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  • 1
    Publication Date: 2021-02-08
    Description: Understanding the mechanisms driving species biogeography and biodiversity remains a major challenge in phytoplankton ecology. Using a model of two phytoplankton species with a gleaner-opportunist trade-off and competing for light and a limiting nutrient, we show that the diel light cycle may be an essential factor to explain large-scale ecological patterns. When only the seasonal light cycle is considered (control scenario) the model predicts that, independently of the nutrient supply, gleaners should dominate across all latitudes and oppor- tunists can obtain a temporal niche only at high latitudes. However, the diel light cycle makes the competition outcome also a function of nutrient supply by affecting the amplitude of diel nutrient oscillations, with gleaners dominating when nutrient supply is low, opportunists when nutrient supply is high, and both species coexisting at intermediate levels of nutrient supply. The combined effects of seasonal and diel light cycles (diel scenario) shape a latitudinal diversity gradient with decreasing diversity towards higher latitudes and a unimodal de- pendence of diversity on nutrient supply and, therefore, on ecosystem productivity. The proposed mechanism can help interpret the biogeography of major phytoplankton functional groups in the global ocean and link them with large-scale biodiversity patterns.
    Type: Article , PeerReviewed
    Format: text
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  • 2
    Publication Date: 2017-11-29
    Description: Antarctic krill (Euphausia superba)—one of the most abundant animal species on Earth—exhibits a five to six year population cycle, with oscillations in biomass exceeding one order of magnitude. Previous studies have postulated that the krill cycle is induced by periodic climatological factors, but these postulated drivers neither show consistent agreement, nor are they supported by quantitative models. Here, using data analysis complemented with modelling of krill ontogeny and population dynamics, we identify intraspecific competition for food as the main driver of the krill cycle, while external climatological factors possibly modulate its phase and synchronization over large scales. Our model indicates that the cycle amplitude increases with reduction of krill loss rates. Thus, a decline of apex predators is likely to increase the oscillation amplitude, potentially destabilizing the marine food web, with drastic consequences for the entire Antarctic ecosystem.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
    Format: application/pdf
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