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  • The Netherlands  (1)
  • eutrophication  (1)
  • 1
    ISSN: 1573-5117
    Keywords: wetland characteristics ; threats ; conservation ; rehabilitation ; management ; ecological research ; The Netherlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Wetlands are among the worlds' most important, but also most threatened, environmental resources. Wetland losses have been in progress particularly from the industrial revolution onwards, because wetland functions could not successfully compete for space with other land uses. Wetlands became recently foci of conservation efforts because of the increased awareness of their importance in water management and wildlife conservation, and because of the diversity of their habitats. The Netherlands are relatively rich in wetlands: 16% of its' territory is regarded as internationally important wetland and 7% has been registered as such. The major Dutch wetland types are: coastal ecosystems, large riverine systems, base-rich freshwater systems, and nutrient-poor freshwater systems. Most threats to the Dutch wetlands are of man-made origin. They comprise: (1) Changes in hydrology leading to changed discharges, currents and desiccation; (2) Acidification; (3) Eutrophication; and (4) Toxification. Long-term threats are largely climate-change related, and concern temperature rise and the UV-B increase in irradiation. General conservation goals also apply to wetlands but Ramsar-registered wetlands have a special status. Conservation of the Dutch wetlands is difficult, because of the high population density of the country and its inherent threats. However, ecological targets and standards are increasingly set in national Policy Plans and international agreements. Rehabilitation and creation of wetlands is presently widely advocated, and sometimes realised. For ecological research, the sustainability of wetlands should get top priority. Such a research programme would focus on understanding the underlying ecological processes in natural and man-dominated wetland systems to prescribe conservation, rehabilitation and management strategies that would enhance the sustainability of these systems. Within this framework special attention should be directed to studies (1) At the ecosystem level of ecosystem parameters, of which natural oscillations and trends in time, and on which the impact of disturbances are quantified. Particularly these studies, in which often simulation models are used as tools for interpretation, can provide the basis for extrapolations in space and time; (2) On adaptation capacity and mechanisms of (groups of) species to extreme environmental conditions; (3) On (mutual) relationships between plants, animals and microorganisms (e.g. competition, grazing and mineralization); (4) On dispersion between small wetlands. For the contemporary quantitative assessment of the long-term effects of climate changes, the effects of temperature rise and increase in UV-B irradiation on individual species, communities and ecosystems should also be studied.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5117
    Keywords: aquatic macrophytes ; eutrophication ; lake restoration ; phosphorus ; aerial photography ; shallow lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The potential importance of the six major emergent and floating-leaved macrophyte species in recycling of sediment phosphorus in the Loosdrecht lakes was studied. Representative plant samples were collected at the time of maximum biomass, and analysed for biomass and carbon, nitrogen and phosphorus contents. Species cover was determined by aerial photography. Total cover in the seven lakes studied ranged between 2 and 26 percent. For the four main species, biomass per unit area increased with lake trophic status. Consistent differences in C, N and P contents per unit biomass were not observed. Although cover values were small, significant amounts of C, N and P were contained in the macrophytes when compared with maximum sestonic content. Potential P loads from macrophyte decay were calculated. In Lake Loosdrecht, the P load represented 15 percent of current external P inputs. The potential importance of macrophyte decay to P recycling in the other lakes is greater. Decay of macrophyte species at the end of the growing season appears to affect autumnal nutrient and chlorophyll a levels in the water column of some lakes. The re-establishment of submerged species following lake restoration may increase the importance of this pathway in the lakes.
    Type of Medium: Electronic Resource
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