Current Projects
ECOLOGICAL MONITORING
Monitoring has been undertaken at subsets of the 40 sites around the atoll each year. The components of the monitoring program are (1) fish community surveys, (2) benthic photographs to assess reef composition and cover, (3) urchin surveys, (4) physical environment assessments including rugosity measurements and slope, and (5) environmental monitoring such as water temperature and nutrients. In 2018 we added turf height measurements. Highlights from this data include a paper by former MSc student focusing on the importance of soft corals and their extreme vulnerability to heat stress, which has received scant previous documentation (Maucieri & Baum 2021 Biological Conservation). In another publication, led by former MSc student Jenn Magel, we showed that reef fishes are highly sensitive to increased water temperatures, declining by 50% during the El Niño-induced heatwave. Reef fishes likely moved to deeper waters to avoid the stressful conditions, and while most species returned to normal numbers within a year of the event, obligate corallivore numbers remain depressed (Magel et al. 2020 Ecological Applications). |
STABLE ISOTOPE ANALYSIS
Stable isotopes are biological tracers that can provide information about the energy source that an organism is feeding from (for example, whether it is feeding from the reef benthos or whether it is feeding up in the water column), as well as the trophic level that an organism feeds at (for example, whether it eats plants, invertebrates, or fish). Organisms across trophic levels - fish, urchins, turf algae, macroalgae, and phytoplankton - have been sampled for stable isotope analysis. We have also examined the stomachs of the collected specimens, to see directly what they had eaten. Our goal from these data is to understand what the coral reef fish food web looks like and how fishing pressure and marine heatwaves change it. We have been working over the past year and a half to analyze this data. |
SYMBIODINIACEAE and MICROBIAL DIVERSITY STUDY
Our goal is to better understand how diversity of coral symbionts (Symbiodininiaceae) and microbes vary over the gradient of human impact and during thermal stress events on Kiritimati, and how these relationships tie into our current understanding of reef resilience. Using molecular techniques to identify coral symbionts and other components of the microbiome, we have examined how interactions between local human impacts and global climate change shape coral symbiont (Claar et al. 2020 Scientific Reports, Claar et al. 2020 Molecular Ecology) and microbiome communities (McDevitt-Irwin et al. 2017 Frontiers Mar Sci, McDevitt-Irwin et al. 2019 Coral Reefs). Unexpectedly, we also discovered that some corals were able to recover from bleaching while still subjected to elevated water temperatures (Claar et al. 2020 Nature Communications). This work was featured in Science. Read more about it on the lab website page. |
HABITAT COMPLEXITY
Rich and varied coral forms provide structurally complex habitat for the many fish and invertebrate species that inhabit tropical reefs which is essential to the ecological functioning of coral reefs. However, rising ocean temperatures and associated coral mortality threatens the structural integrity of coral reefs. Working in collaboration with John Burns of the Mega Lab, we have used structure-from-motion photogrammetry to construct 3D models of permanent plots at shallow forereef sites around Kiritimati since before the El Niño (check out some of the 3D models here). In our first reef complexity publication, led by former MSc student Jenn Magel, we quantified the effects of severe heat stress on 3D reef habitat complexity across a gradient of local human disturbance, demonstrating that habitat complexity declined with increasing levels of human disturbance, and that there were further declines in reef habitat complexity and a loss of habitat volume within a year of the heatwave (Magel et al. 2019 Scientific Reports). |
CORAL RECRUITMENT
After the devastating loss of 90% of the corals due to the El Niño, a part of the research is now focused on recovery. Coral recruitment is the leading source of coral recovery after mortality events and the goal of this project is to document recruitment and the recovery of the reefs. Stay tuned for future publications focusing on this data. |
Previous work
TROPHIC INTERACTIONS
The goal of this project is to evaluate feeding interactions between herbivores, how these vary across the fishing and productivity gradients at Kiritimati, and whether feeding interactions have cascading effects down the food web. This has included surveys of herbivorous fish feeding, and macroalgal biomass quantification. |
URCHIN PREDATION
To test whether predatory fish biomass controls urchin populations through direct predation and indirect behavioural effects, an urchin tethering experiment was conducted to quantify relative predation, and urchin behaviour at sites around Kiritimati. This, coupled with data from fish and urchin surveys, and site information such as rugosity, will help us to understand the role of top down controls in coral ecosystems. |