The Physiology Ecology And Biogeochemistry Of Marine Zooplankton In A Changing Arctic Ocean

The Arctic Ocean and adjacent ice-covered seas are the regions that are most rapidly affected by climate change. Air temperatures are rising four times faster in the Arctic than the global average, leading to a rapid and substantial loss in sea-ice volume. Concurrently, the inflows of warm, saline Atlantic water into the Arctic Basin through Fram Strait and the Barents Sea are increasing, a phenomenon referred to as Atlantification. This Atlantification is not only driving physical changes of the Arctic environment, but also facilitates a northward range shift of boreal taxa. Consequently, polar zooplankton species are confronted with increasing temperatures and changing food web structures whilst at the same time face increasing competition by boreal-Atlantic congeners. This thesis provides a comprehensive approach investigating the different factors of climate change on Arctic zooplankton species, focusing on calanoid copepods Calanus hyperboreus, Calanus glacialis, Paraeuchata glacialis and the hyperiid amphipod Themisto libellula, as key representatives. Boreal-Atlantic congeners Calanus finmarchicus, Paraeuchaeta norvegica and Themisto abyssorum are considered as expatriates, which are extending their distribution ranges into the Arctic in the course of global warming. For the assessment of physiological responses of Arctic and boreal zooplankton species to rising temperatures, their respiration rates were measured from 0 to 10°C. A key finding was the resilience of Arctic species to temperature increases, as evidenced by their wide thermal tolerance and lack of metabolic stress response (low Q10 ratios). On the other hand, boreal species exhibited a more pronounced and rapid increase in respiration rates with rising temperatures, suggesting enhanced metabolic activity and overall performance under warmer conditions. Consequently, the temperature threshold at which boreal species outperform their Arctic congeners is likely to be a key determinant of zooplankton dynamics in a warming Arctic, rather than the absolute physiological limits of the species. Analyses of food webs, utilizing both fatty acid and stable isotope biomarkers, across Arctic and Atlantic-influenced regions in Fram Strait were conducted to explore changes in trophic structures associated with the sea ice decline and increased Atlantification. The results emphasized the importance of (sea ice) diatoms in the Arctic ice-covered regions and shows a shift towards a more flagellate-based food web, with a higher degree of omnivory, in the Atlantic regime. The ability of Arctic Calanus species to rely on alternative food sources other than (sea ice) diatoms highlighted their dietary flexibility, which may become increasingly important with the predicted increase in flagellate production in the future Arctic Ocean. The high relevance of Calanus fatty acid trophic markers in higher trophic levels in the Atlantic regime was likely a reflection of high abundances of C. finmarchicus in this region, showing its importance to the diet of carnivorous zooplankton as Atlantification progresses. Among Arctic and boreal congeners, an increased dietary overlap was observed between C. glacialis and C. finmarchicus as well as between P. glacialis and P. norvegica in areas of co-occurrence. The evaluation of zooplankton data in context with the physical-oceanographic observations of a submesoscale filament emphasized the significance of such dynamics in shaping the pelagic environment. Strong horizontal and vertical velocities associated with these features play a major role in structuring the pelagic ecosystem, facilitating Atlantification processes and influencing species allocation and biological connectivity. Additionally, proteomic fingerprinting was demonstrated as a rapid and accurate methodology for identifying climate-relevant but morphologically similar indicator species C. glacialis and C. finmarchicus to species and even developmental stages level. This technique has thus the potential to significantly enhance species identification in long-term monitoring studies, which is vital for deepening our understanding of ecosystem responses to climate change. In conclusion, this thesis demonstrates that Arctic zooplankton exhibit a considerable resilience and adaptability to environmental changes, including elevated temperatures and alterations in the food web structures. However, it also emphasizes the challenges posed by the intrusion of boreal species, which, under more boreal-like conditions, may outcompete polar Arctic species. The findings underline that the future of Arctic species in a warming ocean depends not only on their physiological tolerance and ecological adaptability but also on the competitive interactions with boreal congeners.

Biological processes in the oceans play a crucial role in regulating the fluxes of many important elements such as carbon, nitrogen, sulfur, oxygen, phosphorus, and silicon. As we come to the end of the 20th century, oceanographers have increasingly focussed on how these elements are cycled within the ocean, the interdependencies of these cycles, and the effect of the cycle on the composition of the earth's atmosphere and climate. Many techniques and tools have been developed or adapted over the past decade to help in this effort. These include satellite sensors of upper ocean phytoplankton distributions, flow cytometry, molecular biological probes, sophisticated moored and shipboard instrumentation, and vastly increased numerical modeling capabilities. This volume is the result of the 37th Brookhaven Symposium in Biology, in which a wide spectrum of oceanographers, chemists, biologists, and modelers discussed the progress in understanding the role of primary producers in biogeochemical cycles. The symposium is dedicated to Dr. Richard W. Eppley, an intellectual giant in biological oceanography, who inspired a generation of scientists to delve into problems of understanding biogeochemical cycles in the sea. We gratefully acknowledge support from the U.S. Department of Energy, the National Aeronautics and Space Administration, the National Science Foundation, the National Oceanic and Atmospheric Administration, the Electric Power Research Institute, and the Environmental Protection Agency. Special thanks to Claire Lamberti for her help in producing this volume.

The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for assessing the science related to climate change. It provides policymakers with regular assessments of the scientific basis of human-induced climate change, its impacts and future risks, and options for adaptation and mitigation. This IPCC Special Report on the Ocean and Cryosphere in a Changing Climate is the most comprehensive and up-to-date assessment of the observed and projected changes to the ocean and cryosphere and their associated impacts and risks, with a focus on resilience, risk management response options, and adaptation measures, considering both their potential and limitations. It brings together knowledge on physical and biogeochemical changes, the interplay with ecosystem changes, and the implications for human communities. It serves policymakers, decision makers, stakeholders, and all interested parties with unbiased, up-to-date, policy-relevant information. This title is also available as Open Access on Cambridge Core.

This open access book presents the proceedings volume of the YOUMARES 8 conference, which took place in Kiel, Germany, in September 2017, supported by the German Association for Marine Sciences (DGM). The YOUMARES conference series is entirely bottom-up organized by and for YOUng MARine RESearchers. Qualified early career scientists moderated the scientific sessions during the conference and provided literature reviews on aspects of their research field. These reviews and the presenters’ conference abstracts are compiled here. Thus, this book discusses highly topical fields of marine research and aims to act as a source of knowledge and inspiration for further reading and research.

This book aims at providing students and researchers an advanced integrative overview on zooplankton ecology, covering marine and freshwater organisms, from microscopic phagotrophic protists, to macro-jellyfishes and active fish larvae. The first book section addresses zooplanktonic organisms and processes, the second section is devoted to zooplankton spatial and temporal distribution patterns and trophic dynamics, and the final section is dedicated to emergent methodological approaches (e.g., omics). Book chapters include comprehensive synthesis, observational and manipulative studies, and sediment-based analysis, a vibrant imprint of benthic-pelagic coupling and ecosystem connectivity. Most chapters also address the impacts of anticipated environmental changes (e.g., warming, acidification).

The Arctic Ocean has undergone unprecedented changes in sea ice extent and thickness in recent years, including record-setting sea ice minimums in 2007 and 2012. These changes are predicted to affect Arctic marine primary productivity (the photosynthetic fixation of carbon dioxide by tiny algae called phytoplankton) because the timing and intensity of the summer phytoplankton bloom are strongly controlled by the dynamics of sea ice and water column stabilization. Satellite-based estimates indicate that primary production in ice-free waters has increased dramatically over the last few decades as a result of the increases in open water and length of the growing season associated with the thinning ice cover. In addition, climate models predict that the Arctic will experience greater and more rapid warming than other areas of the planet over the next century, suggesting that these changes may become even more prevalent in the future. The thinning sea ice has already had a dramatic impact on regional biogeochemistry: in 2011, we observed one of the most massive phytoplankton blooms ever recorded under the sea ice in the Chukchi Sea, an area traditionally thought of as too dark and too cold for massive blooms to occur. In the Chukchi, melt-ponds on the ice surface have proliferated to an extent that, in combination with the thinning ice cover, light penetration through the ice to surface waters is now sufficient for net photosynthesis to occur. The bloom we witnessed in 2011 extended for over 100 km into the> 1 m thick ice pack, and was characterized by extraordinarily high diatom biomass and rates of production. These changes represent a marked shift in our conception of Arctic marine ecosystems and have potential global-scale implications due to feedbacks relating to sea ice albedo, global atmospheric and ocean circulation patterns, and natural greenhouse gas exchanges between the atmosphere and ocean. Chapter 1 presents an overall introduction to the Arctic and discusses the causes and consequences of this changing seasonal cycle of productivity. Chapter 2 presents results from field work performed in the Beaufort Sea in the summer of 2008 exploring the spatial and temporal variability of phytoplankton photosynthesis in the ice-associated region of the flaw-lead polynya (area of perennially open water that rings the Arctic Ocean between land-fast ice and the central Arctic ice pack; it can be used somewhat as an analog for future open-water and ice-edged based productivity). Continuing with this theme of exploring primary productivity and biogeochemical cycles in the changing Arctic, Chapter 3 details the results from photophysiological experiments performed during the summer of 2010-2011 that highlight the unique features allowing Arctic phytoplankton to reach high levels of biomass in the extreme environment under the ice. In Chapter 4, I present data from recent 1-D modeling efforts that utilize the light and nutrient-controlled responses of phytoplankton growing under the ice to explore the consequences and implications of this shifting bloom cycle on regional biogeochemical processes.

Oceans account for 50% of the anthropogenic CO2 released into the atmosphere. During the past 15 years an international programme, the Joint Global Ocean Flux Study (JGOFS), has been studying the ocean carbon cycle to quantify and model the biological and physical processes whereby CO2 is pumped from the ocean's surface to the depths of the ocean, where it can remain for hundreds of years. This project is one of the largest multi-disciplinary studies of the oceans ever carried out and this book synthesises the results. It covers all aspects of the topic ranging from air-sea exchange with CO2, the role of physical mixing, the uptake of CO2 by marine algae, the fluxes of carbon and nitrogen through the marine food chain to the subsequent export of carbon to the depths of the ocean. Special emphasis is laid on predicting future climatic change.

Zooplankton is a major work of reference for researchers in plankton biology, physiology and behavior, which combines behavioral and psychological approaches to the study of plankton on present and interdisciplinary investigation of sensory processes in pelagic environments. The breadth of perspective thus achieved provides valuable insights into the larger scale ecological processes of biological productivity, community structure and population dynamics. Technological advances in almost all aspects of biological research have opened up opportunities for a re-examination of the sensory ecology of planktonic organisms. In this wide-ranging collection, leading researchers in planktonic behavior and physiology address the rapidly developing interface between these two major areas. The studies presented range from the laboratory to the field and from the cell to the whole organism, but share the common goal of understanding the special sensory world of organisms that live in pelagic environments and how their behavior and physiology relate to it.

Marine ecosystems are changing at an unprecedented rate. In addition to the direct effects of e.g. warming surface temperatures, the environmental changes also cause shifts in plankton communities. Plankton makes up the base of the marine food web and plays a pivotal role in global biogeochemical cycles. Any shifts in the plankton community composition could have drastic consequences for marine ecosystem functioning. This Research Topic focuses on causes, effects and consequences of such shifts in the plankton community structure.