Limnology and Oceanography e-Lectures最新文献

Our limited intuition of the small-scale world of the plankton has biased the way we describe and understand ocean ecology. Classical approaches consider fluxes of energy and matter between species and populations to describe marine ecosystems but biological interactions occur between individuals rather than between the abstract entities of ‘populations’ or “trophic levels.” A complementary approach is to derive system properties from mechanistic insights in individual functioning and interactions. Plankton live in a world that is radically different from ours, and to which we have limited access. Visualization is central to developing an intuition for this world, which together with insights in small-scale fluid physics may allow a mechanistic understanding of individual interactions and deduction of properties of populations and ecosystems. This lecture demonstrates the mechanistic approach through a number of examples, including numerous videos.

The goal of this lecture is to provide aquatic scientists and interested laymen with an overview of the potential, methods and exemplary analyses of DNA preserved in lake sediments. This area is an emerging field, as new techniques are opening up avenues for novel studies of the sediment record. Numerous papers in this field have recently been published in Science, PNAS and PLoS ONE. Like many new fields, there are challenges as well as exciting lines of future inquiry, which we dedicate part of the lecture towards.

This lecture starts by providing a brief introduction to paleolimnology, with an emphasis on how DNA studies can expand this field. We then provide information on the ways in which DNA can be archived in sediments & how analyses can differ, depending on the question and target. Examples of the common genetic markers used and how DNA may be sequenced are also highlighted in the methods section. In the second portion of the lecture, we focus on the applications of sedimentary DNA: 1) to the study of particular phytoplankton group dynamics; 2) to the analysis of zooplankton DNA preserved in resting eggs; and, 3) to uncover community-wide changes in plankton. Finally, we close the lecture with a discussion on challenges and future directions in the field. Advances in the development and calibration of different extraction techniques, as well as further enhancement of genetic libraries and bioinformatics pipelines, are all areas ripe for new research.

This lecture has been prepared with a diverse audience in mind. For example, undergraduate or graduate courses that could be interested in our material include Aquatic Ecology, Limnology, Oceanography, Microbial Ecology, Environmental Genomics and Paleoecology. This lecture could also serve as a useful introduction to non-specialist audiences that are interested in the potential of the DNA archive preserved in lake sediments (including funding agencies).

In 1892, François A. Forel created and defined the new science of Limnology as “the oceanography of lakes.” His aim was to establish an integrative discipline for the aquatic sciences in which diverse types of lake studies, from physics, chemistry and biology, to anthropology and economics, would complement and inform each other to produce a meaningful synthesis. Forel grew up in Morges, Switzerland, on the shores of Lake Geneva (lac Léman), and then left for 11 years to universities in France and Germany to study the natural sciences and medicine. Shortly after his return to Switzerland, he was appointed Professor of Anatomy and Physiology at the Academy of Lausanne. In the first years back at the lake, he made important discoveries about deep-living benthic animals and surface seiches that reinforced his early decision to adopt Lake Geneva as his “laboratory and aquarium” and to devote his career to limnological research. Forel's remarkable breadth of interests and expertise culminated in 288 reports and publications, including the first text book in general limnology (published 1901), and the seminal, three-volume monograph on the Limnology of Lake Geneva (1892, 1895 and 1904). Forel's success was the result of his passion for lakes and lake science, an ability to pose and critically evaluate insightful questions about the natural world, a flair for observation and new technologies, a rigorous, encyclopedic ability to collect and synthesize all available information, and a natural talent for networking and collaboration. His view of lakes as coupled physical-chemical-biotic-human systems is particularly relevant to facing the challenges of global change, and the associated rapid shifts in ecosystem services at a planetary scale.

This e-Lecture is rich in images including previously unpublished photographs of materials held in the Forel Archives at the Lake Geneva Museum, Nyon, Switzerland. The e-Lecture also places Forel's work in the broader historical context of the development of limnology in Europe, North America and beyond. Central in this presentation is a description of Forel's goal to achieve an integrated synthesis in his lake studies, and his view of humans as a powerful biotic component within the lake ecosystem.

This lecture provides an overview of climate and biological changes in Pacific-influenced Arctic marine ecosystems. It reviews and examines the major contributing factors to these changes, including changing conditions of sea ice, freshwater input, and the alteration of marine ecosystems. Examples of these factors are provided to illustrate the potential impacts that will have broad-reaching implications for long-term ecosystem structures. This lecture also reviews the progress of various programs undertaken during recent years (i.e. Bering Sea Research Program, Canada's Three Oceans, the Russian/US Long-term Census of the Arctic Ocean, and the Western Arctic Shelf-Basin Interactions) which have provided insights into the key processes influencing ecosystem function and change in the northern Bering and Chukchi shelf regions. Data sets from these programs are included in this L&O e-Lecture, in the context of biological response to sea ice changes in the Pacific Arctic region, with accompanying discussion by the L&O e-Lecture author.

This lecture is designed for undergraduates, to show how satellites contribute to the understanding of ocean dynamics. Satellite sensors can measure properties of the surface ocean with a sampling coverage unachievable from ocean-going research vessels. The four geophysical variables of the ocean that satellites can observe are sea-surface temperature, surface winds, the relative height of the sea surface, and the color of the ocean. Sea surface temperature is measured by sensing the infrared radiation emanating from the ocean. Surface winds are deduced from the roughness of the surface ocean using a radar on the satellite. Sea surface height is estimated from knowing, very accurately the altitude of the satellite relative to the earth. Ocean color is measured with a spectrometer on board the satellite. The lecture will give students appreciation of the power of satellite oceanography, while also considering its limitations. This lecture avoids overly technical information and the particulars of the various satellites, in favor of a description of how the measurements are made that can be understood at the undergraduate level. Students are encouraged to make use of satellite data, which is publicly available.

The overall goal of this lecture is to provide an overview of the process and progress of ocean acidification in the global oceans and its impacts on marine organisms over time scales of days to centuries. Examples of acidification impacts on corals, shellfish, and zooplankton are given to show how acidification can affect different kinds of life processes. This lecture describes what we know and what we don't know about ecosystem responses to acidification and the socio-economic implications for our society. Finally, we discuss the future implications of increased CO₂ levels on the health of our ocean ecosystems and related ocean-based economies.

The overall goal of this lecture is to provide limnology (and oceanography) students an overview of the various methods and approaches currently being used by scientists to study the timing and magnitude of environmental changes affecting aquatic systems at time scales of decades, centuries, and millennia. The lecture includes the steps that paleolimnologists follow in their sedimentary analyses, including core collection, core sampling, dating, and a summary of the main indicators and climate proxies. Smol has also integrated into the lecture slides that highlight research that he and his co-workers have undertaken over the years. The lecture concludes with three case studies: the history of lake acidification, the occurrences of drought on the prairies, and the nature of climate change in the Arctic.

The Biological Carbon Pump includes all those processes in the ocean that cause organic carbon formed photosynthetically by phytoplankton (primary production) in the sunlit surface layer (the euphotic zone) to be removed from contact with the atmosphere. It is a mechanism that sequesters carbon dioxide (CO₂) for weeks to hundreds or even millions of years (geological time-scales). Together with the physical carbon pump, the biological carbon pump constitutes the ocean's CO₂ sink, and these two major processes in the global carbon cycle have removed about 2- 2.5 Pg Carbon per year (last decade average)(I Pg=10¹⁵g). Today, about half of the CO₂ emitted from fossil fuel burning and land use changes remains in the atmosphere, and the other half is captured by land sinks and the ocean.

The modern carbon cycle is often completely separated from the short- and long-term carbon cycles of the geological past, and students from biology or biogeochemistry rarely learn about these processes and the respective timescales in a joint lecture. The purpose of this interdisciplinary lecture thus is to cover processes related to the biological carbon pump and how it functions, while paying close attention to the relevant timescales in the global carbon cycle. Note that we focus mainly on the production and sinking of particulates, we do not delve into detailed mechanisms of carbon sequestration due to the removal of dissolved organic matter. Topics will include an introduction to the different carbon pumps (biological, carbonate and physical), followed by a detailed process-oriented introduction to the biological carbon pumps. This will also include the organismal aspects, such as an introduction to phytoplankton, primary production, distribution of primary producers in the global ocean, and the role of zooplankton in the biological carbon pump. More mechanistic aspects follow, such as the concepts of new and export production, the flux attenuation and the role of mineral ballasting. We cover specific aspects of the lecture as modules (Excursions) that give the reader/lecturer the chance to explore some topics in greater detail. These "Excursions" are entitled "Instrumentation: Quantifying Particle Flux", "Particle Sinking and Degradation" and "The Biological Carbon Pump on Geological Timescales".

The lecture is intended for senior undergraduates/graduates students and can be used in courses such as Oceanography, Biogeochemistry, Geology, and Environmental Life Sciences.