Does Ocean Acidification Benefit Seagrasses in a Mesohaline Environment? A Mesocosm Experiment in the Northern Gulf of Mexico

Ocean acidification is thought to benefit seagrasses because of increased carbon dioxide (CO2) availability for photosynthesis. However, in order to truly assess ecological responses, effects of ocean acidification need to be investigated in a variety of coastal environments. We tested the hypothesis that ocean acidification would benefit seagrasses in the northern Gulf of Mexico, where the seagrasses Halodule wrightii and Ruppia maritima coexist in a fluctuating environment. To evaluate if benefits of ocean acidification could alter seagrass bed composition, cores of H. wrightii and R. maritima were placed alone or in combination into aquaria and maintained in an outdoor mesocosm. Half of the aquaria were exposed to either ambient (mean pH of 8.1 ± 0.04 SD on total scale) or high CO2 (mean pH 7.7 ± 0.05 SD on total scale) conditions. After 54 days of experimental exposure, the δ13C values were significantly lower in seagrass tissue in the high CO2 condition. This integration of a different carbon source (either: preferential use of CO2, gas from cylinder, or both) indicates that plants were not solely relying on stored energy reserves for growth. Yet, after 41 to 54 days, seagrass morphology, biomass, photo-physiology, metabolism, and carbon and nitrogen content in the high CO2 condition did not differ from those at ambient. There was also no indication of differences in traits between the homospecific or heterospecific beds. Findings support two plausible conclusions: (1) these seagrasses rely heavily on bicarbonate use and growth will not be stimulated by near future acidification conditions or (2) the mesohaline environment limited the beneficial impacts of increased CO2 availability

Aspects of ecology and algal physiology in Hawaii's rocky intertidal zones

Ph.D. University of Hawaii at Manoa 2011.Includes bibliographical references.Intertidal zones are vulnerable to anthropogenic impacts that result from human populations concentrated near coastal waters and while the impact on temperate rocky intertidal systems is much studied, comparatively less is known about these habitats in the tropics. To bolster knowledge and facilitate conservation efforts this dissertation investigates aspects of ecology and algal physiology in Hawaii's rocky intertidal zone. I describe an intertidal zone with a flora and fauna well suited for a tropical environment. Assemblages of tidepool fishes and benthic organisms vary among sites and are vertically structured across narrow shores; consistent with the hypothesis that abiotic or biotic factors vary. A survey of nitrogen concentration and isotopic composition in two species of algae collected in nearshore waters along southwest O'ahu provides evidence that much of this algal community is supported by land-based nutrients. In addition, I use infrared thermography to examine thermal ecology on a tidally driven shore. I found that temperature varies over fine-spatial scales and changes rapidly with tides and waves and organisms either 1) associate with cooler habitats 2) tolerate hotter surroundings or 3) have characteristics allowing them to remain cooler than their surroundings. To examine the affect of temperature on physiology, thermal tolerances of 9 species of reef algae were tested in the laboratory. These species are robust to short doses of heated seawater; maintaining rates of photosynthesis up to 35°C. Results from a photosynthetic survey conducted with pulse amplitude fluoremetry documents an intertidal algal community that is high-light adjusted with the ability to respond to daily fluctuations in supraoptimal irradiances. In situ measurements and manipulations reveal that microtidal fluctuations (+1 m) combined with early morning timing of low tide, limits exposure to intense solar radiation and temperature, and facilitates the physiological performance of common reef algae. This is in contrast to temperate shores where algae experience reduced rates of photosynthesis from extended periods of aerial exposure. This dissertation advances methods in intertidal ecology, provides a baseline on which to measure future change, and has important implications for predicting the impacts of ocean warming and eutrophication on the eco-physiology of tropical reef algae

Multi-phenotype analyses of hemostatic traits with cardiovascular events reveal novel genetic associations

Multi-phenotype analysis of genetically correlated phenotypes can increase the statistical power to detect loci associated with multiple traits, leading to the discovery of novel loci. This is the first study to date to comprehensively analyze the shared genetic effects within different hemostatic traits, and between these and their associated disease outcomes. To discover novel genetic associations by combining summary data of correlated hemostatic traits and disease events. Methods: Summary statistics from genome wide-association studies (GWAS) from seven hemostatic traits (factor VII [FVII], factor VIII [FVIII], von Willebrand factor [VWF] factor XI [FXI], fibrinogen, tissue plasminogen activator [tPA], plasminogen activator inhibitor 1 [PAI-1]) and three major cardiovascular (CV) events (venous thromboembolism [VTE], coronary artery disease [CAD], ischemic stroke [IS]), were combined in 27 multi-trait combinations using metaUSAT. Genetic correlations between phenotypes were calculated using Linkage Disequilibrium Score Regression (LDSC). Newly associated loci were investigated for colocalization. We considered a significance threshold of 1.85 × 10 obtained after applying Bonferroni correction for the number of multi-trait combinations performed (n = 27). Across the 27 multi-trait analyses, we found 4 novel pleiotropic loci (XXYLT1, KNG1, SUGP1/MAU2, TBL2/MLXIPL) that were not significant in the original individual datasets, were not described in previous GWAS for the individual traits, and that presented a common associated variant between the studied phenotypes. The discovery of four novel loci contributes to the understanding of the relationship between hemostasis and CV events and elucidate common genetic factors between these traits

Multi-phenotype analyses of hemostatic traits with cardiovascular events reveal novel genetic associations

Background: Multi-phenotype analysis of genetically correlated phenotypes can increase the statistical power to detect loci associated with multiple traits, leading to the discovery of novel loci. This is the first study to date to comprehensively analyze the shared genetic effects within different hemostatic traits, and between these and their associated disease outcomes. Objectives: To discover novel genetic associations by combining summary data of correlated hemostatic traits and disease events. Methods: Summary statistics from genome wide-association studies (GWAS) from seven hemostatic traits (factor VII [FVII], factor VIII [FVIII], von Willebrand factor [VWF] factor XI [FXI], fibrinogen, tissue plasminogen activator [tPA], plasminogen activator inhibitor 1 [PAI-1]) and three major cardiovascular (CV) events (venous thromboembolism [VTE], coronary artery disease [CAD], ischemic stroke [IS]), were combined in 27 multi-trait combinations using metaUSAT. Genetic correlations between phenotypes were calculated using Linkage Disequilibrium Score Regression (LDSC). Newly associated loci were investigated for colocalization. We considered a significance threshold of 1.85 × 10−9 obtained after applying Bonferroni correction for the number of multi-trait combinations performed (n = 27). Results: Across the 27 multi-trait analyses, we found 4 novel pleiotropic loci (XXYLT1, KNG1, SUGP1/MAU2, TBL2/MLXIPL) that were not significant in the original individual datasets, were not described in previous GWAS for the individual traits, and that presented a common associated variant between the studied phenotypes. Conclusions: The discovery of four novel loci contributes to the understanding of the relationship between hemostasis and CV events and elucidate common genetic factors between these traits