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  • Oceanography Society  (2)
  • Springer  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 363 (1997), S. 1-12 
    ISSN: 1573-5117
    Keywords: top-down control ; bottom-upcontrol ; NH4 +regeneration ; nutrientlimitation ; trophodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Although our understanding of the complexity of theplankton and microbial food webs has increasedsubstantially over the past decade or two, there hasbeen little appreciation to date of the interactionsbetween top-down (grazing) control and bottom-up(nutrient supply) control on the structure andnutrient cycling processes within these webs. Thequality of nutrient supply, both in terms of therelative proportion of inorganic: organic nitrogen,as well as the relative proportion of inorganicnitrogen substrates has a direct impact on rates ofnitrogen uptake, and ultimately on the relativecomposition of phytoplankton and bacteria. At thesame time, grazing by microzooplankton andmacrozooplankton also influences both thecomposition of the food web and the rate of supplyof nitrogen. The impact of macrozooplankton onrates of nitrogen cycling in a microbial communityis complex: macrozooplankton release NH4 +,urea, and amino acids by direct excretion and by’sloppy feeding‘, but they also control both therates of nitrogen regeneration and uptake within thecommunity by grazing the microzooplankton, theprimary regenerators of NH4 +, and thephytoplankton, the primary consumers of nitrogen. Thus, grazing and nitrogen recycling are intricatelyconnected: the presence of large zoooplanktonsimultaneously provides top-down control of biomassand bottom-up nutrient supply. These relationshipsvary depending on the scale of interest, and haveimportant consequences for how we measure and modeltotal nitrogen cycling in a natural food web.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © Oceanography Society, 2005. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 18, 2 (2005): 136-147.
    Description: Marine and fresh waters team with life, much of it microscopic, and most of it harmless; in fact, it is this microscopic life on which all aquatic life ultimately depends for food. Microscopic algae also play an important role in regulating atmospheric CO2 by sequestering it during production and transporting it to deeper waters. Yet some of the microscopic “algae” cause problems when they accumulate in sufficient numbers, due either to their production of endogenous toxins, or to their sheer biomass or even their physical shape. These are known as the harmful algae, or, when in sufficient numbers, harmful algal blooms (HABs). These blooms were formerly called “red tides” because many were composed of dinoflagellates containing red pigments that in high densities colored the water red, but blooms may also be green, yellow, or brown, depending on the type of algae present and their pigmentation. As with all blooms, their proliferation results from a combination of physical, chemical, and biological mechanisms and their interactions with other components of the food web that are for the most part poorly understood. Most HABs are dinoflagellates or cyanobacteria, but other classes of algae, including diatoms, have members that may form HABs under some conditions. As stated by J. Ryther and co-workers many years ago, “...there is no necessity to postulate obscure factors which would account for a prodigious growth of dinoflagellates to explain red water. It is necessary only to have conditions favoring the growth and dominance of a moderately large population of a given species, and the proper hydrographic and meteorological conditions to permit the accumulation of organisms at the surface and to effect their future concentrations in localized areas” (Ryther, 1955).
    Description: Funding for these activities has been provided by NSF, NOAA, and the European Commission DG Research-Environment Directorate. GEOHAB is an initiative of SCOR (Scientific Committee on Oceanic Research) and IOC (Intergovernmental Oceanographic Commission of UNESCO). P. Glibert and D. Anderson were funded by the National Oceanic and Atmospheric Administration (NOAA), ECOHAB, MERHAB and NSF.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 3
    Publication Date: 2022-05-25
    Description: Author Posting. © Oceanography Society, 2010. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 23, no. 3 (2010): 126-139, doi: 10.5670/oceanog.2010.28
    Description: Through its promotion of coordinated international research programs, the Intergovernmental Oceanographic Commission (IOC) has facilitated major progress on some of the most challenging problems in oceanography. Issues of global significance—such as general ocean circulation, the carbon cycle, the structure and dynamics of ecosystems, and harmful algal blooms—are so large in scope that they require international collaboration to be addressed systematically. International collaborations are even more important when these issues are affected by anthropogenic processes— such as climate change, CO2 enhancement, ocean acidification, pollution, and eutrophication—whose impacts may differ greatly throughout the global ocean. These problems require an entire portfolio of research activities, including global surveys, regional process studies, time-series observations, laboratorybased investigations, and satellite remote sensing. Synthesis of this vast array of results presents its own set of challenges (Hofmann et al., 2010), and models offer an explicit framework for integration of the knowledge gained as well as detailed investigation of the underlying dynamics. Models help us to understand what happened in the past, and to make predictions of future changes—both of which support the development of sound policy and decision making. We review examples of how models have been used for this suite of purposes, focusing on areas where IOC played a key role in organizing and coordinating the research activities.
    Description: Support from the National Science Foundation, National Aeronautics and Space Administration, National Oceanic and Atmospheric Administration, and National Institute of Environmental Health Sciences. DS acknowledges CLISAP (Integrated Climate System Analysis and Prediction) at the KlimaCampus of the University of Hamburg. PG acknowledges SCOR/ LOICZ Working Group 132.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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