September 2020
New paper in Coral Reefs

New paper in Coral Reefs shows that the late post-settlement survival of pocilloporid recruits is significantly affected by the presence of crustose coralline algae (CCA) and that there is considerable variability in the outcomes of the interaction between CCA and coral recruits depending on habitat and recruit size.

Contrary to the well-accepted view that CCA facilitate coral recruitment, subcryptic CCA species had a negative effect on the survival of small-sized coral recruits relative to dead CCA control. In contrast, exposed CCA species had a positive effect. By examining the causes of death of the recruits in the experimental treatments, we concluded that, in subcryptic habitats, CCA can reduce the survival and/or growth of coral recruits via direct competitive overgrowth, while, in exposed habitats, they can enhance coral recruitment by alleviating competition with turf algae.

Many coral reef scientists and managers equate CCA (all species) to improved recruitment potential for corals. This paper challenges this view using a robust experimental approach, with important consequences for our predictions of reef recovery potential and the way we manage reefs. Good job Hendrikje!

Citation: Jorissen H, Baumgartner C, Steneck RS, Nugues MM (2020) Contrasting effects of crustose coralline algae from exposed and subcryptic habitats on coral recruits. Coral Reefs DOI 10.1007/s00338-020-02002-9

Natural pocilloporid recruits interacting with crustose coralline algae.
Photo: M. Nugues

Hendrikje and Yann Lacube checking up experimental dishes.
Photo: I. Ender

Experimental petridishes showing coral recruits in contact with crustose coralline algae.
Photo: M. Nugues

August 2020
Does distance from macroalgae matter to baby corals?

Chloe and Hugo ran an experiment aiming at testing whether biofilms preconditioned at different distances from macroalgae vary in their abilities to impede coral settlement and recruit survival. Aragonite tiles were preconditioned at different distances from macroalgae for two months in the lagoon of Moorea. To initiate coral settlement, they were placed in glass cylinders filled with seawater together with larvae of the coral Pocillopora damicornis in the laboratory. Settlement rates were estimated after 24h and tiles were replaced in the field to track coral recruit survival after 7 and 15 days. To understand the role of microbes, biofilms were sampled for microbial analyses along with macroalgae-associated bacteria and surrounding seawater. This experiment will be re-launched using coral spawning species next month.

Experimental room with the glass cylinders.
Photo: C. Pozas-Schacre

Structure holding tiles conditioned in the presence of Dictyota bartayresiana.
Photo: C. Pozas-Schacre

Cryptic side of a recruitment tile.
Photo: C. Pozas-Schacre

July 2020
On-going experiments in the water and baby corals

This last two months were marked by the launch of Chloe’s second experiment. This experiment aims to assess whether the effects of macroalgae on reef biofilms are algal species- and distance-dependent and whether these effects are associated with reduced coral recruitment. Once a week, Chloe and Hugo spend one day maintaining and monitoring their experiments in the field. For the first experiment (see May 2020 news), work consists in checking coral health state and macroalgae on algal-removed and control bommies. For the second experiment, the team must maintain macroalgal densities on experimental structures. The two experiments will involve specific tests on larvae of the brooding coral Pocillopora damicornis, which are released from adult colonies once a month. This week, the team will estimate the perfect time to obtain coral larvae.

Chloe & Hugo in front of their experiment “no anchorage” sign
Photo: H. Bischoff

Hugo installing macroalgae on one of the structures of the second experiment
Photo: C. Pozas-Schacre

Chloé removing macroalgae from an experimental bommie
Photo: H. Bischoff

June 2020
Congratulations Dr. Hendrikje Jorissen!

Hendrikje successfully defended her PhD thesis on June 26th after 3.5 years of hard work and dedication. Due to the spread of COVID-19, the defence had to be done using videoconference. It comprised a slide presentation lasting 45 minutes, followed by 2 hours of questions from six jury members. Colleagues, friends and family were able to watch the defence remotely. It’s been great working with you. We are so proud of you!

Hendrikje and Chérine Baumgartner going out in the field.
Photo: M. Streekstra

Hendrikje collecting coral larvae.
Photo: S. Meiling

What a lovely hat! Congrats, Hendrikje!
Photo: O. Van Broek

May 2020
Wet again after 2-month pause due to COVID-19

While Chloe’s PhD fieldwork was in full progress in Moorea, everything got shutdown with the arrival of COVID-19 on the French Polynesian territory in March 2020. Chloé & Hugo Bischoff, a Master student from the University of the French West Indies, had to stay dry at the CRIOBE lab facilities for two long months. However, fieldwork could start again this month. The team cleaned off experimental bommies from macroalgae which had barely grown back. Transplantation of Pocillopora damicornis colonies on the bommies and methodological testing of chemical sampling and flume chambers are now underway. It feels great to be wet again!

Chloé transplanting a Pocillopora damicornis colony.
Photo: H. Bischoff

Hugo pulling a syringe for in-situ extraction of chemical compounds from the water column.
Photo: C. Pozas-Schacre

Chloé dipping fragments of Turbinaria ornata in methanol to extract surface metabolites.
Photo: H. Bischoff

March 2020
ICRS 2020 postponed to 2021 due to COVID-19 | Bremen, Germany

Due to the spread of COVID-19, the 14th ICRS has been postponed to the week of 18 - 23 July 2021. The session "Coralline algae: what are their global contributions to coral reefs now and in future oceans?” co-chaired by Maggy with Christopher Cornwall, Steve Comeau and Guillermo Diaz-Pulido remains in the 2021 ICRS program. We hope to see you at the conference in Bremen, Germany, in July 2021. In the meantime, stay safe and healthy!

December 2019
TURBOCORAIL field experiment launched

In November 2019, Fabio manipulated sea urchin and Turbinaria densities on coral bommies in the lagoon of Moorea. The experiment will be maintained by Chloé and other students for the next few months. With this experiment, we hope to know whether different levels of urchin grazing pressure can regulate the spread and persistence of stands of Turbinaria and associated algae. Fabio also experimented with algal spores and chemicals to determine how the benthos affects settlement success of the alga. These experiments will enhance our understanding of the mechanisms underpinning the expansion of Turbinaria and, hopefully, strategies for its control.

Fabio Bulleri deploying Diadema in the field.
Photo: J. Gasc

Natural stands of Turbinaria ornata in the field.
Photo: F. Bulleri

Two settled germlings of Turbinaria ornata in the lab.
Photo: F. Bulleri

October 2019
International Coral Reef Symposium | ICRS2020 | Bremen, Germany

Maggy is co-chairing a session at ICRS with Christopher Cornwall, Steve Comeau and Guillermo Diaz-Pulido entilted "Coralline algae: what are their global contributions to coral reefs now and in future oceans?We hope to see you at the conference in Bremen, Germany, on July 5-10.