2018 CAPI Student Fellowship recipient Kristina Tietjen
Project title: Coral reef recovery rates along a gradient of local disturbance following unprecedented heat stress
Supervisor: Julia K. Baum, Associate Professor, Department of Biology, 番茄社区
Background
Coral reefs are vitally important ecosystems facing numerous chronic and acute stressors, including an increase in the frequency and severity of pulse-heat stress events, like El Niños. The 2015-16 El Niño triggered catastrophic bleaching around the world. On Kiritimati (Christmas Island), the epicentre of the event, 90% of corals bleached and died during this event. While the full impacts are not fully understood yet, this mass mortality event provides an opportunity to quantify recovery rates and to understand the mechanisms influencing recovery. Coral recruitment is essential to the recovery of coral reefs, and recruitment rates are one of five major factors that determine if a reef will recover or undergo a regime shift. Discovering what drives coral reef recovery will not only help to maintain these important ecosystems, but also has immense implications in human welfare, especially on Pacific Island nations where they rely heavily on healthy coral reefs.
gallery images courtesy Kristina Tietjen:
Proposed Activities
In June 2018 I will return to Kiritimati for three weeks where I will use SCUBA to collect additional recruitment census videos, resample recruitment tiles, and take benthic photographs to assess coral community structure and recovery. Census videos have been collected at 31 sites along the local disturbance gradient since 2013 spanning from before, during, and after the El Niño. Analyses of these videos by myself and two trained volunteers provide high resolution estimates of recruit and juvenile corals populations. Importantly, this field expedition will allow me to collect and sample 280 recruitment tiles that I deployed last summer at 14 sites spanning the atoll’s disturbance gradient. I will quantify recruits from each tile and use DNA sequencing (COI region) to then identify the recruits, thus allowing me to further quantify recruitment rates and characterize the community structure and diversity of coral recruits. By quantifying coral recruitment levels and taxonomic variability across a human disturbance gradient during the initial two years following a mass mortality event, my research will provide new insights into coral reef recovery mechanisms and resilience.
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