The seeming lack of barriers to gene flow in the northwest Atlantic ocean has led to the general assumption that the population of the American lobster (Homarus americanus) is largely panmictic. However, morphological and genetic data presented in this dissertation suggest that lobster populations are less homogenous than once believed with potential for behavioral barriers to mating and selection of locally adaptive traits. Additionally, both long-term fishing pressures and the recent spread of a destructive epizootic shell disease may have impacted population structure. We developed a novel photographic technique to rapidly collect accurate morphological data with the ability to maintain a database of images for the purposes of re-sampling and testing additional hypotheses. During this study, we found significant morphometric differences between samples of lobsters from collection sites as close as 25km apart. Morphological differences may have originated due to differential selection or plastic responses to environmental variation. To analyze population genetic structure, I surveyed genetic variation using RADseq. Analysis of 1614 putatively neutral SNPs found little genetic difference (Average F¬ST=0.00137) between sample sites suggesting a high level of gene flow between regions. Several additional markers appeared to be under divergent selection between sample sites. A genome scan analysis of both neutral SNPs and SNPs under selection found several selected SNPs associated with principal components of morphological characters. A subsequent BLAST analysis identified a number of the selected SNPs lying in the H. americanus transcriptome, suggesting functional importance. Further experimentation is required to quantify the impacts of plasticity or local adaption in the origin of morphological differences between lobster populations, although the significant differences identified in this research are likely due to a combination of the two. The overarching conclusion is that lobster populations are, in fact, more differentiated than previously predicted and, as such, the findings presented here may have significant management implications.

The high latitude thickets of Acropora cervicornis off Broward County flourish despite the presence of natural and anthropogenic impacts. These populations provided a unique study area in contrast to disease-stricken populations of the Florida Keys. This study used time-sequenced photographs to examine how A. cervicornis was affected by tissue loss attributed to white-band disease during 2007–2008. Variables monitored included healthy colony skeletal extension rates, diseased colony skeletal extension rates, and tissue loss. The transmissibility of the three white-band syndromes found in the Scooter and Oakland thickets was examined through tissue grafting experiments. Skeletal extension rates of healthy and diseased colonies were generally not significantly different. Mean skeletal extension for A. cervicornis colonies in Broward County was observed to be 9.6 cm/y (SD=3.95, Range: 1.02–19.9). Mean linear tissue loss from disease signs was 2.6 mm/d (SD=4.3, Range: 0.023–16.8). Although the majority of active disease lesions caused severe tissue loss upon contact with healthy branches, in 25% of the cases there was no tissue loss. Disease signs were also observed in 10% of the control grafting trials. A. cervicornis thickets in Broward County were growing at rates similar to those observed in this species elsewhere in Florida, but faster than other areas of the Western Atlantic. Tissue loss rate from disease lesions was lower than reported elsewhere. White-band disease and/or other tissue loss syndromes are always present in Broward County, but the low prevalence of affected colonies, inconsistent transmission of a presumptive agent that causes the disease signs, and optimum branch skeletal extension seems to limit effects on the thickets. Results of this research are significant as the current protected status of acroporid corals no longer allows manipulative research such as coral grafting for transmissibility of potential disease pathogens.