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Connectivity and Resilience of Coral Reefs Ecosystems

Ballesteros Contreras (2020) Connectivity and Resilience of Coral Reefs Ecosystems. Doctoral thesis (PhD), Manchester Metropolitan University in collaboration with the Marine and Coastal Research Institute - INVEMAR- Colombia.

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Abstract

Coral reefs, one of the most diverse ecosystems on earth, currently show a massive decrease in their populations as a result of climate change and overexploitation. Some Marine Protected Areas (MPAs) have been created to preserve the connectivity between coral reef ecosystems and interdependent organisms, as a biodiversity conservation tool. However, in order to design these reserves, it is necessary to understand the genetic exchange among populations. As a response to this problem, I created ecological genetic tools for deep and shallow coral reefs and performed experiments in aquaria to assess the effect of particularly key environmental factors on growth and survival of corals. I developed seventeen new polymorphic microsatellite markers for the shallow coral Madracis auretenra, using the Galaxy-based bioinformatics pipeline Pal Finder from Illumina Next Generation Sequencing data. I tested the new markers in 330 samples from Colombia, Guatemala, Curacao and Barbados to understand connectivity patterns in the Caribbean. The findings show a high genetic differentiation across the population, increasing across the oceanographic distance in the region. There is also a limited dispersion in M. auretenra despite its reproductive strategies (asexual propagation); the presence of genetic structure through the Caribbean Sea matched with the dispersal pattern from other benthic organisms and physical barriers reported for several authors. In addition, I develop nine microsatellite markers for the deep coral Madracis myriaster, the main reef builder of the Deep Corals National Park (PNNCPR), the first MPA in Colombian deep waters. These new microsatellites can be used in future studies in the PNNCPR or other Caribbean and Atlantic areas, where M. myriaster is reported at similar depths. These markers will also allow solving identification problems for the genus and be a complement for traditional taxonomy. Finally, I explored the effect of high turbidity (light restriction factor) as a result of high sedimentation by runoff rivers, catalogued as a possible physical barrier in Caribbean populations. I assessed in aquarium systems the effect of light intensity on growth rate, calcification and zooxanthellae density, using the coral Montipora sp. The results showed how light restriction affects, in 2 short time periods (weeks), the photosynthesis process, causing a premature symbiont release, nutrient restriction intake, coral tissue loss and coral death. These results showed the advantage of aquarium systems as an accurate tool to evaluate independent variables that in situ would be difficult to measure. The combination of traditional and ecological genetic methods used here bring new biodiversity conservation tools to improve conservation management.

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