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Ecology of Meiofauna from the New Zealand Continental Margin

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Ecology of Meiofauna from the New Zealand Continental Margin ECOLOGY OF MEIOFAUNA FROM THE NEW ZEALAND CONTINENTAL MARGIN BY NORLIANA MOHD ROSLI A thesis submitted for the degree of Doctor of Philosophy at the University of Otago, Dunedin, New Zealand January 2017 Abstract Deep-sea meiofaunal communities vary at a range of spatial scales. However, identifying which scale(s) account for most of the variability in deep-sea communities remains difficult, as few studies have been designed in such a way as to allow meaningful comparisons across more than two spatial scales. Moreover, deep-sea studies have largely focused on particular (macro) habitats in isolation, with few studies considering multiple habitats simultaneously in a comparable manner. In the present study, meiofaunal and nematode community attributes (abundance, diversity, community structure and trophic structure) were investigated at different spatial scales (sediment depth (cm), habitat (slope, canyon, seamount, and seep: 1– 100 km), and region (100–10000 km)) in two regions on the continental slope of New Zealand (Hikurangi Margin and Bay of Plenty), while accounting for the effects of water depth (700, 1000, 1200 and 1500 m). Nematode species new to science encountered during sampling on the continental margin of New Zealand were also described. A consistent pattern for each meiofaunal community attribute was observed. The greatest variability was found between sediment depth layers and between regions, which explained 2–4 times more variability than habitats. Meiofaunal abundance and diversity were higher at surface than subsurface sediment. High abundance of meiofauna was also found in the higher productivity region of Hikurangi Margin than in the Bay of Plenty region, but not diversity, which was slightly higher in the Bay of Plenty region. The variability pattern among spatial scales was not the same i in each region. In the Bay of Plenty region, nematode diversity, community structure and trophic structure consistently showed increased variability from habitat and water depth to sediment depth. However, no consistent pattern was observed in Hikurangi Margin. The findings in this study suggest that meiofaunal community attributes are mostly influenced by sediment characteristics and food availability, but that disturbance (fishing activity and bioturbation) also accounts for some of the variability. These findings provide new insights into the relative importance of processes operating at different spatial scales in regulating meiofaunal communities in the deep-sea, and their potential vulnerability to anthropogenic activities. Two new species and one new species record of the family Comesomatidae from the Hikurangi Margin were described: Vasostoma hexodontium n. sp., Sabatieria dispunctata n. sp., and Laimella subterminata Chen & Vincx, 2000. A total of 159 species have been recorded/described from the New Zealand region, of which 37% are deep-sea species. This study improves understanding of meiofaunal biodiversity and their distribution patterns on the New Zealand continental region, which will help underpin effective management of New Zealand's continental margin communities in the future. ii Acknowledgement First, a big thanks to my supervisors and advisor: Dr. Daniel Leduc and Dr. Ashley Rowden from National Institute of Water and Atmospheric Research (NIWA), and Assoc. Prof. Dr. Keith Probert from Otago University. The guidance and support given by my supervisors and advisor has been very helpful for the completion of my PhD. Without them I would not have been able to pull this off alone. Daniel has taught me laboratory techniques and nematode taxonomy and identification, skills that are hard to find nowadays with taxonomist being considered endangered. Keith has provided guidance, support and funding from Otago university to ensure my study in New Zealand went smoothly. Ashley gave much insightful advice on scientific writing and results presentation. Thanks to NIWA for providing an opportunity to work at the NIWA Wellington research site, and being able to work with other NIWA scientists in a real research environment and facility. My research was conducted as part of the NIWA project ‘Impact of resource use on vulnerable deep-sea communities’ funded by the New Zealand Ministry of Business, Innovation and Employment. And also thanks for giving me an opportunity to work on the NIWA Tangaroa ship, and experience how deep-sea sampling is conducted. It was invaluable experience, even though the trip was rough, and I was seasick for the whole trip. I have learnt a lot through my PhD journey. I am also grateful to Andy McKenzie at NIWA, for his guidance and support with the R software during my PhD. Thanks to him, my office mate, and other staffs at NIWA for providing me help and making me feel so welcome. Andy also has iii given me tremendous support during my PhD journey, and he has always been there when I was feeling down. And not to forget to my flatmates, Syahida Hassan, Najwani Razali and Atiqah Mohtar who are also pursuing their studies at Victoria university. Thanks for their support and encouragement, and being my family here in Wellington. Thanks for all the wonderful experiences I had while I was in New Zealand. The warmest thanks to my beloved family, especially to my mum and dad for their understanding and support through my PhD study. Even though we were far apart, their love and blessings were always with me. Last but not least, my sincere thanks to Universiti Pendidikan Sultan Idris through Ministry of Higher Education of Malaysia and NIWA for funding me during my PhD study. iv Table of contents Abstract ........................................................................................................................ i Acknowledgement ..................................................................................................... iii Table of contents.......................................................................................................... v List of tables .............................................................................................................. ix List of figures ............................................................................................................ xii List of abbreviations ................................................................................................ xvi Chapter 1 Review of recent trends in ecological and taxonomic studies of deep-sea meiofauna, with an emphasis on the New Zealand region .......................................... 1 1.1 Introduction ................................................................................................... 1 1.1.1 Previous reviews of the ecology of deep-sea meiofauna ....................... 3 1.1.2 Ecological studies of deep-sea meiofauna since 2000 ........................... 6 1.1.3 Changes in mesh size and sampling approaches over time ................. 10 1.1.4 Ecological and taxonomic studies of deep-sea meiofauna in the New Zealand region .................................................................................................... 11 1.1.5 Review aim .......................................................................................... 13 1.2 Spatial distribution patterns ........................................................................ 32 1.2.1 Regional scale ...................................................................................... 32 1.2.2 Habitat scale......................................................................................... 36 1.2.3 Local scale ........................................................................................... 47 1.2.4 Small scale ........................................................................................... 50 1.3 Taxonomy of free-living marine nematodes in the New Zealand region ... 55 1.4 Conclusion .................................................................................................. 57 1.5 Research objectives ..................................................................................... 57 1.6 Thesis outline .............................................................................................. 58 Chapter 2 Differences in meiofauna communities with sediment depth are greater than habitat effects on the New Zealand continental margin: implications for vulnerability to anthropogenic disturbance ............................................................... 63 2.1 Abstract ....................................................................................................... 64 2.2 Introduction ................................................................................................. 65 2.3 Material and Methods ................................................................................. 69 2.3.1 Study area and sampling design .......................................................... 69 2.3.2 Sampling and sample processing ......................................................... 71 v 2.3.3 Additional environmental characterisation .......................................... 73 2.3.4 Statistical analysis ................................................................................ 78 2.4 Results ......................................................................................................... 81 2.4.1 Comparison of Hikurangi Margin and Bay of Plenty regions ............. 81 2.4.2 Hikurangi Margin ................................................................................ 84 2.4.3 Bay of Plenty ......................................................................................
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