The dynamics of the surface layer of Prince William Sound are largely influenced by the input of fresh waters from rivers and glaciers.  The timing and amount of fresh water can influence biological productivity, which can “cascade” up ecosystems and influence the amount of food available for larval and juvenile fish like herring and salmon.

In order to more closely monitor changes in freshwater and heat budgets in the nearshore portions of Prince William Sound, the Science Center has begun deploying near real-time satellite telemetered moorings as part of the Alaska Ocean Observing System (AOOS).  A pilot mooring was installed near the Armin F. Koernig hatchery, in Sawmill Bay, which is in the southwestern corner of Prince William Sound, and it is planned to install two more moorings in 2008: one near the Wally Noerenberg Hatchery on Esther Island and one near the village of Tatitlek.

The mooring consists of a Seabird Electronics SBE16 that measures temperature and salinity, and a WetLabs ECO FLNTUSB fluorometer that measures chlorophyll fluorescence (a measure of the amount of plant biomass in the water) and turbidity (a measurement of the cloudiness of the water).  The instruments are set at a fixed depth of 5 m (slightly more than 15 feet). Data is collected from the instruments every 10 minutes, and broadcast by radio to a satellite uplink station at the nearby hatchery.  Power is supplied by a solar panel and battery bank.

The datalogging electronics, solar panel and antenna are mounted onto a Alyeska Pipeline Service Company’s Ship Escort/Response Vessel System (SERVS) buoy.

The instruments are mounted onto a stainless steel cage, and suspended by a plastic-sheathed kevlar cable to a depth of 5 metres.  The large white instrument is a temperature-conductivity recorder (salinity is determined from conductivity), and the smaller black instrument is the fluorometer/turbidometer.  The fluorometer/turbidometer is an optical instrument, and has a rotating copper cover and wiper assembly to reduce bio-fouling and keep the optics clean.

Data collected every ten minutes since the mooring was installed in November 2007.  The temperature conductivity recorder had some corrosion issues beginning in mid January, and data is missing from that time.  A trip to the buoy to modify the mooring cage and swap in a new instrument is planned for April 2008.  Battery voltage is an indicator of the amount of sunlight, voltage increases when the solar panel is producing energy.  The chlorophyll-a signal (green dots) shows the tail end of a fall bloom, as well as the beginning of a spring bloom in late February after low values over the winter.  Turbidity (bottom  panel) also began to increase in April, and should continue to increase towards the summer as glacial silt is carried into the Sound by meltwaters.