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Production and ecology of eelgrass (Zostera marina L.) in the Grevelingen estuary, the Netherlands, before and after the closure
Nienhuis, P.H.; De Bree, B.H.H. (1977). Production and ecology of eelgrass (Zostera marina L.) in the Grevelingen estuary, the Netherlands, before and after the closure. Hydrobiologia 52(1): 55-66
In: Hydrobiologia. Springer: The Hague. ISSN 0018-8158, more
Peer reviewed article  

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Keywords
    Artificial lakes; Dams; Ecology; Light effects; Primary production; Zostera (Zostera) marina Linnaeus, 1753 [WoRMS]; ANE, Netherlands, Grevelingen L. [Marine Regions]; Brackish water

Authors  Top 
  • Nienhuis, P.H., more
  • De Bree, B.H.H.

Abstract
    The Grevelingen estuary was cut off from the North Sea and from the influences of the river Rhine by a dam in 1971, and became a stagnant salt-water lake. Production and ecology of Z. marina were studied in 1968 and in 1973-1975, both through standing stock estimations, biomass increases in permanent quadrats, and correlation of distribution patterns with ecological factors. After the closure of the estuary the intertidal eelgrass population extended downwards to 5m below lake level, probably owing to the increased transparency of the water; the area occupied, and the density of the eelgrass beds increased strongly. Eelgrass annual overground production, based on doubled maximum standing crop values in July-Aug, was estimated at 50g C/m2 in 1968, 121g C/m2 in 1973 and 91 g C/m2 in 1975 Zostera beds, and 4g C/m2 in 1968, 18g C/m2 in 1973 and 23g C/m2 in 1975 for the entire Grevelingen area. A minimum estimate of net production in Zostera beds at a depth of 0.50-0.75m, based on short term changes in biomass in 2 permanent quadrats in 1974 and 1975, was 40.5g C/m2/yr for overground parts and 12.7g C/m2/yr for underground parts. Horizontal distribution of eelgrass is not primarily limited by grain-size distribution, but more by exposure to wave action and currents. On account of irradiance reduction light is a limiting factor in the vertical distribution of the eelgrass population in Lake Grevelingen.

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