Trophic ecology of tropical octocoral: from research gaps to the study of two diferent ecozones

Abstract

Coral reefs are one of the most diverse, complex, productive, and economically valuable marine ecosystems in the world, with an estimated value of US$352,000/hectare/year. However, environmental changes have impacted the complexity and functionality of the structure of these marine forests. Several places worldwide are experiencing a transition in the marine community, where more resilient organisms are occupying space and establishing themselves in the environment to the detriment of those that are more fragile. In this struggle for survival, octocorals are the winners and as a result have become more present in marine corals, while scleractinians are disappearing in some regions, such as the Caribbean Sea. The ability to feed by heterotrophy seems to stand out as one of the main characteristics contributing to these organisms' greater resilience. However, more research is still needed in trophic ecology to improve understanding of this topic. To this end, the thesis provides valuable information divided into 3 chapters in article format that aim to: (chapter 1) investigate the current panorama of studies on trophic ecology in tropical octocorals; (chapter 2) analyze the trophic trends of the octocorals Muriceopsis sulphurea, Plexareulla grandiflora, Phyllogorgia dilatata, which inhabit regions of the South Atlantic through biochemical data (lipids and carbohydrates) and stable isotopes δ15N and Cδ13; (chapter 3) perform a temporal analysis of the biochemical composition (lipids, carbohydrates, proteins and fatty acids) of the octocorals Plexaurella nutans and Pterogorgia anceps from the Caribbean Sea. As result, the need for research in tropical regions of the South Atlantic, in mesophotic areas, to identify the relationship between trophic ecology and reproduction and to investigate the joint effects of disturbances on octocorals was highlighted. Based on biochemical and stable isotope analyses, it was found that three species analyzed of octocorals in the tropical region of the South Atlantic have a heterotrophic tendency and that the analysis of biochemical data from octocoral species in the Caribbean Sea corroborates previously published data that confirm their autotrophic tendency and are related to reproductive aspects of these animals. The results obtained provide new and important information on the trophic ecology of octocorals in tropical regions, contributing to the understanding of the capacity of these organisms to persist in environments subject to increasingly frequent and intense environmental variations.