Browsing by Subject "ocean acidification"
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Item Response of the Toxic Dinoflagellate Karenia brevis to Current and Projected Environmental Conditions: Salinity and Global Climate Change(2013-05-03) Errera, Reagan MichelleHarmful algal blooms (HABs) are increasing in frequency and duration worldwide. Karenia brevis, the major toxic dinoflagellate in the Gulf of Mexico, produces potent neurotoxins, known as brevetoxins. For K. brevis, only minor concentrations of brevetoxins are needed to induce toxicity and environmental conditions appear to have the most direct impact on the cellular content of these toxins. A better understanding of K. brevis biology is essential to understand the mechanisms underlying toxin production and the ecology of such HABs, as well as to better anticipate and respond to such blooms. Here we present findings on the effect of salinity and availability of carbon on cellular physiology and brevetoxin and brevenal production by K. brevis. When grown at salinities of 35 and 27, but otherwise identical conditions, total brevetoxin cellular concentration varied between 0 to 18.5 pg cell-1 and brevenal varied between 0 and 1 pg cell-1. In response to hypoosmotic stress brevetoxin production was triggered, as a result, brevetoxin production increased up to 53%, while growth rates remained unchanged. A significant hypoosmotic event of >11%, was needed to trigger the response in brevetoxin production. To determine if K. brevis was sensing changes in specific ions within seawater (K+, Cl- or Ca2+), we systematically removed one ion while keeping the remaining ions at equivalent molar concentration for salinity of 35. Dilution in seawater K+ concentrations triggered the production of brevetoxins, increasing production ?44%. Ecosystem changes due to climate change have increased the production of toxins in other HAB species; here we examined the impact on K. brevis. We have shown that modification of pCO2 level and temperature did not influence brevetoxin production; however, predicted climate change scenarios (increased temperature and pCO2) did significantly increase the growth rate of K. brevis, by 60% at 25?C and 55% at 30?C. We suggest that K. brevis blooms could benefit from predicted increase in pCO2 over the next 100 years. Overall, our findings close a critical gap in knowledge regarding the function of brevetoxin in K. brevis by identifying a connection between brevetoxin production and osmoacclimation.Item The Combined Effect of Ocean Acidification and Euthrophication on water pH and Aragonite Saturation State in the Northern Gulf of Mexico(2013-04-10) Garcia Tigreros, FenixRising atmospheric carbon dioxide (CO2) concentrations are increasing the rate at which anthropogenic CO2 is accumulating in the ocean, and thereby acidifying ocean water. However, accumulation of anthropogenic CO2 is not the only process affecting coastal oceans. Anthropogenic inputs of nutrients to coastal waters can result in massive algal blooms, a process known as eutrophication. Microbial consumption of this organic matter depletes bottom waters of oxygen and increases acidity through the release of CO2. This study assesses the synergistic effect of ocean acidification and eutrophication in the coastal ocean using data from six cruises to the northern Gulf of Mexico. In addition, this study investigates the effect of the 2011 Mississippi River flood on coastal pH and aragonite saturation states. Data from a model simulation using data collected from the northern Gulf of Mexico indicates that eutrophication is contributing to acidification of subsurface waters and plays a larger role than acidification from atmospheric CO2 uptake. Furthermore, results from the model simulation show that the decrease in pH since the industrial era is 0.04 units greater than expected from ocean acidification and eutrophication combined. The additional decrease was attributed to the reduced buffering capacity of the region and may be related to the uptake of atmospheric CO2 into O2-depleted and CO2-enriched waters, the addition of atmospheric CO2 into O2-rich and CO2-poor waters, the input of CO2 via respiration into waters in equilibrium with high atmospheric CO2, or a combination of all three processes.