Microzooplankton dynamics in relation to the microbial loop in Matang estuarine waters / Yong Yu Lin

Yong , Yu Lin (2021) Microzooplankton dynamics in relation to the microbial loop in Matang estuarine waters / Yong Yu Lin. PhD thesis, Universiti Malaya.

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Abstract

Microzooplankton (20-200 μm), along with phytoplankton, bacteria and heterotrophic nanoplankton in a tropical estuary (Matang Mangrove Forest Reserve, MMFR) were investigated to evaluate their abundance in relation to the various environmental and biotic parameters, along with their interactions in the microbial food web to elucidate the role of microzooplankton in the estuarine water. This study looked into the microzooplankton composition, taxonomically and abundance (Chapter 4) and their feeding interaction with the other microbial component in the estuary (Chapter 5). With this information gathered we can thus fill the knowledge gap of the carbon flow in the estuary. A total of 39 microzooplankton taxa comprising of four major groups, i.e. loricate ciliates (37.72 %), aloricate ciliates (29.46 %), dinoflagellates (24.33 %) and meroplanktonic nauplius (8.49 %) were identified. The loricate ciliates were the most diverse group with 31 taxa recorded. Four major species of loricate ciliates were identified, i.e. Tintinnopsis beroidea, Tintinnopsis rotundata, Stenosemella avellana and Tintinnidium primitivum, while Strombidiidae and Strobilidiidae dominated the aloricate ciliates. Although small loricate ciliates were ubiquitous, redundancy analysis shows marked shifts in microzooplankton community structure, from one that was dominated by loricate ciliates during the drier South West (SW) monsoon, to aloricate ciliates at the onset of the wet North east (NE) monsoon, and then to dinoflagellates towards the end of the drier NE monsoon period. These shifts were associated with rainfall, dissolved inorganic nutrients, salinity, temperature and microbial food abundance. There was no clear lunar effect on abundance of microzooplankton except for Favella ehrenbergii and copepod nauplii that were more abundant during neap than spring tide. Rain-driven monsoonal effects showed significant impacts on microzooplankton herbivory and primary production; both significantly higher during the drierSouth West monsoon. The MMFR was characterised by high primary production (148 to 4021 μgC l-1d-1; 1190 ± 249.6 μgC l-1d-1 ) and low bacterial production (1 to 6.1 μgC l-1d-1 ; 3.7 ± 1.5 μgC l-1d-1). There is no coupling observed among bacterial production and primary production. Microzooplankton grazing on primary production was profound (887.02 μgC l-1d-1), followed by heterotrophic nanoplankton (1.33μgC l-1d-1) and bacterial production (1.28μgC l-1d-1). More than 70% of the primary production was transferred to the microzooplankton via grazing, compared to only about 30% of both bacterial production and HNP production. The present study highlighted the role of microzooplankton as an important consumer of phytoplankton production in the highly turbid but productive mangrove estuary.

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