The effect of environmental modification of predator sensory abilities remains largely unknown, despite the importance of predators to ecosystem function. I conducted a series of experiments to investigate effects of hydrodynamics on the chemosensory search behavior and foraging success of two species of marine gastropods, knobbed whelks (

La industria de la acuicultura se está expandiendo debido a la demanda de alimentos por el crecimiento de la población. En 2019, en España, la producción alcanzó 342.867 toneladas y un valor de primera venta de 501 millones de euros (APROMAR 2020). Las principales especies producidas fueron los mejillones (77%), la lubina (8%) y la dorada (4%), todas especies cultivadas en zonas costeras. Las principales estructuras donde se cultivaban estas especies son bateas y long lines para mejillones (4.793 instalaciones) y jaulas flotantes para lubina y dorada (43 instalaciones) (APROMAR 2020). Ambos cultivos producen enriquecimiento por MO y acumulación de restos de valva de mejillón en los sedimentos marinos. Sin embargo, existe una falta de conocimiento para poder entender todas las consecuencias ecológicas de la interacción entre el enriquecimiento por MO y la acumulación de valvas de mejillón en los ecosistemas bentónicos, ya que aunque se ha estudiado en profundidad el efecto del enriquecimiento por MO sobre los sedimentos (Holmer et al. 2005a; Apostolaki et al. 2007; Holmer et al. 2007), los efectos de acumulación los restos de valva de mejillón en los ecosistemas de sedimentos apenas se han investigado (Newell 2004; Wilding 2012; Wilding and Nickell 2013). Por lo tanto, para mejorar el conocimiento de los impactos de la acuicultura y sus interacciones en los sedimentos, los objetivos generales de la presente tesis doctoral han sido: Capítulo 2) Analizar el efecto de la bioturbación en la capacidad metabólica de los sedimentos a lo largo de un gradiente de enriquecimiento por MO derivado de la acuicultura marina. Capítulo 3) Investigar la interacción entre el enriquecimiento por valva de mejillón y por MO derivado de la acuicultura en flujos biogeoquímicos de sedimentos marinos. Capítulo 4) Comprobar el efecto del enriquecimiento por valva de mejillón y por MO procedente de la acuicultura en la capacidad de bioturbación de la comunidad de la macrofauna de los sedimentos marinos. Las principales conclusiones de esta tesis son: 1. Los sedimentos bioturbados, al promover las condiciones óxicas, pueden amortiguar las consecuencias negativas relacionadas la limitación de oxígeno producidas por el aporte extra de materia orgánica de la actividad acuícola. 2. La prevalencia de condiciones óxicas a través de la bioturbación de la macrofauna puede disminuir la importancia de las vías anaeróbicas de mineralización de la materia organica del sedimento bajo la influencia de la acuicultura, limitando la capacidad metabólica del sedimento. 3. En sedimentos bioturbados, su capacidad metabólica puede no seguir una relación lineal con el nivel de enriquecimiento por materia orgánica derivado de la actividad acuícola, aumentando la acumulación de contenido de MO en el sedimento a altas tasas de aporte de la materia orgánica. 4. Analizar la capacidad metabólica de los sedimentos podría ser una herramienta relevante para predecir la respuesta de los sedimentos frente al enriquecimiento de materia orgánica de los sistemas de acuicultura. 4. El análisis de la capacidad metabólica de los sedimentos puede ser una herramienta relevante para predecir la respuesta de los sedimentos frente al enriquecimiento por materia orgánica derivada de la acuicultura. 5. Los restos de valva de mejillón procedentes de los sistemas acuícolas sobre sedimentos arenosos sin macrofauna, en condiciones de enriquecimiento por materia orgánica, pueden disminuir la tasa de liberación de amonio a la columna de agua, limitando las consecuencias ecológicas negativas derivadas de la eutrofización. 6. Los restos de valva de mejillón, procedentes de los sistemas acuícolas, en sedimentos arenosos contaminados por materia orgánica pueden reducir la acumulación de los subproductos de vías metabólicas anaeróbicas, mejorando el estado ecológico del sedimento impactado. 7. Los restos de valva de mejillón, procedentes de los sistemas acuícolas, pueden modificar la comunidad de la macrofauna de los sedimentos arenosos en áreas oligotróficas, triplicando su abundancia y biomasa, y promoviendo la abundanica de familias con mayor capacidad de bioturbación, específicamente las familias Nassaridae y Nereididae. El efecto de los restos de valva de mejillón en la comunidad de la macrofauna bentónica está modulado por las características del sedimento, específicamente por el tamaño del grano y el contenido natural de materia orgánica. No se han obtenido efectos negativos significativos de los restos de valva de mejillón sobre la comunidad de sedimentos macrofaunales y sobre sus parámetros fisicoquímicos. 10. Los restos de valva de mejillón procedentes de los sistemas acuícolas, que suelen tratarse como un producto de desecho, podrían utilizarse para mitigar los efectos negativos de la contaminación por materia orgánica en los sedimentos marinos, particularmente en sitios defaunados. 11.Mantener los restos de conchas de mejillón derivados del sistema de acuicultura en sedimentos arenosos podría beneficiar la capacidad de bioturbación de la comunidad de la macrofauna que podría mejorar el metabolismo aeróbico de los sedimentos, reduciendo el coste de su gestión de extracción del sedimento y previniendo las posibles perturbaciones asociadas. / La parte experimental de la presente tesis doctoral ha sido costeada por el proyecto del Ministerio de Ciencia, Innovación y Universidades títulado "IMPLICACIONES ECOLOGICAS DE FONDOS MARINOS BIOGENICOS ARTIFICIALES: ACUMULOS DE RESTOS DE BIVALVOS COMO HERRAMIENTA DE MITIGACION ORGANICA Y SUMIDERO DE CARBONO" (CGL2015-70136-R).

No description available.

Effective delineation and management of stream fish populations requires a thorough knowledge of dispersal patterns, because these patterns affect a number of other demographic rates such as population growth, reproduction, survival, and gene flow. Previous studies of stream fish dispersal patterns have generally established species- and stream-specific home ranges and movement rates, but have largely failed to account for the environmental variables that may cause these parameters to vary. Many fishes occupy a variety of streams across a broad spectrum of ecological conditions, and movement rates (and thus population dynamics) may respond to these environmental gradients. Furthermore, enhanced understanding of the ecological features that induce or impede dispersal will help guide future management of stream channels for population connectivity. To determine the instream features that influence the dispersal patterns of darters, I conducted a spatially intensive mark/recapture study of three darter species in the upper Roanoke River watershed. Logistic regression was used to relate observed inter-riffle movements to gradients in riffle and corridor attributes. During the first study period, habitat area loss and habitat spacing drove dispersal patterns. However, a model developed from these data transferred poorly to the second study period, in which density dependence was a more effective predictor of dispersal. Individual size did not seem to influence the probability of emigration, but did influence the distance traveled following emigration, particularly for the two more specialist species. This finding suggests a size-based dominance hierarchy for habitat selection and occupancy in darters. Predation threat had only a minor effect on the probability of traversing inhospitable corridors, but experimentally introduced structural cover significantly elevated dispersal rates through such corridors. Taken together, results of this study indicate that a complex array of ecological features interact to produce heterogeneity in dispersal rates across the stream landscape. Knowledge of these influences can be used to manage stream channels for dispersal permeability. In addition to field studies, laboratory studies were undertaken to determine the efficacy of visible implant elastomer (VIE) and injectable photonic dye (IPD) for marking darters. No previous studies have rigorously evaluated these marks in darters, and comparisons of the two technologies in any taxa are few. Results of the laboratory study indicated that VIE is preferable to IPD for marking darters, particularly when mark longevity greater than 80 days is desired. Individuals marked with VIE exhibited higher survival and mark retention rates than did individuals marked with IPD. Additionally, VIE mark retention was more consistent across body locations. Retention of both marking technologies was biased by color. My study indicates that the results of tagging efficiency studies are not applicable across taxa, and that pilot studies are necessary prior to field use of marks in previously untested species. / Master of Science

Shallow sheltered Baltic Sea bays are ecologically important habitats that harbour a unique vegetation community and constitute vital reproduction areas for many coastal fish species. Knowledge about the invertebrate community in these bays is, however, limited. This thesis examines the macroinvertebrate community in shallow sheltered Baltic Sea bays and how it is affected by: (1) the natural morphometric isolation of bays from the sea due to post-glacial land uplift; and (2) differences in vegetation types. The invertebrate biomass and number of taxa was found to decrease with increased bay isolation. The taxon composition changed from dominance by bivalves and gastropods in open bays to a community composed of a larger proportion of insects in isolated bays. Stable isotope analysis indicated epiphytes and periphyton as the major energy resources for most of the examined consumers, but the relative importance of these in relation to larger plants decreased for some consumers with increased bay isolation. A comparison of invertebrate abundance between plants revealed a close relationship with morphological complexity of the plants. More complexly structured plants had higher invertebrate abundance than plants with simpler morphology. The results suggest that management of these coastal habitats should be dynamic and take into consideration the natural change in invertebrate community resulting from the slow bay isolation process. In addition, the results imply that changes in the aquatic vegetation due to anthropogenic influences could induce changes in the invertebrate community as the plant habitat structure is altered. A changed invertebrate community may in turn affect higher trophic levels since invertebrates are important food for many fish and waterfowl species. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 4: In press.

What will happen to ecosystems if species continue to go extinct at the high rates seen today? Although ecosystems are often threatened by a myriad of physical or chemical stressors, recent evidence has suggested that the loss of species may have impacts on the functions and services of ecosystems that equal or exceed other major environmental disturbances. The underlying causes that link species diversity to ecosystem functioning include species niche complementarity, facilitative interactions, or selection effects, which cause process rates to be enhanced in more diverse communities. Interference competition, antagonistic interactions, or negative selection effects may otherwise reduce the efficiency or resource processing in diverse communities. While several of these mechanisms have been investigated in controlled experiments, there is an urgent need to understand how species diversity affects ecosystem functioning in nature, where variability of both biotic and abiotic factors is usually high. Species functional traits provide an important conceptual link between the effects of disturbances on community composition and diversity, and their ultimate outcomes for ecosystem functioning. Within this framework, I investigated relationships between the decomposition of leaf litter, a fundamental ecosystem process in stream ecosystems, and the composition and diversity of functional traits within the detritivore feeding guild. These include traits related to species habitat and resource preferences, phenology, and size. I focused on disentangling the biotic and abiotic drivers, including functional diversity, regulating ecosystem functioning in streams in a series of field experiments that captured real-world environmental gradients. Leaf decomposition rates were assessed using litter-bags of 0.5 and 10 mm opening size which allow the quantification of microbial and invertebrate + microbial contributions, respectively, to litter decomposition. I also used PVC chambers where leaf litter and a fixed number of invertebrate detritivores were enclosed in the field for a set time-period. The chemical characterisation of stream detritivores and leaf litter, by means of their nitrogen, phosphorus, and carbon concentration, was used to investigate how stoichiometric imbalance between detritivores and leaf litter may affect consumer growth and resource consumption. I found that the diversity and composition of functional traits within the stream detritivore feeding guild sometimes had effects on ecosystem functioning as strong as those of other major biotic factors (e.g. detritivore density and biomass), and abiotic factors (e.g. habitat complexity and agricultural stressors). However, the occurrence of diversity-functioning relationships was patchy in space and time, highlighting ongoing challenges in predicting the role of diversity a priori. The stoichiometric imbalance between consumers and resource was also identified as an important driver of functioning, affecting consumer growth rates, but not leaf decomposition rates. Overall, these results shed light on the understanding of species functional diversity effect on ecosystems, and indicate that the shifts in the functional diversity and composition of consumer guilds can have important outcomes for the functioning of stream ecosystems.

Few studies of tropical fish communities compare fish distributions across the full range of near-shore tropical marine habitats. As a result, our understanding of tropical marine fish communities is often biased towards habitats preferred by researchers. The distribution and habitat preferences of all 136 fish species occurring at 106 stations in three bays off Tortola in the British Virgin Islands were assessed. At a species level, habitat type was often the key factor influencing fish distribution. Of the 44 species occurring at more than 10 stations, 3 were sand specialists, 5 were strongly associated with mangroves, 7 were dependent on seagrass and algal beds and 14 were found only on the forereef. Eleven species were widely distributed both on the forereef and in bays, and 9 of them showed clear evidence of ontogenetic partitioning. The juveniles all preferred bay habitat types and moved onto the forereef as they approached sexual maturity. At a community level, five distinct fish assemblages were found. The assemblage types were classified according to their distribution: 1) forereef, 2) reef flat, 3) non-mangrove associated seagrass, 4) mangrove associated seagrass and 5) eutrophic areas. Forereef stations were the most species-rich with 24 species per station while eutrophic stations had the most depauperate communities with only 4 species per station. Variation in fish species richness at each station was largely explained by a simple habitat complexity index. It accounted for 70% of the variation in fish species richness and 21% of the variation in fish abundance. Rugosity and variety of growth forms were the most important predictors of species richness, but the height of the habitat architecture was the most useful predictor of fish abundance. Artificial reefs were constructed to test the effects of each habitat complexity variable experimentally. Increasing rugosity, variety of growth forms and percentage hard substrate increased the observed number of species but increasing the variety of hole-sizes, and height had no effect. The only complexity variable that had a significant effect on fish abundance was percentage hard substrate. In addition to the static substrate structure, long-spined sea urchins Diadema antillarum affected fish distribution because small fish shelter from predators in their spines. The urchins increase species richness and abundance in low complexity seagrass beds, but on artificial reefs, where shelter was not a limiting factor, the effect was less pronounced. Organic pollution is another factor that negatively affects the fish community by reducing fish species richness and abundance. Poor water quality often alters the natural habitat, confounding observations, but fish species richness was reduced in polluted areas even when artificial reefs were used as habitat controls. The applications of these findings to the management and conservation of fish in the British Virgin Islands are discussed.

Abstract Despite the great amount of in-stream restorations conducted in the past decades there is still a disturbing lack of knowledge about the outcome of these measures. The overall goal of this study was to assess the effect of enhanced streambed heterogeneity on the ecology of stream salmonids and stream retention efficiency. Substratum heterogeneity is often considered as one of the most important limiting factors for organisms living in running waters. Winter ecology of rivers has not been broadly studied regardless of the general belief that wintertime conditions strongly influence the survival and population size of stream salmonids. In an experimental study, the paucity of wintertime habitat in simplified channels caused temporary mass loss in age-0 trout. In late spring, channelized stream trout performed catch-up growth with potentially negative effects on long-term fitness. A management implication of this study is that increasing cover availability by in-stream restoration structures may enhance the long term success of juvenile salmonids although the short term effects were minor. Densities of salmon parr in the River Kiiminkijoki showed no response to streambed restoration. Suitable habitat area for salmon parr increased after restoration under summer conditions. However, restoration-induced benefits to winter habitats were marginal, with one study reach indicating even negative values. Most of the areas with good habitat values were located along river margins, indicating that restoration measures had only limited impact on the mid-sections of the river channel. Dredging of small streams may have caused depletion of allochthonous organic matter due to the reduction of retentive structures. In a leaf release experiment, moss cover enhanced retentiveness as well as did various restoration structures (boulders, large wood). Only a very high amount of wood clearly enhanced retention capacity. This underlines the importance of wood as an effective retention structure in headwater streams. This study indicates that habitat complexity as such may be less important than life-stage specific habitat requirements of fish (e.g. cover for overwintering salmonids). Importantly, restoration may only be successful if the measures used target the limiting factor(s) of the ecosystem or the species; for salmonids, habitat complexity does not seem to be this factor. / Tiivistelmä Uiton jälkeisten kunnostustoimenpiteiden määrä Suomessa on ollut huomattava, mutta vaikutusten arviointi, pelkästään kalastonkin kannalta, on jäänyt vähäiselle huomiolle. Tässä työssä selvitettiin kunnostusten merkitystä lohen ja taimenen poikasvaiheille, huomioiden etenkin pohjan rakenteellisen monimuotoisuuden vaikutus. Työssä selvitettiin myös kunnostusten vaikutuksia lehtikarikkeen pidätyskykyyn, joka on erityisesti latvapurojen ekosysteemien tärkeimpiä perustoimintoja. Lohikalojen talviekologinen tutkimus on viime aikoihin saakka ollut vähäistä, vaikka talviolosuhteiden uskotaan rajoittavan pohjoisten virtavesien eliöstön elinmahdollisuuksia. Kokeellisessa työssä rännimäisissä uomissa talvehtiminen aiheutti taimenenpoikasille tilapäisen painon alenemisen ja nopean kompensaatiokasvun loppukeväällä. Kompensaatiokasvu voi vaikuttaa negatiivisesti koko kalan eliniän, joten kunnostusten tuoma hyöty sopivien suojapaikkojen lisääntymisenä voi edesauttaa lohikalojen pitkäaikaista menestymistä. Kiiminkijoella lohenpoikasten tiheydet eivät muuttuneet kunnostuksen myötä ja vuosien välinen vaihtelu oli kuuden vuoden seurantajaksolla huomattavan suurta. Elinympäristömallinnuksen perusteella soveltuvan elinympäristön lisäys ei ollut merkittävää, koska etenkin talviaikaisten alueiden puute jäi huomattavaksi. Suurin osa soveltuvasta elinympäristöstä sijaitsi joen reuna-alueilla, joten kunnostusvaikutus joen keskiosaan jäi odotettua pienemmäksi. Uittoperkaus on voinut johtaa latvavesien ekosysteemien köyhtymiseen maalta tulevan orgaanisen aineksen pidättymiskyvyn vähentyessä. Kokeellisen työn perusteella kuitenkin nykypäivän tilanne vuosikymmeniä uiton loppumisen jälkeen osoittautui lähes yhtä pidättäväksi kuin nykyisin käytetyt kunnostusrakenteet (kivi tai puu). Kunnostusrakenteeseen tulisi lisätä huomattava määrä puuta, jotta lehtikarike pidättyisi korkeallakin virtaamatasolla. Tulosten perusteella elinympäristöjen muuttaminen monimuotoisemmiksi ei takaa kunnostustoimien onnistumista, sillä etenkin kalapopulaatioita rajoittavat yleensä useat tekijät. Jos kuitenkin elinympäristö on populaatiota rajoittava resurssi ja sitä pystytään lisäämään (kuten talviaikaiset suojapaikat), voidaan kunnostuksella saada näkyviä tuloksia. On ilmeistä, että kunnostustoimien tulisi olla nykyistä kattavampia ja paremmin suunnattuja rajoittaviin tekijöihin, jotta tulokset näkyisivät.

<p>Diss. (sammanfattning) Umeå : Umeå universitet, 1995, härtill 6 uppsatser.</p> / digitalisering@umu

No description available.