Studier visar att dagens elever känner oro inför framtiden och de klimatförändringar vår värld utsätts för. Skolverkets nationella kartläggning utav miljöundervisning i skolan visar dock att cirka hälften av de tillfrågade gymnasielärarna inte bedriver någon undervisning i ämnet. Denna studie beskriver en alternativ modell för undervisning i klimatfrågor. Elever ges genom modellering av ekosystem möjlighet att fördjupa sin förståelse kring klimatförändringar i samband med exploatering av topp-predatorer. Detta är ett realistiskt problem då en mängd studier visar att dagens ekosystem utsätts för en mängd stressfaktorer, med ursprung i klimatförändringar, och att exploatering av topp-predatorer kan leda till konsekvenser med artutdöende som följd. Modellen som används i undersökningen är en generell Lotka-Volterra-modell vilken fungerar som analytiskt verktyg. Skolverket betonar matematikens roll som ämnesöverskridande verktyg och modellekosystem ger elever möjlighet att använda matematiska kunskaper i ett verkligt scenario. I studien undersöks även hur pass stor exploatering topp-predatorer kan utsättas för i takt med ökade klimatförändringar. De undersökta områdena inbegriper tre- och fyr-artssystem i marina och terrestra miljöer. Resultaten visar att exploateringen måste minska i takt med ökade klimatorsakade förändringar i samtliga fall, undantag terrestra tre-artsystem som utsätts för förändrade interaktionsstyrkor. / Studies show that today's students are worried about the future and the increasing climate change. A survey made by the Swedish National Agency for Education about environmental education shows that approximately half of the surveyed secondary school teachers are not engaged in teaching in the field. This study describes an alternative model for teaching environmental issues. Students are by the modeling of ecosystem given an opportunity to deepen their understanding of climate change associated with the exploitation of top predators. This is a realistic problem, numerous studies show that today's ecosystems are exposed to a variety of stressors, with the origin of climate change, and the exploitation of top predators can lead to serious consequences with extinction as a result. The model used in this study is a generalized Lotka-Volterra model which works as an analytical tool. The Swedish National Agency for Education emphasizes the role of mathematics as interdisciplinary tools and model ecosystem gives students the opportunity to use math skills in a real scenario. The study also investigated how much exploitation top predators can be exposed to in line with increased climate change. The research sites include three-and four-species system of marine and terrestrial environments. The results show that the exploitation must be reduced in line with increased climate-caused changes in all cases, except terrestrial three-species system exposed to changes in interaction strengths.

No description available.

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

The overall aim of this thesis was to elucidate the relative importance of the bacterial and fungal energy channels within the soil food web and to differentiate and appreciate the differences in niche of the soil fauna when affected by differing land management. Feeding niche of the soil fauna is ambiguous and has been previously determined by observation, inference or biochemical studies. One method that can determine feeding preferences in situ is the use of stable isotopes. Stable isotopes trace the passage of C and N through different trophic levels, both at natural abundance and by the addition of a pulse of enrichment. The work described within this thesis describes the development of methods of culturing and labelling organisms for use in stable isotope studies. Bacteria, protozoa and fungi were cultured with stable isotopes enriched to 99 atom% and their growth and survival monitored. Utilising stable isotope enriched organisms means that empirical testing of the feeding interactions can occur and that differences between the bacterial and fungal energy channels can be explored. Two field sites were chosen to assess how management changes affect the food web, both sites were historically grassland with the same soil type, but one was converted to a willow woodland twenty years ago. The results of these studies have shown, at natural abundance a grassland and woodland habitat with very different stable isotope signatures, reflecting plant and soil composition, as well as differences in trophic niche and C drivers. The introduction of enriched bacteria illustrated that bacterial feeding was more widespread than normally portrayed in food web diagrams. The introduction of enriched protozoa highlighted that protozoan feeding by soil fauna was more prevalent in the grassland habitat; reflecting differences in linkages between trophic levels within the two habitats. Methods were also developed to “grow” enriched fungal hyphae back into soil food webs in a comparable way to the investigation of the bacterial energy channel. Different species of saprotrophic fungi were found to fractionate to differing extents when grown on the same natural abundance media and the fungus Absidia cylindrospora's growth was impacted when grown on a dually enriched medium. We can now infer that the bacterial energy channel is not as divergent from the fungal energy channel as previously hypothesised. The majority of soil fauna were found to be omnivorous through empirical results, consuming bacteria and protozoa, even when they were considered to be fungal feeders by the literature. The different habitats within the study were found to have different C drivers, with roots and soil being the primary driver in the grassland whilst litter was in the woodland, consequently favouring different food webs. This work makes a first step in measuring the contribution of the different feeding channels and feeding interactions occurring within the different trophic levels in the two habitats and shows the effect that one change in management has had over the entire faunal assemblage.

Stable isotope analysis (SIA) is a valuable tool in ecotoxicology because δ13C and δ15N may provide insights into the trophic transfer of contaminants in a food web. The relationship between a species’ trophic position (TP, determined from δ15N) and internal concentration of biomagnifying contaminants can be established and used for regulatory purposes. However, the exposure of organisms to xenobiotics incurs physiological costs, and the stable isotope signature of a consumer reflects not only diet but also a physiological state. The latter raises questions regarding the interpretation of stable isotope signatures in contaminated areas. Therefore, the aim of this Thesis was to evaluate the behaviour of consumers’ stable isotope signatures in stressed systems, with a primary focus on the effects of environmental contaminants. In paper I, the physiological costs of chemical exposure were found to alter incorporation rates of dietary nitrogen and carbon in a consumer by influencing both growth and metabolic turnover, with resulting changes in isotope signatures relative to a control system. In paper II, the diet-consumer discrimination factors for 15N and 13C were confirmed to increase under chemical exposure mediated via increased metabolic costs. However, the physiological response was low and translated into only minor shifts in the δ13C and δ15N. The predictability of exposure effects on the stable isotope signature was demonstrated in paper III, in which animals exposed to a chemical with a known mode of action presented expected effects on elemental composition, body size, biomarkers of oxidative stress and the stable isotope signatures. Moreover, consumers’ oxidative balance was found to be related to their δ15N values, thus providing evidence of the kinetic isotope effect on the oxidative status. However, despite the alterations in stable isotope signatures observed in laboratory settings (papers I-III), the effect of xenobiotics on the TP estimates was nil or minor in the field-collected animals. Moreover, the TP values were not significantly different between the animals in the contaminated and the reference habitats because of the high overall uncertainties in the TP estimates (paper IV). Also, the TP estimates based on δ15N in bulk material were more similar between the contaminated and the reference systems than TP estimates based on δ15N values in amino acids. Therefore, the latter method appears more sensitive towards xenobiotics (and, possibly, other environmental stressors) and thus less suitable for TP assessment in contaminated areas. This Thesis improved the overall understanding of the applicability of SIA in stressed systems by establishing relationships between various exposure regimes, physiological responses and the stable isotope signatures in consumers. In model species at low trophic levels, the exposure to xenobiotics was found to significantly affect δ13C and δ15N values, which can be expected whenever physiological responses are detected. However, because of the overall high uncertainty in TP estimates, no significant differences between contaminated and control systems were detected, although the estimated TP were consistently higher in the contaminated systems. Future research should focus on higher trophic levels, in which effects of a greater magnitude can be expected. Moreover, the effects in entire food webs should be addressed rather than single prey–consumer relationships as well as other environmental variables that may contribute to the stable isotope variability in and among systems under various environmental pressures. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>

Annual energy flow and mean annual biocontent of eighteen compartments were determined for a 0.94 ha north central Texas pond ecosystem. Annual primary production was 7,780 kcal m^-2 yr^-2, and community production-to-respiration ratio was 1.49. One-third of annual primary production accumulated on the substrate as silt and sedimentation. Community production, production-respiration ratio, and biocontents of all compartments except aquatic insects were large in summer, small in winter. Biocontents of four trophic levels in the pond were all of the same order of magnitude, approximately 50 kcal m^-2. Suspended and benthic organic material forprimary consumers and terrestrial insects for tertiary consumers were substantial allochthanous energy imports into the pond system.

La palourde japonaise (Ruditapes philippinarum) a été introduite au début des années 1980 dans le bassin d’Arcachon à des fins aquacoles. Elle s’est rapidement répandue dans toute la zone intertidale de la lagune, créant actuellement le premier gisement français en terme de stock exploitable. Cependant, de récentes évaluations du stock ont démontré une structure en taille déséquilibrée avec un déficit en juvéniles et en adultes de taille supérieure à 38 mm. Ce constat alarmant a posé des questions sur le devenir des populations de palourdes japonaises dans le bassin d’Arcachon et a motivé la présente thèse. Cette étude vise à mieux comprendre la dynamique de population de cette espèce et certains facteurs contrôlant cette dynamique. Le but in fine était d’améliorer la gestion du stock exploitable de cette espèce dans la lagune grâce à un modèle, incrémenté des différents résultats obtenus lors de cette étude. Les paramètres de croissance K et L8 du modèle de Von Bertalanffy ont été déterminés d’une part par un suivi régulier des populations naturelles, et d’autre part par une expérience de marquage-recapture d’une durée de deux ans. Les résultats montrent une croissance lente avec un K homogène dans tout le bassin et un L8 variable suivant le site. Cette étude met aussi en évidence une mortalité naturelle normale mais une reproduction déficiente (indices de condition bas, mauvais recrutement). Parmi les facteurs pouvant expliquer cette dynamique, différents pathogènes ont été suivis durant deux ans : les trématodes digènes, la maladie de l’anneau brun, la perkinsose. De plus, une pathologie émergente (maladie du muscle marron, BMD) a été découverte. Seules la perkinsose et la BMD ont révélé de fortes prévalences et intensités. La perkinsose entraîne des effets mitigés sur la croissance tandis que la BMD entraîne une remontée des palourdes en surface puis leur mort. Les ressources trophiques sont également importantes pour expliquer la croissance et ont été étudiées ici grâce aux isotopes stables de l’azote et du carbone. Cette étude a révélé une hétérogénéité des sources trophiques au sein de la lagune et une alimentation dominée par du phytoplancton. La proportion de phytoplancton ingérée a été corrélée à L8. Les paramètres de croissance et de mortalité ont été ensuite intégrés dans un modèle de gestion qui nous a permis de voir que si rien n’était fait en terme de gestion, le stock de palourdes continuerait de se dégrader. Ce modèle nous a permis de simuler différentes situations de gestion et suite aux résultats obtenus, un certain nombre de mesures a ensuite été adopté par les organismes gestionnaires. / The Manila clam (Ruditapes philippinarum) was introduced into Arcachon Bay at the beginning of the 1980s for aquaculture purposes. It rapidly naturalized in all intertidal flats of the lagoon. Nowadays, Arcachon Bay ranks at the first French place in terms of exploitable stock. However, recent stock assessments have shown an unbalance size structure with a deficit in juvenile and adult clams (> 38 mm shell length). These alarming patterns asked many questions on the sustainability of Manila clam populations within Arcachon Bay and have motivated the present thesis. This study aimed to better understand the population dynamics of this species and also some factors controlling this dynamic. The final objective was to improve the Manila clam fishing management with a model raised with results of the study. Von Bertalanffy growth parameters (K and L8) were both determined by a field survey of populations and by a tagged-recapture experiment during two years. Growth appeared slow with a homogeneous K within the bay and different L8 according to the sites. This study also evidenced a normal natural mortality and an inefficient reproduction (low condition index, low recruitment). Among the factors that could explain these dynamics, different pathogens were monitored during two years: digenean trematodes, brown ring disease and perkinsosis. Moreover, an emergent pathology (brown muscle disease, BMD) has been discovered. Only perkinsosis and BMD revealed high prevalences and intensities. Perkinsosis induced mitigated effects on growth whereas BMD-infected clams rise to the surface of the sediment and died. Trophic sources were also important to explain growth and were studied with carbon and nitrogen stable isotopes. This study displayed a heterogeneous repartition of Manila clam trophic sources within the bay and a phytoplankton dominated diet. The proportion of ingested phytoplankton was correlated with L8. Growth and mortality parameters were integrated in a management model. If no new management measures were taken, the clam stock will continue to decrease. Different management situations have been simulated and new measures have been adopted by administrator organisms.

Artificial reefs may enhance the biological production of reef-associated flora and fauna, but their trophic structure relative to that of natural reefs remains understudied. We assessed trophic dynamics by comparing δ13C and δ15N in 43 fish species from artificial and natural reef tracts of Broward County, Florida. We tested the effect of sampling location (artificial, first, and second reef), general feeding strategy (herbivore, omnivore, planktivore, invertivore, and carnivore), phylogeny, and standard length. For all samples, δ13C and δ15N ranged from -19.5 to -13.1‰ and 6.7 to 13.3‰, respectively. Lower trophic level feeding behavior resulted in more depleted δ13C and δ15N and higher trophic level feeding behavior resulted in more enriched δ13C and δ15N. We detected significant effects of both general feeding strategy and phylogeny. We also detected significant differences in δ13C and δ15N profiles between artificial and natural reefs; however, these differences were not great enough to suggest changes in the feeding strategy or trophic dynamics of individual fish taxa.

This Ph.D. Thesis is focused on the effect of submerged vegetation on the structure of lake ecosystem and trophic relationships among fishes. Succession of submerged vegetation is a dynamic process and the vegetation community may change dramatically even during a year. Many environmental factors have impact on the succession of submerged vegetation and consequently the presence of the vegetation has substantial impact on the aquatic ecosystem. Nutrient level (mainly nitrogen and phosphorus) plays a key role in the succession of freshwater ecosystems. Further, herbivory significantly influences species composition and biomass of macrophytes and macroalgae. Herbivory of fish is a foraging strategy that is dependent on temperature. Foraging preferences of fish may suppress the palatable species. The rate of herbivory affects plant growth patterns and thus inpalatable species may be advantaged in the competition among plants. In aquatic ecosystems, herbivory is often performed by omnivorous species. The diet preferences of omnivorous fish differ among aquatic ecosystems and submerged vegetation can shape their trophic niches substantially.

Os estudos realizados em diversas partes do mundo sobre a utilização de pesticidas e os impactos que estes podem causar ao ambiente são uma das ações prioritárias para o desenvolvimento da agricultura, principalmente para aqueles pesticidas que são persistentes ao meio biótico e abiótico, como o inseticida heptacloro, que apesar de seu uso restrito para tratamento de madeira, ainda é muito usado no Brasil clandestinamente para outros fins. A maioria dos estudos realizados até agora sobre biomagnificação envolve o meio terrestre e uma pequena porcentagem desses é direcionada para o meio aquático e tem sido realizada em modelos de campo. O objetivo deste projeto foi determinar a CL50 96 horas para peixes a acumulação, biomagnificação e depuração do heptacloro em um modelo de sistema aquático. Como não existe nenhuma norma que defina o efeito cumulativo através dos níveis tróficos, pretendeu-se com esta pesquisa estimar a biomagnificação e depuração do heptacloro. Este estudo foi realizado em laboratório, em um modelo dividido em compartimentos individualizados, no qual somente as algas (Pseudokirchneriella subcapitata) foram submetidas por um período de 7 dias ao heptacloro, obtendo-se uma concentração final de 0,10 x 10-5µg heptacloro/µg algas, as quais posteriormente serviram de alimento para os microcrustáceos (Daphnia magna) durante 9 dias, que ao final concentraram 0,12 x 10-5 µg heptacloro/µg organismos. Por último, os peixes (Danio rerio) foram alimentados com microcrustáceos, no período de 5 dias, alcançando uma concentração final de 0,62 x 10-8 µg heptacloro/µg organismos. Nos últimos 9 dias, durante o período de depuração, os peixes foram alimentados em dias intercalados com microcrustáceos e ração sem contaminação com o produto, atingindo uma concentração final de 0,25 x 10-8 µg heptacloro/µg organismos. Nos testes realizados com esses três organismos, observou-se que a concentração ficou maior conforme o nível dentro do modelo proposto era mais alto, comprovando assim a hipótese do poder de bioacumulação, biomagnificação e depuração do heptacloro. / The studies carried out in different parts of the world about the pesticides use and the impacts that they can cause to the environment, are one of the priority actions for the agriculture development, mainly for those pesticides that are persistents in the biotic and abiotic environment, such as the heptachlor insecticide, which is still illegally used for others purposes in Brazil, although its use is limited for the wood treatment. The majority of the studies carried out until now about biomagnification involves the terrestrial environment and a small percentage of these studies are directed for the aquatic environment, and this small percentage has been carried out in field models. The aim of this project was to determine the LC50 96 hours for fish, accumulation, biomagnifications, and depuration of heptachlor in an aquatic system model and, as there isn?t any norm that defines the cumulative effect through trophic levels, it was claimed with this research to esteem the heptachlor biomagnification and depuration. This study was carried out in a laboratory, in a model divided in single chambers, in which the algae (Pseudokirchneriella subcapitata were submitted during 7 days to the heptaclhor, getting a final concentration of 0.10 x 10-5µg heptaclhor/µg algae, which was later served as food for the microcrustaceans (Daphnia magna) were submitted during 7 days to the heptaclhor, getting a final concentration of 0.10 x 10-5Mµg heptaclhor/µg algae, which was later served as food for the microcrustaceans (Daphnia magna) were fed with microcrustaceans, in the period of 5 days, reaching a final concentration of 0.62 x 10-8 µg heptaclhor/µg organisms. In the last 9 days, during the period of depuration, the fish were fed in days intercalated with microcrustaceans and ration without contamination with the product, reaching a final concentration of 0.25 x 10-8 µg heptacloro/µg organisms. In tests carried out with these three organisms, it was observed that the concentration was bigger as higher the level inside of the considered model, thus proving the hypothesis of the bioaccumulation, biomagnification, and depuration power of heptachlor.