Tesis Doctorals - Departament - Ecologia

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Planktonic coccolithophores of the NW Mediterranean
(Universitat de Barcelona, 2001-05-08) Cros i Miguel, M. Lluïsa; Margalef, Ramon, 1919-2004; Universitat de Barcelona. Departament d'Ecologia
[eng] This thesis deals with haptophytic algae that in a continuous way or at some point in their life cycle they produce and carry coccolites. To these algae are called coccolithophorals, coccolithophorids and also coccolithophores; Currently, its name is the subject of debate and its taxonomy is ongoing change. The work has been carried out in the Catalan-Balearic Sea, in the northwest of the Mediterranean. Seawater samples were used to carry out this study collected at different depths (mainly between 0 and 100 meters) and surface samples of sediments were also observed. The recognition and counting of the species has been carried out with the techniques Scanning Electron Microscopy (SEM). In order to compare methodologies, seawater samples were filtered with and without prior fixation (the fixation used was neutralized formaldehyde). It was observed that the previously fixed samples presented important losses of coccolithophores, especially of the most delicate taxa. In the present study, 166 coccolithophores have been recognized, of which only 102 species and subspecies have formal names in the literature. It is noteworthy the discovery of a significant number of combined cocospheres, that they carry coccolites belonging to species recognized as different; These "hybrid" specimens are considered very valuable to understand life cycles, as they can represent a moment of phase change of the organism. The different taxa found as well as the cocospheres are illustrated in this report with micrographs carried out with the MEB.
Environmental shaping and carbon cycling in a macrophyte-dominated Mediterranean coastal lagoon
(Universitat de Barcelona, 2009-06-03) Obrador Sala, Biel; Pretus Real, Joan Lluís; Universitat de Barcelona. Departament d'Ecologia
[spa] Las lagunas litorales son sistemas altamente dinámicos en los que la vegetación sumergida juega un papel estructural y funcional fundamental. En esta tesis se ha realizado una aproximación a la ecología funcional de una laguna litoral mediterránea dominada por macrófitos (s'Albufera des Grau, Menorca, Islas Baleares). Se han estudiado los principales procesos determinantes de su funcionamiento ecológico, con aproximaciones a la hidrología, al régimen lumínico subacuático y a la dinámica de las praderas de macrófitos. Finalmente se ha caracterizado el metabolismo y el ciclaje del carbono en el sistema como descriptores del funcionamiento del mismo. Se han utilizado distintas escalas temporales de observación para abarcar la máxima variabilidad posible, desde escalas subdiarias, a análisis interanuales o Incluso decadales. La Albufera des Grau es un sistema dominado por el macrófito Ruppia cirrhosa, que muestra un claro ciclo estacional de producción -descomposición. La elevada producción anual de esta especie sitúa la laguna en el rango superior de producción para este tipo de sistemas. La distribución espacial de las praderas viene determinada por la disponibilidad lumínica y por el efecto perturbador de los intensos vientos de componente norte. Por otro lado, la dinámica interanual de la vegetación sumergida está relacionada con los niveles de salinidad y disponibilidad lumínica en verano y primavera respectivamente. El efecto de la disponibilidad de luz sobre la producción primarla bentónica también se pone de manifiesto al analizar el régimen lumínico subacuático. Una fracción importante del bentos de la laguna está potencialmente limitada por luz durante el periodo de crecimiento macrofítico. En las partes profundas de la laguna, esta limitación vendría dada exclusivamente por cambios en la atenuación de la luz en el agua, mientras que en las zonas someras, donde la limitación es menos probable, el nivel del agua también tendría un papel importante. La atenuación de la luz en la columna de agua está determinada, en este sistema, a partes iguales por el fitoplancton y por el carbono orgánico disuelto, mientras que los sólidos inorgánicos en suspensión juegan un papel muy secundario. La hidrología de la laguna ha sido correctamente descrita por un modelo dinámico simple basado en balances diarios de agua y sal en la laguna y en un balance de agua en la cuenca hidrológica. El modelo, calibrado y validado en series independientes de datos, se ajusta correctamente a la dinámica diaria del nivel del agua y la salinidad del sistema y simulaciones para un periodo histórico de 30 años han permitido caracterizar el balance hídrico de la laguna. A pesar de la enorme variabilidad interanual, se ha observado una clara relación de la salinidad media anual con la precipitación total anual, con la cual se ha definido una salinidad de equilibrio para la laguna. La elevada actividad de las praderas de macrófitos se pone de manifiesto en los descriptores metabólicos a nivel de sistema, estimados a partir de variaciones nictemerales de carbono inorgánico disuelto, DIC, y de oxigeno disuelto, DO, en distintas localidades de la laguna. En la dinámica de estos dos componentes influyen, además de los procesos de metabolismo de las praderas, procesos bacterianos anaeróbicos y reacciones químicas que tienen lugar en la columna de agua y en la interfase entre agua y sedimento. A pesar de la importancia del metabolismo interno en la dinámica nictemeral de DIC, a una escala estacional e interanual este componente se ve afectado también por flujos hidrológicos, por el intercambio atmosférico de Co2, y por la precipitación de carbonato cálcico. A nivel de balance de carbono, la laguna actúa como fuente o sumidero en función de la presencia o ausencia estacional de vegetación sumergida, con perturbaciones de este ciclo básico por parte de crecimiento masivos de fitoplancton. La laguna muestra, además, una clara variabilidad interanual. Por otro lado, la estimación de los distintos flujos de carbono orgánico y la exploración isotópica de la red trófica del sistema sugieren que hay un bajo consumo de la gran producción macrofítica, cuyo destino principal sería la rápida descomposición y secundariamente el enterramiento en el sedimento.
Revisión de la biología y ecología de la familia Brachylaimidae Joyeux et Foley, 1930 (Trematoda: Digenea) con especial énfasis en las especies parásitas de mamíferos
(Universitat de Barcelona, 1984) Montoliu Sanllehy, Isabel de; Mas-Coma, S.; Gállego Berenguer, Jaime, 1920-2009; Universitat de Barcelona. Departament d'Ecologia
[spa] La finalidad de la presente obra es la de contribuir al conocimiento de la biología y ecología de los Digénidos representantes de la familia Brachylaimidae, mediante el estudio detallado del ciclo vital y de la evolución de los estadíos larvarios y adulto de distintas especies parásitas de Mamíferos (Insectívoros y Roedores) y la revisión de cuantos datos sobre biología y ecología de Brachyláimidos cabe encontrar en la literatura publicada hasta la fecha. Para ello hemos efectuado una división en cuatro grandes capítulos. El primero se ha destinado a una exposición detallada de los materiales analizados y de los métodos y técnicas empleados en el estudio. El segundo capítulo versa sobre los antecedentes, concretamente los conocimientos actuales sobre biología y ecología de Brachylaimidae existentes en la bibliografía. El tercer capítulo concierne a la exposición de nuestros trabajos parasitológicos, llevados a cabo tanto en la Naturaleza como experimentalmente en el Laboratorio, y que constituyen nuevas aportaciones sobre la biología y ecología de especies de la familia Brachylaimidae. El cuarto y último capítulo sirve a modo de colofón y va destinado a efectuar la discusión global de los trabajos efectuados y su comparación con los antecedentes bibliográficos y a exponer las conclusiones generales finales.
The functional role of emergent macrophytes in nature-based solutions (NBS) aiming to mitigate nutrient loading in freshwater ecosystems
(Universitat de Barcelona, 2021-01-29) Nikolakopoulou, Myrto-Georgia; Sabater i Comas, Francesc; Argerich, Alba; Universitat de Barcelona. Departament d'Ecologia
[eng] Freshwater degradation has been largely attributed to excess nutrient concentrations of anthropogenic origin. Freshwater degradation in combination with water scarcity are the reason of severe stress on water resources globally. As one third of the world’s population does not have access to clean drinking water, nutrient pollution is imperative to be addressed. Nature-based solutions (NBS) is a recent concept to address several societal challenges, using techniques inspired by nature, or by nature itself, while preserving ecosystem sustainability. Water security is among the essential societal challenges that NBS can address, with nutrient pollution of freshwater systems being one of its primary aspects. While NBS projects aiming to address nutrient loading in freshwater systems, conspicuously include emergent macrophytes in their design, there is a lack in mechanistic understanding of how these aquatic plants enhance water treatment performance. In the present doctoral thesis, we focused on bridging this knowledge gap by investigating the plants’ physical, chemical and biological influence on the subsurface aquatic environment and the implications for nutrient mitigation. Specifically, we examined subsurface solute transport and nutrient retention under the presence of three emergent macrophyte species; Iris pseudacorus L., Phragmites australis L., and Scirpus lacustris L., while we also explored the influence of dissolved organic carbon (DOC) quality on nitrogen cycling. To this aim, we performed a series of three studies in a setup of 12 artificial flumes, where we used traditional methods of stream ecology (i.e. pulse additions of conservative and reactive tracers) to characterize subsurface solute transport and to estimate nutrient spiraling metrics. Likewise, we experimentally modified DOC lability in the flumes, and we characterized root system architecture of the used emergent macrophytes. Regarding the physical effect of macrophytes, our results showed that macrophytes root architecture can substantially influence subsurface solute transport. Specifically, a dense root system of fine roots results in increased hydraulic retention, while an architecture of thicker roots leads to inverse results, facilitating infiltration. Further, we found that the chemical and biological influence of emergent macrophytes on the subsurface aquatic environment is species specific, and depends on physiological differences between the species, and on the plants’ capacity to create long residence times in the subsurface. Additionally, the presence of emergent macrophytes was found to facilitate N removal, while the availability of a labile C source mostly increased microbial respiration, rather than denitrification. Finally, in the general discussion of the thesis, we discuss the above results and further synthesized them with information from the literature, within the context of NBS. Overall, the present doctoral thesis elucidates some unclear aspects of the functional role of emergent macrophytes in NBS aiming nutrient mitigation, highlight the importance of suitable macrophyte species selection in NBS systems to optimize treatment performance, and provides valuable guidelines to NBS practitioners for successful macrophyte species identification.
Ecología y sistemática de los quironómidos (Insecta, Diptera) de los embalses españoles
(Universitat de Barcelona, 1978-06-21) Prat i Fornells, Narcís; Margalef, Ramon, 1919-2004; Universitat de Barcelona. Departament d'Ecologia
[spa] Se estudian los quironómidos desde diferentes ángulos tanto su sistemática como algunos aspectos de su ecología en los embalses españoles. La tesis se divide en tres partes: dos de sistemática y una de ecología. En la primera parte se estudian las especies que pueblan los fondos de los embalses españoles, tanto en su zona litoral como en su zona profunda. Sólo tres especies pueden considerarse muy frecuentes en el fondo de los embalses. Algunos factores ecológicos pueden explicarnos la presencia o no de los diversos géneros; entre ellos se resalta la importancia de la profundidad a que se tomaron las muestras, la temperatura, la época del año y el nivel trófico del embalse. Los quironómidos de los fondos de los embalses españoles pueden utilizarse como indicadores de condiciones ecológicas siendo diferentes géneros indicadores de diversos grados de eutrofia. En la segunda parte de la tesis se estudian los quironómidos adultos encontrados cerca de los embalses se citan 56 especies de las cuales 35 son nuevas para la fauna española. Finalmente se presenta una clave de identificación de los generos larvarios.
Effects of flow discontinuities on carbon gas fluxes in a Mediterranean fluvial network = Efecte de les dicontinuitats hidrològiques sobre els fluxes gasosos de carboni en una xarxa fluvial Mediterrània
(Universitat de Barcelona, 2017-02-10) Gómez Gener, Lluís; Obrador Sala, Biel; Schiller Calle, Daniel von; Universitat de Barcelona. Departament d'Ecologia
[eng] Inland waters are active components of the global carbon (C) cycle that transform, store and outgas more than half of the C they receive from adjacent terrestrial ecosystems. However, fundamental uncertainties regarding the spatiotemporal patterns, controls and sources of C gas fluxes in fluvial networks still exist. For instance, current biogeochemical models addressing C transport and processing in fluvial networks from a continuous perspective, do not integrate the effects of local discontinuities such as river impoundment or stream flow intermittency on the dynamics of C gas fluxes. The present dissertation aims to examine how flow discontinuities (i.e., river impoundment, flow fragmentation and drying) shape the spatiotemporal patterns, the controls and the sources of C gas fluxes in a Mediterranean fluvial network. The study was performed from December 2012 to March 2015 in the Fluvià river (NE Iberian Peninsula), characterized by a high density of impounded waters associated to small water retention structures (SWRS; i.e., weirs and small to very small impoundments with surface area < 0.1 km2 and a volume < 0.2 hm3) as well as fragmented river sections dominated by isolated water pools and dry riverbeds coinciding with dry periods. Results of this dissertation show that river discontinuities associated to SWRS and flow intermittency modulate the spatiotemporal patterns, controls and sources of C gas fluxes in the studied fluvial network. However, the magnitude of these effects varied depending on the nature of the discontinuity (i.e., river impoundment or flow intermittency), the type of C gas (i.e., carbon dioxide (CO2) or methane (CH4)) and the hydrological condition (i.e., high or low flow). The presence of SWRS, despite their relatively small water capacity, attenuated the turbulent conditions occurring in free-flowing river sections. As a consequence, the diffusive CO2 emissions from impounded waters were significantly lower than from free-flowing river sections. Contrarily, no reduction in CH4 emissions from impounded river sections associated to the presence of SWRS was detected. This result suggests that the higher internal CH4 production at the impounded river sections, which remained very stable over time, compensated the attenuated physical effect on CH4 emissions. Despite potential inaccuracies in capturing the temporal and spatial heterogeneity, the ebullition was the predominant pathway of CH4 emissions in impounded river sections. Moreover, sources other than internal metabolism (i.e., external inputs, internal geochemical reactions or photochemical mineralization) sustained most of the fluvial network CO2 emissions. Specifically, the magnitude and sources of CO2 emissions depended on flow conditions in the free-flowing sections, whereas they remained relatively stable and independent of hydrological variation in the impounded river sections. The channels of temporary rivers remain as active biogeochemical habitats processing and degassing significant amounts of CO2 to the atmosphere after flow cessation. In contrast, the CH4 efflux from dry beds was undetectable in almost all cases, most likely due to the high aeration limiting the redox requirements for microbial CH4 production. Our results also suggest that the source of CO2 emitted from dry riverbeds remains unclear, although CO2 produced from biological mineralization of fresh and labile organic matter fractions could be an important source. Future hydrological scenarios considering the combined effects of climate change and human pressures on water resources in the Mediterranean regions show the rather low sensitivity of the annual CO2, CH4 and total C emissions to shifts in river discharge. In contrast, they stress the high sensitivity of annual CH4 and total C emissions to shifts in the surface area of lentic waterbodies associated to SWRS. Overall, the main findings of this dissertation point to the need for a shift away from a continuous and system-centric view to a more inclusive approach that incorporates spatiotemporal discontinuities (i.e., SWRS and flow fragmentation and drying) as a suitable framework to understand the dynamics of C gas fluxes in fluvial networks.
Insights into seascape ecology: landscape patterns as drivers in coastal marine ecosystems = Perspectives en l'ecologia del paisatge marí: els patrons del paisatge com a factors de control en els ecosistemes marins costaners
(Universitat de Barcelona, 2016-04-08) Martínez Ricart, Aurora; Romero, Javier (Romero Martinengo); Pérez Vallmitjana, Marta; Universitat de Barcelona. Departament d'Ecologia
[eng] Habitats commonly occur as more or less interconnected patches constituting spatial heterogeneous mosaics. Connectivity and interactions among habitats can determine their functioning. Therefore, ecological patterns and processes within these habitats, and among them, are modulated by the spatial structure of the entire mosaic. Landscape ecology is aimed at understanding how the composition (patch types and sizes) and configuration (how those patches are arranged spatially) of habitats in a mosaic influence the functioning of the overall system and its individual components (the patches and the species moving across), at a panoply of spatial scales. Interactions at landscape level are usually associated either to the movement of organisms (active mobile entities) or to the transfer of materials (passive mobile entities) from one habitat to another. Applying landscape ecology, the interactions among and within ecosystems can be identified and evaluated to optimize conservation efforts across broad spatial scales. This approach, although has been successfully used in terrestrial ecosystems, remains poorly explored in the marine realm. This thesis is an attempt to assess the influence of landscape patterns in the ecological function of marine habitats. The thesis focus on the study of coastal landscapes (or seascapes) due to its resemblance to terrestrial ones, and because they are among the most vulnerable to human action and climate change. With this objective we focus on the study of three main processes of special importance in the coastal systems. First, we focus on the study of landscape patterns influence on fluxes of material among habitats of the coastal seascape and resource-driven processes, such as trophic webs and recycling of nutrients. Secondly, we study how landscape patterns can influence on sediment carbon storage in coastal habitats, particularly in seagrass ecosystems. And in third place we study the influence of landscape patterns in shaping communities. In particular we study the role of landscape patterns in shaping littoral fish assemblages, as due to its mobility they can be strongly affected by the landscape structure and their biology could also play an important role.). Doing this, we attempt not only to improve general knowledge on seascape ecology, but also to provide new insights useful for management. Therefore, this thesis provide new evidence emphasizing the importance of landscape-level interactions and processes in driving coastal ecosystems, and underlining how the relative abundance of habitats and their spatial arrangement influence ecological functions across the coastal ecosystem mosaic.
Flora and vegetation of the Guayana highlands : past dynamics, global warming and conservation guidelines = Flora i vegetació de les Terres de Guayana : dinàmica del passat, escalfament global i directrius de conservació
(Universitat de Barcelona, 2016-02-09) Safont Crespo, Elisabet; Vegas Vilarrúbia, Teresa Elena; Rull del Castillo, Valentí; Universitat de Barcelona. Departament d'Ecologia
Aquesta tesi té com a objectiu l'estudi de la flora i la vegetació de les Terres Altes de Guayana (TAG), un conjunt de -50 muntanyes tabulars (anomenades tepuis) situades al nord d'Amèrica del Sud, amb especial èmfasi en la potencial migració altitudinal de les plantes vasculars com a resposta a l'escalfament global. Els cims dels tepuis contenen una diversitat i endemisme de plantes vasculars excepcional. Aquest estudi suggereix que el 30-50% de les espècies endèmiques de les TAG podrien desaparèixer per pèrdua total d'hàbitat cap a l'any 2100 segons els escenaris d'escalfament B1 (més optimista) i A2 (més pessimista), respectivament. S'ha calculat un Valor d'Impacte Ambiental per a cada espècie amenaçada per a la posterior classificació d'aquestes espècies en categories de prioritat (10 pel B1 i 13 per l'A2), les quals haurien de ser utilitzades en una seqüència cronològica per orientar les accions de conservació i recerca. Posteriorment, s'ha establert una línia base de diversitat florística, endemisme i vegetació al cim del Roraima-tepui per a la verificació del fenomen migratori a les TAG. L'inventari florístic d'aquest cim tepuià conté 227 espècies, incloent 44 nous registres, una espècie nova per a la ciència i 13 espècies exòtiques. S'han identificat cinc tipus de comunitats vegetals principals, amb les seves corresponents espècies diagnòstiques. També s'ha dut a terme una caracterització ambiental d'aquestes comunitats. Finalment, l'estudi paleoecològic de la seqüència sedimentària del Uei-tepui ha permès documentar la resposta de les espècies als canvis ambientals dels últims 2000 anys. Els resultats suggereixen que el foc ha estat el principal factor que ha modelat la vegetació del Uei durant aquest període. Els esdeveniments de focs locals molt probablement van ser causats per activitats humanes i van assolir el cim des de la Gran Sabana afavorits per les condicions climàtiques. La preservació de la flora de les TAG enfront de l'escalfament global s'hauria d'adreçar, com a mínim parcialment, mitjançant tècniques de conservació ex situ, a causa de la naturalesa de l'amenaça (pèrdua d'hàbitat). No obstant, la documentació en aquest estudi d'altres impactes humans (trepig de la vegetació, espècies exòtiques, canvis en les propietats del sòl, etc.) i l'aparició del foc com a potencial agent pertorbador del bioma tepuià posen de manifest que la conservació in situ mitjançant àrees protegides pot ser també molt important.
Palaeoecological study of vegetation dynamics in the Neotropical Gran Sabana since the Late Glacial = Estudio paleoecológico de la dinámica de la vegetación en la Neotropical Gran Sabana desde el Tardiglaciar
(Universitat de Barcelona, 2016-02-08) Ballesteros Larrotta, Tania Marcela; Vegas Vilarrúbia, Teresa Elena; Montoya Romo, Encarnación; Universitat de Barcelona. Departament d'Ecologia
La Gran Sabana (GS, Norte de Sur América) es una región de sabana húmeda con una larga historia de cambios de vegetación bajo perturbaciones de fuego. En esta tesis se realizó una evaluación detallada de la dinámica de la vegetación y de los procesos ecológicos de la GS desde el Tardiglaciar hasta el presente, basada en el análisis palinológico de dos archivos sedimentarios. En la cuenca de la Laguna Encantada, los resultados sugieren que la interacción multifactorial entre el régimen de fuegos, diversidad, erosión, disponibilidad de pastos, humedad y tasas de recuperación podría haber causado los cambios de vegetación durante los últimos 8700 años. La vegetación fue resiliente al fuego durante períodos específicos, en una escala centenal. La sabanización comenzó en la cuenca aproximadamente hace 5400 años, la cual se ha acentuado en los últimos dos mil años, dando lugar a la vegetación actual (pastizales con bosque de galería monoespecíficos de Mauritia flexuosa). En la localidad Fidencio, el reemplazo de densos parches de bosque por pastizales en el Tardiglaciar (sabanización), al parecer fue causado por la sinergia entre el rápido calentamiento del Dryas Reciente (Younger Dryas, YD), clima seco, fuego, disminución de diversidad y disponibilidad de pastos. Este sinergismo podría haber erosionado la resiliencia de los bosques del Tardiglaciar. Este cambio de vegetación (origen de los pastizales) en la transición YD¬Holoceno podría considerarse como un análogo del pasado del entorno ambiental actual de la GS. Esto sugiere que la vegetación de sabana podría expandirse en el futuro en la GS, de forma similar a la que ocurrió históricamente. En ambas localidades, los cambios de vegetación de áreas forestales a sabana parecen haber sido irreversible en las escalas de tiempo estudiadas. La retroalimentación positiva entre el fuego y los pastos acentuó los procesos de sabanización en ambas localidades, los cuales estuvieron asociados con pérdida de diversidad.
Invertebrate community responses to pollutants in mediterranean basins : insights from ecotoxicological approaches = Respostes de la comunitat d'invertebrats als contaminants en conques mediterrànies: aproximacions ecotoxicològiques
(Universitat de Barcelona, 2016-02-05) Castro Català, Núria de; Muñoz Gràcia, Isabel; Universitat de Barcelona. Departament d'Ecologia
Els sistemes aquàtics estan subjectes a la pressió de múltiples pertorbacions que afecten l'estructura i el funcionament de les comunitats i ecosistemes. Una de les principals pressions antropogèniques que afecten als ecosistemes aquàtics és la contaminació. La producció química a gran escala ha donat lloc a l'alliberament de substàncies d’origen agrícola, industrial i urbà als sistemes fluvials. Aquesta contaminació és una amenaça complexa i múltiple, degut a la diversitat de compostos presents i a la dinàmica i interacció d'aquests amb els compartiments físics (aigua, sediments) i biològics (organismes). A les conques fluvials mediterrànies, on la variabilitat hidrològica és important, aquesta contaminació és motiu d'especial preocupació especialment en el període d’estiatge, quan disminueix la capacitat de dilució dels rius. A més dels contaminants prioritaris legislats, molts estudis han posat de manifest la presència generalitzada de microcontaminants, també anomenats contaminants emergents. Aquesta tesi proporciona evidència dels efectes dels contaminants emergents i prioritaris en les comunitats d'invertebrats en quatre conques mediterrànies de la Península Ibèrica: l'Ebre, el Llobregat, el Xúquer i el Guadalquivir, emprant mètodes ecològics, biomarcadors, i bioassaigs in vitro i in vivo. Els efectes ecotoxicològics s’han detectat a nivell de comunitat, de població i d’individu, i s’ha vist que tant els contaminants presents a l’aigua com els acumulats en els sediments superficials afecten l’estructura de la comunitat (riquesa específica i abundàncies). També s’ha vist que la contaminació afecta la capacitat de reproducció (nombre d’ous), el desenvolupament, l’alimentació, el creixement i l’activitat d’enzims antioxidatius (catalasa). En concret, els principals responsables de l’alt risc ecotoxicològic identificats han estat els plaguicides, els alquilfenols industrials, i els metalls. Addicionalment, la tesi es completa amb un experiment de laboratori on es testen els efectes directes i indirectes de dos contaminants concrets en el detritívor Gammarus pulex. Aquesta tesi integra aproximacions observacionals i experimentals de múltiples disciplines ambientals (química ambiental, ecotoxicologia i ecologia) per dilucidar els efectes dels diferents contaminants. La combinació dels assajos experimentals amb estudis de les comunitats naturals permet comprendre millor els efectes de les pertorbacions a diferents escales i prevenir la degradació dels ecosistemes aquàtics, així com millorar la seva gestió.
Biology and population ecology of uncultured Archaea in natural environments analyzed by taxon-specific molecular markers = Biología y ecología poblacional de Archaeas no cultivadas en ambientes naturales analizadas mediante marcadores moleculares específicos
(Universitat de Barcelona, 2016-02-05) Restrepo Ortiz, Claudia Ximena; Ortega Casamayor, Emilio; Muñoz Gràcia, Isabel; Universitat de Barcelona. Departament d'Ecologia
Los microorganismos del Dominio Archaea son un componente común del plancton que ha pasado, mayoritariamente desapercibido para la Limnología durante mucho tiempo. Sólo tras la aplicación de técnicas moleculares en ecología microbiana se ha descubierto su enorme riqueza biológica y abundancia tanto en ambientes acuáticos como terrestres, más allá del grupo de las archaea metanógenas. Estudios recientes han demostrado que los hábitats de agua dulce tienen la mayor diversidad filogenética y representan entornos prometedores para el descubrimiento de nuevos linajes de Archaea. Uno de los ambientes que constituyen una fuente inexplorada de riqueza de nuevos filotipos de Archaea son los lagos alpinos, donde diferencias llamativas en la composición filogenética y abundancia de las arqueas se han reportado recientemente. Esto hace que los sistemas lacustres sean un modelo útil para comprender los factores ecológicos y la influencia de la heterogeneidad del hábitat sobre la composición de microorganismos Archaea, y para vincular los rasgos ecológicos y metabólicos de las arqueas con el funcionamiento del ecosistema. Esta tesis tiene como objetivo combinar microbiología ambiental, técnicas moleculares y aproximaciones bioinformáticas para progresar en el conocimiento de la distribución ecológica y ecofisiología de filotipos representativos de las arqueas de agua dulce superando la limitación de su baja cultivabilidad. Para este propósito, se diseñaron y optimizaron cebadores específicos para el gen SAGMGC-1 16S rRNA y los diferentes ecotipos de archaea oxidadoras de amonio, AOA (gen amoA), y se cuantifico mediante qPCR las distribuciones espacio-temporales a lo largo de una exploración anual en un lago profundo de alta montaña, donde las deposiciones atmosféricas son la principal fuente de nitrógeno reactivo. Adicionalmente se exploraron las diferencias espacio-temporales en el plancton superficial de un gran conjunto de lagos con gradientes ambientales marcados, mediante el diseño y optimización de cebadores específicos para el gen 16S rRNA de los grupos de euryarchaeota MEG y DSEG. Por último, se construyo una base de datos genética detallada del gen ribosómico 16S rRNA de Archaea utilizando SILVA y nuestros propios datos genéticos generados a partir de trabajos anteriores, a partir de esto se diseño y optimizo la sonda específica de CARDFISH para el grupo taumarchaeota SAGMGC-1, combinando aproximaciones in silico, in vitro e in situ. Posteriormente se cuantificó selectivamente dicha población a lo largo de un gradiente ambiental
Ecology and bioindicator potential of benthic macroinvertebrates in a Mediterranean salt wedge estuary: the Ebro River case
(Universitat de Barcelona, 2016-01-29) Nebra Costas, Alfonso; Ibáñez, Carles; Marinheiro Caiola, Nuno Alberto; Universitat de Barcelona. Departament d'Ecologia
[eng] The Ebro Delta-Estuary complex is one of the largest wetland areas in the western Mediterranean, and it is considered one of the most important estuarine zones in Europe. In 2013, the Ebro watershed, including its deltaic plain, was declared World Biosphere Reserve by the UNESCO. Due to its singularity, a total of 7.736 ha of Delta are protected under the Spanish Natural Park figure (including coastal lagoons, freshwater springs, bays and adjacent coastline) which stands out by its faunal (mainly, ornithological and ichthyological) and halophilic floral composition. The Ebro River flows into the Mediterranean Sea and forms a salt wedge or highly stratified estuary, a unique estuary type only found in microtidal coasts worldwide. Diverse human activities occur in this area such as tourism, shooting, commercial fishing and agriculture, as a consequence the entire Delta-Estuary complex is under permanent anthropogenic pressures threatening its ecological integrity; therefore, its conservation should be a priority task. The main objective of the present PhD thesis was to analyze the ecology of the benthic macroinvertebrate community from the Ebro Estuary, in order to evaluate its potential use as biological indicator of highly stratified Mediterranean estuaries. To achieve this goal the study of the macroinvertebrate community was carried out at a high level of taxonomic resolution and its spatiotemporal dynamics in relation with the estuarine environmental gradients was assessed. An exhaustive environmental description of benthic condition of the Ebro Estuary was done, including water physico-chemistry, grain size characterization and total organic estimation in sediments. Furthermore, due to the relevance of river discharge on salt wedge dynamics and therefore on estuarine benthic ecology, a comparison between current salt wedge dynamics and past near natural conditions was done using historical data available at the Ebro basin authority database. Finally, the bioindicator potential of macroinvertebrates to assess the ES according to the WFD criteria was examined throughout the analysis of the response of macrozoobenthos based metrics to the main human pressures in the Ebro estuary, nutrient enrichment and altered flow regime
Fire legacies in Mediterranean streams: the key roles of the riparian canopy and the top predator on food webs
(Universitat de Barcelona, 2016-01-29) Rodríguez Lozano, Pablo; Prat i Fornells, Narcís; Rieradevall i Sant, Maria; Universitat de Barcelona. Departament d'Ecologia
[eng] Wildfires are expected to increase in frequency and intensity because of climate change and changes in land use and management. In last decades, the research on fire effects on aquatic systems has grown, but it has been mainly conducted in the short- and mid-term (<5 years). Therefore, longer time frames are needed to assess fire effects on freshwater ecosystems. For instance, fire impacts on riparian and upland forests can be long-lived and wildfires often extirpate fish populations from streams, which may not recover due to barriers within the river network. Regarding fish extirpations, it is worth noting that freshwater fish are one of the most threatened fauna worldwide, especially the small-bodied species. In this context, the overarching goal of this PhD thesis was to investigate the long-term effects of a wildfire in Mediterranean streams. Specifically, this PhD thesis covered the indirect effects of two fire legacies: (1) the riparian canopy reduction and (2) the local extinction of the top predator in these streams, the endangered small-bodied fish Barbus meridionalis. The findings of this PhD thesis showed how the fire legacy in the riparian forest accelerated leaf-litter breakdown in an intermittent Mediterranean stream eight years after fire. The opening of the riparian forest canopy by fire increased light levels and water temperatures and reduced terrestrial-to-aquatic litter inputs. The increased water temperatures engendered by removal of canopy cover enhanced microbial mediated leaf breakdown. The reduction in leaf-litter inputs probably led to lower benthic organic matter levels, bringing to the observed increased shredder aggregation in leaf packs, thereby accelerating leaf breakdown rates. Our results demonstrated that the apex consumer was functionally irreplaceable, its local extinction led to the loss of an important functional role that resulted in major changes to the ecosystem's structure and function. Our mesocom experiment showed that Barbus meridionalis absence led to 'mesopredator release, and also to 'prey release despite intraguild predation, which contrasted with traditional food web theory. Top predator extirpation also changed whole macroinvertebrate community composition and increased total macroinvertebrate density. Regarding ecosystem function, periphyton primary production decreased in apex consumer absence. Moreover, we studied the feeding ecology of B. meridionalis from a functional perspective. Our results indicated that prey morphological and behavioral traits may explain prey vulnerability to predation. Specifically, the trait-based analysis showed that 10 of the 13 traits tested significantly influenced food choice (e.g. body size, concealment, locomotion, aggregation tendency, feeding habits). In addition, the leaf bags experiment confirmed that top predator absence enhanced leaf-litter breakdown, which was caused by the increase in shredder and scraper biomass in the absence of the predatory fish top-down control. Fish absence reduced leaf fungal biomass, but did not decrease microbially mediated leaf breakdown. These results suggested that leaf fungal biomass was stimulated from the bottom-up through nutrient recycling by the top predator. This PhD thesis demonstrated that past fires may have current influence on the structure and function of Mediterranean streams. Moreover, our findings evidenced that intermittent streams can be affected by the consequences of apex consumers’ extinctions, and that the loss of small-bodied top predators can lead to complex ecosystem changes. This PhD thesis interconnected several current topics in ecology research (i.e. fire effects on aquatic systems, top predator declines, and intermittent streams). Its relevance lies in the projected increase in fires in the Mediterranean region and in the current high extinction risk of small-bodied fish in freshwater ecosystems.
Modelling Social-Ecological Systems in the Catalan Coastal Zones
(Universitat de Barcelona, 2016-01-20) Tomlinson, Benjamin John; Maynou i Hernàndez, Francesc; Canals Artigas, Miquel; Universitat de Barcelona. Departament d'Ecologia
[eng] The Systems Approach Framework (SAF) is a methodological framework designed to enhance the efficacy of human decision-making processes within social-ecological systems with regard to sustainability. The SAF was applied in two case studies in the coastal zone of Catalonia, in two separate European Commission Framework Programme projects entitled “Science and Policy Integration for Coastal System Assessment” (SPICOSA) and “Vectors of Change in Oceans and Seas-marine Life, Impact on Economic Sectors" (VECTORS). During the SPICOSA application, a common issue of interest to most stakeholders was the water quality (harmful bacteria and water clarity) of the local city beaches, particularly following combined sewer overflow events, and mitigating this impact by using stormwater collectors. Water quality influences the beach users’ decision whether to stay at the beach or to leave, thus affecting the revenue received by the bars and restaurants on the beach front. A social-ecological model was constructed using the methodology outlined in the SAF to represent this issue, so that it could be used as a tool for deliberation between the stakeholders. The model output implies that the stormwater collectors have been useful in improving beach water quality in Barcelona, but there will be diminished returns in constructing more. The value of the beach is clearly large in terms of both non-market value and revenues generated in the nearby bars and restaurants. However, the impact changes in water quality would have on the recreational appeal of the beach is estimated to be low and further research is recommended to determine beach users’ sensitivity to beach closures (bacteria limit exceeded) and turbidity. At the beginning of the VECTORS project, stakeholders who had participated during the previous SAF application expressed a lack of willingness to engage due to a lack of human resources. The scientific team therefore chose to continue the application with the aspiration of demonstrating the SAF model and results at a later date if the stakeholders found the required resources to engage with the process. There is a general perception that jellyfish abundances are increasing along the Catalan coast. Local authorities are concerned about the stranding events and arrivals of jellyfish to beaches and believe it could reduce the recreational appeal of the beaches. Previous studies also demonstrate the predation of jellyfish (Pelagia noctiluca ephyrae) upon some small pelagic fish larvae (Engraulis encrasicolus). Small pelagics are the principal source of revenue for the local fisheries. A social-ecological model was created in order to capture the effects of changes in abundance of Pelagia noctiluca upon the local fisheries, the tourist industry and the wider economy. Various future scenarios for different abundances of jellyfish blooms were run. Given the changes that these scenarios would cause on the regional gross domestic product and employment, this study concludes that the overall impact of either of these scenarios on the economy would not be significant at the regional scale. The inclusion of stakeholders in the SAF methodology is rightly fundamental, but in practice, it can be extremely difficult to persuade key stakeholders to participate, and this is a flaw in the SAF which needs addressing. SAF Application model builders are dependent on stakeholders sharing important data or knowledge but this may be withheld for a variety of reasons including, but not limited to, lack of resources to participate, disinterest, and concern about how the results will be used. The SAF is a well-structured methodology for cases where a mathematical model is both relevant and feasible and should be considered as a useful step-by-step guide for managing coastal zone systems towards sustainability.
Fish as local stressors of Pyrenean high mountain lakes: Arrival process and impact on amphibians and other organisms
(Universitat de Barcelona, 2016-01-08) Miró Pastó, Alexandre; Ventura Oller, Marc; Muñoz Gràcia, Isabel; Universitat de Barcelona. Departament d'Ecologia
[eng] Pyrenean high mountain lakes are naturally fishless due to natural barriers that have prevented the natural colonisation of fish species from lower streams. However, there have been numerous trout introductions to such ecosystems, both in historical and recent periods. Differing from other high mountain regions, some high mountain lakes of the Pyrenees were exploited traditionally for trout cultivation. This activity started at least centuries ago and lasted until 1950s, affecting approximately 25% of the lakes. Since 1950, and similar to other high mountain regions, a wave of modern introductions with exotic species has affected among 35% and 85% of the lakes depending on the valley. In recent decades, minnows have also been introduced, being present in 2000 in 27% of Pyrenean high mountain lakes, as a result of recreational fishing with livebait. The first part of the thesis was intended to provide an objective description of the fish introduction process in the Pyrenees. For that purpose we collected data on trout and minnow occurrence from 520 high mountain lakes >0.5 ha of the southern Pyrenees and quantified, by generalized additive models, which particular factors either environmental or anthropogenic, best explained their present distribution and as a result their lake conservation status. The distribution of Salmo trutta in the southern slope of the Pyrenees was best explained by both, anthropogenic factors and lake characteristics, while only anthropogenic factors linked to recreational fishing were associated with the distribution of the exotic trout Salvelinus fontinalis and Oncorhynchus mykiss. For the case of minnow occurrence, previous presence of trout in the lake was the most explanative variable, confirming its association with recreational fishing using them as livebait. Trout and minnow introductions can cause large ecological problems and ecosystem alterations in high mountain lakes and ponds, since both trout and minnows occupy the top of a lake’s food chain. In the second part of the thesis, we sampled 1736 Pyrenean high mountain lakes and ponds at different levels of intensity and investigated the effects of introduced fish on indicator faunal groups such as amphibians and conspicuous macroinvertebrates in the littoral, and crustaceans from the plankton. We also studied if there was a trophic cascade from fish to the littoral epilithic community of these ecosystems. Our results showed that fish presence was linked with the disappearance of most amphibian species and of most conspicuous macroinvertebrates. Minnows also showed sizeable impact on the pelagic habitat reducing the abundance of some herbivorous species of zooplankton that appeared to be unaffected by trout. In the case of amphibian species, we found that, although introduced fish had a high local impact, western-eastern patterns of some environmental variables are the main drivers of amphibian species distribution at Pyrenean range scale. In addition, we confirmed the presence of a littoral trophic cascade that define most of the characteristics of the littoral epilithon of Pyrenean high mountain lakes and ponds, through fish predation of tadpoles and hence, by a drastic reduction of grazing activity.
Conservation of marine habitat-forming species under climate change: population genetics and demographic responses of the Mediterranean red gorgonian Paramuricea clavata.
(Universitat de Barcelona, 2015-11-25) Arizmendi Mejía, Rosana; Linares Prats, Cristina; Ledoux, Jean-Baptiste; Universitat de Barcelona. Departament d'Ecologia
[eng] Climate change, along with other anthropogenic pressures (e.g. water pollution, overfishing and habitat degradation), is severely impacting oceans around the world, producing important changes in its physical and biological structure, and causing marine biodiversity to decline. In this context, the enhancement of conservation and management strategies that mitigate such stressors (e.g. Marine Protected Areas, MPAs) is urgent. In this thesis, we studied the population genetics and ecological responses to warming of the Mediterranean red gorgonian Paramuricea clavata (Risso 1826), in order to contribute to the design of more effective conservation and management measures for this and other similar species. P. clavata is a long-lived, slow-growing, low dispersal and highly vulnerable habitat-forming organism from the coralligenous assemblages. During the last decades, it has been severely impacted by mass mortality events (MME) caused by climate change-related thermal anomalies. P. clavata is essential to maintain biodiversity as it forms habitat for other organisms and it greatly contributes to habitat's biomass and complexity. Although the inclusion of habitat formers in the design of MPAs is fundamental to improve the effectiveness of biodiversity protection, these organisms have been generally neglected in the planning of MPAs, which, instead, have been historically designed for the protection of commercially important species. In this thesis, we developed an interdisciplinary approach focused on (i) population genetics, emphasizing on evolutionary processes acting over contemporary timescales, and (ii) on demographic responses to warming. First, we compared the functioning of continuous and isolated metapopulations of P. clavata, in terms of spatial genetic structure and underlying evolutionary processes. A group of genetically differentiated populations was detected in a geographically continuous area, indicating that in addition to geographic isolation, genetic isolation should also be considered in the design of MPAs. Genetically isolated metapopulations exhibited significantly lower genetic diversity and higher genetic differentiation compared to continuous metapopulations. Moreover, the influence of drift was higher in isolated metapopulations. These results suggest that isolated metapopulations may be at higher extinction risk than their continuous counterparts. Second, we used an eco-evolutionary approach combining demographic and genetic data to establish conservation priorities in an isolated metapopulation. We demonstrated a relation between partial mortality (caused by MME), effective population size (Ne) and number of alleles that indicated that the less diverse and most isolated demes, which were undergoing the largest effect of drift, were the most affected by MME. These populations should therefore be of high conservation priority. We detected a newly established population, which was also prioritized for conservation, as it was mainly composed by juvenile colonies. Surprisingly, no founder effect was observed, as its genetic diversity was high and colonies came from different populations Third, we experimentally tested the role of reproductive maturity and sex on the vulnerability of the red gorgonian to warming. The highest vulnerability of adults versus juveniles and of females versus males results in a decline of fertilization rates, larval production and recruitment success, suggesting that red gorgonian populations may collapse in a warmer future. The relevance of our results is discussed in the light of climate change, and several conservation and management strategies that should be implemented to enhance the conservation of P. clavata and its associated communities are proposed. Moreover, this thesis provides valuable information to improve the effectiveness of MPAs within the context of climate change and it strengthen the previous foundations of knowledge that are essential to pursue further research. Given the key role of P. clavata as a habitat former, the results obtained in this work may also serve as guidelines to enhance the protection of other habitat-forming species with similar life history traits.
The influence of Mediterranean riparian zones on stream nitrogen dynamics: A catchment approach.
(Universitat de Barcelona, 2015-11-16) Lupon Navazo, Anna; Bernal Berenguer, Susana; Sabater i Comas, Francesc; Universitat de Barcelona. Departament d'Ecologia
[cat] Durant l'última dècada, les activitats antropogèniques han doblat el nitrogen disponible, provocant nombrosos problemes ambientals. En un context de conca, els boscos de ribera tenen la capacitat de reduir els excessos de nitrogen que els hi arriben dels ecosistemes terrestres adjacents i, per tant, poden ser fonamentals per determinar la concentració de nitrogen al riu i l'exportació d'aquest nutrient aigües avall. L'objectiu d'aquesta tesi és analitzar la influència dels boscos de ribera sobre els recursos hídrics i la dinàmica del nitrogen en una conca mediterrània. Durant l'estudi, els sòls de ribera exhibiren unes taxes netes de mineralització i nitrificació clarament superiors als boscos de capçalera (alzinar i fageda), les quals foren atribuïdes als estocs de fullaraca i a l'alta humitat dels sòls riparians. A més, els sòls de ribera foren importants fonts de nitrat al riu, especialment quan les altes temperatures o les fortes precipitacions provocaren pics d'activitat microbiana que contribuïren > 25% en termes anuals. Hidrològicament parlant, la vegetació ripariana tingué un paper clau sobre els recursos hídrics de la conca, perquè regulà el cabal fluvial a diferents escales temporals, i promogué la pèrdua d'aigua del riu cap a la ribera en el fons de vall. Tanmateix, la ribera no retingué nitrogen durant el període de retenció hidràulica, així com tampoc durant la resta de l'any. Per contra, el baix cabal i les altes temperatures incentivaren la nitrificació a la llera del riu durant l'estiu. A més, durant la primavera, l'augment de llum previ al desenvolupament de la capçada de ribera afavorí la producció primària bruta en el riu, la qual provocà clares fluctuacions diàries en les concentracions de nitrat i reduí un 10% les exportacions d'aquest nutrient aigües avall. Conjuntament, els resultats d'aquesta tesi no només qüestionen la idea que les zones de ribera són filtres naturals de nitrogen en regions mediterrànies, sinó que manifesten la importància d'una visió integradora de tots els components del paisatge per tal per tal d'avançar en el nostre coneixement sobre la hidrologia i la biogeoquímica a escala de conca.
Mediterranean forests in a changing environment - Impacts of drought and temperature stress on tree physiology
(Universitat de Barcelona, 2015-07-24) Sperlich, Dominik; Sabaté i Jorba, Santi; Peñuelas, Josep
[eng] The Mediterranean Basin is a climate-change hotspot of the world. Predicted reductions in annual precipitation, increases in mean temperature, and increases in the variability and occurrence of extreme droughts and heat waves are likely to affect species abundance and distribution. The existence of sympatric plants with different morphological and phenological strategies raises the question how they will respond to novel climate conditions. There is a strong need to improve the mechanistic understanding of key foliar ecophysiological parameters in response to abiotic stressors on a small scale if we are to predict the carbon budget of plant ecosystems in larger scales. We first reviewed contrasting growth responses to temperature of angio- and gymnosperms in the Iberian Peninsula. Secondly, we studied the seasonal acclimation of different foliar ecophysiological traits in two leaf positions of four Mediterranean tree species in extensive field experiments. We aimed to shed light on the mechanistic understanding of the foliar respiratory and photosynthetic responses to abiotic stress such as drought and temperature. We found contrasting demographic responses in Mediterranean conifer and angiosperm trees. Widespread forest successional advance of angiosperms and negative growth responses of gymnosperms to temperature are currently occurring in the Iberian Peninsula. Trait-based differences in these two groups contribute to explain their different responses to temperature and their different role during successional processes. The acclimation behaviour of photosynthetic and morphological traits to seasonal variable growth conditions was strongly pronounced in all tree species. Photosynthetic machineries were resilient to moderate drought, whereas severe drought induced acclimation of morphological traits, photosynthetic downregulation and leaf abscission. The lack of replenishment of soil-water reserves during the early growing season critically enforced the summer drought. We also observed a notable seasonal acclimation of the thermal optima and of the curvature of temperature responses of photosynthetic assimilation. The photosynthetic system was better acclimated to lower temperatures in winter and to heat stress in the drier and hotter year. Mild winter temperatures provided a period of growth and recovery that resulted in biochemical recovery, new shoot growth, and moderate transpiration across all evergreen species. High radiation and sudden low temperatures had a combinatory negative effect on the photosynthetic apparatus leading to photoinhibitory stress -especially in sunlit leaves. Species-specific acclimation partly offset these overall trends in responses to drought and temperature stress. Quercus ilex L. and to a lesser extent Q. pubescens Wild. showed the highest plasticity in photosynthetic traits whereas Pinus halepensis Mill. was most tolerant across the seasons with the most stable temperature response pattern. Arbutus. unedo L. was the most vulnerable to drought and photoinhibitory stress in winter. A. unedo and Q. pubescens had a less sclerophyllic leaf habit and invested the least in acclimation of the morphological structure being most vulnerable to drought-induced leaf abscission. Shaded leaves showed generally a lower photosynthetic potential, but cushioned negative impacts under stress periods. A long-term rainfall-exclusion experiment in a Q. ilex forest increased the foliar carbon-use efficiency and the plasticity of foliar respiratory and photosynthetic traits, but did not affect the biochemical photosynthetic potential. A favourable growth period was thus exploited more efficiently. Overall, our results indicate that Mediterranean climax-species exhibit a strong acclimatory capacity to warmer and drier conditions, but can be sensitive to extreme drought and extreme temperature stress. The performance of the plants during winter might give important insights in the dynamics of Mediterranean forest communities under novel environmental conditions. Leaf position is an indispensable factor when estimating the canopy carbon balance. Angiosperms and gymnosperms had fundamental different photosynthetic strategies of stress-avoidance versus stress-tolerance, respectively.
Scale-dependent factors modulate sea urchin predation in macrophyte communities
(Universitat de Barcelona, 2015-07-10) Farina, Simone; Alcoverro i Pedrola, Teresa; Romero, Javier (Romero Martinengo)
[eng] Many nearshore temperate coastal ecosystems are strongly regulated by top-down control. This is particularly true of shallow macrophyte communities, where habitat structuring is heavily dependent on the ability of predators to control populations of herbivorous sea urchins. Released from predation pressure, urchins can quickly transform macroalgal ecosystems to unproductive barrens. While temperate seagrasses are less dramatically affected, top-down processes still play critical roles in mediating trophic interactions and habitat structure. There has been considerable attention paid to understanding the role predator numbers (mostly fish) play in influencing the strength of predator-prey interactions in macrophyte communities. However, several factors apart from abundance can influence these interactions, which have received far less attention. In this thesis, I examine how the structure of the habitat itself can mediate top trophic interactions and how these processes vary with spatial scale. I begin by exploring how predation activity varies in relation to Posidonia oceanica habitat structure. Meadows can vary considerably in their structural attributes, and in the first Chapter I examine how canopy height and the height of the unburied rhizome matte influence predation intensity. My results show that meadow structure (canopy height and unburtied matte height) within habitats play critical roles in determining predation rates in these systems by mediating the availability of benthic refuge for urchins. I carry this work forward in Chapter two by comparing relative rates of predation across a gradient of increasing habitat structure across macrophyte communities (turf habitats, macroalgal habitats, low structured seagrass and high structured seagrass). To make these results generalizable, I compared these predation patterns across three different regional seascapes — the Caribbean, the Mediterranean and Western Australia — each with their own unique guild of fish and benthic predators. Habitat structure clearly regulated predation in all regions, but interestingly, the direction of its influence was highly dependent on the predator guild; regions dominated by visual fish predators showed a negative relationship between predation intensity and habitat structure, whereas where benthic predators (sea stars or molluscs) were common, predation increased with structure. How nearshore habitats are distributed in space (patch configuration, the spatial relationship between patches, aggregation patterns, etc.) can have strong effects on how predators and prey species move between and within habitats and, in Chapter three I examined the influence these landscape mosaic features had on modifying trophic interactions. My results indicate that these mosaics can generate lumpiness in the distribution of trophic function, with cold- and hot-spots of predation dependent on area-perimeter relationships, the presence of rocky substrates or the degree of habitat clumping in space. Overall, my thesis provides critical insights on how the predation function varies across scales in nearshore marine macrophyte communities. Sea urchins are often a keystone herbivore in these systems, and my thesis shows that their control is heavily influenced by the habitat itself. In particular, habitat can: (i) modify the interaction strength as a function of structure, (ii) can change the direction of the interaction depending on the dominant predator guild and (iii) generate hotspots of predation as a function of spatial configuration. My work indicates that predator abundance, while critical, does not reflect the true complexity of predator-prey interactions. Given the importance of predator-urchin dynamics to the functioning of nearshore macrophyte habitats, we need much more understanding of habitat characteristics at fine and large scales to be able to effectively manage these systems and the functions they embody.
Tracking environmental change in seagrass meadows: understanding indicator behaviour across space and time
(Universitat de Barcelona, 2015-07-06) Roca Carceller, Guillem; Alcoverro i Pedrola, Teresa; Romero, Javier (Romero Martinengo)
[eng] Nearshore marine ecosystems like seagrass meadows face a wide range of anthropogenic influences, impacting the system at different spatial and temporal scales. Managing these systems in the face of these pressures requires detailed knowledge of how seagrass habitats respond to these various threats. A plethora of useful indicators have been developed to help managers and policy makers track seagrass meadow health and status, detect environmental impacts or measure the effectiveness of management interventions. However, choosing between these indicators can often be a daunting task since they vary considerably in their overall behaviour in relation to ecosystem and environmental changes. This thesis assesses the most commonly employed seagrass indicators to determine if they are adequate and appropriate to the specific needs of coastal ecosystem management. This assessment is based on evaluating three fundamental characteristics of each indicator – the robustness of its response, the specificity or generality of its response, and the time of response. We use a variety of complementary approaches to explore indicator behaviour. In Chapter 3, we use field-based studies to assess how seagrass indicators respond to the construction of a breakwater in the vicinity of a Posidonia oceanica seagrass meadow. Chapters 4 and 5 examine long-term trends in seagrass indicators to improving water quality conditions after significant regional management interventions. In addition, in Chapter 6, we comprehensively review seagrass indicator responses to multiple stressors. Chapters 3, 4 and 5 focus largely on the Catalan Coast in the Mediterranean with Posidonia oceanica as a target species. Chapter 6 in contrast is a broad review of a wide range of indicators used across several seagrass species worldwide. A central learning across these studies was that the level of biological organisation of the indicator (i.e. Physiological, biochemical, growth, morphological, structural or demographic) is critical in determining the specificity or generality of response: the lower the level (e.g. biochemical), the most specific the response, while the higher the level (e.g. population, community), the wider the response. Thus, biochemical indicators are ideal to determine the identity or even the origin of a pressure while structural indicators, in contrast, are useful as generic indicators of declining conditions. Response times are also heavily determined by the level of organisation, particularly in the detection of improving environmental quality along the Catalan coast. Biochemical indicators responded unequivocally to water quality improvements observed both in the experimental field study (Chapter 3) as well as in the analysis of the long-term data series (Chapters 4 and 5). The meta-analysis confirmed that these trends in specificity and response time were not unique to Posidonia oceanica or the Catalan coast and highlighted the critical role of plant size in determining indicator time responses. Large species take considerably longer to register a response to environmental degradation as well as improvement – a critical factor that needs to be accounted for in designing monitoring programmes and interpreting ecosystem trends. Taken together, these results suggest that differences in the behaviour of seagrass indicators require that they should be carefully selected to match the objectives of management. Based on the results reported in this thesis, where different sets of indicators have been proven successful for given management objectives, we finally develop a simple decision tree to help managers chose the most reliable sets of indicators matching their objectives. Understanding the diversity of responses that seagrass indicators display can make them a powerful set of tools in the ecosystem manager’s toolkit. Carefully employed, they can serve as bespoke solutions to a wide range of management objectives as we seek to monitor and protect these vital ecosystems and coastal water quality in the face of increasing coastal pressures.

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