(1) Mesopredators can switch prey in response to coral reef degradation at expense to their condition
Abstract: Mesopredators represent an important component of coral reef ecosystems, both ecologically, as a vital link in the transfer of energy from lower trophic levels to apex predators, and economically, as a valuable component of reef fisheries. There is however a concerning paucity of knowledge about how this functional group is affected by reef habitat degradation, a gap which is this focus of my PhD. Diet specificity is likely to be an important predictor of how mesopredators will be able to adapt to changes in their prey base resulting from disturbance. Long term monitoring of the reefs of the Keppel Islands on the Southern Great Barrier Reef shows that as live coral cover has declined over the past decade due to flooding and bleaching events, the prey fish community available to mesopredators has changed substantially. This change is characterized by a shift from pelagic planktivorous damselfishes towards benthic algal-feeding species, representing a shift in the dominant carbon pathways in the foodweb. Using stable isotopes, I investigated whether coral trout (Plectropomus maculatus) are able to alter their diets to take advantage of this change in prey availability. The results of the isotope analyses show a shift in the trout’s δ13C isotopic signal from a pelagic towards a benthic carbon signature, suggesting that these mesopredators may be able to switch their diet to ameliorate the impacts of habitat degradation. A corresponding decline in the ratio of percentage carbon to nitrogen in the trout muscle tissue, however, indicates that trout energy stores have decreased, suggesting that this dietary shift may be at the expense of their condition.
Biography: Tessa grew up on a farm in the savannas and escarpment forests of South Africa, an environment that instilled in her a passion for ecology from a young age. After a year in Tasmania as a Rotary Scholar, she began her undergraduate studies via correspondence with the University of South Africa (UNISA) while travelling and working in SCUBA diving. In 2003 she returned to South Africa to complete her BSc. in Botany and Zoology at the University of Cape Town (UCT), followed by a BSc. Hons in Zoology, a field course in the Kruger National Park with the Organisation for Tropical Studies (OTS) and a MSc. in Conservation Biology from the same university. Her study subjects ranged from the impacts of elephants on savanna vegetation and bat community ecology to upwelling system dynamics, crinoid symbionts and the effects of dynamite fishing on coral reefs in Tanzania. Since graduating she has worked as a conservation manager for the Sustainable Seas Trust (SST), sailed the South American coast, volunteered as a researcher on the Aldabra Atoll World Heritage Site in the Seychelles and managed diving and marine logistics on Vamizi Island in the Quirimbas Archipelago of Mozambique, before deciding it was time to fulfill a lifetime aspiration of pursuing a PhD in coral reef ecology at James Cook University.
(2) Long-term changes in the structure of inshore coral assemblages on the Great Barrier Reef
Abstract: There is a general consensus that coral cover has declined significantly on the Great Barrier Reef over the past 30 years, although not all regions have been equally affected. Inshore reefs in the Townsville section of the GBR are among those worst affected. However, few studies have sufficient taxonomic resolution to identify changes in coral assemblage structure, nor identify those taxa most at risk from repeated disturbance or those that might benefit. Here, I document changes in coral assemblage structure over 15 years following a mass bleaching event in 1998, and subsequent disturbance such as floods, cyclones and low tide events, at two depths on four near shore reefs in the Townsville region of the GBR. In 2013, colony abundance was only 50% of that in the initial survey, however, these low values are influence by a number of recent disturbances, such as tropical cyclone Yasi in 2011. None of the top 10 most abundant taxa in 1998 have been lost and Montipora and Turbinaria are relatively more abundant in 2013 than in 1998. All 8 sites have experienced at least two cycles of degradation and recovery with some sites returning to pre-bleaching abundance and generic richness within2 years. However, assemblage structure took from 2 to 14 years to return to the pre-bleaching status at some sites and never returned at others In general, broadcast spawning taxa, such as Montipora and Porites have recruited abundantly between disturbances, whereas many brooding taxa that were abundant prior to 1998, such as Seriatopora, Stylophora and Pocillopora damicornis, have failed to recruit. Repeated cycles of recovery at many sites suggest that the system remains resilient to disturbance, however, recovery to pre-1998 assemblage structure will take an extended period of little to no disturbance.
Biography: Chao-yang grew up in Taipei, Taiwan. He completed his BSc in 2003 in the Department of Marine Resources at National Sun Yat-sen University (NSYSU), followed by a MSc at the Institute of Marine Biology at NSYSU and National Museum of Marine Biology and Aquarium.Chao-yang has worked as a research assistant for Dr. Chaolum Allen Chen (Acadamia Sinica) and Dr Joshua Madin (Macquarie University). Chao-yang started his PhD at James Cook University in March 2013. His supervisors are Prof. Andrew Baird, Prof. Morgan Pratchett and Prof. Terry Hughes. His PhD research aims to define functional groups in scleractinian corals.