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 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).
Dissolution of atmospheric CO 2 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 CO 2 , 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 (CO 2 ) 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, CO 2 , 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.
