Graduate Thesis Or Dissertation
 

Modeled Larval Connectivity Patterns in two Coral Reef Regions : the Western Caribbean and the Kenyan-Tanzanian Shelf

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/vx021j22h

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  • Tropical coral reef ecosystems are very important from both the ecological and economical points of view. However, they are also particularly fragile, and have been declining in recent years in most regions of the world, since they are highly susceptible to anthropogenic stressors operating at global scales (e.g., global warming and ocean acidification) and local scales (e.g., pollution/eutrophication, fishing, overcommercialization for recreation). Coral reef ecosystems are complex communities with very high species diversity. Most reef species have a bipartite life history with a planktonic larval stage and a benthic associated adult life. Therefore most adult reef organisms are distributed in metapopulations connected by pelagic larvae that disperse subject to the ocean currents. Knowledge of population connectivity among individual reef habitats within a broader geographic region of coral reefs has been identified as key to developing efficient spatial management strategies to protect marine ecosystems. The study of larval connectivity of marine organisms is a complex multidisciplinary challenge that is difficult to address with direct observations. This research examines the temporal and spatial, physical and ecological processes influencing connectivity of two important coral reef genera among isolated reef habitats within two regions: the Kenyan-Tanzanian and the Western Caribbean coasts. High resolution ocean circulation models were developed for each region and coupled to individual based models (IBM) that track particles (virtual larvae) released from each reef habitat. The connectivity patterns for two coral reef species groups having contrasting larval behavior and development duration where characterized in the two study regions: Acropora, a genus of branching corals with passive larvae and fast development (pelagic larval duration (PLD)<12 days), and Acanthurus, a genus of highly mobile, herbivorous fish, with long PLD (>50 days). Additional simulations were done to represent better the complexity of the Acanthurus larval life: one experiment included an idealized ontogenetic vertical migration behavior; another experiment examined how temperature-determined larval duration influenced trajectories and settlement patterns. The more complicated behavioral and development models were evaluated by comparing connectivity matrices to the passively transported case. To investigate interannual variations in connectivity patterns and percentage of successful settlement experiments were done for two contrasting years 2000 and 2005. Environmental seasonal and interannual variability in the ocean circulation models was analyzed to detect the mechanisms controlling connectivity in the two regions. The connectivity patterns and the mechanisms causing them were compared among the two study regions. Results are interpreted in the context of marine spatial management, describing the implications of the modeled connectivity patterns for currently established Marine Protected Areas. The connectivity patterns, and the processes controlling connectivity for different taxa, provide policy relevant scientific information that enables managers and decision-makers to make more informed choices regarding the size, spacing and optimal spatial design of marine protected networks.
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