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The influence of bivalve filter feeders on bacteria populations and seston in Gazi bay and Wadden Sea
Mwangi, S. N. (1994). The influence of bivalve filter feeders on bacteria populations and seston in Gazi bay and Wadden Sea. MSc Thesis. Vrije Universiteit Brussel: Brussel. 88, appendix pp.
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| Beschikbaar in | Auteur |
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Documenttype: Doctoraat/Thesis/Eindwerk
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| Abstract |
This study investigated the effect that bivalve filter feeders had on the bacteria and seston concentration of the water that flowed through their beds, the tidal influence on food availability for the bivalves and seasonal changes of bacteria and seston concentrations. The study was carried out in an oyster culture plot in Gazi bay, Kenya and in the Dutch Wadden Sea where intensive mussel culture is carried out. In a few occasions, the oysters in Gazi were observed to reduce the bacteria biovolume and thus the biomass, reduce chlorophyll-a concentration in the water and take up the easily degradable organic material. Bacteria and the total seston concentration in the water varied with the tide thus influencing food availability for the oysters. Resuspension during both flood and ebb tides resulted in a general increase in bacteria abundance and biomass, dissolved oxygen, suspended matter, easily degradable organic material , POC and chlorophyll-a. In the Wadden Sea, the water overlying mussel beds was observed to have a high bacteria abundance but of low biovolume thus low total biomass in autumn. There were more indications of enhanced bacteria abundance than bacteriovory. Phytoplankton uptake was not clearly observed probably due to the prevailing hydrodynamic conditions. The total microbial biomass was not strongly influenced by the tide and bacteria contributed the highest proportion of the biomass. Respiratory activity was not high and was also not strongly influenced by the tide. In spring, increase in bacteria biomass through increased biovolumes was observed with indications of bacteriovory. A reduction of POC and chlorophyll-a in the water overlying the mussel beds was observed suggesting the uptake of organic matter and Phytoplankton. There were high tidal fluctuations of POC, chlorophyll-a and bacteria abundance and biomass. Bacteria contributed less to the total microbial biomass in spring. |
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