Use of the dilution technique to determine microzooplankton herbivory in three contrasting oceanic systems
The dilution technique has been used during both laboratory experiments and in the field in three contrasting oceanic systems: the northeast Atlantic, Bellingshausen Sea and Arabian Sea. Laboratory dilution grazing studies, using Oxyrrhis marina as the predator and Dunaliella tertiolecta as prey, ha...
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| Format: | Thesis |
| Language: | English |
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University of Southampton
2000
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| Online Access: | https://eprints.soton.ac.uk/466968/ https://eprints.soton.ac.uk/466968/1/818183.pdf |
| Summary: | The dilution technique has been used during both laboratory experiments and in the field in three contrasting oceanic systems: the northeast Atlantic, Bellingshausen Sea and Arabian Sea. Laboratory dilution grazing studies, using Oxyrrhis marina as the predator and Dunaliella tertiolecta as prey, have demonstrated a significant linear relationship between apparent phytoplankton growth and dilution factor. The daily turnover of prey by Oxyrrhis ranged between 45 and 95%. Growth of prey was constant at all dilutions demonstrating that phytoplankton growth was density independent. Studies carried out during summer along a transect in the northeast Atlantic between 60°N and 47°N showed microzooplankton to consume between 0.5 and 17mg phytoplankton C d"\ This was equivalent to between 288 and 589 mg C m ^ d"^ being grazed in the mixed layer. Microzooplankton grazing impact was highest at the southerly end of the transect. During the spring-bloom period in 1990, microzooplankton grazed between 28 and 78% and between 26 and 55% of the daily primary respectively. The microzooplankton community was dominated by small cells (<20|jm). In the Bellingshausen Sea, microzooplankton consumed between 0.04 and 31.21 mg C m ^ d'\ and were estimated to graze between 21 and 3260 mg C m ^ d'^ in the pack ice and open water station respectively. In the Arabian Sea, microzooplankton grazed between 1 and 17 mg C m"^ d'\ In the mixed layer microzooplankton grazed between 161 and 415 mg C m"^ d"^ during the SW monsoon and between 110 and 407 mg C m"^ d"^ during the intermonsoon period. Substantial grazing of phytoplankton biomass by the microzooplankton occurred in all three oceanic systems. Variations in the grazing and phytoplankton growth rates can be attributed to differences in the phytoplankton and microzooplankton communities encountered. Results demonstrate a tight coupling between growth of prey and consumption for the northeast Atlantic and Bellingshausen Sea. production in May and June |
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