Microzooplankton community composition, abundance, biomass and grazing impact were assessed, along with measurements of ciliate growth and mortality, during the onset of the spring bloom in the north-east Atlantic. The study was undertaken as part of the UK Blogeochemical Ocean Flux Study during I May to 15 June 1990. The microzooplankton community was composed of protozoans and metazoan developmental stages with respective mixed-layer depth integrated biomass values ranging from 127 to 638 and 74 to 394 mg C m(-2). High numbers of aloricate ciliates (up to 35,000 cells 1(-1)) dominated the microzooplankton community during early May prior to the onset of the spring bloom. Ciliate abundance then declined rapidly during mid-May with community growth rates ranging from -0.71 to 0.23 d(-1). High abundances of metazoplankton (up to 400 1(-1)) were also recorded at this time and may have contributed to the decline in ciliate numbers. In late May and early June the protozoan community comprised a more even mix of dinoflagellates, tintinnids and aloricate ciliates. Phytoplankton mortality rates, measured using a dilution technique, ranged from 0.2 to 0.5 d(-1). The microzooplankton consumed 8 to 44 mu g C I(-1)d(-1), equivalent to between 16 and 40% of the chlorophyll biomass and 38 and 154% of primary production. These high rates of herbivory reflect the predominance of small ( <5 mu m in length) phytoplankton cells present throughout the first half of the study and support previous studies demonstrating the microzooplankton to be the main grazers of phytoplankton in the north-cast Atlantic. However, there is also evidence that a disparity between predator and prey may have prevented a response by the microzooplankton to rapid increases in phytoplankton biomass and production during the spring bloom.
- COMMUNITY STRUCTURE
- Marine & Freshwater Biology
- EQUATORIAL PACIFIC
Fileman, ES., & Leakey, R. (2005). Microzooplankton dynamics during the development of the spring bloom in the northeast Atlantic. J MAR BIOL ASSOC UK, (5), 741-753. https://doi.org/10.1017/S0025315405011653