The EuroMarine Webinairs are being developed on a range of topics from short modules (5 min) to full lectures (45 min). The talks are shown in Adobe Connect. You might be asked to make an installation on your pc to view the recording. The installation will only take a short time. The link will be open access until the end of this year.
Webinar 1. Artur Palacz, Technical University of Denmark - National Institute for Aquatic Resources (DTU Aqua)
Controlling mechanisms in nutrient dynamics and biological productivity in the eastern equatorial Pacific Ocean (45 min)
The equatorial Pacific has been recognized for decades as a major region of enhanced biological production which is due to persistently cool waters of equatorial upwelling. Early observations of unused nitrate and relatively low phytoplankton biomass in the equatorial Pacific led to the question of "Why isn't the equatorial Pacific greener?" The main objective of my work was to unravel the roles and interactions of regulatory mechanisms in the eastern equatorial Pacific Ocean, challenged and inspired by the progress represented by the JGOFS EqPac (1992) and the Equatorial Biocomplexity (2004 and 2005) projects, as well as some recent development of modeling capabilities. In this study, I used a box model approach to construct a complete iron budget in the equatorial Pacific, which revealed the importance of upwelling in supplying this growth-limiting nutrient. Moreover, through coupled physical and biological model simulations for 2004 and 2005, I revealed the important role that tropical instability waves play in regulating supply and diatom uptake of another limiting nutrient – silicate. Extending the model simulations from 1991 to 2009, I then examined the role of El Nino Southern Oscillation in controlling interannual to decadal variability in nutrient dynamics and biological productivity in the eastern equatorial Pacifc. The results of this research work pointed at a surprising resilience of the biological system to long-term changes in physical environment in the Pacific Ocean. I speculate that silicate and iron co-limitation and a strong grazing pressure create a well-balanced ecosystem where the diatom population cannot thrive, thus explaining why the equatorial Pacific is not greener.
Webinar 2. Kai W Wirtz, Helmholtz-Zentrum Geesthacht, Ins. Coastal Res., Germany
Starting from Aristotle: a mechanistic and trait-based description of the plankton (57 min)
Plankton dynamics is frequently observed to vary much stronger at daily to annual scales than predicted by state-of-the-art models. It can be thought that such limitation of plankton models is ultimately due to a widely lacking mechanistic basis underlying almost all ''standard'' model formulations. In this talk, I will refer to Aristotle to renew a concept where biophysics is meld with a generalised optimality approach. This concept leads to the formulation of a mechanistic trait-based model. The model describes and explains variability in plankton dynamics apparent in the German Bight long-term time series and in a suite of mesocosm experiments conducted in Kiel. Mechanistic trait-based modelling thus helps us to better understand the changing responses of phyto- and zooplankton to external forcings. The approach, however, also demands for a large developing effort as many unresolved questions of plankton physiology and ecology need to be assessed. For example, how are trophic interactions determined by factors such as prey size, predator size, or (optimal) predator behaviour? The burden to address such problems can be seen as an argument both against and in favour of mechanistic trait-based modelling.
Webinar 3. Brian R MacKenzie, DTU Aqua
Impact of climate change on fish population dynamics in the Baltic Sea: A dynamical downscaling investigation (41 min)
Understanding how climate change, exploitation and eutrophication will affect populations and ecosystems of the Baltic Sea can be facilitated with models which realistically combine these forcings into common frameworks. Here, we evaluate sensitivity of fish recruitment and population dynamics to past and future environmental forcings provided by three ocean-biogeochemical models of the Baltic Sea. Modelled temperature explained nearly as much variability in reproductive success of sprat (Sprattus sprattus; Clupeidae) as measured temperatures during 1973-2005, and both spawner biomass and temperature have influenced recruitment for at least 50 years. The three Baltic Sea models estimate relatively similar developments (increases) in biomass and fishery yield during 21st century climate change (ca. 28% range among models). However, this uncertainty is exceeded by the one associated with the fish population model, and by the source of global climate data used by regional models. Knowledge of processes and biases could reduce these uncertainties.
Webinar 4. Vlastimil Krivan, University of South Bohemia, Czech Republic
The Ideal Free Distribution as a population game concept (45 min)
In my talk I will discuss the Ideal Free Distribution as a game theoretical concept describing distribution of population(s) in a patchy environment consisting of habitat or foraging patches. Under the IFD, payoff in all occupied patches is the same and individuals cannot increase their fitness by changing their strategy. Thus, the IFD is a Nash equilibrium of the underlying habitat selection game. Originally, this concept was defined for a single population that does not undergo population dynamics. In my talk I will discuss some extensions of his concept to situations with more interacting populations (e.g., two competing species), and with populations that undergo population dynamics. I will show that distributional models based on the IFD when combined with population dynamics can lead to new insights on the effect of adaptive animal behaviors on their population dynamics. Some of these simple models that combine population dynamics with distributional dynamics can be analyzed provided we assume time scale separation. In my talk I will focus on the situation where behavioral (distributional) dynamics operate on fast time scale when compared with population dynamics.
Webinar 5. Elena Litchman, Michigan State University
Trait-based approaches to phytoplankton ecology and evolution (51 min)
Predicting how plankton communities will re-organize under global change is a major challenge facing aquatic ecologists and oceanographers. Trait-based approaches provide ways to mechanistically understand the structure and dynamics of ecological communities and their organization along various environmental gradients. Answering fundamental questions on the relationships among traits, such as the nature of trait trade-offs and trait differences among different functional groups, helps increase our understanding of plankton community organization. I will present some examples of key traits in phytoplankton such as the resource utilization and thermal tolerance traits and discuss how they can be used to explain and predict community organization and evolution under different environmental conditions, including climate change scenarios.
Webinar 6. Keith Brander, DTU Aqua
Detection, attribution, prediction and adaption: what does climate change science offer marine managers and fishermen? (48 min)
Human activities have caused changes in atmospheric composition that have consequences for the global heat budget and for global biogeochemistry. The resultant climate changes inevitably affect biological processes, populations and ecosystems and there are many examples from terrestrial and marine systems where changes have been detected. However, changes in biological systems occur for a variety of reasons, including internal dynamics as well as external forcing, not least due to other human pressures such as habitat destruction, pollution and fishing. Estimating what fraction of observed change can be attributed to climate is not easy, particularly when dealing with regional or local examples. In fact some scientists argue that attribution is so difficult that we should not devote time and resources to it. I think this argument is wrong for several reasons. Attribution studies help to identify and scale the processes causing change and are essential for trying to predict future change and for advising on adaptation strategies. They play a very important role in guiding human responses to the threat posed by climate, by providing case studies of impacts at regional and local levels and by quantifying the relative effects of climate and other drivers of change, such as fishing. Timely and effective guidance needs to be designed to reach the agents for adaptation (policy makers, managers, fishing enterprises, communities, individuals) in a form that they can understand and act on when planning strategies, evaluating risks and making decisions. Scientists have a tendency to think about these “stakeholders” only when writing their funding proposals and when delivering a final report and therefore fail to work on the appropriate scales and issues for adaptation.
Webinar 7. Andrew G. Hirst, Queen Mary University of London
Changing size in a warming world? How do organisms change size with changing temperature? (25 min)
The Temperature Size-Rule is near universal in ectotherms, and describes how, within species, organisms mature at a smaller size when subjected to higher temperatures. The rule provides fundamental insights into physiological processes, and is a potential outcome of climate change. In this talk we develop a conceptual understanding of how organisms change size. This scheme shows the importance of the adult to progeny size ratio in metazoans, we examine this ratio using meta-analysis, and find that progeny size is much less temperature dependent than adult size. In effect size is 'reset' at birth. This leads us to the prediction that growth and development rates must have different temperature dependence in metazoans. We next test this prediction rigorously using marine copepods as a rich source of data, and the outcome confirm our prediction. The wider implications of these findings are finally addressed. Importantly there are different mechanisms in how size changes are brought about in uni-cells (with divide by binary fission) and metazoans, and the work highlights important short comings in the assumptions of the Metabolic Theory of Ecology.
Webinar 8. Friederike Prowe, Technical University of Denmark, DTU Aqua
Effect of feeding formulations on phytoplankton diversity and ecosystem functioning in ecosystem models (37 min)
The potential of marine ecosystems to adapt to ongoing environmental change is largely unknown, making prediction of consequences for nutrient and carbon cycles particularly challenging. Realizing that biodiversity might influence the adaptation potential, recent global model approaches have identified bottom-up controls on patterns of phytoplankton diversity regulated by nutrient availability and seasonality. Top-down control of biodiversity by zooplankton feeding, however, has not been considered in depth in such models. Here we demonstrate how zooplankton predation with variable food preferences can enhance phytoplankton diversity in a self-assembling global ecosystem-circulation model. Simulated diversity increases more than three-fold with variable preferences relative to grazing with fixed preferences. Simulations with variable preferences yield better agreement with observed distributions of phytoplankton diversity. The variable grazing pressure creates refuges for less competitive phytoplankton types, which reduces exclusion and improves the representation of seasonal phytoplankton succession during blooms. Such phytoplankton communities have higher diversity and primary production than less diverse assemblages shaped by competitive exclusion. In the global model ocean, such a positive relationship between diversity and productivity can only be sustained in regions with ample nutrient supply. Developing detailed representations of zooplankton feeding might thus improve the representation of plankton diversity in models and potentially affect predictions of marine ecosystems under environmental change.
Webinar 9. Georg Pohnert, Friedrich Schiller University, Jena
Deciphering highly dynamic chemically mediated interactions of diatoms using a combined metabolomics/bioassay approach (46 min)
It is well established that unicellular algae from the plankton have established means to interact with other organisms in their environment. Especially interactions mediated by chemical compounds have gained a lot of attention during the last years. Algal exudates and metabolites stored in the cells can mediate feeding activity of herbivores, algal algal interactions but also interactions of an alga with the surrounding microbial community. We introduce an approach to address such chemically mediated interactions based on the metabolomic investigation of the cellular and released metabolites of diatoms. The metabolomic survey indicates that diatoms exhibit a high plasticity of metabolite production during their development. Metabolite concentration changes dramatically in between growth phases but also pronounced circadian variability can be observed. Our results indicate that the regulation of biosynthetic pathways in diatoms is highly dependent on environmental abiotic factors as well as biotic interactions. We used bioassays to demonstrate that the variable chemical properties of the algae are also causing pronounced variability of the chemical interaction of phytoplankton with the environment. Examples of diatom defense against herbivores, bacteria and of diatom-diatom interactions will be introduced. Consequences for future investigations of diatom physiology and chemical interactions are discussed.