Copepod nauplii are numerically dominant metazoan plankton in many marine ecosystems and play important ecosystem roles both as grazers and as prey, but have historically been understudied due to small body size and challenges in identification of taxa. Little is known about naupliar grazing and the effects of environmental forcing on early life history stages of copepods in subtropical ecosystems. In this study, I measured the grazing rates and trophic impacts of two calanoid copepod nauplii on natural prey assemblages and investigated the population dynamics of four common species of copepod nauplii in a subtropical embayment, Kane‘ohe Bay, Hawai‘i, under several ecosystem states. I found that grazing experiments can be biased by methods; extending the duration of grazing incubations from 6 h to 24 h reduced grazing rate estimates by up to 75%. Bestiolina similis nauplii were more selective against 2-5 ìm prey than the closely related species, Parvocalanus crassirostris, and P. crassirostris nauplii were capable of significantly impacting prey populations, removing up to 12.9% of chlorophyll from the water column when this species was abundant. Species-level studies of nauplii in mixed field samples required the development of a quantitative PCR (qPCR)-based technique to distinguish species and estimate naupliar biomass across five orders of magnitude. Application of the qPCR method to study naupliar populations during a non-storm period and after two ecosystem perturbation events (i.e. storms), revealed temporal differences in recruitment rates and biomass loss between the four dominant species. After the early-season storm event, naupliar biomass was observed to increase by up to an order of magnitude within days of the storm, biomass was lost by up to 99% in the earliest developmental stages in the days following the storm, and the community structure rapidly returned to levels similar to my observations for a non-storm summer period. My results demonstrate that copepod nauplii can be selective grazers and have important trophic impacts in subtropical marine plankton communities. I also show that ecosystem perturbations alter species-specific copepod recruitment rates and biomass loss across development, promoting ephemeral shifts in species dominance within the naupliar community.
|School:||University of Hawai'i at Manoa|
|School Location:||United States -- Hawaii|
|Source:||DAI-B 78/08(E), Dissertation Abstracts International|
|Subjects:||Ecology, Biological oceanography, Zoology|
|Keywords:||Copepod nauplii, Grazing, Marine food webs, Plankton|
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