Limnology and Oceanography e-Lectures最新文献

Natural and anthropogenic radionuclides are used to study a suite of environmental processes. Yet their applications in aquatic systems are hindered by a general lack of knowledge regarding the underlying concepts of radioactivity, the occurrence of radionuclides in ecosystems, and the equations used to describe their decay mechanisms in environmentally applicable ways. The goal of this lecture is to provide upper level undergraduate and graduate students with a basic understanding of how the naturally occurring uranium-thorium radioactive decay series can be used to address a range of environmentally relevant questions in marine systems. The lecture begins with a brief introduction to uranium-thorium series decay patterns and their distribution in the marine environment. The remaining lecture focuses on four case studies that cover a range of applications where uranium-thorium series radionuclides are used and includes: scavenging, air-sea gas exchange, tracing groundwater, and sedimentation/age dating. This lecture is the second of a four-part lecture series on radionuclides in the marine environment.

Natural and anthropogenic radionuclides are used to study a suite of environmental processes. Yet their applications in aquatic systems are hindered by a general lack of knowledge regarding the underlying concepts of radioactivity, the occurrence of radionuclides in ecosystems, and the equations used to describe their decay mechanisms in environmentally applicable ways. The goal of this lecture is to provide upper level undergraduate and graduate students with a basic understanding of how cosmogenic and anthropogenically produced radionuclides can be used to address a range of environmentally relevant questions in marine systems. The lecture begins with a brief introduction to cosmogenic and anthropogenic radionuclide production and sources to the marine environment. The remaining lecture focuses on specific case studies using these radionuclides in a range of applications including: ocean circulation and mixing, particle scavenging, and sedimentation/age dating. This lecture is the third of a four-part lecture series on radionuclides in the marine environment.

Natural and anthropogenic radionuclides are ubiquitous in the marine biosphere. They are used to study a suite of environmental processes, including those related to marine food webs, yet they also potentially negatively impact marine biota and humans. The goal of this lecture is to provide upper level undergraduate and graduate students with a basic understanding of marine radioecology and how marine organisms bioaccumulate and influence the cycling of radionuclides in the environment. The lecture begins with a brief introduction to the methods and models used to understand biological radionuclide uptake and loss, followed by how organisms biogeochemically and physically transfer radioactive substances throughout the ocean. The remaining lecture focuses on current methods for assessing potential radiological impacts on marine biota and risks associated with contaminated seafood consumption. This is the last lecture of a four-part lecture series on radionuclides in the marine environment.

Natural and anthropogenic radionuclides are used to study a suite of environmental processes. Yet their applications in aquatic systems are hindered by a general lack of knowledge regarding the underlying concepts of radioactivity, the occurrence of radionuclides in ecosystems, and the equations used to describe their decay mechanisms in environmentally applicable ways. The goal of this lecture is to provide upper level undergraduate and graduate students with a basic understanding of the fundamentals of radiochemistry, including the origin and stability of elements, radioactive decay mechanisms, and the fundamental equations that govern radioactive decay. This lecture is the first of a four-part lecture series on radionuclides in the marine environment.

This lecture (∼ 45-55 slides) will be aimed at senior undergraduate students and graduate students in aquatic sciences with little background in phycology. This lecture could be used in a Aquatic Ecology or Sciences (Limnology) course, an Ecology course, a Phycology course, Environmental Science.

Cyanobacteria that may lead to blooms encompass a wide range of different functional groups. We will present:

1) the evolutionary history of cyanobacteria (2-3 slides) (this helps explain some of their present-day traits)

2) basic biology and physiological/ecological traits of planktonic cyanobacteria that are most often associated with visible biomass accumulations (“blooms”) in freshwater/brackish systems of various regions of the world. Traits to be considered include: capacity for N fixation, nutrient uptake and storage (C, N, P), siderochromes, buoyancy regulation (gas vacuoles, mucilage), life cycles, growth rates vs. loss rates (resistance to grazing), allelopathy (negative vs. positive biotic interactions) Functional groups. Planktonic genera may also produce toxins, contributing to harmful algal blooms. (∼12-14 slides).

3) Cyanotoxins: the principal types of toxins produced and their effects (persistence) will be compared, along with theories as to the biological function of these compounds. (∼ 6 slides)

4) Specific case studies of blooms types under different climates: e.g. scum-forming, metalimnetic, dispersed (∼6)

5) The factors that appear to explain and control cyanobacterial dominance will be presented, including nutrient effects, temperature, and food chain changes. These factors vary across temporal and spatial scales. Evidence for eutrophication and climate change in mediating directly or indirectly the frequency and severity of freshwater cyanobacterial blooms will be considered (∼8-10).

6) Research avenues Controversial or unresolved topics: e.g. invasiveness?, cosmopolitan or geographically restricted (e.g. endemism? in hot spring taxa), toxin concerns and bioaccumulation), nitrogen fixation (“pretenders”), nutrient stoichiometry. Unexplored diversity at different levels (molecular, chemical, taxonomic), techniques for controlling cyanobacteria blooms, the future for cyanobacteria under climate change scenarios (∼4)

7) General references, web resourcess and primary articles. (∼2)

8) Questions and potential experiments for instructors and students will be provided at the end of the lecture (supplementary slides).

The oxygen flux between benthic systems and the water above is a widely used proxy for benthic primary production and organic carbon mineralization and is one of the most measured variables in marine and freshwater research. This presentation reviews the relatively new aquatic eddy covariance technique for measuring this flux. Because the approach relies on measurements that integrate over a large area (multiple m²) without disturbing the benthic system or the natural drivers of flux, it allows non-invasive studies of whole-system benthic metabolism that are not possible with any other approach. After summarizing the basic principles of eddy covariance, the instruments used, and key steps in the data evaluation, the rapidly growing body of research utilizing aquatic eddy covariance is presented with examples of the new kinds of insights that can be attained. These examples focus on benthic surfaces where traditional flux methods are difficult or problematic to apply and include highly dynamic benthic environments such as coral reefs, Arctic sediments, dense seagrass meadows, and permeable sands. Finally, future applications of the technique, new areas for development, and avenues to disseminate data and outcomes between new and experienced users are recommended.

The number of ocean acidification (OA) studies has increased significantly over the last decade. Most of this was due to studies on biological responses of organisms to OA. The lack of a protocol to document biological response OA data prevents the research community from properly archiving, discovering, accessing, and utilizing this important body of OA data sets. In this e-Lecture, we present how to document an OA data set by explaining major components of a metadata template, which can be applied to a broad spectrum of OA studies, including those studying the biological responses to OA. The major metadata components include Investigators, Title, Abstract, Temporal coverage, Spatial coverage, Geographic names, Location of organism collection, Platforms, Variable metadata clusters, Publications describing the data set, and Supplementary information. Of these components, Variable metadata clusters (variables and their metadata sub-elements) are treated as the focal point of the template. In addition to variable name , other metadata elements include the observation type, whether it is an in-situ observation, manipulation condition, or response variable, biological subject, life stage of the biological subject, etc. Information about how to access the metadata template files is also stated.

Dissolution of atmospheric CO₂ in seawater has lowered ocean pH and carbonate ion concentrations with impacts on marine organisms and ecosystems. The geological record contains long-term evidence for a variety of global environmental perturbations, including ocean acidification, and the biotic responses associated with them, and can provide insight into consequences of current anthropogenic acidification. This e-lecture focuses on the paleo-perspective of ocean acidification, proxy evidence for pH changes and several events exhibiting evidence for elevated atmospheric CO₂, global warming, and ocean acidification over the past ˜300 million years are reviewed. Comparison between these events and the present suggests that the current and projected rate of acidification may be unprecedented in past events with unknown consequences for marine life and humans who depend on it.

The target audiences for this e-Lecture are upper division undergraduate students and graduate students with some previous background in oceanography and paleoceanography. This could be a lecture in an “introduction to paleoceanography” class that discusses archives and proxies or a lecture in a topical “ocean acidification” class covering paleo ocean acidification. Depending on audience background the lecture may take 50 minutes (students versed in paleoceanography) or 90 minutes (novice students).

A suite of parallel anthropogenic changes affects contemporary marine ecosystems. Excessive carbon dioxide (CO₂) pollution results in warmer, more acidic oceans with lower dissolved oxygen (DO) levels, meanwhile the emission of reactive nitrogen/phosphorus results in eutrophication, excessive microbial degradation and thus metabolic hypoxia and acidification. Despite decades of empirical research how each individual stressor of the ‘climate-change syndrome’ (i.e., temperature, CO₂, DO) affects the fitness of marine organisms, we still know little about the combined effects of these stressors. This lecture gives an overview over the nascent field of multi-stressor approaches evaluating the climate sensitivity of marine organisms across taxa. In most studied cases, combined effects of these stressors exceeded those observed individually. Effects of combined warming, acidification, and deoxygenation have mostly been additive (no stressor interaction) or synergistically negative (stressor interaction). The occurrence and strength of synergistic stressor interactions in some species, life history stages, and traits comprises a vexing challenge but hints at potentially greater sensitivities of organisms to marine climate change than previously recognized. This lecture is intended for post-secondary students, providing them with illustrated examples from the most resent literature, while aiding in communicating the urgent need for empirical data from multi-stressor approaches.