Time-series electrochemical studies in the lower Delaware Bay and at the 9 degrees 50' north East Pacific Rise hydrothermal vent field.

摘要

The research conducted in here is an effort towards meeting the needs of the ocean observing community by designing, and applying voltammetric instruments in conjunction with other sensors on autonomous platforms. These studies were conducted in the Delaware Bay and at the 9°50'N East Pacific Rise hydrothermal vent site. Data collected by these instruments were then used towards gaining a better understanding of primary production in these systems.;Dissolved oxygen and other physical and biological factors were monitored in the lower Delaware Bay using an autonomous buoy. Six weeks of data from the summer of 2007 provide insight into the processes occurring in the lower bay. Dissolved oxygen concentrations vary at both tidal and diel periodicities and are super-saturated for most of the summer, with day time maxima of up to 390 muM (140% saturation). Extended periods of high wind speed reduce the dissolved oxygen concentration to saturation, after which it can take up to 4 days for the system to recover. Reaeration and net oxygen production rates (primary productivity respiration) were calculated using the measured dissolved oxygen concentrations, wind speed, and tidal currents. Oxygen production was modeled using the Delta method and a primary productivity and respiration model. The lower Delaware Bay is net autotrophic, producing oxygen at a rate of 2.8 muM d-1. These results demonstrate the need for time series studies in marine systems, where complex physical and biogeochemical processes would be over-looked by discrete, infrequent observations. When combined with modeling techniques, time series studies provide a tool to investigate processes occurring in natural systems.;Chemistry and temperature were monitored during 6 deployments of an in situ electrochemical analyzer between December, 2004 and January, 2007 in diffuse flow sites at the 9°50'N East Pacific Rise hydrothermal vent site. Au/Hg micro-electrodes and temperature loggers were placed near the mussel Bathymodiolus thermophilus, and the tubeworms Riftia pachyptila and Tevnia jerichonana to monitor the conditions in which these organisms reside, and to investigate the physical and chemical processes occurring at these diffuse flow sites. Results reveal that temperature can be used as a proxy for chemistry, as long as the site is well characterized. Additionally, a site needs to be observed for at least one tidal cycle to monitor the full range of conditions an organism living there experiences. Data were also used in conjunction with previous lab based studies to calculate the rates of sulfide and oxygen uptake near mussels and tubeworms. Additionally, the results suggest that Bathymodiolus and Riftia are found in similar habitats, and that Tevnia favor low O2, high H2S uptake environments.