Functional repercussions of riparian biodivesity loss in streams. Multifunctionality, diversity metrics and underlying mechanisms.

152 p.El objetivo de esta tesis es abordar cuestiones clave poco exploradas en la investigación de la relación entre la biodiversidad y el funcionamiento de los ecosistemas (BEF, por sus siglas en inglés). Concretamente se estudia cómo la pérdida de diversidad en el bosque ripario puede alterar el funcionamiento del ecosistema fluvial. Primeramente, se explora cómo la pérdida de diversidad de hojarasca puede afectar de manera simultánea a múltiples procesos fundamentales para los arroyos de cabecera. Los resultados evidencian efectos en múltiples procesos y demuestran que, a pesar de la utilidad de las métricas de multifuncionalidad para evaluar los impactos generales en el ecosistema, el análisis individual de diferentes procesos es esencial para comprender completamente cómo los organismos, las redes tróficas y, en última instancia, los ecosistemas, se ven alterados por la pérdida de diversidad. Los efectos más marcados y consistentes se detectaron sobre el reciclado de nutrientes. Además, se analiza la potencial interacción de la vía detrítica con la autótrofa, dentro de la cadena trófica de los arroyos de cabecera. Los resultados evidencian la existencia de interacciones débiles entre ambas, sin relaciones complejas entre la biodiversidad y los procesos de los ecosistemas a través de las vías. La siguiente cuestión abordada es la relevancia de diferentes métricas de biodiversidad (riqueza de especies, distancia filogenética y variabilidad de los rasgos biológicos) dentro del contexto BEF. Los diferentes estudios, tanto de campo como de laboratorio, revelaron diferencias importantes entre estas métricas, destacando el papel principal de rasgos concretos de la hojarasca (principalmente las concentraciones de los nutrientes principales) como promotores de las relaciones BEF. Por último, con el objetivo de mejorar nuestra comprensión de los mecanismos subyacentes dichas relaciones, se explora la importancia relativa de los efectos de complementariedad y selección entre las especies de hojarasca. La complementariedad de recursos resultó ser, en la mayoría de los casos, el mecanismo dominante, lo que destaca la relevancia de las interacciones interespecíficas como mediadoras de los efectos de la biodiversidad en el funcionamiento de los ecosistemas. En su conjunto, esta tesis proporciona un avance importante en la comprensión de cómo la pérdida y el reemplazo de especies de plantas riparias puede causar alteraciones significativas en múltiples procesos que son fundamentales para el funcionamiento de los arroyos de cabecera

Functional repercussions of riparian biodivesity loss in streams. Multifunctionality, diversity metrics and underlying mechanisms.

152 p.El objetivo de esta tesis es abordar cuestiones clave poco exploradas en la investigación de la relación entre la biodiversidad y el funcionamiento de los ecosistemas (BEF, por sus siglas en inglés). Concretamente se estudia cómo la pérdida de diversidad en el bosque ripario puede alterar el funcionamiento del ecosistema fluvial. Primeramente, se explora cómo la pérdida de diversidad de hojarasca puede afectar de manera simultánea a múltiples procesos fundamentales para los arroyos de cabecera. Los resultados evidencian efectos en múltiples procesos y demuestran que, a pesar de la utilidad de las métricas de multifuncionalidad para evaluar los impactos generales en el ecosistema, el análisis individual de diferentes procesos es esencial para comprender completamente cómo los organismos, las redes tróficas y, en última instancia, los ecosistemas, se ven alterados por la pérdida de diversidad. Los efectos más marcados y consistentes se detectaron sobre el reciclado de nutrientes. Además, se analiza la potencial interacción de la vía detrítica con la autótrofa, dentro de la cadena trófica de los arroyos de cabecera. Los resultados evidencian la existencia de interacciones débiles entre ambas, sin relaciones complejas entre la biodiversidad y los procesos de los ecosistemas a través de las vías. La siguiente cuestión abordada es la relevancia de diferentes métricas de biodiversidad (riqueza de especies, distancia filogenética y variabilidad de los rasgos biológicos) dentro del contexto BEF. Los diferentes estudios, tanto de campo como de laboratorio, revelaron diferencias importantes entre estas métricas, destacando el papel principal de rasgos concretos de la hojarasca (principalmente las concentraciones de los nutrientes principales) como promotores de las relaciones BEF. Por último, con el objetivo de mejorar nuestra comprensión de los mecanismos subyacentes dichas relaciones, se explora la importancia relativa de los efectos de complementariedad y selección entre las especies de hojarasca. La complementariedad de recursos resultó ser, en la mayoría de los casos, el mecanismo dominante, lo que destaca la relevancia de las interacciones interespecíficas como mediadoras de los efectos de la biodiversidad en el funcionamiento de los ecosistemas. En su conjunto, esta tesis proporciona un avance importante en la comprensión de cómo la pérdida y el reemplazo de especies de plantas riparias puede causar alteraciones significativas en múltiples procesos que son fundamentales para el funcionamiento de los arroyos de cabecera

Teknologia kimikoa. Sistema kimikoen datuak eta konposatu kimikoen parametroak

50 p.Teknologia kimikoaren alorrean (ingeniaritzako kimika-arloa) ezinbestekoa da bibliografian agertzen diren sistema kimikoen zenbait datu eta konposatu kimiko industrialen hainbat propietate erabiltzea. Lehenengo aipatutakoen artean oreka-konstanteak, erredukziozko potentzialak edo erreakzio kimikoen entalpia-aldaketak daude; konposatuen propietateen artean, berriz, lurrun-presioa, bero-ahalmena edo entropia absolutua aurki daitezke. Datu horiek oinarrizkoak dira ingeniaritza kimikoko kalkuluak gauzatu ahal izateko; hala nola, bero-trukatzaile batean trukatzen den bero kantitatea zenbatesteko, galbanizazio elektrolitiko batean ezarriko den metalaren kantitatea aurreikusteko edo erreaktore baten tenperatura zehazteko. Datu horiek guztiak, normalean, liburu espezializatuen «Taulak» esaten zaien eranskinetan agertzen dira. Hala ere, nahiz eta oinarrizkoak diren, zaila izaten da ingeniaritza kimikoko kalkulu jakin bat egiteko beharrezkoak diren datu guztiak liburu bakarrean aurkitzea, liburu bakoitza bere edukian jorratutako gaietan baino ez delako ardazten. Ohikoa da zientzia kimikoa lantzen duten liburu klasikoetan zientzia kimikoaren datuak agertzea, besteak beste, elementuen elektronegatibotasuna, formazio-entalpiak, hainbat azido eta base ahulen oreka-konstanteak, konposatu ezorganikoen disolbagarritasun-biderkadura edo erredukzio-potentzial estandarrak. Ingeniaritza edo teknologia kimikoko bibliografian, aldiz, oinarrizko kimikaren konstanteak eta parametroak alde batera utzi ohi dira. Mota horretako liburuetan, prozesu industrial kimikoen unitateak diseinatzeko erabilgarriak diren datuak biltzen dira, hala nola: hainbat konposaturen urtze-, sublimazio- eta lurruntze-bero sorrak, bero espezifikoak, Antoineren parametroak, etab. Hori dela eta, normalean ikasleei iturri desberdinetatik hartutako datuak ematen zaizkie eta batzuetan datu horiek erreferentzia desberdinekin kalkulatuta daude. Esate baterako, ohikoa da tenperaturaren menpekoak diren konposatuen propietateak, bero-ahalmena kasu, tenperatura diferenteetan aurkitzea iturriaren arabera. Beste batzuetan, propietate berbera unitate ezberdinetan agertzen da liburuaren arabera, askotan sistema internazionala ez den unitate-sistemaren batean (sistema anglo-saxoia oraindik ere oso hedatuta dago teknologia kimikoaren arloan). Horretaz aparte, esan gabe doa arlo honetan eskuragarri dauden datu eta propietate gehienak ingelesez (nagusiki) eta gaztelaniaz argitaratuta daudela. Ondorioz, eskuarki ikasleei emandako «taulak» euskara ez den beste hizkuntza batean agertu ohi dira. Erakutsitako arrazoi guztiak direla eta, egileek uste dute dokumentu honetan aurkezten den datubilduma oso erabilgarria izan daitekeela unibertsitatean teknologia kimikoko arloan ikasten eta lan egiten duten ikasle, irakasle eta ikertzaileentzat

Teknologia kimikoa. Sistema kimikoen datuak eta konposatu kimikoen parametroak

50 p.Teknologia kimikoaren alorrean (ingeniaritzako kimika-arloa) ezinbestekoa da bibliografian agertzen diren sistema kimikoen zenbait datu eta konposatu kimiko industrialen hainbat propietate erabiltzea. Lehenengo aipatutakoen artean oreka-konstanteak, erredukziozko potentzialak edo erreakzio kimikoen entalpia-aldaketak daude; konposatuen propietateen artean, berriz, lurrun-presioa, bero-ahalmena edo entropia absolutua aurki daitezke. Datu horiek oinarrizkoak dira ingeniaritza kimikoko kalkuluak gauzatu ahal izateko; hala nola, bero-trukatzaile batean trukatzen den bero kantitatea zenbatesteko, galbanizazio elektrolitiko batean ezarriko den metalaren kantitatea aurreikusteko edo erreaktore baten tenperatura zehazteko. Datu horiek guztiak, normalean, liburu espezializatuen «Taulak» esaten zaien eranskinetan agertzen dira. Hala ere, nahiz eta oinarrizkoak diren, zaila izaten da ingeniaritza kimikoko kalkulu jakin bat egiteko beharrezkoak diren datu guztiak liburu bakarrean aurkitzea, liburu bakoitza bere edukian jorratutako gaietan baino ez delako ardazten. Ohikoa da zientzia kimikoa lantzen duten liburu klasikoetan zientzia kimikoaren datuak agertzea, besteak beste, elementuen elektronegatibotasuna, formazio-entalpiak, hainbat azido eta base ahulen oreka-konstanteak, konposatu ezorganikoen disolbagarritasun-biderkadura edo erredukzio-potentzial estandarrak. Ingeniaritza edo teknologia kimikoko bibliografian, aldiz, oinarrizko kimikaren konstanteak eta parametroak alde batera utzi ohi dira. Mota horretako liburuetan, prozesu industrial kimikoen unitateak diseinatzeko erabilgarriak diren datuak biltzen dira, hala nola: hainbat konposaturen urtze-, sublimazio- eta lurruntze-bero sorrak, bero espezifikoak, Antoineren parametroak, etab. Hori dela eta, normalean ikasleei iturri desberdinetatik hartutako datuak ematen zaizkie eta batzuetan datu horiek erreferentzia desberdinekin kalkulatuta daude. Esate baterako, ohikoa da tenperaturaren menpekoak diren konposatuen propietateak, bero-ahalmena kasu, tenperatura diferenteetan aurkitzea iturriaren arabera. Beste batzuetan, propietate berbera unitate ezberdinetan agertzen da liburuaren arabera, askotan sistema internazionala ez den unitate-sistemaren batean (sistema anglo-saxoia oraindik ere oso hedatuta dago teknologia kimikoaren arloan). Horretaz aparte, esan gabe doa arlo honetan eskuragarri dauden datu eta propietate gehienak ingelesez (nagusiki) eta gaztelaniaz argitaratuta daudela. Ondorioz, eskuarki ikasleei emandako «taulak» euskara ez den beste hizkuntza batean agertu ohi dira. Erakutsitako arrazoi guztiak direla eta, egileek uste dute dokumentu honetan aurkezten den datubilduma oso erabilgarria izan daitekeela unibertsitatean teknologia kimikoko arloan ikasten eta lan egiten duten ikasle, irakasle eta ikertzaileentzat

Extreme temperature events alter stream ecosystem functioning

Extreme temperature events have increased in intensity, duration and frequency in the last century, with potential consequences on organisms and ecosystems. In many streams, leaf litter of terrestrial origin is a key resource for microorganisms and some detritivores, and its decomposition has a main role on ecosystem functioning and is often used as an indicator of ecological integrity. As litter is often exposed to atmospheric conditions before entering the stream, extreme warming and freezing events may alter its physicochemical structure and affect decomposition and associated detritivores. We tested this prediction in a microcosm experiment by exposing litter of three tree species (in single-species treatments and the 3-species mixture) to different temperature pre-treatments: heating (40 degrees C), freezing ( - 20 degrees C) and both (heating followed by freezing). We then examined changes in litter traits due to leaching (72 h), litter decomposition in the absence and presence of detritivores, and detritivore growth (28 d), with focus on mass and nutrient (nitrogen and phosphorus) changes. Nutrient leaching was promoted mostly by the heating pre-treatment, which apparently produced lower-quality litter. However, microbial activity mostly resulted in litter mass and nutrient gain, which were reinforced by the heating pre-treatment, while freezing had the opposite effect. When detritivores were present, decomposition showed high variation among litter types but, again, the heating and freezing pre-treatments tended to reduce and enhance nutrient loss, respectively. The greatest and more consistent effects occurred for detritivore growth, which was reduced by temperature pre-treatments, particularly in the highest-quality litter type. In general, the sequential application of heating and freezing pre-treatments showed no synergistic effect, and the litter mixture showed similar responses to single-species treatments. Our results demonstrate that short-term extreme temperatures can modify litter quality in riparian soils and have subsequent effects on its decomposition within the stream and associated fauna, potentially altering stream food webs, ecosystem functioning and biogeochemical cycles.This study was funded by the Spanish Ministry for Science, Innovation and Universities and FEDER (project BioLoss, Ref. RTI2018-095023-B400), Basque Goverment funds (Ref. IT951-16) and Initiation Fondecyt Project (Ref. 11170390). I. Diaz and U. Apodaka-Etxebarria contributed to the sample processing

Effects of gamma irradiation on instream leaf litter decomposition

Leaf litter decomposition is a key process in stream ecosystems, the rates of which can vary with changes in litter quality or its colonization by microorganisms. Decomposition in streams is increasingly used to compare ecosystem functioning globally, often requiring the distribution of litter across countries. It is important to understand whether litter sterilization, which is required by some countries, can alter the rates of decomposition and associated processes. We examined whether litter sterilization with gamma irradiation (25 kGy) influenced decomposition rates, litter stoichiometry, and colonization by invertebrates after weeks of instream incubation within coarse-mesh and fine-mesh litterbags. We used nine plant species from three families that varied widely in litter chemistry but found mostly consistent responses, with no differences in decomposition rates or numbers of invertebrates found at the end of the incubation period. However, litter stoichiometry differed between irradiated and control litter, with greater nutrient losses (mostly phosphorus) in the former. Therefore, the effects of irradiation on litter chemistry should be taken into account in studies focused on stoichiometry but not necessarily in those focused on decomposition rates, at least within the experimental timescale considered here

No evidence of biodiversity effects on stream ecosystem functioning across green and brown food web pathways

[EN] Biodiversity loss is known to affect the two fundamental and opposite processes controlling carbon and nutrient cycles globally, that is, primary production and decomposition, which are driven by green and brown food web compartments, respectively. However, biodiversity in these two food web compartments has been mostly studied independently, and potential reciprocal effects of biodiversity loss on ecosystem processes remain unclear. We conducted a 35-day stream mesocosm experiment with two levels of algal diversity (natural and diluted periphyton communities) and three levels of litter diversity (no litter, monocultures of poplar, maple, and oak, and the three-spp. mixture) to simulate changes in biodiversity in both the green and brown pathways of an aquatic food web. We then measured multiple ecosystem processes pertaining to carbon cycling. We predicted that algal diversity would enhance decomposition and sporulation of fungal decomposers, while litter diversity would enhance algal growth and net primary production, due to the more diverse algal exudates or litter nutrients being released from more diverse mixtures. In contrast to this hypothesis, we only found biodiversity effects on an ecosystem process within the green pathway: there was a relationship between algal diversity and biofilm carrying capacity. Nevertheless, we found that this relationship was affected by the presence or absence of litter (algal diversity increased the carrying capacity in presence of litter and decreased it in its absence), which also influenced the algal community structure. Our mesocosm experiment did not evidence relationships between biodiversity and ecosystem processes across different food web compartments, but further studies in more realistic conditions would be necessary to confirm this result. If supported, the lack of biodiversity-ecosystem functioning relationships across compartments would facilitate the prediction of the impacts of biodiversity loss on ecosystems.Spanish Ministry for Science, Innovation and Universities and FEDER; U.S. National Science Foundation, Grant/Award Number: 133234

A common fungicide impairs stream ecosystem functioning through effects on aquatic hyphomycetes and detritivorous caddisflies

Fungicides can reach streams through runoff or adhered to leaf litter, and have the potential to adversely affect processes such as litter decomposition and associated communities. This study investigated the effects of chlorothalonil, a widely used fungicide, on litter decomposition, detritivorous invertebrates (larvae of the insect Sericostoma pyrenaicum) and aquatic hyphomycetes (AHs), using stream microcosms. We considered the single and combined effects of two exposure modes: waterborne fungicide (at two concentrations: 0.125 mu g L-1 and 1.25 mu g L-1) and litter previously sprayed with the fungicide (i.e., pre-treated litter, using the application dose concentration of 1250 mu g L-1). We also assessed whether fungicide effects on invertebrates, AHs and decomposition varied among litter types (i.e., different plant species), and whether plant diversity mitigated any of those effects. Invertebrate survival and AH sporulation rate and taxon richness were strongly reduced by most combinations of fungicide exposure modes; however, invertebrates were not affected by the low waterborne concentration, whereas AHs suffered the highest reduction at this concentration. Total decomposition was slowed down by both exposure modes, and microbial decomposition was reduced by litter pre-treatment, while the waterborne fungicide had different effects depending on plant species. In general, with the exception of microbial decomposition, responses varied little among litter types. Moreover, and contrary to our expectation, plant diversity did not modulate the fungicide effects. Our results highlight the severity of fungicide inputs to streams through effects on invertebrate and microbial communities and ecosystem functioning, even in streams with well-preserved, diverse riparian vegetation.We thank Richard Pearson and two anonymous reviewers for their comments on the manuscript. This study was derived from AC's PhD thesis and AA's MSc thesis. AC was supported by a fellowship of the National Secretariat of Science, Technology and Innovation (SENACYT) and the National Research System of Panama (SNI). SM was supported by a postdoctoral grant from the University of the Basque Country. Additional funding was obtained from the Spanish Ministry for Science, Innovation and Universities and FEDER (project BioLoss, RTI2018095023-B-I00) and Basque Government funds (IT951-16)

Key plant species and detritivores drive diversity effects on instream leaf litter decomposition more than functional diversity: A microcosm study

Anthropogenic impacts on freshwater ecosystems cause critical losses of biodiversity that can in turn impair key processes such as decomposition and nutrient cycling. Forest streams are mainly subsidized by terrestrial organic detritus, so their functioning and conservation status can be altered by changes in forest biodiversity and composition, particularly if these changes involve the replacement of functional groups or the loss of key species. We examined this issue using a microcosm experiment where we manipulated plant functional diversity (FD) (monocultures and low-FD and high-FD mixtures, resulting from different combinations of deciduous and evergreen Quercus species) and the presence of a key species (Alnus glutinosa), all in presence and absence of detritivores, and assessed effects on litter decomposition, nutrient cycling, and fungal and detritivore biomass. We found (i) positive diversity effects on detritivore-mediated decomposition, litter nutrient losses and detritivore biomass exclusively when A. glutinosa was present; and (ii) negative effects on the same processes when microbially mediated and on fungal biomass. Most positive trends could be explained by the higher litter palatability and litter trait variability obtained with the inclusion of alder leaves in the mixture. Our results support the hypothesis of a consistent slowing down of the decomposition process as a result of plant biodiversity loss, and hence effects on stream ecosystem functioning, especially when a key (N-fixing) species is lost; and underscore the importance of detritivores as drivers of plant diversity effects in the studied ecosystem processes.This study was funded by the 2014–2020 FEDER Operative Program Andalusia (RIOVEGEST project, Ref. FEDER-UAL18 -RNM -B006 – B, to J.J.C). Additional support was provided by the Spanish Ministry for Science, Innovation and Universities and FEDER (BioLoss project, Ref. RTI2018-095023- B-I00, to L.B.). Rubio-Ríos was supported by an FPU grant of the Spanish Ministry of Education, Culture and Sports (reference FPU16/03734)

Sustainable mold biomachining for the manufacturing of microfluidic devices

Biomachining has been investigated as a sustainable and effective alternative to conventional prototyping techniques for molding polymeric materials for their subsequent use as microfluidic devices. A novel and simple process based on the combination of a Pressure Sensitive Adhesive mask and a varnish has been proposed for preparing metal workpieces as an alternative to photolithography, with the latter being the most widely used technique for protecting workpieces. As far as the bioprocess is concerned, it has been applied in successive mold-etching and oxidant bio-regeneration stages. Metal solubilization has proven to be repeatable in several consecutive mold-etching stages when using the regenerated oxidant solution. As a result, the lifespan of the biomachining medium has been prolonged, contributing to process sustainability. An equation with two restrictions has been proposed to predict the time required to obtain a mold with a fixed height, as metal solubilization evolves differently between the first and subsequent hours. Finally, the bio-engraved copper pieces have acted as effective molds in the fabrication of self-powered polydimethylsiloxane microfluidic devices. This new biomachining application is therefore an effective and ecofriendly process for producing microfluidic devices.This work was supported by the State Agency for Research (AEI) of the Spanish Government-European Regional Development Fund (FEDER-ERDF, EU) [grant number: CTM2016-77212-P], Spain’s Ministry of Science and Education [grant number: PID2020-120313 GB-I00/AIE/10.13039/501100011033], and the Basque Government’s Department of Education for the consolidation of research groups [grant number: IT1633-22]. Professor L. N. López de la Calle is acknowledged for his assistance with the copper samples