From Coral reefs to Algal Reefs: why reefs become overgrown by Lobophora ?

Master Thesis subject (30 ECTS)
Oceans and Lakes
Coral reefs are among the most biologically diverse and economically important ecosystems on the planet, providing ecosystem services that are vital to human societies and industries through fisheries, coastal protection, building materials, new biochemical compounds, and tourism. Yet in the last decade, coral reefs have continued to deteriorate as a result of human influences. A common phenomenon is the transitions from coral dominated systems to algal reefs. Many of these shifts involve the brown alga Lobophora. The latter seaweed, distributed worldwide in tropical and temperate regions, represents a major benthic component in tropical reefs. Its capacity to dominate large reefs areas following coral mortality and herbivory declines, attracted ecologists interest since the 80s. Surprisingly, its species richness has only recently been revealed, with an estimated >100 species distributed worldwide. To understand the causes behind Lobophora genetic diversity and ecological success, we will apply a population genetic approach. No population genetics study has yet been done on this genus. This thesis aims to examine if sexual versus asexual reproduction influences the capacity of the seaweed to outcompete corals. Thereto we study the mating system: defining the sexual phenotype (hermaphroditic or dioecious, selfing or outcrossing), detecting asexual/sexual reproduction, determine the haploid:diploid ratios; investigate the fine-scale population genetic diversity and structure within and among Caribbean (Curacao, Bonaire, Sababank) and Macaronesian (Canary Islands, Madeira, Azores, Cap Verde) populations of 3 species using 8-10 microsatellite; and evaluate the genetic drift of Lobophora populations (at fine to large scales). Practical work involves: (1) DNA extraction and microsatellite amplification, (2) Scoring of polymorphisms, (3) analysis of genotypic diversity, and (4) analysis of genetic structure. The project may also include fieldwork.
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Reference Number: RP-48991