Utility of photochemical traits as diagnostics of thermal tolerance amongst great barrier reef corals

© 2018 Nitschke, Gardner, Goyen, Fujise, Camp, Ralph and Suggett. Light availability is considered a key factor regulating the thermal sensitivity of reef building corals, where excessive excitation of photosystem II (PSII) further exacerbates pressure on photochemical pathways already compromised by heat stress. Coral symbionts acclimate to changes in light availability (photoacclimation) by continually fine-tuning the photochemical operating efficiency of PSII. However, how this process adjusts throughout the warmest months in naturally heat-tolerant or sensitive species is unknown, and whether this influences the capacity to tolerate transient heat stress is untested. We therefore examined the PSII photophysiology of 10 coral species (with known thermal tolerances) from shallow reef environments at Heron Island (Great Barrier Reef, Australia), in spring (October-November, 2015) vs. summer (February-March, 2016). Corals were maintained in flow-through aquaria and rapid light curve (RLC) protocols using pulse amplitude modulated (PAM) fluorometry captured changes in the PSII photoacclimation strategy, characterized as the minimum saturating irradiance (Ek), and the extent of photochemical ([1-C], operating efficiency) vs. non-photochemical ([1-Q]) energy dissipation. Values of Ek across species were > 2-fold higher in all coral species in spring, consistent with a climate of higher overall light exposure (i.e., higher PAR from lower cloud cover, rainfall and wind speed) compared with summer. Summer decreases in Ek were combined with a shift toward preferential photochemical quenching in all species. All coral species were subsequently subjected to thermal stress assays. An equivalent temperature-ramping profile of 1°C increase per day and then maintenance at 32°C was applied in each season. Despite the significant seasonal photoacclimation, the species hierarchy of thermal tolerance [maximum quantum yields of PSII (Fv/Fm), monitored at dawn and dusk] did not shift between seasons, except for Pocillopora damicornis (faster declines in summer) and Stylophora pistillata (total mortality in spring). Furthermore, the strategy for dealing with light energy (i.e., preferential photochemical vs. non-photochemical quenching) was unchanged for thermally tolerant species across seasons, whereas thermally sensitive species switched between preferential [1-Q] and [1-C] from spring to summer. We discuss how such traits can potentially be used as a diagnostic of thermal tolerance under non-stressed conditions

Unlocking how corals have acclimatised to thrive within the temperate waters of Sydney Harbour

University of Technology Sydney. Faculty of Science.Whilst corals are under immense anthropogenic pressure from increasingly altered environments, growing evidence suggests that some coral populations have evolved to thrive within present day marginal environments. Marginal coral populations are therefore significant to understand the adaptive and acclimative capacities required to tolerate future climates. Genetic shifts within the coral microbiome are being increasingly recognised for their importance to holobiont functioning under extremes, and is considered in this thesis in terms of symbiont (Symbiodiniaceae) and bacterial diversity in response to variable environmental conditions. Promising new “omics” approaches are allowing us to create species-specific metabolite profiles and further uncover the complex mechanisms of cell metabolism under environmental stress. When coupled to measurements of coral physiological variables (photosynthesis, respiration and calcification), the molecular regulation of corals under various environmental conditions can be elucidated. This thesis focuses on two coral species, and surviving under highly variable environmental conditions in Sydney Harbour. Specifically, coral heat stress tolerance was investigated during the 2016 El Niño event, which lead to the first report of coral bleaching in Sydney Harbour, showing that these high-latitude corals bleach in a similar way to tropical corals. Sampling for microbial diversity analysis was conducted ahead of coral bleaching in February, during coral bleaching in April and during coral recovery in August. Parallel measurements of coral metabolic rates (photosynthesis, respiration and calcification) were made in aquaria. Only . showed a bleaching response and a switch towards a heterotrophic nutrient acquisition mode during bleaching highlighting the different bleaching susceptibilities of these two-coral species. Microbial community composition showed clear species-specific associations and shifts in diversity and abundance of key bacterial taxa in response to the thermal anomaly event and over a 2-year study with seasonal environmental change. Metabolite profiling conducted using GC-MS showed overall between species similarity with lipid compounds dominating the metabolome of both coral species. Under acute heat stress, increases in fatty acid metabolism significantly correlate to holobiont photosynthesis, suggesting a predictive capacity of metabolomic analysis in determining coral performance under heat stress. The systematic approach implemented in this thesis highlights some of the potential mechanisms of coral persistence in marginal environments. This is relevant as high-latitude regions such as Sydney have been proposed as coral refuge environments with climate change. This research will also open up a new level of biodiversity complexity quantification that is used to designate Sydney Harbour’s high conservation value

Empathy and critical thinking: primary students solving local environmental problems through outdoor learning

© 2013,Institute for Outdoor Learning.The present study explores the outcomes of teaching empathy and critical thinking to solve environmental problems. This investigation was done throughout the duration of an environmental education course within a primary school located in central Chile. A community-based research methodology was used to understand the formation of empathy and critical thinking. The findings reveal a significant benefit in using empathy strategies to engage students regarding the thinking processes involved with solving environmental problems. Using these elements as teaching techniques for environmental education courses can be very helpful in reaching the aims of creating a sustainable citizenry