Projeto de pesquisa

Species/populations targeted for the zooxanthellae community profiling will be sampled at 12 localities along the Brazilian coast, including 3 oceanic islands. In addition, in situ experiments will be performed at the Alcatrazes Archipelago (SP) and Natal (RN), key sites holding particularly interesting environmental conditions. The first experiment is part of an ongoing research monitoring M. hispida at the Alcatrazes Archipelago. This archipelago is under the influence of a wind-driven upwelling, which changing the water temperature by up 10 ºC within a day. Such a particular condition provides a completely different thermal environment for colonies according to their depth distribution, with colonies from the shallower depths (4 m deep) experiencing higher temperatures (especially during climate anomalies), mid-water colonies (4-8 m depth) experiencing strong temperature fluctuations, and deeper-water individuals being protected from rising temperatures by the cold South Atlantic Central Water Mass (SACW). On this locality, several colonies distributed within a ~500 m2 area from 2 to 12 m depth were tagged in May 2021 and are being continuously monitored. Tissue samples, along with images under natural (using a coral watch card) and ultraviolet lights (taken at night), will be taken at the beginning of the experiment and at every six months. Further samplings will be performed in specific cases such as bleaching alarms from NOAA, bleaching events, and bleaching recovering.
The second in situ experiment will be performed in Natal, where the target species S. stellata can be found in two highly divergent thermal environments such as tide pools, where seawater temperature can reach over 36 ºC, and infra-littoral areas with “normal” temperatures. To investigate if and how the zooxanthellae community from S. stellata from one environment shifts to acclimatize the holobiont to divergent conditions, four colonies from tide pools and four colonies from the infra-littoral sites will be divided into two fragments, one of which will be transplanted between the two environments. Transplants will be performed reciprocally between sites. Colonies will be fragmented and left to heal for two weeks when the first tissue sampling will be taken (T0). One day after the reciprocal transplants were performed, another tissue sample will be taken (T1). Additional two sub-samples will be collected on the 10th (T2) and 30th (T3) day. After T3, fragments will be relocated to their respective original sites and sub-sampled at the same time range as described above (T4-T6).
For the third experiment (ex situ), three specimens from M. hispida and M. decactis will be collected on the same day from six sites to be chosen along the Brazilian coast and maintained in a common garden (10,000 L tank). Sites will be selected to encompass areas with divergent environmental conditions. All colonies will be transported to the Center for Marine Biology and kept in an open-water system for acclimation and with freshly collected plankton offered as food every day. After acclimation (~30-40 days), the open water system will be closed and the thermal experiment will start (temperature still to be decided). Samples are planned to be taken from each colony before, during (10th day), and after the experiment has finished (~20 days). Changes in sampling time might happen as a consequence of colonies’ health.
For all the collected samples, total genomic DNA will be extracted and the identification of endosymbionts composition will be performed throughout metabarcoding (using the internal transcribed spacer 2 of the ribosomal DNA; ITS2 rDNA; ~243-266bp).