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Primary production of the benthic microflora living on tidal flats in the Dutch Wadden Sea
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579; e-ISSN 1873-1406, meer
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| Auteurs | | Top |
- Cadée, G.C., meer
- Hegeman, J.
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| Abstract |
The mean annual production of the microflora living on tidal flats in the western Wadden Sea amounts to 100± 40 g C/m² year, based on 5 years of measurements. This figure equals literature values for comparable tidal flats. Phytoplankton production in the water over the tidal flat adds 20g C/m² year. Primary production of benthic microflora was significantly correlated with, in order of significance, temperature, solar radiation and functional chlorophyll a. These factors could not explain the relatively large year-to-year variation. The excretion was only 1% of the annual primary production. UV light (310 to 375 nm) had no adverse effects on the benthic microflora and absence of an inhibition of photosynthesis at high light intensities is assumed to be due to this absence of UV light influence. A large amount of functional chlorophyll a was present below the sediment surface, down to 10 cm depth, of which 25% is contained in the top 1 cm of the sediment. Active migration, and sediment displacement during gales cause this vertical distribution. The algae in the sediment start to photosynthesize when brought into light and therefore form an important stock of primary producers when tidal flats are disturbed by gales. Primary production per square metre of the benthic microflora living on the tidal flats was equal to phytoplankton production per square metre in the tidal channels in the area as measured by POSTMA & ROMMETS (1970) and estimated by CADÉE & HEGEMAN (1974). As tidal flats comprise 40 to 59% of the Wadden Sea the benthic microflora is as important as the phytoplankton in the primary production of the area. Macrophytobenthos production data are not yet available, but they are supposed to be of minor importance in the Wadden Sea. POSTMA (1954) found for the western Wadden Sea a supply of organic matter from the North Sea of 80 g C/m² year. This makes the total amount of organic carbon available for secondary producers 200 g C/m² year. Compared with other marine coastal habitats this figure is not very high. Therefore the relatively rich invertebrate bottom fauna must be ascribed to the fact that in shallow seas a greater part of this organic matter is used by the benthos, whereas in deeper water zooplankton consumption will be more important. |
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