Circulation in Pamlico Sound and Predicted Oyster Larval Dispersal and Connectivity

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Title: Circulation in Pamlico Sound and Predicted Oyster Larval Dispersal and Connectivity
Author: Haase, Amy Tresa
Advisors: Ping-Tung Shaw, Committee Member
Ruoying He, Committee Member
David Eggleston, Committee Chair
Rick Luettich, Committee Member
Abstract: A critical component to understanding connectivity of spatially-separated populations of marine organisms is quantifying hydrodynamic paths of dispersal, and variation in the strength of these hydrodynamic connections. We mimicked larval dispersal of the Eastern oyster (Crassostrea virginica) by replicating wind-driven circulation patterns in Pamlico Sound (PS), NC using a numerical hydrodynamic model (ADCIRC, ADvanced CIRCulation) to produce 3-dimensional flow-fields, followed by predicted trajectories of virtual larvae using a particle-tracking model (PTM). Predicted larval trajectories were then used to estimate a larval connectivity matrix for PS to help guide oyster restoration efforts via a network of no-take oyster broodstock reserves. To force the ADCIRC model, we used wind observations during the time that oyster larvae would have been dispersing in PS, and used velocity observations from two bottom-mounted ADCP (Acoustic Doppler Current Profiler) instruments to validate velocities predicted from ADCIRC. Field observations of trajectories from 12 Pacific Gyre surface drift buoys released during the summer of 2007 were used to validate the paths of virtual larvae produced by the PTM. The 3D ADCIRC model reliably predicted variation in velocities at different locations in PS, especially currents near-surface. The PTM also reliably simulated trajectories of surface drift buoys under varying wind regimes, thereby providing confidence in qualitative predictions of dispersal of virtual larvae, and potential larval connectivity in PS. Potential oyster larval connectivity was not uniform among broodstock sanctuaries in PS, ranging from 20 to 65% connectivity from a given sanctuary. Moreover, potential self-recruitment to a given broodstock sanctuary also varied spatially. Thus, when spatial variation in the degree of potential oyster larval connectivity in PS identified in this study is combined with the results of related studies on spatial dynamics of oyster populations in PS (see below), there is strong evidence for an oyster metapopulation and possibly source versus sink population within PS.
Date: 2009-12-22
Degree: MS
Discipline: Marine, Earth and Atmospheric Sciences

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