economy and Knowledge (BP2016- 00215), EE by a predoctoral grant from the Basque Government (2014-2017), AB by a Generalitat de Catalunya—Beatriu de Pinós (BP-00385-2016), AMG-F by a predoctoral research grant (BES-2013-065770) from the Spanish Ministry of Economy and Competitiveness, MAr by a postdoctoral grant from the Basque Government, MIA by a Juan de la Cierva postdoctoral grant (FJCI-2015-26192), PR-L by a Margalida Comas postdoctoral contract (PD/031/2018) funded by the Government of the Balearic Islands and the European Social Fund, AP by a Ramón Areces Foundation Postdoctoral Scholarship, and AL by a Kempe Foundation stipend. DOMIPEX project was founded by the First Call of Collaborative Projects among Young Researchers of the Iberian Association of Limnology (AIL; 2013-2015).Peer reviewe

AIMSurv: First pan-European harmonized surveillance of Aedes invasive mosquito species of relevance for human vector-borne diseases

Human and animal vector-borne diseases, particularly mosquito-borne diseases, are emerging or re-emerging worldwide. Six Aedes invasive mosquito (AIM) species were introduced to Europe since the 1970s: Aedes aegypti, Ae. albopictus, Ae. japonicus, Ae. koreicus, Ae. atropalpus and Ae. triseriatus. Here, we report the results of AIMSurv2020, the first pan-European surveillance effort for AIMs. Implemented by 42 volunteer teams from 24 countries. And presented in the form of a dataset named “AIMSurv Aedes Invasive Mosquito species harmonized surveillance in Europe. AIM-COST Action. Project ID: CA17108”. AIMSurv2020 harmonizes field surveillance methodologies for sampling different AIMs life stages, frequency and minimum length of sampling period, and data reporting. Data include minimum requirements for sample types and recommended requirements for those teams with more resources. Data are published as a Darwin Core archive in the Global Biodiversity Information Facility- Spain, comprising a core file with 19,130 records (EventID) and an occurrences file with 19,743 records (OccurrenceID). AIM species recorded in AIMSurv2020 were Ae. albopictus, Ae. japonicus and Ae. koreicus, as well as native mosquito species

Global changes in headwater streams: effects of hydrological and nutrient fluctuations on the quality of basal resources = Canvis globals en rius de capçalera: efectes de les fluctuacions hidrològiques i dels nutrients en la qualitat dels recursos basals

[cat] Els rius són ecosistemes complexes i molt diversos. Dins la xarxa fluvial, les rius de capçalera (de 1er a 3er ordre) tenen una gran importància. Els rius de capçalera representen la major part de la longitud total, influencien l’estructura i el funcionament dels rius d’ordre més gran, generen la major part del cabal i donen suport a taxes altes de processament biogeoquímic, amb una alta taxa d’eliminació de nutrients. A més a més, contenen un gran diversitat d’hàbitats, tant dins dels rius com entre ells. De tota la conca, és la zona ripària la que té una més gran influència en l’estructura i el funcionament d’aquests rius. La caiguda de la vegetació i el lixiviat de les fullaraca són importants fonts d’energia per les xarxes tròfiques. Tota l’energia disponible pels consumidors prové dels productors primaris tant de dins com de fora del riu i les xarxes tròfiques estan sustentades per una complexa barreja de recursos al•lòctons i autòctons. En els rius de capçalera, els recursos basals al•lòctons són generalment més importants que les fonts d’energia autòctones. Tot i això, tant la quantitat com la qualitat dels recursos al•lòctons i autòctons influencies l’estructura i el funcionament d’aquests rius. La qualitat dels recursos determina el seu valor nutritiu potencial pels invertebrats que s’alimenten d’ells. La qualitat nutritiva de la matèria orgànica (MO) es pot ser avaluada mesurant la composició elemental o de biomolècules (contingut de polisacàrids, proteïnes i lípids). Els lípids són els components d’emmagatzematge d’energia més eficients, i dins dels lípids, els àcids grassos I els esterols inclouen molècules essencials pels consumidors. En un context de canvi global, els rius estan afectats de forma molt important per múltiples impactes antròpics directes i indirectes, tals com el canvi climàtics, els canvis d’usos del sòl i les alteracions dels cursos fluvials; els quals afecten la hidrologia i la disponibilitat de nutrients i llum, els quals al seu torn, afecten la quantitat i la qualitat dels recursos basals en els rius de capçalera. Dels múltiples factors ambientals afectats pel canvi global, aquest estudi es centra en els canvis en la hidrologia i la disponibilitat de llum i nutrients, en particular als rius de capçalera Mediterranis. Aquest estudi ha estat realitzat principalment a Fuirosos, un riu Mediterrani al nord-est de la Península Ibèrica, però també als canals artificials de Mayfly creek, a les muntanyes de la costa Pacífica de Canadà. En aquest estudi s’han utilitzat diversos mètodes, tal i com la mesura dels fluxos de MO particulada i dissolta, la composició elemental de la MO, l’addició de nutrients; el contingut de clorofil•la, la densitat bacteriana i les activitats enzimàtiques extracel•lulars del biofilm i la mesura de la qualitat bioquímica dels recursos basals (és a dir, els biofilms epilítics i epipsàmics, les fulles i la MO particulada i dissolta transportada). Hem demostrar que El Niño/Oscil•lació del Sud (ENOS) va afectar les aportacions ripàries al riu a través de teleconnexions que van alterar la precipitació mitjana (durant els períodes de El Niño, la precipitació mitjana anual era més baixa, provocant un augment de les aportacions ripàries, degut a l’estrès hídric dels arbres, mentre que durant els períodes de La Niña, la precipitació era més alta que en altres moments, portant a una disminució de les aportacions ripàries). Els períodes de sequera van causar una distribució bimodal de les aportacions ripàries anuals i van reduir la qualitat dels recursos basals, mentre que els episodis de sequera acumulats van provocar la disminució de les aportacions ripàries). Les avingudes van provocar la disminució de la MO bentònica, van augmentar la quantitat de MO transportada i van modificar la seva qualitat. L’addició de nutrients va portar a una disminució del contingut de carboni, i una disponibilitat més alta de llum va provocar una disminució del contingut de proteïnes dels recursos al•lòctons. La qualitat del biofilm era generalment més alta amb l’addició de nutrients quan la disponibilitat de llum era més alta. Considerem que la qualitat nutritiva dels recursos basals és un paràmetre complex. Tot i que la composició elemental i bioquímica poden estar relacionades en alguns casos, el coneixement d’aquesta última permet una millor comprensió dels mecanismes a través dels quals els canvis abiòtics afecten la qualitat dels recursos. Tot i això, la complexitat de mesurar la composició elemental, la composició bioquímica i els àcids grassos, augmenta gradualment. Així doncs, suggerim que la tria dels indicador de qualitat utilitzats dependrà de l’objectiu de l’estudi que es vulgui realitzar i en el balanç entre l’esforç d’anàlisi i la informació que es vol obtenir. Com que les xarxes tròfiques estan sustentades per una complexa barreja de recursos al•lòctons i autòctons, la quantitat i la qualitat d’aquests recursos són factors que limiten la producció secundària en el riu. Així doncs, els canvis observats en aquest estudi, afectaran probablement les xarxes tròfiques fluvials.[eng] Streams are complex and highly diverse ecosystems. Within the stream network, headwater streams (1st to 3rd order) are highly important. Headwaters represent most of the total length, influence the structure and functioning of higher order streams, generate most of the water flow and support higher rates of biogeochemical processing, with a higher rate of nutrient removal. Moreover, they offer high habitat diversity, both within and among streams. From all the drainage basin, it is the riparian zone which has the greatest influence in the structure and functioning of these streams. The in-fall of vegetation and leaching from plant litter are major sources of energy for stream food webs. All energy available to consumers originates from primary producers from either out- or in-stream and food webs are fuelled by a complex mixture of allochthonous and autochthonous resources. In headwaters, allochthonous basal resources are generally larger than autochthonous energy sources. However, both the quantity and quality of allochthonous and autochthonous resources influence the stream structure and functioning. Quality of resources determines their potential nutritional value for the invertebrates feeding on them. The nutritional quality of organic matter (OM) can be assessed by measuring the elemental or biomolecule composition (polysaccharide, protein and lipid content). Lipids are the most efficient energy-storing compounds, and within lipids, fatty acids and sterols include essential molecules for consumers. In a context of global change, streams are highly affected by multiple direct and indirect anthropic impacts, such as climate change, land use changes and water course alterations, affecting hydrology and nutrient and light availability, which in turn affect the quality and quantity of basal resources. The aim of this thesis was to determine how environmental factors influence the quantity and quality (biochemical composition) of basal resources in headwater streams. Of the multiple environmental factors affected by global change, the present study focused on changes in hydrology and nutrient and light availability, with particular reference to headwater Mediterranean streams. This study has been mainly performed in Fuirosos, a Mediterranean stream in the northeast of the Iberian Peninsula, but also in the Mayfly creek artificial channels, in the Pacific Coast Mountains of Canada. Several methods were used, such as the measure of particulate and dissolved OM fluxes, elemental composition of OM, nutrient addition; chlorophyll content, bacterial density and extracellular enzymatic activities of biofilms, and the measurement of the biochemical quality of the basal resources. (i.e., epilithic and epipsammic biofilms, leaves and, transported particulate and dissolved OM). We have demonstrated that the El Niño Southern Oscillation (ENSO) affected riparian inputs to the stream through teleconnections that alter average precipitation (during El Niño periods, average annual precipitation was lower than in other periods, causing higher riparian inputs, due to the hydric stress of riparian trees while, during La Niña periods, precipitation was higher than at other times, leading to decreased riparian inputs). Drought periods caused a bimodal distribution of annual riparian inputs and reduced the quality of basal resources, whereas accumulated drought events diminished the riparian inputs. Floods decreased the benthic OM, increased the amount of transported OM and modified its quality. The addition of nutrients led to a decrease in carbon content, and higher light availability led to a decrease in protein content of allochthonous resources. Biofilm quality was generally higher with the addition of nutrients when light availability was higher. We consider that the nutritional quality of basal resources is a complex parameter. Whilst elemental and biochemical composition can sometimes be related, knowledge on the latter enables a better understanding of the mechanism by which abiotic changes affect the quality of resources. However, the complexity of measuring elemental composition, biochemical composition and fatty acid composition gradually increases. Hence, we suggest that the choice of the indicators of quality used would depend on the goal of the study that want to be performed and on the trade-off between analysis effort and information that wants to be obtained. Because food webs are fuelled by a complex mixture of allochthonous and autochthonous resources, the quantity and quality of these resources are limiting factors for stream secondary production. Hence, the changes observed in this study, will probably affect stream food webs