Bourses Tahiti Perles – IRCP :

Dans le cadre des bourses Tahiti Perles – IRCP en 2013, plusieurs candidats ont été sélectionnés : Sarah W. Davies (M. Sc. University of Texas at Austin), Jérôme Patrice Payet (Oregon State University, Department of Microbiology) et Verena Witt (Ludwig-Maximilians University (LMU) Munich, Germany).

Bourse à Sarah W. Davies (Texas)

Title of the Project : Investigating Host-Symbiont Genetic Structure in Moorean Corals

Abstract : Coral reefs on and surrounding Moorea are interesting for studying population connectivity because, since the 1980’s, these reefs have experienced several major perturbations. These events include outbreaks of corallivorous crown-of-thorns starfish (Acanthaster planci), multiple cyclones (i.e. Cyclone Oli), and a number of intense bleaching events (Adjeroud et al. 2009; Trapon et al. 2011; Pratchett et al. 2011). However, even though reef cover during these events has been highly reduced, especially on the forereef, juvenile coral recruitment has been remarkably high (Adam et al. 2011), indicating some level of connectivity between neighboring reefs. Moorea also has a unique long term monitoring project that has set up six sites around Moorea in three different habitats since 2005 so adding a genetic component to this monitoring project will greatly ameliorate our biological understanding as well as management.

Overarching Hypothesis: Due to their relatively long pelagic larval durations I hypothesize that Moorean acroporid corals will exhibit large dispersal ranges, while their symbionts will be highly differentiated in comparison to the host.

Main results and perspective : Aim 1. Determine the connectivity patterns and distribution of genetic diversity in two species of acroporid corals (Acropora hyacinthus & Acropora digitifera) on Moorean reefs. Aim 2. Determine the connectivity patterns and distribution of genetic diversity in symbionts of two coral hosts (Acropora hyacinthus & Acropora digitifera) on Moorean reefs. These aims represent complementary approaches to better understand reef connectivity, and will test the theory of local adaptation in the symbionts of broadcast spawning corals.

Bourse à Jérôme Patrice Payet (Oregon)

Title of the project : Ecology and diversity of viruses in the Moorea coral reefs

Abstract : Specifically, this proposed research aims to i) evaluate whether the coral reef ecosystem surrounding the island of Moorea harbors abundant, active and diverse marine viruses, ii) test whether changes in nutrient conditions (e.g. nutrient pollution) alter viral
dynamics, infection activities and genetic structures in coral-­‐associated microbial assemblages on corals, iii) determine whether certain viral subsets are associated with particular coral diseases. Overall this work aims to validate the hypothesis that viruses influence the health of corals in the Moorea reef ecosystem. Hypotheses and experimental design.

H1: Seawater surrounding coral reefs in Moorea harbors abundant, active and diverse marine viruses.
H2: Nutrient enrichment results in unique shifts in viral abundance, infection activities and diversity.
H3: The genetic structure of viral assemblages is different in diseased corals vs healthy corals.

Main results and perspective : This research will provide the first glimpse of viral ecology and diversity in the Moorea coral reef ecosystem, and generate unique data for the scientific community. Including viral components in coral reef ecological models will allow scientists to better predict the effects of anthropogenic stressors and natural threats to coral reefs and improve long-­‐term reef
management. In addition, because viruses could play a role in controlling proliferation of opportunistic microbial pathogens, this work could also be relevant to reef seawater quality. Furthermore, this work will provide a career development opportunity for a young French researcher from l’Île de La Réunion, who has a great interest in tropical reef systems.

Bourse à Verena Witt (Germany)

Title of the project : Bacterial diversity and metabolism in tropical coral reef biofilms and sponges

Abstract : Water quality in coastal regions around the world is declining in response to global (i.e., ocean warming and acidification) and local (i.e., land-based activities) anthropogenic impacts. Terrestrial runoff leads to decreased salinity, increased nutrient and reduced light availability to nearshore coral reefs with adverse effects. Bacterial communities associated with biofilms and sponges shift rapidly in response to changes in water quality and hence may serve as bioindicators for reef health. However, the potential of microbial bioindicators in reef organisms and whether microbial community shifts also alter community functioning remain unexplored. This study will therefore aim to identify microbial target indicator species, investigate the recovery/adaption potential of biofilm and sponge-associated microbes and determine potential consequent changes in organism functioning. Biofilms will be established on artificial substrates for 30 d in aquaria and sponges will be collected in situ along a water quality gradient comprising of inshore and offshore sites. Biofilms and sponges will then be exposed to inshore coastal sites highly exposed to terrestrial runoff (low light, high nutrient availability) and more pristine sites (high light, low nutrient availability). Transplant experiments will be performed with biofilm and sponge replicates (transplanted from impacted to pristine and vice versa) and sampled after 3 and 10 d exposure to the new site. 454 Tag-pyrosequencing will provide in-depth insight into the bacterial community composition and diversity. A metagenomic approach and direct measurement of biogeochemical O2 fluxes (dark/light incubations/luminescent optode) will reveal whether community shifts also alter the function of whole bacterial communities in biofilms and sponges. Findings may contribute to understanding consequences of terrestrial runoff on ecosystem functioning and resilience, and to the application of microbial biofilms/sponges in long-term water quality monitoring programmes and future coastal management.

Main results and perspective : It is important to investigate the diversity and function of bacteria in order to investigate their potential as bioindicators and furthermore to understand the resilience of coral reef ecosystems. Understanding qualitative and metabolic responses of biofilms to terrestrial runoff will contribute importantly to understanding coral reef ecosystems and further, may contribute to future coastal management which may be readily adaptable to other tropical regions.