A gradual rise in Earth's surface temperature marks a transition from the late Paleocene to the early Eocene ca. 58-51 Ma. Paleocene/Eocene boundary (∼55.5 Ma) sediments deposited in the midst of this slow warming ubiquitously reveal evidence for a massive isotopically light carbon injection and an associated rapid but transient global warming event, or hyperthermal, that has been termed the Paleocene Eocene Thermal Maximum (PETM) and attributed to a carbon injection from multiple potential sources. The PETM has gained importance over the past two decades as a potential geologic analog to the modern anthropogenic carbon injection and climate change. However significant questions surrounding the nature of the carbon injection at the onset of the PETM remain. The Clarence River valley, located in the Marlborough region, South Island, New Zealand, contains a series of outcrops of lithified late Paleocene to early Eocene sediments originally deposited on a paleo-slope margin. Within these sections, the Lower Limestone Member of the Amuri Limestone Formation records the interval of interest. A Lower Limestone prominent recessed unit consisting of multiple marl-rich beds and recording a pronounced negative carbon isotopic excursion (CIE) marks the PETM at sections that have been bisected by tributaries to the Clarence River, including Mead Stream and Dee Stream. Here I detail and discuss Clarence valley Lower Limestone sections and relate these records to global trends with an emphasis on adding constraints to the PETM carbon injection. Specifically, I document the lithologic and carbon isotopic expression of the PETM and two younger paired sets of early Eocene events that, similar to the Mead Stream and Dee Stream PETM sections, reveal negative CIEs and expanded marl-rich units coincident to identical CIEs and condensed carbonate dissolution horizons in deep-sea sections. I further quantify the abundance of bioturbating macrofauna trace fossils through the PETM at both Mead Stream and Dee Stream and argue that New Zealand margin intermediate waters became hypoxic precisely coincident to the PETM carbon injection. In concert, these findings suggest a PETM carbon addition mechanism capable of both diminishing intermediate water dissolved oxygen and of repeated early Eocene injections. / U.S. National Science Foundation (NSF); Joint Oceanographic Institutions (JOI), Inc.

No description available.

Meiofauna are an abundant, diverse and important component of the marine biota, however, much of their ecology has been neglected. Despite their high densities, meiofaunal abundance is often patchy. Meiofauna present in high numbers at one site will often be less abundant in seemingly similar adjacent sites. What factors govern this variability? How readily do these animals colonize new patches? How do various biological and environmental factors affect meiofaunal colonization rate and resulting assemblage structure? The response of meiofauna to changes in abiotic factors, including sediment grain size, depth, exposure and distance from the ocean floor, was quite variable. Often one factor would affect certain taxa and not others. Even slight increases in depth resulted in drastic declines of harpacticoid copepods while nematodes were unaffected. Meiofauna were also fewer in sediments with large interstitial spaces. Some meiofauna were most abundant in sediments placed closer to the ocean floor. Other taxa colonized distant substrata as rapidly as they did substrate located closer to the ocean floor. This suggested differences between taxa in their rates of active dispersal. The effects of macrofauna on meiofauna have been debated. In particular, how do clams affect the colonization and assemblage structure of meiofauna? Certain characteristics of clams were isolated and evaluated: feeding behaviour, bioturbation rate/depth and metabolic byproducts. Clams that caused the greatest meiofauna declines were shallow burrowing deposit-feeders. Constant disturbance to the upper sediment by these clams was likely responsible for meiofaunal impact. Conversely, suspensionfeeding clams that passed quickly to deeper sediment and remained stationary had little impact on meiofauna. Finally, a survey of local marine nematodes added nine genera new to Canada and 24 genera new to British Columbia. A review was also compiled that shows nematodes and other meiofauna have been neglected for much of Canada. Although these small and abundant animals are quick to colonize even distant habitats they are quite sensitive to cues from the surrounding biotic and abiotic environment. This sensitivity combined with their ease of collection make meiofauna a valuable asset to any number of ecological investigations. / Ecology

The ant building activity of the nest represents an important phenomenon, influencing ambient environment. If we want to know, which factors are affecting this process, we will describe its details. This paper aims to detrmine the factors which influence nest building activity, by an experiment using the species of Lasius niger (L.) in the artifical formicaria.

Research in salt marshes dominated by the grass Sporobolus alterniflorus indicates that plant characteristics affect fiddler crab burrowing and in turn, crab activity can enhance primary productivity by increasing soil oxygen and nutrient cycling. Crab-plant interactions are less understood in microtidal Gulf Coast marshes compared to Atlantic Coast tidal marshes. It is unknown how structure of the dominant Gulf Coast vegetation zones (salt marsh, brackish marsh, fresh marsh and salt pannes) affects density of crab burrows and how burrows may influence primary productivity. I hypothesized that fiddler crabs would be most abundant in marsh zones with intermediate substrate hardness and vegetation density (Goldilocks Hypothesis). A seasonal habitat preference study was conducted during 2016-2017 in tidal marshes at Grand Bay National Estuarine Research Reserve in coastal Mississippi using burrow density as a proxy for crab abundance. Plant above- and below-ground biomass, burrow proximity to vegetation, and soil hardness were also surveyed as potential drivers of fiddler crab populations. The results indicated that fiddler crabs burrow in all four zones, but to varying degrees, and that burrow density was highest during autumn. The fresh marsh had the highest average density of burrows, as well as vegetation and soil parameters most representative of intermediate habitat, thereby supporting the “Goldilocks Hypothesis”. The brackish marsh also proved to be important fiddler crab habitat. Preferential fiddler crab usage of habitat upslope of salt marsh, e.g., fresh and brackish marsh, in Gulf Coast sites suggests that they may avoid immediate impacts of rising sea levels and possibly even migrate to higher ground if needed.

Mangrove plants are a productive ecosystem that provide several benefits for marine organisms and industry. They are considered to be a food source and habitat for many organisms. However, mangrove growth is limited by nutrient availability. According to some recent studies, the dwarfism of the mangrove plants is due to the limitation of nitrogen in the environment. Biological nitrogen fixation is the process by which atmospheric nitrogen is fixed into ammonium. Then, this fixed nitrogen can be uptaken by plants. Hence, biological nitrogen fixation increases the input of nitrogen in the mangrove ecosystem. In this project, we focus on measuring the rates of nitrogen fixation on Red Sea mangrove (Avicennia marina) located at Thuwal, Saudi Arabia. The nitrogen fixation rates are calculated by the acetylene reduction assay. The experimental setup will allow us to analyze the effect of crab bioturbation on nitrogen fixing rates. This study will help to better understand the nitrogen dynamics in mangrove ecosystems in Saudi Arabia. Furthermore, this study points out the importance of the sediment microbial community in mangrove trees development. Finally, the role of nitrogen fixing bacteria should be taken in account for future restoration activities.

Ökosystem-Ingenieure sind Organismen, deren Auswirkung auf die Funktion von Ökosystemen im Vergleich zu ihrer Anzahl und Biomasse überproportional groß ist. Ein klassisches Beispiel für Ökosystem-Ingenieure sind grabende Organismen, deren Aktivitäten (Bioturbation) sowohl die Sedimentmatrix als auch das Porenwasser in aquatischen Sedimenten beeinflussen. Solche Tiere wirken auf eine große Anzahl von biogeochemischen Prozessen in benthischen Ökosystemen ein, unter anderem auf die aerobe Atmung (Respiration). Die Respiration aquatischer Sedimente umfasst häufig über 50 % der gesamten Respiration von aquatischen Systemen und spielt eine große Rolle im globalen Kohlenstoffkreislauf. Die vorliegende Doktorarbeit beschäftigt sich mit den Auswirkungen der physikalischen Umwelt (Sedimenteigenschaften, am meistens hydraulischer Leitfähigkeit) auf die mikrobielle Respiration von Sedimenten, in denen Bioturbation durch Chironomidenlarven stattfindet. Um die Auswirkungen von Bioturbation auf Respiration zu messen und zu identifizieren, wurde eine neue Messmethode entwickelt (Kapitel 4.1). Kapitel 4.2 zeigt, dass der Einfluss von Bioturbation auf die Respiration des Sediments mit zunehmender Temperatur ansteigt. Kapitel 4.3 belegt, dass Resazurin auch für die Messung der Respiration in marinen Sedimenten geeignet ist. Kapitel 4.4 vergleicht und begutachtet die große Anzahl und Vielfalt hydrologischer, biogeochemischer und ökologischer Tracer einschließlich Resazurin. Die physikalische Umwelt (Sedimentmatrix) kontrolliert wie stark die Auswirkungen der Bioturbation auf die Respiration des Sedimentes sind. Dementsprechend liefert diese Doktorarbeit die Basis für das Verständnis der Auswirkungen benthischer Bioturbation auf Respiration und Kohlenstoffumsatz in limnischen und marinen Sedimenten. / Ecosystem engineers are organisms, whose impact on ecosystem functioning is disproportionally large compared to their abundance and biomass. A classic example of ecosystem engineers are burrowing organisms whose activities (bioturbation) affect the sediment matrix and pore solutes in aquatic sediments. Bioturbating animals are impacting on a number of biogeochemical processes in benthic ecosystems, including, among others, aerobic respiration. Respiration of aquatic sediments often comprises over 50% of the total respiration of aquatic systems, and plays a tremendous role in the global carbon cycle. The present thesis deals with the impacts of the physical environment (sediment characteristics, mainly hydraulic conductivity and grain fractions) on the (microbial) respiration of bioturbated sediments. In order to disentangle the effects of bioturbation on respiration, a novel measurement method has been developed (Chapter 4.1). Chapter 4.2 reveals that the impact of bioturbation on sediment respiration increases with increasing temperature. Chapter 4.3 shows that resazurin can also be used for the measurement of respiration in bioirrigated marine sediments. Chapter 4.4 reviews the large number and diversity of hydrological, biogeochemical and ecological tracers including resazurin. The present thesis shows that in sediments with low hydraulic conductivity (diffusion-dominated sediments) (Chapters 4.1,4.2) bioturbation is altering sediment respiration to a larger extent than in sediments with high hydraulic conductivity (advection-dominated sediment) (Chapter 4.3). The physical environment (sediment matrix) controls the intensity of the impacts of bioturbation on sediment respiration. Thus, this thesis provides a basis for understanding the impact of benthic bioturbators on respiration and carbon sequestering in freshwater and marine sediments.

Le remaniement sédimentaire, défini comme l’ensemble des mouvements de particules sédimentaires induits par les organismes benthiques, est l’une des deux composantes du phénomène de bioturbation. Il constitue un processus clé du fonctionnement des écosystèmes côtiers. Ce manuscrit présente une étude intégrée de ce depuis l’échelle de la simple particule sédimentaire jusqu’à celle de la communauté benthique in toto.Le développement d’une nouvelle approche expérimentale basée sur l’acquisition à haute fréquence et l’analyse de séries temporelles d’images de mouvements de luminophores le long de la paroi d’aquariums plats a permis de mesurer directement les mouvements élémentaires de particules de sédiment effectués par le bivalve A. alba. Cette approche a ainsi conduit à la première détermination expérimentale d’ « empreintes » du remaniement sédimentaire d’un invertébré marin, d’après le formalisme du modèle CTRW (Continuous Time Random Walk).Dans un second temps, le déploiement de cette nouvelle approche a permis d’évaluer, de manière dynamique (i.e. pendant des expériences de 48h) et sur l’ensemble de la partie de la colonne sédimentaire affectée par ce bivalve, le contrôle exercé par la température et par la disponibilité de matière organique fraîche sur les caractéristiques du processus de remaniement sédimentaire effectué par A. alba.Enfin, l’intensité du remaniement sédimentaire effectué par l’ensemble de la communauté benthique a été mesurée in-situ dans le Bassin d’Arcachon, à la fois dans un herbier à Zostera noltii et dans une zone de vase nue d’où celui-ci a disparu. Ceci a permis de déterminer les effets limitant de la présence d’herbier et de certaines espèces benthiques clés, sur le remaniement sédimentaire. / Sediment particle mixing, defined as the movements of sediment particles induced by benthic fauna, is one of the two components of bioturbation by benthic organisms. It is a key process of the ecological functioning in coastal areas. This manuscript presents an integrated study of sediment particle mixing process from the single sediment particle to the whole benthic community.The development of a new experimental approach, coupling high frequency acquisition of time series images of luminophores motions along thin aquaria glass walls, allowed for the direct measurement of elementary particle motions induced by the bivalve Abra alba. This constitutes the first experimental assessment of sediment particle mixing “fingerprints” in a marine invertebrate, according to the CTRW (Continuous Time Random Walk) model formulation.The deployment of this new approach also allowed for the determination of the control of water temperature and of fresh organic matter availability on sediment particle mixing induced by Abra alba. Moreover, the temporal (i.e., during 48h experiments) and spatial (i.e., over the whole section of the sediment column affected) dynamics of these effects were considered.At last, sediment particle mixing intensities induced by the whole benthic community were assessed in-situ in Arcachon Bay, within both a Zostera noltii meadow and a bare sediment mudflat where phanerogams were previously present. These results highlighted the restrictive effect of phanerogams themselves and of a restricted number of key benthic species, on sediment particle mixing.

Le but de cette thèse était de déterminer l’impact de deux types de nanoparticules métalliques (sulfure de cadmium – CdS - et or - Au) sur deux organismes aquatiques modèles (vers tubifex et poisson zèbre Danio rerio). L’approche a consisté à doper le sédiment de la Garonne avec les deux types de nanoparticules et caractériser l’effet de cette contamination sur les deux organismes en utilisant plusieurs marqueurs à différents niveaux d'organisation biologique (réponses biochimiques, activité de neurotransmission, génotoxicité, expression génétique et activité de bioturbation). Les effets ont été évalués après exposition aux sédiments contaminés dans des systèmes expérimentaux de types microcosmes durant une vingtaine de jours. Dans un certain nombre de cas, ce travail a révélé un effet des nanoparticules qui n’était pas dû au métal mais aux propriétés nanoparticulaires. En effet, dans le cas des nanoparticules de CdS, nous avons observé des altérations du génome ainsi que la modification de l’activité de bioturbation des vers tubifex en réponse à la contamination aux nanoparticules mais pas à celle de la forme ionique. Dans ce travail nous avons pu observer le relargage des nanoparticules d’or depuis le sédiment vers la colonne d’eau, et sa biodisponibilité potentielle pour les poissons. Ces nanoparticules provoquaient des altérations de l’ADN chez les deux organismes, la modification de l’expression de certains gènes et l’augmentation de l’activité de l’acétylcholinestérase chez le poisson zèbre. Les résultats de bioturbation n’ont pas montré d’effets des nanoparticules d’or sur le mouvement des vers. / The aim of this thesis was to determine the impact of two types of metal nanoparticles (cadmium sulphide - CdS - and gold - Au) on two aquatic models (tubifex worms and zebrafish Danio rerio). The approach has been to dope the Garonne sediment with the two types of nanoparticles and characterize the effect of this contamination on the two animals using multiple markers at different levels of biological organization (biochemical responses, neurotransmission activity, genotoxicity, gene expression and bioturbation activity). The effects were evaluated after exposure to contaminated sediment in experimental microcosms systems for twenty days. In a number of cases this work revealed an effect of the nanoparticles that was not due to metal but to the nanoparticulate properties. Indeed, in the case of CdS nanoparticles, we observed alterations in the genome as well as the modification of the bioturbation activity of worms tubifex in response to the contamination of nanoparticles but not to that of the ionic form. In this work we observed the release of gold nanoparticles from the sediment into the water column, and its potential bioavailability to fish. These nanoparticles were causing DNA damage in both organisms, modifying the expression of certain genes and increased acetylcholinesterase activity in zebrafish. Bioturbation results showed no effects of gold nanoparticles on the movement of worms.

Anlagda våtmarker i avrinningsområden från jordbruksmarker mottar ofta vatten med höga halter av partikelbunden fosfor. Den viktigaste processen för avskiljning av inkommande partikelbunden fosfor är sedimentation. Resuspension är en process som motverkar netto-sedimentationen av partiklar och kan således minska våtmarkers förmåga att hålla kvar fosfor. Syftet med den här studien var att undersöka om A. aquaticus påverkar resuspensionen av partiklar, och om större tätheter av A. aquaticus orsakar större turbiditet i vattenmassan. Två försök genomfördes i plastakvarier med sediment insamlat från våtmarker anlagda på lerjord. Varje försöksuppställning bestod av en behandling och en kontroll utan några djur. I det första försöket innehöll behandlingen A. aquaticus motsvarande en täthet på 2083 individer m-2 och i det andra försöket en täthet på 500 individer m-2. Turbiditeten mättes med en turbidimeter en gång per dag under sju dygn. Aktiviteten hos A. aquaticus orsakade en signifikant högre turbiditet i vattenmassan i behandlingen än i kontrollen. Turbiditeten var i genomsnitt 161 NTU i akvarier med 2083 individer m-2 och 37 NTU i akvarier med 500 individer m-2. Slutsatsen som drogs är att förekomst av A. aquaticus skulle kunna öka resuspensionen av partiklar i våtmarker. Detta kan i sin tur ha en påverkan på våtmarkers förmåga att hålla kvar fosfor som är bundet till lerpartiklar. / Constructed wetlands in agricultural catchments with clay soils often receive water with high concentrations of particle-bound phosphorus. Sedimentation of particle-bound phosphorus is the main retention process. Resuspension is a process that counteracts net sedimentation of the particles and can therefore reduce phosphorus retention in wetlands. The aim of this study was to investigate if A. aquaticus through bioturbation affects the resuspension of particles, and if a larger density of A. aquaticus causes a larger turbidity in the water column. The experimental design included plastic aquariums with sediment collected from wetlands constructed on clay soils. There were two experiments, each with a treatment and a control with no animals. In the first experiment, the treatment contained A. aquaticus at a density of 2083 individuals m-2. In the second experiment the treatment contained A. aquaticus at a density of 500 individuals m-2. Turbidity was measured with a turbidimeter once a day over the course of seven days. The bioturbation activity of the A. aquaticus caused a significantly larger turbidity in the water column in the treatment than in the control. The turbidity was on average 161 NTU in the presence of 2083 individuals m-2 and 37 NTU in the presence of 500 individuals m-2. The conclusion was that the presence of A. aquaticus can increase resuspension of particles in wetlands. This could have a negative impact on the ability of wetlands to retain phosphorus that is bound to particles.