Response and regulation of cell-surface hydrolases to nutrient stress in river-influenced coastal areas

Conceptually, the hydrolysis product of ectoenzyme activity is used to relieve nutrient stress or acquire a type of molecule not immediately accessible in the environment. When properly characterized, ectoenzyme activities can offer greater insight into the nutrient requirements of organisms and how they use organic matter. This dissertation analyzes enzyme activity data from two river-influenced coastal regions, locations of variable inorganic nutrient concentrations, dissolved organic matter concentrations, and biomass. It is the ultimate goal of this dissertation to provide a quantitative means of interpreting ectoenzyme activity or, at the very least, to provide possible interpretations of activity that go beyond the overly-simplistic and qualitative views currently dominant in the ectoenzyme literature. In addition, it highlights the advantages of automated biological measurements, and promotes their use in future work. The first section explores the role of nitrate on LAP expression, and how LAP activities can reflect (and participate in) different biogeochemical regimes within the Hudson River outflow. The second section describes a simple model predicting the influence of leucine aminopeptidase (LAP) activity on a nitrate-limited phytoplankton population. The model includes predictions of the strength of nitrate limitation, ability of LAP to overcome the limitation, coupling strength between hydrolysis and uptake, and a phytoplankton nitrate requirement. The third section expands upon current research in alkaline phosphatase (AP) activity in the Louisiana shelf. This work provides a first look at high resolution time-series of AP activity and other environmental variables, and how the interpretation of AP activity measurements may be improved by considering a time lag between variables and a temporal control on AP expression.Ph.D.Includes bibliographical referencesIncludes vitaby Brian Matthew Gaa