Schweitzer Fachinformationen
Wenn es um professionelles Wissen geht, ist Schweitzer Fachinformationen wegweisend. Kunden aus Recht und Beratung sowie Unternehmen, öffentliche Verwaltungen und Bibliotheken erhalten komplette Lösungen zum Beschaffen, Verwalten und Nutzen von digitalen und gedruckten Medien.
An authoritative and up-to-date exploration of how the competition-defence trade-off has shaped the marine microbial food web
In The Marine Microbial Food Web: Competition and Defence as Shaping Forces from Ecosystem to Genes, distinguished researcher Tron Frede Thingstad delivers an insightful and practical discussion of the microbial portion of the ocean's food web. The author describes how specific factors, including evolution, biodiversity, organism life strategies, genome organization, biogeochemistry, food web structure, and population dynamics, can be understood as the consequences of the balance between competition and defence.
Using modular idealized mathematical models developed from classical Lotka-Volterra formulations, the book describes models that explain the balance between production and consumption of organic material in the photic zone and the potential for export to the ocean's interior. It also explains how the models are relevant to contemporary climate change and a variety of other modern applications.
Readers will also find:
Perfect for researchers, students, and instructors of marine ecology, marine microbiology, and microbial oceanography, The Marine Microbial Food Web will also prove invaluable to limnologists, oceanographers, and students with an interest in applied mathematics.
Tron Frede Thingstad works in the Department of Biological Sciences at the University of Bergen in Norway. He is a renowned scientist in the field of marine microbial ecology and is the co-author of the award-winning Microbial Loop paper published in 1983. His work focuses on combining the flagellate, diatom, and microbial food chains into the microbial food web.
Intention: This chapter provides a basis for the biological and biogeochemical knowledge needed for the rest of this book.
To make the subsequent chapters accessible to readers with different backgrounds, this introductory chapter has three parts: (1) an introduction to the world's oceans and the role of microbes in its biogeochemical processes; (2) a brief introduction to the competitive and defensive traits of main functional groups of marine micro-organisms; (3) a short review of how the combination of new methodologies and new concepts has shaped contemporary ideas about the functioning of the marine microbial food web (MMFW).
Important concepts:
About two-thirds of the earth's surface is covered by ocean. Because of the conditions for life in water, primary producers in this biotope are micro-organisms. As a result, about 50% of the world's primary production occurs in the MMFW (Mattei and Scardi, 2021), not only feeding the world's large fisheries but also leading to an ocean sequestration of about 30% of the CO2 emissions from our burning of fossil fuels (Gruber et al., 2019).
The solar energy absorbed by the earth is dissipated through two systems: physical and biological. Most of this energy is dissipated through the physical systems consisting of the circulations in the atmospheric and the ocean and the associated hydrological cycle. A small part of the energy (about 1-2% (Thompson et al., 2024)) enters photosynthesis where the organic material synthesized fuels the food webs that drive cycles of biologically active elements and oxidate the organic-C back to CO2.
The physical dissipation system is a main driver of the biological systems. The key role of the hydrological cycle for terrestrial systems is demonstrated by the earth's large desert regions. In the ocean, where water is not a limiting factor, a main coupling comes from how dominant wind systems affect water circulation and the availability of growth-limiting elements, primarily N, P and Fe in the photic zone. When warm air rises along equator, it is replaced by air from higher latitudes. Deflected by the Coriolis force, this sets up an east-to-west wind along the equator. When this warm air is cooled in the upper atmosphere, it sinks back down at around 30° latitude, now forming a dominant west-to-east wind. In the Atlantic, these winds are known as the trade-winds because European traders used them to sail via West Africa to America along the Equator, returning at more northernly latitudes in the Atlantic. Where these dominant winds blow off the continents, surface water is transported away from the coast and replaced by nutrient-rich deep-water. The resulting combination of light and nutrients generates huge phytoplankton blooms, particularly visible off western Africa and Peru (Figure 1.1).
The El Niño phenomenon is when, in the Pacific, the equatorial east-west current changes the direction. The upwelling along the Peruvian coast then shifts to downwelling, nutrient-poor surface waters, reduced primary production, and a food chain that cannot support the plankton feeding anchovies.
North and south of the equator, there are large chlorophyll-poor regions (Figure 1.1) called the oceanic gyres. These are caused by a permanent thermocline that prevents mixing between the nutrient-poor photic zone and the nutrient-containing deep-water. The result is a permanently low photic zone nutrient content and therefore little biomass. The photic zone nutrient content does not only regulate how much biomass can be formed but is also an important driver for the structure of the MMFW: in the oligotrophic gyres, it is dominated by small (0.5-1.5?µm) pico-phytoplankton (Figure 1.2), while upwelling areas are typically dominated by large-celled (1-2 orders of magnitude larger, typically diatoms) species. The background for this can be understood from a simple steady-state argument: When the nutrient exchange between the photic and aphotic zones is in a steady state, import and export from the photic zone must be balanced. When the import is low, as in the gyres, the steady-state structure of the photic zone MMFW must produce little export. Sinking rates increase rapidly with size (as r2 for a spherical particle). A food web dominated by free-living picoplankton will therefore produce much less export than one dominated by large diatoms ballasted with a heavy silicate frustule.
Figure 1.1 Global distribution of chlorophyll. Yearly average. From Global Chlorophyll (nasa.gov).
Source: Figure from NASA/SeaWiFS Project.
Figure 1.2 Traditional size-class divisions of plankton (logarithmic scale).
The vertical export of organic matter is an important biogeochemical function of the photic zone food web. It transports carbon, fixed by photosynthesis in the photic zone, to the ocean's interior (Figure 1.3). Most of this is oxidized to CO2 in deep-waters, but the carbon will not be exposed to exchange with the atmosphere until the deep-water is returned to the surface by ocean circulation. The average age of dissolved organic carbon (DOC) as determined from the content of the radioactive 14C isotope is 4000-6000?years (Druffel et al., 2016). This has traditionally been taken as evidence for recalcitrance of the material accumulating. An alternative hypothesis is that it is not the chemical nature, but the low concentration of individual components that limits the degradation rate (Arrieta et al., 2015). The two mechanisms are not mutually exclusive and may both contribute to the high observed age.
Central in this process is the ocean's conveyor...
Dateiformat: ePUBKopierschutz: Adobe-DRM (Digital Rights Management)
Systemvoraussetzungen:
Das Dateiformat ePUB ist sehr gut für Romane und Sachbücher geeignet – also für „fließenden” Text ohne komplexes Layout. Bei E-Readern oder Smartphones passt sich der Zeilen- und Seitenumbruch automatisch den kleinen Displays an. Mit Adobe-DRM wird hier ein „harter” Kopierschutz verwendet. Wenn die notwendigen Voraussetzungen nicht vorliegen, können Sie das E-Book leider nicht öffnen. Daher müssen Sie bereits vor dem Download Ihre Lese-Hardware vorbereiten.Bitte beachten Sie: Wir empfehlen Ihnen unbedingt nach Installation der Lese-Software diese mit Ihrer persönlichen Adobe-ID zu autorisieren!
Weitere Informationen finden Sie in unserer E-Book Hilfe.